mbl.is
Mon, 05 Oct 2009 16:43 EDT
A police dash-cam catches a fireball lighting up the sky in the south of Iceland
Translation of article:
The police in Selfoss caught these weird lights in the sky on tape shortly after midnight last night. The officers were going east during a routine highway patrol on Eyrarbakka-road when they noticed a spectacular flare which to them seemed to be heading to the river Ölfusá. Speculations are that this was a meteorite entering the atmosphere.
Many saw the flare and notified the police, and the flare was seen all around the south of Iceland and in Akranes. It is believed impossible to have been an emergency flare.
The sheriff in Selfoss says there has not been any aftermath to his knowledge, and no unusal visitors have been seen that could possibly have fallen from the sky.
In
1980, Luis Alvarez and his collaborators stunned the world with their
discovery that an asteroid impact 65 million years ago probably killed
off the dinosaurs and much of the the world's living organisms. But
ever since, there has been an ongoing debate about how long it took for
life to return to the devastated planet and for ecosystems to bounce
back.
Now, researchers from MIT and their collaborators have found that at least some forms of microscopic marine life - the so called "primary producers," or photosynthetic organisms such as algae and cyanobacteria in the ocean - recovered within about a century after the mass extinction. Previous research had indicated the process might have taken millions of years.
It has taken so long to uncover the quick recovery because previous studies looked mostly at fossils in the layers of sediment from that period, and apparently the initial recovery was dominated by tiny, soft-bodied organisms such as cyanobacteria, which do not have shells or other hard body parts that leave fossil traces. The new research looked instead for "chemical fossils" - traces of organic molecules (compounds composed of mostly carbon and hydrogen) that can reveal the presence of specific types of organisms, even though all other parts of the organisms themselves are long gone.
The new research, published in the Oct. 2 issue of Science, was led by Julio Sepúlveda, an MIT postdoc who carried out part of the work while still a graduate student at the University of Bremen, Germany, and MIT Professor of Geobiology Roger Summons, among others.
The team had two major advantages that helped to make the new findings possible. One was a section of the well-known cliff face at Stevns Klint, Denmark, that happens to have an unusually thick layer of sediment from the period of the mass extinction - about 40 centimeters thick, compared to the few cm thickness of the layers that Alvarez originally studied from that period at Gubbio (Italy) and Stevns Klint (Denmark). And team members tapped one of the most powerful Gas Chromatograph-Mass Spectrometers (GC-MS) in the world, a device that can measure minute quantities of different molecules in the rock. MIT's advanced GC-MS is one of only a few such powerful instruments currently available at U.S. universities.
When people look at microfossils in the sediments from the period but are unable to detect the chemical biomarkers with the level of sensitivity the MIT team was able to achieve, they "miss a big part of the picture," Sepúlveda says. "Many of these microorganisms" that were detected through molecular signatures "are at the base of the food chain, but if you don't look with biochemical techniques you miss them."
The analysis clarified the sequence of events after the big impact. Immediately after the impact, certain areas of the ocean were devoid of oxygen and hostile to most algae, but close to the continent, microbial life was inhibited for only a relatively short period: in probably less than 100 years, algal productivity showed the first signs of recovery. In the open ocean, however, this recovery took much longer: previous studies have estimated that the global ocean ecosystem did not return to its former state until 1 to 3 million years following the impact.
Because of the rebound of primary producers, Sepúlveda says "very soon after the impact, the food supply was not likely a limitation" for other organisms, and yet "the whole ecology of the system remained disrupted" and took much longer to recover.
The findings provide observational evidence supporting models suggesting that global darkness after the impact was rather short. "Primary productivity came back quickly, at least in the environment we were studying," says Summons, referring to the near-shore environment represented by the Danish sediments.
"The atmosphere must have cleared up rapidly," he says. "People will have to rethink the recovery of the ecosystems. It can't be just the lack of food supply" that made it take so long to recover.
The team hopes to be able to study other locations with relatively thick deposits from the extinction aftermath, to determine whether the quick recovery really was a widespread phenomenon after the mass extinction.
These findings seem to rule out one theory about how the global ecosystem responded to the impact, which held that for more than a million years there was a "Strangelove ocean" - a reference to the post-apocalyptic scenario in the movie Dr. Strangelove - in which all the primary producers remained absent for a prolonged period, Summons says.
In addition to Sepúlveda and Summons, the work was carried out by Jens Wendler of the Friedrich-Schiller University in Jena, Germany, and Kai-Uwe Hinrichs of the University of Bremen. The work was funded by the DFG, European Graduate College Europrox and the NASA Astrobiology and Exobiology Programs.
Journal reference:
1. Julio Sepúlveda, Jens E. Wendler, Roger E. Summons, and Kai-Uwe Hinrichs. Rapid Resurgence of Marine Productivity After the Cretaceous-Paleogene Mass Extinction. Science, 2009; DOI: link
Translation of article:
The police in Selfoss caught these weird lights in the sky on tape shortly after midnight last night. The officers were going east during a routine highway patrol on Eyrarbakka-road when they noticed a spectacular flare which to them seemed to be heading to the river Ölfusá. Speculations are that this was a meteorite entering the atmosphere.
Many saw the flare and notified the police, and the flare was seen all around the south of Iceland and in Akranes. It is believed impossible to have been an emergency flare.
The sheriff in Selfoss says there has not been any aftermath to his knowledge, and no unusal visitors have been seen that could possibly have fallen from the sky.
Science Daily
Sat, 03 Oct 2009 19:55 EDT
© Don Davis/NASA
An artist's rendering of the asteroid impact that took place 65 million years ago and likely killed off nearly every large vertebrate species on the planet, including, many think, the dinosaurs.
An artist's rendering of the asteroid impact that took place 65 million years ago and likely killed off nearly every large vertebrate species on the planet, including, many think, the dinosaurs.
Now, researchers from MIT and their collaborators have found that at least some forms of microscopic marine life - the so called "primary producers," or photosynthetic organisms such as algae and cyanobacteria in the ocean - recovered within about a century after the mass extinction. Previous research had indicated the process might have taken millions of years.
It has taken so long to uncover the quick recovery because previous studies looked mostly at fossils in the layers of sediment from that period, and apparently the initial recovery was dominated by tiny, soft-bodied organisms such as cyanobacteria, which do not have shells or other hard body parts that leave fossil traces. The new research looked instead for "chemical fossils" - traces of organic molecules (compounds composed of mostly carbon and hydrogen) that can reveal the presence of specific types of organisms, even though all other parts of the organisms themselves are long gone.
The new research, published in the Oct. 2 issue of Science, was led by Julio Sepúlveda, an MIT postdoc who carried out part of the work while still a graduate student at the University of Bremen, Germany, and MIT Professor of Geobiology Roger Summons, among others.
The team had two major advantages that helped to make the new findings possible. One was a section of the well-known cliff face at Stevns Klint, Denmark, that happens to have an unusually thick layer of sediment from the period of the mass extinction - about 40 centimeters thick, compared to the few cm thickness of the layers that Alvarez originally studied from that period at Gubbio (Italy) and Stevns Klint (Denmark). And team members tapped one of the most powerful Gas Chromatograph-Mass Spectrometers (GC-MS) in the world, a device that can measure minute quantities of different molecules in the rock. MIT's advanced GC-MS is one of only a few such powerful instruments currently available at U.S. universities.
When people look at microfossils in the sediments from the period but are unable to detect the chemical biomarkers with the level of sensitivity the MIT team was able to achieve, they "miss a big part of the picture," Sepúlveda says. "Many of these microorganisms" that were detected through molecular signatures "are at the base of the food chain, but if you don't look with biochemical techniques you miss them."
The analysis clarified the sequence of events after the big impact. Immediately after the impact, certain areas of the ocean were devoid of oxygen and hostile to most algae, but close to the continent, microbial life was inhibited for only a relatively short period: in probably less than 100 years, algal productivity showed the first signs of recovery. In the open ocean, however, this recovery took much longer: previous studies have estimated that the global ocean ecosystem did not return to its former state until 1 to 3 million years following the impact.
Because of the rebound of primary producers, Sepúlveda says "very soon after the impact, the food supply was not likely a limitation" for other organisms, and yet "the whole ecology of the system remained disrupted" and took much longer to recover.
The findings provide observational evidence supporting models suggesting that global darkness after the impact was rather short. "Primary productivity came back quickly, at least in the environment we were studying," says Summons, referring to the near-shore environment represented by the Danish sediments.
"The atmosphere must have cleared up rapidly," he says. "People will have to rethink the recovery of the ecosystems. It can't be just the lack of food supply" that made it take so long to recover.
The team hopes to be able to study other locations with relatively thick deposits from the extinction aftermath, to determine whether the quick recovery really was a widespread phenomenon after the mass extinction.
These findings seem to rule out one theory about how the global ecosystem responded to the impact, which held that for more than a million years there was a "Strangelove ocean" - a reference to the post-apocalyptic scenario in the movie Dr. Strangelove - in which all the primary producers remained absent for a prolonged period, Summons says.
In addition to Sepúlveda and Summons, the work was carried out by Jens Wendler of the Friedrich-Schiller University in Jena, Germany, and Kai-Uwe Hinrichs of the University of Bremen. The work was funded by the DFG, European Graduate College Europrox and the NASA Astrobiology and Exobiology Programs.
Journal reference:
1. Julio Sepúlveda, Jens E. Wendler, Roger E. Summons, and Kai-Uwe Hinrichs. Rapid Resurgence of Marine Productivity After the Cretaceous-Paleogene Mass Extinction. Science, 2009; DOI: link
Associated Press / Boston.com
Wed, 07 Oct 2009 20:20 EDT
Buenos Aires, Argentina - Pedro Elias Zadunaisky, an Argentine
astronomer and mathematician whose calculations helped determine the
orbit of Saturn's outermost moon, Phoebe, as well as Halley's Comet,
died Wednesday. He was 91.
Zadunaisky was a pioneer in celestial mechanics, applying mathematical models to determine how gravity and other forces alter the orbits of other objects in the solar system.
Zadunaisky also was a Senior Astronomer at the Smithsonian Astrophysical Observatory and in the 1960s researched the orbits of celestial bodies at NASA's Goddard Space Flight Center, calculating the orbits of the first U.S. Earth satellite, Explorer I, as well as other satellites during the U.S. space race against Russia.
Born in the Argentine city of Rosario on Dec. 10, 1917, Zadunaisky earned a civil engineering degree at the National University of Rosario, then pursued applied mathematics and specialized in celestial mechanics. He earned three Guggenheim fellowships for research at Columbia University in 1957, Princeton University in 1958 and at the University of Texas at Austin in 1977.
Zadunaisky left Argentina in 1966 along with many other professors and scientists after a crackdown on university protests against a military coup known as "the night of the long clubs."
Zadunaisky soon returned, and eventually taught at both the University of Buenos Aires and the National University of La Plata. He also directed astrodynamical investigations at Argentina's National Commission on Space Activity.
In 2000, an asteroid discovered by a team of his former students was named 4617 Zadunaisky in his honor.
His research was published in more than 40 publications worldwide, including the text book A Guide to Celestial Mechanics, edited by the Harvard Smithsonian Center for Astrophysics.
A new model for comet production revises the theory of their origins
The chunks of ice and dust that make their home in the Oort cloud, far beyond the orbit of Pluto, sometimes become dislodged and head into the solar system as streaky comets. Some disruptions, caused by passing stars and other interactions with the Milky Way galaxy, are severe enough to send Oort comets into orbits that buzz or even collide with Earth. New simulations have revealed a novel mechanism for their entry into our part of the solar system, a method that also suggests that comet showers may not have been strongly involved in major extinctions on Earth.
Comet dynamics depend heavily on Jupiter and Saturn: their huge gravitational fields tend to keep objects away from Earth. Comets that manage to skirt Jupiter and Saturn, the conventional thinking goes, had to have originated in the outer reaches of the Oort cloud, where perturbations from outside the solar system can be felt most strongly and are writ large across vast cometary orbits that take hundreds of years to complete. Only during comet showers caused by close stellar passages, the theory holds, have extreme gravitational disruptions brought inner Oort cloud comets into the mix.
A computer simulation by Nathan Kaib and Thomas Quinn, both at the University of Washington, have upended this thinking. They have found that the comets that manage to cross the Jupiter-Saturn barrier do in fact originate in large numbers in the inner Oort cloud, even in the absence of a large disruption causing a comet shower. Specifically, they found that the relatively nearby objects of the inner Oort cloud can be kicked into the reaches of the outer cloud via interactions with the massive planets. Those newly far-flung comets, suddenly enjoying a longer orbit and greater gravitational perturbations from interstellar space, can find their orbits so changed that, by the time they pass through the planetary region again, they slip past the gas giants. "They can basically hop over the Jupiter-Saturn barrier," Kaib says.
Kaib and Quinn estimate that more than half of the comets we observe streaking in from the Oort cloud reach our neighborhood via this route, and other researchers agree the simulation appears valid. "This mechanism, this dynamical path, as we call it, could work and could be a significant contributor," says Paul Weissman, a senior research scientist at the NASA Jet Propulsion Laboratory.
The new research presents a route for comet production "that goes some way" toward resolving discrepancies between the standard model and the observations, says Scott Tremaine, an astrophysicist at the Institute for Advanced Study in Princeton, N.J. "One of the issues is that [the conventional view of] the cometary formation process is so inefficient; in order to produce the number of comets that we see, you'd need a really massive protoplanetary disk, one that appears to be incompatible with our best estimates from other sources," Tremaine says.
Kaib and Quinn used their newfound mechanism, as well as the number of observed comets, to estimate an upper limit on how much material could be in the inner Oort cloud. They then produced a statistical model of how many comets would have hit Earth in comet showers in the past several hundred million years. Their conclusion: large cometary showers were few and hence probably did not cause more than one extinction event.
Using cometary dynamics to unwind the extinction history on Earth will likely meet with some controversy. Weissman notes that the extinction implications of Kaib and Quinn's analysis would involve comet showers, not comets in general, and that even a diminished profile of showers does not rule out the role of comets in extinctions. One big strike, rather than a shower of small ones, is all that's needed to trigger extinctions, he points out.
Pasadena,
California -- Using updated information, NASA scientists have
recalculated the path of a large asteroid. The refined path indicates a
significantly reduced likelihood of a hazardous encounter with Earth in
2036.
The Apophis asteroid is approximately the size of two-and-a-half football fields. The new data were documented by near-Earth object scientists Steve Chesley and Paul Chodas at NASA's Jet Propulsion Laboratory in Pasadena, Calif. They will present their updated findings at a meeting of the American Astronomical Society's Division for Planetary Sciences in Puerto Rico on Oct. 8.
"Apophis has been one of those celestial bodies that has captured the public's interest since it was discovered in 2004," said Chesley. "Updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036, for Apophis has dropped from one-in-45,000 to about four-in-a million."
A majority of the data that enabled the updated orbit of Apophis came from observations Dave Tholen and collaborators at the University of Hawaii's Institute for Astronomy in Manoa made. Tholen pored over hundreds of previously unreleased images of the night sky made with the University of Hawaii's 2.2-meter (88-inch) telescope, located near the summit of Mauna Kea.
Tholen made improved measurements of the asteroid's position in the images, enabling him to provide Chesley and Chodas with new data sets more precise than previous measures for Apophis. Measurements from the Steward Observatory's 2.3 meter (90-inch) Bok telescope on Kitt Peak in Arizona and the Arecibo Observatory on the island of Puerto Rico also were used in Chesley's calculations.
The information provided a more accurate glimpse of Apophis' orbit well into the latter part of this century. Among the findings is another close encounter by the asteroid with Earth in 2068 with chance of impact currently at approximately three-in-a-million. As with earlier orbital estimates where Earth impacts in 2029 and 2036 could not initially be ruled out due to the need for additional data, it is expected that the 2068 encounter will diminish in probability as more information about Apophis is acquired.
Initially, Apophis was thought to have a 2.7 percent chance of impacting Earth in 2029. Additional observations of the asteroid ruled out any possibility of an impact in 2029. However, the asteroid is expected to make a record-setting -- but harmless -- close approach to Earth on Friday, April 13, 2029, when it comes no closer than 29,450 kilometers (18,300 miles) above Earth's surface.
"The refined orbital determination further reinforces that Apophis is an asteroid we can look to as an opportunity for exciting science and not something that should be feared," said Don Yeomans, manager of the Near-Earth Object Program Office at JPL. "The public can follow along as we continue to study Apophis and other near-Earth objects by visiting us on our AsteroidWatch Web site and by following us on the @AsteroidWatch Twitter feed."
The science of predicting asteroid orbits is based on a physical model of the solar system which includes the gravitational influence of the sun, moon, other planets and the three largest asteroids.
NASA detects and tracks asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.
JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. Cornell University, Ithaca, N.Y., operates the Arecibo Observatory under a cooperative agreement with the National Science Foundation in Arlington, Va.
Zadunaisky was a pioneer in celestial mechanics, applying mathematical models to determine how gravity and other forces alter the orbits of other objects in the solar system.
Zadunaisky also was a Senior Astronomer at the Smithsonian Astrophysical Observatory and in the 1960s researched the orbits of celestial bodies at NASA's Goddard Space Flight Center, calculating the orbits of the first U.S. Earth satellite, Explorer I, as well as other satellites during the U.S. space race against Russia.
Born in the Argentine city of Rosario on Dec. 10, 1917, Zadunaisky earned a civil engineering degree at the National University of Rosario, then pursued applied mathematics and specialized in celestial mechanics. He earned three Guggenheim fellowships for research at Columbia University in 1957, Princeton University in 1958 and at the University of Texas at Austin in 1977.
Zadunaisky left Argentina in 1966 along with many other professors and scientists after a crackdown on university protests against a military coup known as "the night of the long clubs."
Zadunaisky soon returned, and eventually taught at both the University of Buenos Aires and the National University of La Plata. He also directed astrodynamical investigations at Argentina's National Commission on Space Activity.
In 2000, an asteroid discovered by a team of his former students was named 4617 Zadunaisky in his honor.
His research was published in more than 40 publications worldwide, including the text book A Guide to Celestial Mechanics, edited by the Harvard Smithsonian Center for Astrophysics.
John Matson
Scientific American
Thu, 01 Oct 2009 00:01 EDT
© Bettmann Corbis
Cometary commotion: A new mechanism for how icy bodies get past Jupiter and Saturn suggests that comet showers did not play a big role in Earth's extinctions.
Cometary commotion: A new mechanism for how icy bodies get past Jupiter and Saturn suggests that comet showers did not play a big role in Earth's extinctions.
The chunks of ice and dust that make their home in the Oort cloud, far beyond the orbit of Pluto, sometimes become dislodged and head into the solar system as streaky comets. Some disruptions, caused by passing stars and other interactions with the Milky Way galaxy, are severe enough to send Oort comets into orbits that buzz or even collide with Earth. New simulations have revealed a novel mechanism for their entry into our part of the solar system, a method that also suggests that comet showers may not have been strongly involved in major extinctions on Earth.
Comet dynamics depend heavily on Jupiter and Saturn: their huge gravitational fields tend to keep objects away from Earth. Comets that manage to skirt Jupiter and Saturn, the conventional thinking goes, had to have originated in the outer reaches of the Oort cloud, where perturbations from outside the solar system can be felt most strongly and are writ large across vast cometary orbits that take hundreds of years to complete. Only during comet showers caused by close stellar passages, the theory holds, have extreme gravitational disruptions brought inner Oort cloud comets into the mix.
A computer simulation by Nathan Kaib and Thomas Quinn, both at the University of Washington, have upended this thinking. They have found that the comets that manage to cross the Jupiter-Saturn barrier do in fact originate in large numbers in the inner Oort cloud, even in the absence of a large disruption causing a comet shower. Specifically, they found that the relatively nearby objects of the inner Oort cloud can be kicked into the reaches of the outer cloud via interactions with the massive planets. Those newly far-flung comets, suddenly enjoying a longer orbit and greater gravitational perturbations from interstellar space, can find their orbits so changed that, by the time they pass through the planetary region again, they slip past the gas giants. "They can basically hop over the Jupiter-Saturn barrier," Kaib says.
Kaib and Quinn estimate that more than half of the comets we observe streaking in from the Oort cloud reach our neighborhood via this route, and other researchers agree the simulation appears valid. "This mechanism, this dynamical path, as we call it, could work and could be a significant contributor," says Paul Weissman, a senior research scientist at the NASA Jet Propulsion Laboratory.
The new research presents a route for comet production "that goes some way" toward resolving discrepancies between the standard model and the observations, says Scott Tremaine, an astrophysicist at the Institute for Advanced Study in Princeton, N.J. "One of the issues is that [the conventional view of] the cometary formation process is so inefficient; in order to produce the number of comets that we see, you'd need a really massive protoplanetary disk, one that appears to be incompatible with our best estimates from other sources," Tremaine says.
Kaib and Quinn used their newfound mechanism, as well as the number of observed comets, to estimate an upper limit on how much material could be in the inner Oort cloud. They then produced a statistical model of how many comets would have hit Earth in comet showers in the past several hundred million years. Their conclusion: large cometary showers were few and hence probably did not cause more than one extinction event.
Using cometary dynamics to unwind the extinction history on Earth will likely meet with some controversy. Weissman notes that the extinction implications of Kaib and Quinn's analysis would involve comet showers, not comets in general, and that even a diminished profile of showers does not rule out the role of comets in extinctions. One big strike, rather than a shower of small ones, is all that's needed to trigger extinctions, he points out.
Jet Propulsion Laboratory
Mon, 12 Oct 2009 19:52 EDT
© UH/IA
Asteroid Apophis was discovered on June 19, 2004.
Asteroid Apophis was discovered on June 19, 2004.
The Apophis asteroid is approximately the size of two-and-a-half football fields. The new data were documented by near-Earth object scientists Steve Chesley and Paul Chodas at NASA's Jet Propulsion Laboratory in Pasadena, Calif. They will present their updated findings at a meeting of the American Astronomical Society's Division for Planetary Sciences in Puerto Rico on Oct. 8.
"Apophis has been one of those celestial bodies that has captured the public's interest since it was discovered in 2004," said Chesley. "Updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036, for Apophis has dropped from one-in-45,000 to about four-in-a million."
A majority of the data that enabled the updated orbit of Apophis came from observations Dave Tholen and collaborators at the University of Hawaii's Institute for Astronomy in Manoa made. Tholen pored over hundreds of previously unreleased images of the night sky made with the University of Hawaii's 2.2-meter (88-inch) telescope, located near the summit of Mauna Kea.
Tholen made improved measurements of the asteroid's position in the images, enabling him to provide Chesley and Chodas with new data sets more precise than previous measures for Apophis. Measurements from the Steward Observatory's 2.3 meter (90-inch) Bok telescope on Kitt Peak in Arizona and the Arecibo Observatory on the island of Puerto Rico also were used in Chesley's calculations.
The information provided a more accurate glimpse of Apophis' orbit well into the latter part of this century. Among the findings is another close encounter by the asteroid with Earth in 2068 with chance of impact currently at approximately three-in-a-million. As with earlier orbital estimates where Earth impacts in 2029 and 2036 could not initially be ruled out due to the need for additional data, it is expected that the 2068 encounter will diminish in probability as more information about Apophis is acquired.
Initially, Apophis was thought to have a 2.7 percent chance of impacting Earth in 2029. Additional observations of the asteroid ruled out any possibility of an impact in 2029. However, the asteroid is expected to make a record-setting -- but harmless -- close approach to Earth on Friday, April 13, 2029, when it comes no closer than 29,450 kilometers (18,300 miles) above Earth's surface.
"The refined orbital determination further reinforces that Apophis is an asteroid we can look to as an opportunity for exciting science and not something that should be feared," said Don Yeomans, manager of the Near-Earth Object Program Office at JPL. "The public can follow along as we continue to study Apophis and other near-Earth objects by visiting us on our AsteroidWatch Web site and by following us on the @AsteroidWatch Twitter feed."
The science of predicting asteroid orbits is based on a physical model of the solar system which includes the gravitational influence of the sun, moon, other planets and the three largest asteroids.
NASA detects and tracks asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.
JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. Cornell University, Ithaca, N.Y., operates the Arecibo Observatory under a cooperative agreement with the National Science Foundation in Arlington, Va.
koat.com
Tue, 13 Oct 2009 02:15 EDT
A New Mexico astronomer is hoping you can help solve a mystery.
He caught a spectacular fireball on video and he said you can help him track down what's left of it.
Thomas Ashcraft caught a cosmic fireball on camera. It flashed through the sky for about eight seconds just after 2 Friday morning.
"Probably originating in the vicinity of Taos, and then streaking across the sky to Wagon Mound or Springer area," said Ashcraft.
Ashcraft works in a lab the size of a small barn. He bought or built most of the electronics himself, except for a special camera on loan from Sandia Labs.
The camera looks like a parking lot surveillance camera except it's parking lot is the sky.
"Actually up to Denver, into Utah, into southwest Kansas, and northern Mexico," said Ashcraft.
The camera runs from dusk to dawn recording everything that flashes through the heavens. It's synched to a radio telescope that records the sound of the objects shredding the ionosphere.
"Maybe somebody recorded this on surveillance camera. So if there's other videos, then we might be able to triangulate and see if there's a meteorite that landed somewhere," said Ashcraft.
Thomas says that this fireball was created by something about the size of a filing cabinet, but he can spot something as small as this bolt burning through the atmosphere.
Britney E. Schmidt, a UCLA
doctoral student in the department of Earth and space sciences, wasn't
sure what she'd glean from images of the asteroid Pallas taken by the
Hubble Space Telescope. But she hoped to settle at least one burning
question: Was Pallas, the second-largest asteroid, actually in that
gray area between an asteroid and a small planet?
The answer, she found, was yes. Pallas, like its sister asteroids Ceres and Vesta, was that rare thing: an intact protoplanet.
"It was incredibly exciting to have this new perspective on an object that is really interesting and hadn't been observed by Hubble at high resolution," Schmidt said of the first high-resolution images of Pallas, which is believed to have been intact since its formation, most likely within a few million years of the birth of our solar system.
"We were trying to understand not only the object, but how the solar system formed," Schmidt said. "We think of these large asteroids not only as the building blocks of planets but as a chance to look at planet formation frozen in time."
The research appears Oct. 9 in the journal Science.
"To have the chance to use Hubble at all, and to see those images come back and understand automatically this could change what we think about this object - that was incredibly exciting to me," Schmidt said.
Pallas, which is named for the Greek goddess Pallas Athena, lies in the main asteroid belt between the orbits of Jupiter and Mars. Schmidt likens it to the size of Arizona, her home state. The massive body is unique, she said, partly because "its orbit is so much different from other asteroids. It's highly inclined."
Hubble had tried to snap pictures of the round-shaped body before but came up short. So when the space telescope took images again in September 2007, Schmidt and her colleagues had several goals.
"We wanted to learn about Pallas itself - what its shape is like, what its surface is like, does it have large impact craters, does it have significant topography," she said.
With the Hubble images, Schmidt and her colleagues were able to take new measurements of Pallas' size and shape. They were able to see that its surface has areas of dark and light, indicating that the water-rich body might have undergone an internal change in the same way planets do.
Pallas wasn't just a big rock made of hydrated silicate and ice, they found.
"That's what makes it more like a planet - the color variation and the round shape are very important as far as understanding, is this a dynamic object or has it been exactly the same since it's been formed?" Schmidt said. "We think it's probably a dynamic object."
For the first time, Schmidt and her colleagues also saw a large impact site on Pallas. They were unable to determine if it was a crater, but the depression did suggest something else important: that it could have led to Pallas' small family of asteroids orbiting in space.
"It's interesting, because there are very few large, intact asteroids left," Schmidt said. "There were probably many more. Most have been broken up completely. It's an interesting chance to almost look into the object, at the layer underneath. It's helping to unravel one of the big questions that we have about Pallas, why does it have this family?"
Schmidt's co-authors include Peter C. Thomas, a senior researcher at Cornell University; James Bauer, a researcher with the Jet Propulsion Laboratory; J.Y. Li, a postdoctoral student at the University of Maryland; Schmidt's Ph.D. adviser, UCLA professor of geophysics and space physics Christopher T. Russell; Andrew Rivkin, a researcher at Johns Hopkins University; Joel William Parker, a researcher at the Southwest Research Institute in Boulder, Colorado; Lucy McFadden, a faculty member at the University of Maryland; S. Alan Stern of the Southwest Research Institute; Max Mutchler, a researcher at the Space Telescope Sciences Institute; and Chris Radcliffe, a digital artist in Santa Monica.
"When people think of asteroids, they think of 'Star Wars' or of tiny little rocks floating through space," Schmidt said. "But some of these have been really physically dynamic. Around 5 million years after the formation of the solar system, Pallas was probably doing something kind of interesting."
Asteroid isn't just a dry heap of rubble
Two independent teams have found what may
be the first direct evidence of water ice on the surface of an
asteroid. The discovery lends support to the idea that asteroids could
have helped deliver water to the early Earth.
Asteroids are generally considered to be rocky, and comets icy. That's because ice in the early solar system is thought to have formed beyond a "snow line" lying somewhere between Mars and Jupiter. Asteroids forming beyond that boundary could contain ice.
But it is not clear how common ice might be in the main asteroid belt, because sunlight is expected to quickly vaporise ice on the surfaces of airless bodies that fly closer to the sun than Jupiter.
In 2008, however, Andrew Rivkin of Johns Hopkins University in Laurel, Maryland, and Joshua Emery of the SETI Institute in Mountain View, California, found hints that the asteroid 24 Themis, which sits in the main asteroid belt between Mars and Jupiter, could have water ice on its surface. The team found the water signal by measuring the spectrum of infrared light radiated by the object.
Now a second team has found the water ice signature using the same telescope, NASA's Infrared Telescope Facility in Hawaii.
The new observations suggest water ice, mixed with organic molecules, is "widespread on the surface of the asteroid", Humberto Campins of the University of Central Florida in Orlando reported at a meeting of the American Astronomical Society's Division of Planetary Sciences in Fajardo, Puerto Rico, last week.
Icy parent
That is surprising, since the asteroid's distance from the sun means it should lose about 1 metre of ice each year. "This ice is unstable, and therefore we need a process to explain why there is ice on the surface now," Campins said at the meeting.
One possiblity is that an icy object might have collided with 24 Themis, leaving behind a layer of ice. Alternatively, the ice could have been part of the asteroid's parent body, which is thought to have broken up about 2.5 billion years ago, producing a family of asteroids with orbits similar to that of 24 Themis.
In that case, the ice seen on the surface now would once have been buried beneath dust and rock that insulated it from the sun's heat and prevented it from escaping into space. Impacts could then have churned the surface to expose the ice.
Watery hints
Until now, the possibility of present-day water ice on asteroids has only been hinted at. The density of the mammoth main-belt asteroid Ceres suggests it contains a large amount of water ice, but no clear-cut sign of ice has been found on its surface.
"This Themis result is really nice because it's been confirmed by two independent groups," says Henry Hsieh of Queen's University Belfast in the UK, though he notes that the spectral evidence for ice may not be entirely water-tight.
"It's a messy region [of the spectrum] that's hard to observe," says Clark Chapman of Southwest Research Institute in Boulder, Colorado. "In some sense, it's a matter of judgment whether it's a hint of water ice or an almost certain detection or somewhere in between."
Still, Chapman says, he would not be surprised to see water ice on asteroids, adding that the distinction between comets, traditionally considered to be icy, and asteroids, which have been largely thought of as rocky, is becoming increasingly blurred.
Comet tails
In recent years, Hsieh and others have discovered a handful of main-belt asteroids with comet-like tails that could be created by sublimating ice.
These so-called "main-belt comets" are too distant and faint for astronomers to scan their spectra for signs of water ice. Two of the four detected so far are part of the same family of asteroids as 24 Themis, which is the family's largest member.
"What is most likely the case is that the parent body [of this family] was water-ice-rich, was broken up, and now the surface of its largest fragment, Themis, has been impact-excavated, revealing the ice that was once deep in a larger object," says Britney Schmidt of UCLA, who was not affiliated with Campins's study. "It is exciting to finally get a glimpse inside a water-rich body."
Mismatched isotopes
David Jewitt of UCLA, co-discoverer of the first main-belt comets, agrees. "These objects may hold ice and preserve a record of conditions at formation between the orbits of Mars and Jupiter," he told New Scientist.
The detection could also go a long way towards explaining how the Earth got its water. Soon after the solar system's formation, the sun's heat is thought to have broken apart most water molecules that lay close to the sun.
Comets, which formed far from the sun, have been proposed as an alternate way of delivering water to the Earth, but the relative amounts of different isotopes of hydrogen in the water on comets do not match up with Earth's. "If there was water in the asteroids, it could be enough to fill the oceans," Hsieh says.
No evidence of an extraterrestrial impact 13,000 years ago, studies say.
An independent study has cast more doubt on a controversial theory that a comet exploded over icy North America nearly 13,000 years ago, wiping out the Clovis people and many of the continent's large animals.
Archaeologists have examined sediments at seven Clovis-age sites across the United States, and did not find enough magnetic cosmic debris to confirm that an extraterrestrial impact happened at that time, says the report in the Proceedings of the National Academy of Sciences (PNAS). It is the latest of several studies unable to support aspects of the impact hypothesis.
In 2007, a team led by Californian researchers announced a theory that a comet or asteroid had exploded over the North American ice sheet, creating widespread fire and an atmospheric soot burst followed by a cooling period known as the Younger Dryas.
Sometime after this, the Clovis people, sophisticated large-animal hunters known for their spear points, mysteriously disappeared; the team linked their vanishing to the environmental effects of the proposed impact.
Key evidence came in the form of magnetic microspherules discovered in sediments at 25 locations, including eight Clovis-age sites. Richard Firestone, of Lawrence Berkeley National Laboratory in California, and his colleagues argued that the microspherules were remnants of cosmic debris from an explosion.
But in more than 18 months of sedimentary analysis, a team led by Todd Surovell, an archaeologist at the University of Wyoming in Laramie, was unable to detect microspherule peaks. Two of the seven sites the group studied were places where Firestone's team identified spherule peaks.
"I spent hundreds of hours at the microscope examining sediment samples," says Surovell, "and I didn't find any physical evidence to support their theory."
Standing firm
The other team isn't backing down. "Their study doesn't negate our hypothesis," says James Kennett, a palaeoceanographer at the University of California at Santa Barbara and one of Firestone's co-authors. Another co-author, avocational geophysicist Allen West of Prescott, Arizona, says that Surovell's group didn't use the correct technique to extract, identify and quantify the microspherules.
Several other groups have been unable to support important aspects of the comet theory.
In a PNAS article published in February, Jennifer Marlon, a doctoral geography student at the University of Oregon in Eugene, and her colleagues found no systematic burning of biomass - as would have occurred if continent-wide fires had happened - at the time of the Younger Dryas in pollen and charcoal records at 35 sites. And at the Ecological Society of America meeting in Albuquerque, New Mexico, in August, Jacquelyn Gill, a palaeoecology doctoral student at the University of Wisconsin-Madison, reported finding no evidence of massive burning in sediment cores taken from lake beds in Ohio and Indiana.
Kennett, however, calls these studies "flawed". In August, his team published a report saying they had found nanometre-sized diamonds, purportedly created during an impact, and soot in sediments dated to the Younger Dryas on Santa Rosa Island, off the coast of California.
More studies of the theory - both critical and supportive - are in the publishing pipelines at other journals.
Surovell's co-author Vance Holliday, an archaeologist at the University of Arizona in Tucson, and his colleagues have an article in press at Current Anthropology that says the archaeological and geochronological records don't support a collapse of Clovis people at the time of the purported impact.
He caught a spectacular fireball on video and he said you can help him track down what's left of it.
Thomas Ashcraft caught a cosmic fireball on camera. It flashed through the sky for about eight seconds just after 2 Friday morning.
"Probably originating in the vicinity of Taos, and then streaking across the sky to Wagon Mound or Springer area," said Ashcraft.
Ashcraft works in a lab the size of a small barn. He bought or built most of the electronics himself, except for a special camera on loan from Sandia Labs.
The camera looks like a parking lot surveillance camera except it's parking lot is the sky.
"Actually up to Denver, into Utah, into southwest Kansas, and northern Mexico," said Ashcraft.
The camera runs from dusk to dawn recording everything that flashes through the heavens. It's synched to a radio telescope that records the sound of the objects shredding the ionosphere.
"Maybe somebody recorded this on surveillance camera. So if there's other videos, then we might be able to triangulate and see if there's a meteorite that landed somewhere," said Ashcraft.
Thomas says that this fireball was created by something about the size of a filing cabinet, but he can spot something as small as this bolt burning through the atmosphere.
ScienceDaily
Tue, 13 Oct 2009 12:40 EDT
© Science/AAAS
Pallas's largest crater-like feature seen in the digital model (left) and from two perspectives: appearing face-on (upper right) and edge-on along the limb (lower right).
Pallas's largest crater-like feature seen in the digital model (left) and from two perspectives: appearing face-on (upper right) and edge-on along the limb (lower right).
The answer, she found, was yes. Pallas, like its sister asteroids Ceres and Vesta, was that rare thing: an intact protoplanet.
"It was incredibly exciting to have this new perspective on an object that is really interesting and hadn't been observed by Hubble at high resolution," Schmidt said of the first high-resolution images of Pallas, which is believed to have been intact since its formation, most likely within a few million years of the birth of our solar system.
"We were trying to understand not only the object, but how the solar system formed," Schmidt said. "We think of these large asteroids not only as the building blocks of planets but as a chance to look at planet formation frozen in time."
The research appears Oct. 9 in the journal Science.
"To have the chance to use Hubble at all, and to see those images come back and understand automatically this could change what we think about this object - that was incredibly exciting to me," Schmidt said.
Pallas, which is named for the Greek goddess Pallas Athena, lies in the main asteroid belt between the orbits of Jupiter and Mars. Schmidt likens it to the size of Arizona, her home state. The massive body is unique, she said, partly because "its orbit is so much different from other asteroids. It's highly inclined."
Hubble had tried to snap pictures of the round-shaped body before but came up short. So when the space telescope took images again in September 2007, Schmidt and her colleagues had several goals.
"We wanted to learn about Pallas itself - what its shape is like, what its surface is like, does it have large impact craters, does it have significant topography," she said.
With the Hubble images, Schmidt and her colleagues were able to take new measurements of Pallas' size and shape. They were able to see that its surface has areas of dark and light, indicating that the water-rich body might have undergone an internal change in the same way planets do.
Pallas wasn't just a big rock made of hydrated silicate and ice, they found.
"That's what makes it more like a planet - the color variation and the round shape are very important as far as understanding, is this a dynamic object or has it been exactly the same since it's been formed?" Schmidt said. "We think it's probably a dynamic object."
For the first time, Schmidt and her colleagues also saw a large impact site on Pallas. They were unable to determine if it was a crater, but the depression did suggest something else important: that it could have led to Pallas' small family of asteroids orbiting in space.
"It's interesting, because there are very few large, intact asteroids left," Schmidt said. "There were probably many more. Most have been broken up completely. It's an interesting chance to almost look into the object, at the layer underneath. It's helping to unravel one of the big questions that we have about Pallas, why does it have this family?"
Schmidt's co-authors include Peter C. Thomas, a senior researcher at Cornell University; James Bauer, a researcher with the Jet Propulsion Laboratory; J.Y. Li, a postdoctoral student at the University of Maryland; Schmidt's Ph.D. adviser, UCLA professor of geophysics and space physics Christopher T. Russell; Andrew Rivkin, a researcher at Johns Hopkins University; Joel William Parker, a researcher at the Southwest Research Institute in Boulder, Colorado; Lucy McFadden, a faculty member at the University of Maryland; S. Alan Stern of the Southwest Research Institute; Max Mutchler, a researcher at the Space Telescope Sciences Institute; and Chris Radcliffe, a digital artist in Santa Monica.
"When people think of asteroids, they think of 'Star Wars' or of tiny little rocks floating through space," Schmidt said. "But some of these have been really physically dynamic. Around 5 million years after the formation of the solar system, Pallas was probably doing something kind of interesting."
Asteroid isn't just a dry heap of rubble
Rachel Courtland
New Scientist
Mon, 12 Oct 2009 14:29 EDT
© NASA/ESA/J. Parker/SWRI/P. Thomas/Cornell U/L. McFadden/University of Maryland/M. Mutchler/Z. Levay/STScI
The largest asteroid, Ceres (shown), appears to contain a lot of water ice beneath its surface. Now ice has been detected on the surface of the asteroid 24 Themis, which lies about three times as far from the sun as Earth does.
The largest asteroid, Ceres (shown), appears to contain a lot of water ice beneath its surface. Now ice has been detected on the surface of the asteroid 24 Themis, which lies about three times as far from the sun as Earth does.
Asteroids are generally considered to be rocky, and comets icy. That's because ice in the early solar system is thought to have formed beyond a "snow line" lying somewhere between Mars and Jupiter. Asteroids forming beyond that boundary could contain ice.
But it is not clear how common ice might be in the main asteroid belt, because sunlight is expected to quickly vaporise ice on the surfaces of airless bodies that fly closer to the sun than Jupiter.
In 2008, however, Andrew Rivkin of Johns Hopkins University in Laurel, Maryland, and Joshua Emery of the SETI Institute in Mountain View, California, found hints that the asteroid 24 Themis, which sits in the main asteroid belt between Mars and Jupiter, could have water ice on its surface. The team found the water signal by measuring the spectrum of infrared light radiated by the object.
Now a second team has found the water ice signature using the same telescope, NASA's Infrared Telescope Facility in Hawaii.
The new observations suggest water ice, mixed with organic molecules, is "widespread on the surface of the asteroid", Humberto Campins of the University of Central Florida in Orlando reported at a meeting of the American Astronomical Society's Division of Planetary Sciences in Fajardo, Puerto Rico, last week.
Icy parent
That is surprising, since the asteroid's distance from the sun means it should lose about 1 metre of ice each year. "This ice is unstable, and therefore we need a process to explain why there is ice on the surface now," Campins said at the meeting.
One possiblity is that an icy object might have collided with 24 Themis, leaving behind a layer of ice. Alternatively, the ice could have been part of the asteroid's parent body, which is thought to have broken up about 2.5 billion years ago, producing a family of asteroids with orbits similar to that of 24 Themis.
In that case, the ice seen on the surface now would once have been buried beneath dust and rock that insulated it from the sun's heat and prevented it from escaping into space. Impacts could then have churned the surface to expose the ice.
Watery hints
Until now, the possibility of present-day water ice on asteroids has only been hinted at. The density of the mammoth main-belt asteroid Ceres suggests it contains a large amount of water ice, but no clear-cut sign of ice has been found on its surface.
"This Themis result is really nice because it's been confirmed by two independent groups," says Henry Hsieh of Queen's University Belfast in the UK, though he notes that the spectral evidence for ice may not be entirely water-tight.
"It's a messy region [of the spectrum] that's hard to observe," says Clark Chapman of Southwest Research Institute in Boulder, Colorado. "In some sense, it's a matter of judgment whether it's a hint of water ice or an almost certain detection or somewhere in between."
Still, Chapman says, he would not be surprised to see water ice on asteroids, adding that the distinction between comets, traditionally considered to be icy, and asteroids, which have been largely thought of as rocky, is becoming increasingly blurred.
Comet tails
In recent years, Hsieh and others have discovered a handful of main-belt asteroids with comet-like tails that could be created by sublimating ice.
These so-called "main-belt comets" are too distant and faint for astronomers to scan their spectra for signs of water ice. Two of the four detected so far are part of the same family of asteroids as 24 Themis, which is the family's largest member.
"What is most likely the case is that the parent body [of this family] was water-ice-rich, was broken up, and now the surface of its largest fragment, Themis, has been impact-excavated, revealing the ice that was once deep in a larger object," says Britney Schmidt of UCLA, who was not affiliated with Campins's study. "It is exciting to finally get a glimpse inside a water-rich body."
Mismatched isotopes
David Jewitt of UCLA, co-discoverer of the first main-belt comets, agrees. "These objects may hold ice and preserve a record of conditions at formation between the orbits of Mars and Jupiter," he told New Scientist.
The detection could also go a long way towards explaining how the Earth got its water. Soon after the solar system's formation, the sun's heat is thought to have broken apart most water molecules that lay close to the sun.
Comets, which formed far from the sun, have been proposed as an alternate way of delivering water to the Earth, but the relative amounts of different isotopes of hydrogen in the water on comets do not match up with Earth's. "If there was water in the asteroids, it could be enough to fill the oceans," Hsieh says.
Rex Dalton
Nature News
Mon, 12 Oct 2009 10:00 EDT
© Vance Holliday
Sediments at the San Jon site, in eastern New Mexico, contained very low abundances of magnetic spherules said to be evidence of an impact.
Sediments at the San Jon site, in eastern New Mexico, contained very low abundances of magnetic spherules said to be evidence of an impact.
An independent study has cast more doubt on a controversial theory that a comet exploded over icy North America nearly 13,000 years ago, wiping out the Clovis people and many of the continent's large animals.
Archaeologists have examined sediments at seven Clovis-age sites across the United States, and did not find enough magnetic cosmic debris to confirm that an extraterrestrial impact happened at that time, says the report in the Proceedings of the National Academy of Sciences (PNAS). It is the latest of several studies unable to support aspects of the impact hypothesis.
In 2007, a team led by Californian researchers announced a theory that a comet or asteroid had exploded over the North American ice sheet, creating widespread fire and an atmospheric soot burst followed by a cooling period known as the Younger Dryas.
Sometime after this, the Clovis people, sophisticated large-animal hunters known for their spear points, mysteriously disappeared; the team linked their vanishing to the environmental effects of the proposed impact.
Key evidence came in the form of magnetic microspherules discovered in sediments at 25 locations, including eight Clovis-age sites. Richard Firestone, of Lawrence Berkeley National Laboratory in California, and his colleagues argued that the microspherules were remnants of cosmic debris from an explosion.
But in more than 18 months of sedimentary analysis, a team led by Todd Surovell, an archaeologist at the University of Wyoming in Laramie, was unable to detect microspherule peaks. Two of the seven sites the group studied were places where Firestone's team identified spherule peaks.
"I spent hundreds of hours at the microscope examining sediment samples," says Surovell, "and I didn't find any physical evidence to support their theory."
Standing firm
The other team isn't backing down. "Their study doesn't negate our hypothesis," says James Kennett, a palaeoceanographer at the University of California at Santa Barbara and one of Firestone's co-authors. Another co-author, avocational geophysicist Allen West of Prescott, Arizona, says that Surovell's group didn't use the correct technique to extract, identify and quantify the microspherules.
Several other groups have been unable to support important aspects of the comet theory.
In a PNAS article published in February, Jennifer Marlon, a doctoral geography student at the University of Oregon in Eugene, and her colleagues found no systematic burning of biomass - as would have occurred if continent-wide fires had happened - at the time of the Younger Dryas in pollen and charcoal records at 35 sites. And at the Ecological Society of America meeting in Albuquerque, New Mexico, in August, Jacquelyn Gill, a palaeoecology doctoral student at the University of Wisconsin-Madison, reported finding no evidence of massive burning in sediment cores taken from lake beds in Ohio and Indiana.
Kennett, however, calls these studies "flawed". In August, his team published a report saying they had found nanometre-sized diamonds, purportedly created during an impact, and soot in sediments dated to the Younger Dryas on Santa Rosa Island, off the coast of California.
More studies of the theory - both critical and supportive - are in the publishing pipelines at other journals.
Surovell's co-author Vance Holliday, an archaeologist at the University of Arizona in Tucson, and his colleagues have an article in press at Current Anthropology that says the archaeological and geochronological records don't support a collapse of Clovis people at the time of the purported impact.
Comment: For a more in-depth view, read: The Younger Dryas Impact Event and the Cycles of Cosmic Catastrophes - Climate Scientists Awakening
PhysOrg
Tue, 13 Oct 2009 00:00 EDT
The Tunguska Mystery
In The Tunguska Mystery by Vladimir Rubtsov, the efforts put forth by generations of Russian scientists, technicians, and others are documented. What did they find? Was it a meteorite, as had first been thought? Was it an asteroid? Was it a comet? Some support the idea that this was not a "natural" event at all but one caused by the explosion of an alien spaceship trying to land on Earth. Is there any evidence for this? How did the Russian scientific and world community react to this theory?
The mystery has been very difficult to solve, but it is important - perhaps even urgent - to solve it. We live in a very violent universe, and we are extremely vulnerable to its vagaries. How can we prevent another "Tunguska" if we don't even know what it was? And next time, the event might not occur in a remote, barely inhabited region of Earth. It may take many thousands of lives and destroy whole cities.
Vladimir Rubtsov was born in 1948 in Kharkov, Ukraine. He received his Ph.D. degree in the Philosophy of Science from the Institute of Philosophy of the Academy of Sciences of the USSR, having defended in 1980 the doctoral thesis: "Philosophical and Methodological Aspects of the Problem of Extraterrestrial Civilizations," the first of its kind in the former USSR. Dr. Rubtsov has authored two monographs and some 120 scientific and popular science articles in the Soviet, post-Soviet and international press.
Thaindian News
Tue, 13 Oct 2009 14:32 EDT
Asteroids are generally considered to be rocky, and comets icy. That's because ice in the early solar system is thought to have formed beyond a "snow line" lying somewhere between Mars and Jupiter.
Asteroids forming beyond that boundary could contain ice.
But, it is not clear how common ice might be in the main asteroid belt, because sunlight is expected to quickly vaporise ice on the surfaces of airless bodies that fly closer to the sun than Jupiter.
In 2008, however, Andrew Rivkin of Johns Hopkins University in Laurel, Maryland, and Joshua Emery of the SETI Institute in Mountain View, California, found hints that the asteroid 24 Themis, which sits in the main asteroid belt between Mars and Jupiter, could have water ice on its surface.
The team found the water signal by measuring the spectrum of infrared light radiated by the object.
Now, according to a report in New Scientist, a second team has found the water ice signature using the same telescope, NASA's Infrared Telescope Facility in Hawaii.
The new observations suggest water ice, mixed with organic molecules, is "widespread on the surface of the asteroid," said Humberto Campins of the University of Central Florida in Orlando.
That is surprising, since the asteroid's distance from the sun means it should lose about 1 metre of ice each year.
"This ice is unstable, and therefore we need a process to explain why there is ice on the surface now," said Campins.
One possibility is that an icy object might have collided with 24 Themis, leaving behind a layer of ice.
Alternatively, the ice could have been part of the asteroid's parent body, which is thought to have broken up about 2.5 billion years ago, producing a family of asteroids with orbits similar to that of 24 Themis.
"What is most likely the case is that the parent body (of this family) was water-ice-rich, was broken up, and now the surface of its largest fragment, Themis, has been impact-excavated, revealing the ice that was once deep in a larger object," said Britney Schmidt of UCLA.
"It is exciting to finally get a glimpse inside a water-rich body," she added.
Alexis Madrigal
Wired
Mon, 12 Oct 2009 17:43 EDT
The hovercraft
Since then, no scientific vessel has been back over the area to collect more data. The massive icebreakers that have crunched through the Arctic since the 1990s can't reach the spot, said Yngve Kristofferson, a scientist and explorer at the University of Bergen in Norway.
Kristofferson became intrigued with Hall's data and in 2004, the two of them met in Bergen to talk Arctic science from eight in the morning to 10 in the evening. At the end of their time together, they came to a decision: They needed a hovercraft.
Luckily, Hall is a partial heir to the fortune his grandfather made as head of the American Chicle Company, the trust that ran the American bubble gum game early in the 20th century, so he was able to buy the vehicle with private funds. A customized Griffon Hovercraft 2000TD, it is now going through the paces, hitting the Arctic from its home at Longyearbyen for the first time in 2008, and hoping to reach its full potential next spring.
Hall delivered a speech detailing the craft's capabilities and mission at Columbia University's Lamont Doherty Earth Observatory on Oct. 6.
"The neat thing with a hovercraft is that you drive with the same ease over 10 centimeter-thick ice as you do with five meter thick ice," Kristofferson told Wired.com.
Despite their futuristic reputation, hovercraft have been commercially available for decades. The concept is actually quite simple. A big engine or turbine pumps air into a rubber skirt that allows the vehicle to tread lightly on whatever it's touching. The R/H Sabvabaa, for example, weighs six tons but exerts no more pressure on any patch of ice than a seagull standing on one leg would by standing on it. The rest of the power from the engine is devoted to propulsion, allowing the craft to skip along at speeds up to 50 miles per hour.
For the strange terrain of the Arctic, it works perfectly, Hall and Kristofferson wrote in an article in the journal The Leading Edge in August.
"The craft has proved to be useful for a variety of scientific tasks," they wrote. "It appears more efficient than any other platform for ice-thickness measurements and oceanographic work."
Their hovercraft push comes as money has flooded into Arctic research. With Arctic ice melting, the nations adjacent to the ocean are rushing to stake their claims not just on the water, but on the oil and natural gas that lie under the sea floor, leading to calls to establish a National Park to protect the area.
The most fascinating target for the hovercraft is the area of very thick ice closer to Ellesmere Island and northern Greenland. Not even nuclear-powered icebreakers have ventured into the region. It was just Hall's good fortune to have been aboard the floating ice island doing research when it passed near this apparent sea floor anomaly. The duo, along with several other colleagues, described the discovery in a 2008 paper in the Norwegian Journal of Geology.
Fletcher’s Ice Island Camp
To Kristofferson and Hall, the evidence suggests that a pressure wave caused by a pieces of a large asteroid crashing into the Arctic Ocean created these strange features.
"Our working hypothesis is that the spectrum and scale of the observed disturbances are best explained as the effect of a shock wave generated by the impact of an extraterrestrial object," they wrote.
But the hypothesis remains just that without more data. The hovercraft works well, but with its on-board fuel, its range is limited to around 500 miles. For that reason, the scientists imagine they'll use a larger vessel as a base of operations.
"What we really want to do is go along with an icebreaker into the Arctic. You can greatly enhance the scientific output if you have a hovercraft. If you have more of them, even better," Kristofferson said. "We can go out and do our own science and be away for many days. If the icebreaker gets stuck, we're not stuck."
Still, both Hall and Kristofferson know they face an uphill battle to get other scientists to take both the hovercraft and asteroid impact ideas seriously.
"The task is to figure out the real message in the data - the dream challenge for any scientist," Kristofferson told the Lamont Doherty alumni magazine earlier this year. "So far, we have mostly met shaking heads, which just makes it more fun."
Dutch News
Wed, 14 Oct 2009 16:51 EDT
The police emergency number, Dutch coastguard and KNMI weather bureau report dozens of phone calls about the meteorite, which was seen in Germany and Belgium.
'I was standing in front of my window when there was a bright flash of light and a white fireball in the sky fell apart into three smaller ones,' eyewitness Erik Alberts from Zuidbroek in Groningen province told Nos tv. 'Like fireworks. A few seconds later, perhaps half a minute, there was a low rumble and the windows shook.'
Peter Downs
The Tribune / Sun Media
Wed, 07 Oct 2009 22:02 EDT
A composite photograph of the meteor that streaked across southern Ontario Sept. 25. It is believed meteorites landed in the Grimsby area.
Astronomers will be digging through farmers' fields Thursday and Friday on the hunt for hunks of a meteor that blazed across the skies of southern Ontario Sept. 25 shortly after 9 p.m.
The beachball-sized meteor was first picked up by cameras operated by the University of Western Ontario's physics and astronomy department 100 kilometres above Guelph as the fireball streaked southeastward at a speed of about 75,000 km/h.
Astronomers at the university have traced the meteor's path and believe chunks of it may have landed above the escarpment within a 10-km radius of Grimsby.
"We're pretty certain something came down," said Phil McCausland, a postdoctoral fellow with the university's astronomy department.
"It's hard to put an X on the map and say, 'There,' because what happens is at the end of the fireball path the lights go out. There's no camera record of that."
It's likely small pieces of the meteor - anywhere between the size of a golf ball or a fist - made it through the atmosphere and hit the ground, he said.
"It could be dozens, it could be one or two. It's hard to say, but if it's one or two, they will be on the largish size - probably more than a kilogram."
Researchers are keen to find any of the meteorites because it's extremely rare to have their fall to Earth documented so well with photo evidence.
Based on all of the information already known about the rocks, it's possible for astronomers to determine which orbit they came from and learn more about the early history of the solar system.
"There's only a handful, perhaps a dozen, meteorites that have this kind of orbital information," McCausland said.
The rural area where the meteorites are believed to have landed is largely farmland with some forest.
McCausland has already spent several days over the past week searching for the rocks and interviewing landowners in the area.
He was expected to be back on the hunt again Thursday with other researchers.
"Even though the (cameras) we have narrows it down quite nicely, it's still a large area to search. We're still talking about 12 to 16 kilometres," he said.
Doug Welch, an astrophysicist at McMaster University, will be joining the search.
Welch monitors one of Western's meteor-seeking sky cameras at the Hamilton university.
The fireball that torched across the sky two weeks ago practically went directly overhead of the Hamilton camera.
"It's really spectacular. ... I've seen them live, but it's very rare for them to be this bright," he said.
Recovering meteorites that may have fallen gives researchers a rare opportunity to learn more about the formation of the solar system, he said.
"These are free samples from elsewhere in the solar system delivered to your door. We have sample-return missions that cost hundreds of millions of dollars."
Meteorologist and Grimsby resident Kerry-Ann Lecky Hepburn spends much of her spare time photographing the stars and planets.
But the night the fireball streaked towards Grimsby, she didn't have her camera trained on the sky. She was watching TV with her meteorologist husband in their home atop the escarpment.
"We saw a bright flash and thought, 'How can it be a thunderstorm. There shouldn't be any storms around.'"
A quick check online the following morning confirmed for Lecky Hepburn the bright light was a meteor.
"It would have been nice to see something other than just the bright flash," she said.
Researchers are calling for anyone who has found pieces of meteorite to contact them, as well as people in the area who witnessed the fireball.
Meteorites are typically dark, smooth on the surface, heavier than rocks of a similar size and able to attract magnets because of the metals they contain.
Under Canadian law, meteorites become the property of whoever owns the property where they are recovered.
Photos and video footage of the meteor can be found online.
The Standard
Thu, 15 Oct 2009 17:00 EDT
A fragment of meteorite the size of a golf ball smashed in the windshield of a Grimsby family's sport utility vehicle on Sept. 25, according to a media release from the University of Western Ontario.
Astronomers released a video Oct. 7 of a blinding meteor streaking across the skies of Southern Ontario three weeks ago, estimating pieces may have landed in Grimsby or West Lincoln.
Meteorite hunters have been scouring the area ever since.
A press conference to discuss the find is scheduled for Friday morning.
Gadi Schwartz and Matthew Kappus
KOB.com
Mon, 12 Oct 2009 17:20 EDT
A Santa Fe astronomer was able to catch the fiery streak on video. Thomas Ashcraft says the fireball didn't disintegrate when it hit the atmosphere. It may have landed somewhere near Taos.
"If we can get other camera angles, than we can put all the positions together and possibly hunt for an important--scientifically important--meteorite," he said.
The event was also captured by cameras at Sandia National Labs. Scientists estimate the meteor was about the size of a basketball all the way up to that of a small car.
Scientists at Sandia think it disintegrated over Chaco Canyon.
ScienceDaily
Thu, 15 Oct 2009 05:00 EDT
Three-dimensional reconstruction of the submerged Shiva crater (~500 km diameter) at the Mumbai Offshore Basin, western shelf of India from different cross-sectional and geophysical data.
"If we are right, this is the largest crater known on our planet," Chatterjee said. "A bolide of this size, perhaps 40 kilometers (25 miles) in diameter creates its own tectonics."
By contrast, the object that struck the Yucatan Peninsula, and is commonly thought to have killed the dinosaurs was between 8 and 10 kilometers (5 and 6.2 miles) wide.
It's hard to imagine such a cataclysm. But if the team is right, the Shiva impact vaporized Earth's crust at the point of collision, leaving nothing but ultra-hot mantle material to well up in its place. It is likely that the impact enhanced the nearby Deccan Traps volcanic eruptions that covered much of western India. What's more, the impact broke the Seychelles islands off of the Indian tectonic plate, and sent them drifting toward Africa.
The geological evidence is dramatic. Shiva's outer rim forms a rough, faulted ring some 500 kilometers in diameter, encircling the central peak, known as the Bombay High, which would be 3 miles tall from the ocean floor (about the height of Mount McKinley). Most of the crater lies submerged on India's continental shelf, but where it does come ashore it is marked by tall cliffs, active faults and hot springs. The impact appears to have sheared or destroyed much of the 30-mile-thick granite layer in the western coast of India.
The team hopes to go India later this year to examine rocks drill from the center of the putative crater for clues that would prove the strange basin was formed by a gigantic impact.
"Rocks from the bottom of the crater will tell us the telltale sign of the impact event from shattered and melted target rocks. And we want to see if there are breccias, shocked quartz, and an iridium anomaly," Chatterjee said. Asteroids are rich in iridium, and such anomalies are thought of as the fingerprint of an impact.
Space.com
Mon, 12 Oct 2009 17:10 EDT
Opportunity stumbled upon this new meteorite, dubbed "Shelter Island," less than three weeks after driving away from a larger meteorite that the rover examined for six weeks.
The rover began its approach to the meteorite with a 92-foot (28-meter) backwards drive on Oct. 1, the rover's 2,022nd day on Mars.
Opportunity and its twin rover Spirit - which is currently embedded in a soft spot of soil called Troy - have been on the Martian surface for more than five years.
Shelter Island is a pitted rock is about 18.5 inches (47 cm) long. The meteorite was first detected in images taken two Martian days earlier. (A Martian day is 24 hours and 40 minutes long.)
Two Martian days after its backward drive, Opportunity turned around to face the meteorite. In the days that followed, it made a final 3.3-foot (1-meter) move to put the rock within reach of the rover robotic arm . Mission managers are now planning to use the arm to contact the meteorite and make measurements.
Opportunity has driven about 2,300 feet (700 meters) since it finished studying the meteorite called "Block Island" on Sept. 11, 2009.
Block Island weighs at least half a ton, is composed of iron and nickel, and is likely too large to have plunged through the current thin atmosphere of Mars without being obliterated upon impact, scientists say.
Both meteorites have been found during Opportunity's trek to its next target, Endeavour Crater.
Opportunity also found a third meteorite, Heat Shield Rock, in 2004.
TheSpec.com
Fri, 16 Oct 2009 10:41 EDT
.
Comment: You can read a report of this sighting here
The Daily Mail
Fri, 16 Oct 2009 10:43 EDT
Experts believe the 4lb dark grey object had been orbiting Earth for at least a decade
The 75-year-old had been in his bedroom when he heard a smash and found the football-sized lump of extra terrestrial debris in the loft of his home in Hull.
The great-grandfather said: 'It was a hell of a shock. If it had landed in the street and hit anybody it would have killed them.'
As it was too hot to handle he brought it downstairs using oven gloves.
The 4lb dark grey object was removed by Humberside Police before being taken away by the Ministry of Defence for investigation.
Mr Welton and wife Mair, 62, then received a phone call from the RAF, who said the metal mass was most likely to be space junk. This could mean anything from part of a spacecraft to a piece of abandoned satellite.
RAF spokesman Squadron Leader Jeff Brock confirmed the finding, which was the first the RAF's Defence Flying Complaints Investigation Team had encountered.
Peter Welton, 76, was in his home is Hull when the space debris slammed into his loft
'This is the first bit of space debris that we have got our hands on - we have never until this occasion had anything relating to it at all.'
The DFCIT, based in Henlow, in Bedfordshire, investigates complaints related to military flying. Experts initially thought the object may have come from an aircraft.
However, its size and appearance was found to be 'entirely consistent' with space junk, and its heavy mass meant it was more likely to have been in a state of decaying orbit for a decade or more.
Russia (then the Soviet Union) put the first object into space just 51 years ago - Sputnik One. Since then we have created a swarm of perhaps tens of millions of items of space junk. The debris ranges in size from paint flecks to defunct satellites.
The oldest piece of space junk still circling is the Vanguard 1 communications satellite that was launched by the U.S in 1958, but stopped working in 1964.
Most hug close to the surface, 200-300 miles up in low-earth-orbit, where they are a hazard to telescopes and the astronauts on the International Space Station.
The 4lb piece of debris fell to Earth and landed in West Hull
There has only been one recorded incident of a person being hit by human-made space debris. In 1997, Lottie Williams from Oklahoma was hit in the shoulder by a 5.1" piece of blackened metal. It was later confirmed to be part of the a rocket fuel tank launched the year before. Luckily she was not injured.
Despite narrowly escaping being hit, Mrs Mair said she was excited to hear the experts' findings.
'I think it's wonderful,' she said.
Mail's online video report on the event
Mark McNeil
The Hamilton Spectator
Fri, 16 Oct 2009 11:36 EDT
University of Western Ontario researchers confirmed the rock was a meteorite. It will be unveiled today at a media conference.
The fireball was captured on video Sept. 25 by a network of cameras administered by Western that regularly watch the skies at night. One of the cameras is located at McMaster University.
For the past two weeks, a search team headed by Phil McCausland, a postdoctoral fellow at Western's Centre for Planetary Science and Exploration, has been scouring the Grimsby area after working out mathematical models that suggest the fireball crashed there.
McCausland believes there are other meteorites on the ground that have yet to be found because the meteor weighed as much as a tonne when it hit Earth's atmosphere.
He returned to Grimsby yesterday with a search team of a few people looking around the residential area where the meteorite was discovered by a Grimsby resident.
"It was a very unusual rock, so the finder just held onto it," McCausland said. "They began to think it was a meteorite after the media coverage happened."
He would not be specific about where the rock was located, only that it was "just barely" within the 12-square-kilometre area south of the town of Grimsby that searchers were focusing on.
Tests are being done to try to find out more about the 50-gram object.
The discovery, he said, has buoyed enthusiasm that other pieces will be found and it will turn out to be a major find for the astronomy community.
Meteorites are relatively common, but it is highly unusual to find one from a meteor videotaped coming through the atmosphere.
"You don't stop when you find one piece. You keep going," said McCausland. "Finding one is confirmation that something came down here and there are probably many others."
They are looking intensively in the area of the first find because "meteorites don't care where they land. They could hit a house, a roof. They can end up anywhere."
mmcneil@thespec.com
905-526-4687
Trak.in News/Asian News International
Mon, 19 Oct 2009 00:00 EDT
According to a report in National Geographic News, amateur photographer Robert Mikaelyan captured the phenomenon on camera.
Mikaelyan managed to capture several shots of the fireball as it swung low over the northern city of Groningen, Netherlands, and began to break apart into smaller chunks.
"I suddenly saw a light in the sky coming fast and quickly got the pictures taken," Mikaelyan said.
A few seconds after the fireball had been sighted, witnesses heard a sonic boom followed by low rumbles that rattled windows-signatures of a high-altitude explosion.
The object was most likely a rogue space rock that disintegrated shortly after hitting Earth's atmosphere, according to experts, who speculate that pieces of the meteor may have landed in the North Sea.
"Indeed it was a huge event," said Theo Jurriens, of the Kapteyn Astronomical Institute at the University of Groningen.
Earth is constantly being bombarded by smaller debris from comets, asteroids, and even other rocky planets in the solar system.
But a fireball of this size and brightness is likely seen anywhere in the world only every 20 to 25 years, according to Jurriens.
Comment: Every 20-25 years? Somebody's not been paying attention. These are from the past 3 weeks:
October 9th: Caught on camera: Meteorite streaks across New Mexico sky
October 5th: Video: Fireball lights up sky over Iceland
Septmber 28th: Cosmic shock and awe: Fireball explodes over Argentina
September 25th: Spectacular Fireball filmed over Canada
Cheng Chi-feng and Sofia Wu
Central News Agency
Mon, 19 Oct 2009 19:05 EDT
Tsai Yuan-sheng discovered the asteroid along with an assistant at the Lulin Observatory on Yushan, also known as Jade Mountain, March 20 and tentatively named it "Kaohsiung" after his hometown.
In August, the International Astronomical Union's Committee on Small Body Nomenclature (IAU's CSBN) -- an international organization responsible for the naming of asteroids and comets -- formally approved the designation and gave Tsai's discovery a permanent number "215080." It was the first asteroid discovered by an amateur Taiwanese astronomy buff to have won international recognition.
The asteroid, located between Mars and Jupiter, is similar in size to Kaohsiung International Airport. At perihelion, the closest point to the sun in its orbit, the asteroid is 350 million kilometers from the sun and at aphelion, its most distant point from the sun in its orbit, it is about 450 million kilometers from the sun.
It takes about four years for the newly identified asteroid to complete its orbit around the sun.
Tsai and Lin Chi-sheng, an astronomical observation assistant at Lulin Observatory, spotted the asteroid using highly advanced digital equipment.
Tsai recalled that he first detected that the body could both rotate around its own axis and circle the Sun and that its position coordinates varied each day.
"I then took photos of the object consecutively for analytical comparison and finally came to the conclusion that it was an asteroid that had never been documented before," Tsai recalled.
According to Tsai, most larger asteroids have been discovered and only small asteroids that cannot be detected with the naked eye are still left to be spotted with highly sophisticated instruments.
Tsai, 40, began to develop his interest in observing the stars while studying at a military preparatory school as a teenager. At the time, he was required to stand guard at night, and the long hours with nothing to do led him to fall in love with stargazing.
He later dropped out of the naval academy to pursue his hobby more freely. He now often takes his wife and children high into the mountains to observe the stars at night.
Tsai has documented 13 asteroids, but "Kaohsiung" is the only one to have been recognized by the IAU's CSBN.
"I was so jubilant to obtain international recognition of my latest discovery and thus decided to name it 'Kaohsiung' to honor my beloved homeland," Tsai said.
"I also want to share my happiness in discovering the new body with all fellow Kaohsiung residents, " Tsai said at the asteroid model presentation ceremony at the city's Gangho Elementary School.
For her part, Mayor Chen said the discovery of the asteroid and its designation as "Kaohsiung" are not only the "pride of Kaohsiung" but also the "pride of Taiwan." Noting that Tsai's achievement has inspired a "star chasing" fad in the city, Chen said the city government will step up efforts to promote astronomical education and cultivate more talent in the field.
Chen said she has directed the city's Bureau of Education to allocate NT$1 million (US$31,056) annually to help finance the operations of the Gangho Elementary School's astronomy observatory.
She also proposed that an astronomy-themed science park be established after Kaohsiung City and Kaohsiung County merge next year.
Tsai Ching-hua, director of the municipal education bureau, said the discovery of the asteroid has set a good model for the city's astronomy education and pledged to study the feasibility of setting up an astronomy theme park in the new Kaohsiung municipality.
Space Weather
Tue, 20 Oct 2009 15:16 EDT
"I woke up early in the morning to observe the shower through my bedroom window," says Teng. "This one was quite bright considering the light pollution in Shanghai."
Forecasters expect the shower to peak on Wednesday, Oct. 21st, with dozens of meteors per hour. The best time to look is during the dark hours before sunrise. For best results, get away from city lights, but as Teng discovered, country darkness is not absolutely necessary.
Associated Press
Mon, 26 Oct 2009 10:07 EDT
Scientists were investigating Monday whether a large crater found in a meadow in northern Latvia had been created by meteorite. One expert said it was likely a hoax.
Experts in the Baltic country rushed to the site after reports that a metorite-like object had crashed late Sunday in the Mazsalaca region near the Estonian border.
Uldis Nulle, a scientist at the Latvian Environment, Geology and Meteorology Center, said his first impression after observing the site late Sunday was that the 27-foot (nine-meter) wide and nine foot (three-meter) deep crater had been caused by a meteorite. He said there was smoke coming out of the hole when he arrived.
When asked about Ozols' theory, Nulle refused to comment, saying he needed more time to make tests at the site.
Inga Vetere of the Fire and Rescue Service said they received a call about the alleged meteorite on Sunday evening from an eyewitness. She said a military unit was dispatched to the site and found that radiation levels were normal. There were no injures.
Experts outside Latvia said it would be unusual for such a large meteorite to hit the Earth. The planet is constantly bombarded with objects from outer space, but most burn up in the atmosphere and never reach the surface.
In 2007, a meteorite crashed near Lake Titicaca in Peru, causing a crater about 40 feet (12 meters) wide and 15 feet (five meters) deep.
Henning Haack, a lecturer at Copenhagen University's Geological Museum said more information was needed to confirm that the crater was indeed caused by a meteorite.
"With all these kind of reports we get there always is a pretty large margin of error," he said.
Daily Mail
Mon, 26 Oct 2009 10:14 EDT
A fiery object struck farmland creating a large crater near a small town in northern Latvia.
No-one was injured in the incident and geologists are now studying the object, which may be a meteorite.
Locals claimed the object fell near a farmhouse on the outskirts of Mazsalaca town in the district of Valmiera last night.
It created a crater which measured 50 feet across and 16 feet deep.
A witness who claimed to have seen the incident described the 'meteorite' as making a noise similar to the one of an aircraft flying at a low altitude.
ldis Nulle, a scientist at the Latvian Environment, Geology and Meteorology Center, said there was smoke coming out of the crater when he arrived at the crash site late Sunday in the Mazsalaca region near the Estonian border.
'My first impression is that, yes, it was a meteorite,' he said. 'All the evidence suggests this when compared to pictures of real meteorite craters.'
Experts outside Latvia said it was unusual for such a large meteorite to hit the Earth. The planet is constantly bombarded with objects from outer space, but most burn up in the atmosphere and never reach the surface.
In 2007, a meteorite crashed near Lake Titicaca in Peru, causing a crater about 40 feet (12 metres) wide and 15 feet (5 metres) deep.
Asta Pellinen-Wannberg, a meteorite expert at the Swedish Institute of Space Research, said she didn't know the details of the Latvian incident, but that a rock would have to be at least three feet (one metre) in diameter to create a hole that size.
Henning Haack, a lecturer at Copenhagen University's Geological Museum said more information was needed to confirm that the crater was indeed caused by a meteorite.
In Latvia, Nulle said a group of experts would examine the crater today and bring rock samples back to the capital, Riga, for testing.
Nulle rushed to the site after people in the area reported seeing a fiery object falling from the sky.
Inga Vetere of the Fire and Rescue Service said a military unit has tested the site and found that radiation levels are normal. There were no injures.
She said police have cordoned off the area to prevent souvenir hunters from taking away the soil.
'We are not finally sure that this is a meteorite,' she told Itar-Tass news agency. 'Eyewitnesses said something fell from the sky and fire started.'
Russian blogs posted YouTube video that claimed to show the remains of the meteor burning brightly shortly after the crash, but the validity of the video has not yet been confirmed.
RIA Novosti
Mon, 26 Oct 2009 10:59 EDT
According to media reports, the meteorite fell near a residential house on the outskirts of Mazsalaca town in the Valmiera district of Latvia, leaving a crater of some 20 meters (66 feet) in diameter and 10 meters (33 feet) deep.
A spokesperson for the Latvian State Fire and Rescue Service said that rescuers and soldiers immediately cordoned off the territory, however, it is still not clear whether it was an asteroid or a space satellite.
"The territory has been immediately cordoned off as we still do not know what fell down from the sky. According to preliminary information, it was a meteorite. However, it is possible that it was a [space] satellite or its fragment. A radioactive contamination is also possible," she said.
A witness, who saw the object falling from the sky and leaving a burning trace behind, said it was making a noise similar to the one of an aircraft flying at a low altitude.
On March 2 this year, a 35-meter asteroid came within 72,000 kilometers of Earth. The size of the space rock was comparable to the asteroid that caused the Tunguska disaster, but there was no danger of a collision.
On June 30, 1908, an explosion equivalent to between 5 and 30 megatons of TNT occurred near the Podkamennaya Tunguska River in a remote region of Russia's Siberia.
The Tunguska blast flattened 80 million trees, destroying an area of around 2,150 sq km (830 sq miles).
It is assumed that a huge meteorite had hit the area, although research expeditions failed to find an obvious crater.
Comment: Update: This incident appears to have been staged
'Meteorite' that landed in Latvia is a hoax, experts say
Tony Halpin
Times Online
Mon, 26 Oct 2009 18:09 EDT
Dramatic video of a fireball at the bottom of an impact crater on farmland outside the town of Mazsalaca was shown all over the world, taken by a group of film students who said that they had heard the meteor strike.
But experts who examined the scene were less star-struck. Dr Ilgonis Vilks, chairman of the scientific council at the University of Latvia's Institute of Astronomy, said: "It's a fake. It's very disappointing, I was full of hope coming here, but I am certain it is not a meteorite."
Setting aside the astronomical odds of a group of film students happening to be at the ready when a meteorite hits the Earth, Dr Vilks said that several other tell-tale signs had given the game away.
There was green grass inside the crater despite the intense heat supposedly generated by the meteorite. The impact crater, initially reported as 10 metres deep, was actually only 3 metres including a lip of soil a metre high around the hole.
Dr Vilks said that there was neither ejected material from the hole nor any fragments of meteorite on the surrounding land. Finally, there was the flaming "meteorite" itself.
"It's a ball of clay that was burning. We took some samples from it and geologists from the university will examine it," Dr Vilks said. "There was a small blast heard by local people but this was not strong enough to create the crater and there's only a small area in the hole that is burnt."
Dainis Ozols, a nature conservationist who also examined the scene, said that he believed somebody had dug the hole and burnt a pyrotechnic compound at the bottom to make it appear like a meteorite crater.
The alert was first raised on Sunday evening by Ancis Steinbergs, who said that he had been out filming for a university project with his girlfriend and a fellow undergraduate. He was refusing to answer his telephone tonight to answer questions about the experts' assessments.
He had earlier told The Times that the trio had heard a loud roaring sound "like an airplane falling from the sky" seconds before the alleged meteorite hit the field behind some trees.
Mr Steinbergs said: "We saw something burning in the sky like a ball and it was moving very fast and then there was a loud noise. We went to find it and there was this big hole with fire burning in it.
"It was so hot that the camera was misting up. We thought it was really dangerous because there might be an explosion."
Video taken by the group showed them approaching the lip of the crater and filming the glowing hot "meteor" at the bottom as they talked excitedly among themselves. The clip bears similarities in style to the Blair Witch Project, a 1999 film based on supposedly "amateur" footage shot by three missing film students.
Mr Steinbergs said that he called Latvia's Fire and Rescue Service. Inga Vetere, a spokeswoman, said that fire crews had attended the site and cordoned it off. Tests had recorded normal levels of radiation and nobody had been hurt.
Local news agencies reported that the landowner, Larisa Gerasimova, had been quick to capitalise on interest surrounding the crater and had begun to charge curious visitors $2 to view the site.
Earth is bombarded by thousands of small celestial objects every year but most burn up in the atmosphere before they reach the surface. The last recorded meteorite strike on land was in 2007 near Lake Titicaca in Peru, when it left a crater 12 metres wide (40ft) and five metres deep (15ft).
David Shiga
New Scientist
Tue, 27 Oct 2009 00:04 EDT
On 8 October an asteroid detonated high in the atmosphere above South Sulawesi, Indonesia, releasing about as much energy as 50,000 tons of TNT, according to a NASA estimate released on Friday. That's about three times more powerful than the atomic bomb that levelled Hiroshima, making it one of the largest asteroid explosions ever observed.
However, the blast caused no damage on the ground because of the high altitude, 15 to 20 kilometres above Earth's surface, says astronomer Peter Brown of the University of Western Ontario (UWO), Canada.
Brown and Elizabeth Silber, also of UWO, estimated the explosion energy from infrasound waves that rippled halfway around the world and were recorded by an international network of instruments that listens for nuclear explosions.
The explosion was heard by witnesses in Indonesia. Video images of the sky following the event show a dust trail characteristic of an exploding asteroid.
Sudden impact
The amount of energy released suggests the object was about 10 metres across, the researchers say. Such objects are thought to hit Earth about once per decade.
No telescope spotted the asteroid ahead of its impact. That is not surprising, given that only a tiny fraction of asteroids smaller than 100 metres across have been catalogued, says Tim Spahr, director of the Minor Planet Center in Cambridge, Massachusetts. Yet objects as small as 20 or 30 metres across may be capable of doing damage on the ground, he says.
"If you want to find the smallest objects you have to build more, larger telescopes," says Spahr. "A survey that finds all of the 20-metre objects will cost probably multiple billions of dollars."
The White House must develop a policy to address the asteroid hazard by October 2010 under a deadline imposed by Congress. It is likely to be influenced by a report from the National Research Council on the asteroid problem, which is expected by year's end.