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Officials are now saying the bright fireball seen over Virginia in the US on Sunday was probably a natural meteor event and not part of a Russian rocket, a reversal from yesterday’s initial analysis. Space.com reported that an official from the U.S. Naval Observatory believed the loud boom and flash of light seen in the skies over Norfolk and Virginia Beach was likely the second stage of the Soyuz rocket that launched Expedition 19 to the International Space Station last Thursday. However, U.S. Strategic Command has since reported that the rocket re-entered Earth’s atmosphere near Taiwan, on the other side of the world, several hours after the reports of the fireball. So both its timing and entry location rule out the rocket as the explanation for the fireball. But the investigation is continuing to determine exactly what the object was.
The Joint Space Operations Center at Vandenberg Air Force Base in California also confirmed “the ‘bright light’ that was reported on the East Coast on Sunday, 29 March at 9:45 p.m. EST was not a result of any trackable manmade object on reentry,” according to Patricia Phillips at the Space News Examiner.
Space rocks the size of small cars plunge into Earth’s atmosphere several times a year, typically burning up before reaching the ground. “The atmosphere is very good at protecting us from falling rocks,” said Bill Cooke of NASA’s Marshall Space Flight Center. Ones that do reach the ground go unreported since they fall over uninhabited areas or in the ocean.
A few space rocks do occasionally make it to the surface though. In recent years, pieces of a bolide were found after a meteor event in western Canada, and fragments of a meteor that originated from an asteroid that blew up over the skies of Africa last October were also recovered in the Sudanese desert.
Map of the Nubian Desert of northern Sudan with the groundprojected approach path of the asteroid 2008 TC3 and the location of the recovered meteorites. Credit: P. Jenniskens, et. al
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Remember in October 2008 when Asteroid 2008 TC3 hit the scene – literally? This was the first asteroid that was predicted –and predicted correctly — to impact the Earth. Luckily, it wasn’t big enough to cause any problems, and its path was over a remote area in Africa. It streaked into the skies over northern Sudan in the early morning of October 7, 2008, and then exploded at a high 37 km above the Nubian Desert, before the atmosphere could slow it down. It was believed that the asteroid likely had completely disintegrated into dust. But meteor astronomer Peter Jenniskens thought there might be a chance to recover some of the remains of this truck-sized asteroid. And he was right.
Never before have meteorites been collected from such a high altitude explosion. Additionally, as it turns out, the assembled remnants are unlike anything in our meteorite collections, and may be an important clue in unraveling the early history of the solar system.
A meteor astronomer with the SETI Institute’s Carl Sagan Center, Jenniskens established a collaboration with Mauwia Shaddad of the Physics Department and Faculty of Sciences of the University of Khartoum. The two traveled to the Sudan. Various meteorites from 2008 TC3. Credit: P. Jenniskens, et. al. Click image for full description
Fifteen fresh-looking meteorites with a total mass of 563 g were recovered by 45 students and staff of the University of Khartoum during a field campaign on December 5-8, 2008. A second search on December 25-30 with 72 participants raised the total to 47 meteorites and 3.95 kg. Masses range from 1.5 g to 283 g, spread for 29km along the approach path in a manner expected for debris from 2008 TC3
“This was an extraordinary opportunity, for the first time, to bring into the lab actual pieces of an asteroid we had seen in space,” said Jenniskens, the lead author on a cover story article in the journal Nature that describes the recovery and analysis of 2008 TC3.
Click here for several images from NASA about the asteroid hit and the recovery of the meteorites.
Picked up by Arizona’s Catalina Sky Survey telescope on 6 October, 2008, Asteroid 2008 TC3 abruptly ended its 4.5 billion year solar-system odyssey only 20 hours after discovery, when it broke apart in the African skies. The incoming asteroid was tracked by several groups of astronomers, including a team at the La Palma Observatory in the Canary Islands that was able to measure sunlight reflected by the object.
Studying the reflected sunlight gives clues to the minerals at the surface of these objects. Astronomers group the asteroids into classes, and attempt to assign meteorite types to each class. But their ability to do this is often frustrated by layers of dust on the asteroid surfaces that scatter light in unpredictable ways.
Jenniskens teamed with planetary spectroscopist Janice Bishop of the SETI Institute to measure the reflection properties of the meteorite, and discovered that both the asteroid and its meteoritic remains reflected light in much the same way — similar to the known behavior of so-called F-class asteroids.
“F-class asteroids were long a mystery,” Bishop notes. “Astronomers have measured their unique spectral properties with telescopes, but prior to 2008 TC3 there was no corresponding meteorite class, no rocks we could look at in the lab.” Petrography of Almahata Sitta. Credit: Jenniskens, et. al. Click for full description
The good correspondence between telescopic and laboratory measurements for 2008 TC3 suggests that small asteroids don’t have the troublesome dust layers, and may therefore be more suitable objects for establishing the link between asteroid type and meteorite properties. That would allow us to characterize asteroids from afar.
Rocco Mancinelli, a microbial ecologist at the SETI Institute’s Carl Sagan Center, and a member of the research team, says that “2008 TC3 could serve as a Rosetta Stone, providing us with essential clues to the processes that built Earth and its planetary siblings.”
In the dim past, as the solar system was taking shape, small dust particles stuck together to form larger bodies, a process of accumulation that eventually produced the asteroids. Some of these bodies collided so violently that they melted throughout.
2008 TC3 turns out to be an intermediate case, having been only partially melted. The resulting material produced what’s called a polymict ureilite meteorite. The meteorites from 2008 TC3, now called “Almahata Sitta,” are anomalous ureilites: very dark, porous, and rich in highly cooked carbon. This new material may serve to rule out many theories about the origin of ureilites.
In addition, knowing the nature of F-class asteroids could conceivably pay off in protecting Earth from dangerous impactors. The explosion of 2008 TC3 at high altitude indicates that it was of highly fragile construction. Its estimated mass was about 80 tons, of which only some 5 kg has been recovered on the ground. If at some future time we discover an F-class asteroid that’s, say, several kilometers in size — one that could wipe out entire species — then we’ll know its composition and can devise appropriate strategies to ward it off.
As efforts such as the Pan-STARRS project uncover smaller near-Earth asteroids, Jenniskens expects more incidents similar to 2008 TC3. “I look forward to getting a call from the next person to spot one of these,” he says. “I would love to travel to the impact area in time to see the fireball in the sky, study its breakup and recover the pieces. If it’s big enough, we may well find other fragile materials not yet in our meteorite collections.”
Bolide in Italy. Credit: Ferruccio Zanotti of Ferrara, Italy, via Spaceweather.com
A fireball seen over Texas during the daytime on Sunday, Feb. 15th, triggered widespread reports that debris from the recent satellite collision was falling to Earth. The FAA even issued a statement that airplanes should watch for falling debris. However, those reports and statements were premature. Researchers have studied video of the event and concluded that the object was more likely a natural meteoroid about one meter wide traveling more than 20 km/s–much faster than orbital debris. Meteoroids hit Earth every day, and the Texas fireball was apparently one of them. Additionally, a spokeswoman for U.S. Strategic Command said the fireball spotted in the Texas skies Sunday was unrelated to the satellite collision. And as always, the Bad Astronomer was on top of it from the beginning, so check out his first post here (which includes several updates as the news broke), and a follow-up here. There were other fireballs, too….
There was one bolide event in central Kentucky on Friday, February 13. People heard loud booms, felt their houses shake, and saw a fireball streaking through the sky. This occurred just hours after another fireball at least 10 times brighter than a full Moon lit up the sky over Italy. Although it is tempting to attribute these events to debris from the Feb. 10th collision of the Iridium 33 and Kosmos 2251 satellites, the Kentucky and Italy fireballs also seem to be meteoroids, not manmade objects. Italian scientists are studying the ground track of their fireball, which was recorded by multiple cameras, and they will soon begin to hunt for meteorites.
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Air Force Major Regina Winchester said that Joint Space Operations Center at California’s Vandenberg Air Force Base has been monitoring the debris from the collision, and that could not have caused the dramatic sight. She also said the fireball was not related to the estimated 18,000 man-made objects that the center also monitors.
“There was no predicted re-entry,” Winchester said about the objects in Earth’s orbit.
She said it was likely a natural phenomenon such as a meteorite.
The Bejar bolide photographed from Torrelodones, Madrid, Spain. The incoming fireball is the streak to the right of the floodlit house. The bright light at the top is the overexposed Moon. Credit: J. Perez Vallejo/SPMN.
Astronomers have analyzed the cometary fireball that blazed across the sky over Europe last year and concluded it was a dense object, about a meter (3.2 feet) across and with a mass of nearly two tons — large enough that some fragments probably survived intact and fell to the ground as meteorites.
Last July, people in Spain, Portugal and France watched the brilliant fireball produced by a boulder crashing down through the Earth’s atmosphere. In a paper to be published in the journal Monthly Notices of the Royal Astronomical Society, astronomer Josep M. Trigo-Rodríguez, of the Institute of Space Sciences in Spain, and his co-authors present dramatic images of the event. The scientists also explain how the boulder may originate from a comet which broke up nearly 90 years ago, and suggest that chunks of the boulder (and hence pieces of the comet) are waiting to be found on the ground.
“If we are right, then by monitoring future encounters with other clouds of cometary debris, we have the chance to recover meteorites from specific comets and analyse them in a lab,” Dr Trigo-Rodríguez said. “Handling pieces of comet would fulfil the long-held ambitions of scientists — it would effectively give us a look inside some of the most enigmatic objects in the Solar System.”
Fireballs (or bolides) are the name given by astronomers to the brightest meteors, popularly referred to as shooting stars. On the afternoon of July 11, a brilliant fireball was recorded over southwestern Europe. At maximum intensity, the object was more than 150 times brighter than the full Moon. It was first picked up at a height of 61 miles (98.3 km) and disappeared from view 13 miles (21.5 km) above the surface of the Earth, tracked by three stations of the Spanish Fireball Network above Bejar, near Salamanca in Spain. At the same time, a professional photographer took a picture of the fireball from the north of Madrid.
A close-up image of the Bejar bolide, photographed from Torrelodones, Madrid, Spain. Credit: J. Perez Vallejo/SPMN.
From these images, the astronomers have demonstrated that before its fiery demise, the boulder traveled on an unusual orbit around the Sun, which took it from beyond the orbit of Jupiter to the vicinity of Earth. This orbit is very similar to that of a cloud of meteoroids known as the Omicron Draconids, which on rare occasions produces a minor meteor shower and probably originates from the breakup of Comet C/1919 Q2 Metcalf in 1920. The authors suggest the boulder was once embedded in the nucleus of that comet.
Comet C/1919 Q2 Metcalf was discovered by Joel Metcalf from Vermont in August 1919, and was visible until February 3, 1920. The orbit was not well determined and no subsequent appearances are known. The Omicron Draconids meteor stream was discovered to be following a similar orbit to this comet by Allan F. Cook in 1973. The stream characteristically produces bright fireballs and rare meteor outbursts.
In the mid-1980s, the astronomers Tamas I. Gombosi and Harry L.F. Houpis first suggested that the nuclei of comets consist of relatively large boulders cemented together by a ‘glue’ of smaller particles and ice. If the rocky and icy nucleus of a comet disintegrates, then these large boulders are set loose into space. If the Bejar bolide was formed in this way, it confirms the glue model for at least some comets.
Bolide impact on Mars. Credit: NASA/JPL/University of Arizona
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Incoming! Hundreds of small objects, mostly asteroid fragments, impact Mars every year. Sometimes, like on Earth, objects break up in the Martian atmosphere. But Mars’ atmosphere is much thinner than Earth’s, meaning more stuff hits the ground on the Red Planet. If a bolide breaks apart and but doesn’t disintegrate, the result can be a cluster of craters. The image here is an example of that, with this group of recently made small impact craters. Although small Martian crater clusters are common, this example is unusual because there is a dark line between the two largest craters. The HiRISE scientists hypothesize that atmospheric breakup created two nearly equal-size objects that impacted close together in space and time so the air blasts interacted with each other to disturb the dust along this line. Wow!
The impact occurred sometime between May 2003 and September 2007. A dark spot is not present in the previous image of this location with sufficient resolution to have detected it, acquired by the visible THEMIS camera on Mars Odyssey in May 2003. Check out the THEMIS site, where you can find images by clicking on a map of Mars. This impact was first discovered as a dark spot in an image taken by the Mars Reconnaissance Orbiter’s CTX (Context) Imager acquired in March 2008, but later found to be partly visible at the very edge of a CTX image acquired in September 2007. The CTX team has been discovering many new impact events on Mars, and then they request HiRISE follow-up imaging to confirm an impact origin and to identify and measure the craters.
Here’s the full HiRISE image: Full HiRISE Image. Credit: NASA/JPL/University of Arizona
This area is just a few hundred meters wide.The dark markings are created by removing or disturbing the surficial dust cover, and so far new impact sites have been discovered only in dust-covered regions of Mars.
A comparable number of small objects impact Earth every year as on Mars, but most explode in the upper reaches of our atmosphere and provide us with “shooting stars.”
Cloudbait Observatory all-sky camera image of the bright explosion on Dec. 6th at 1:28 am MST. No larger image available (Chris Peterson)
[/caption]Last night, the Colorado skies played host to a dazzling fireball event. The meteor blasted through the atmosphere, detonated and outshone the Moon by 100 times. It is therefore expected that there were many eyewitnesses, and the Cloudbait Observatory (5 km north of the town of Guffey, CO) is appealing to people to report their accounts of the fireball. Fortunately, the observatory managed to capture an all-sky camera video of the early morning explosion.
The Colorado fireball comes shortly after a similar event over Canada on November 20th, where over two dozen meteorite fragments have been recovered from agricultural land. We wait in anticipation to see if this huge Colorado fireball produced any similar fragments, but eyewitness accounts will be critical to aid such a search…
In the early hours of this morning, a large explosion dominated the Colorado skies. It was yet another large meteor ploughing through the atmosphere, ending its journey in an energetic detonation. Fortunately this event didn’t suffer from the same affliction the Sudan 2008 TC3 meteoroid impact back on October 7th (i.e. lack of observers), and put on a show much like last month’s Saskatchewan fireball (and the October Ontario meteor). All in all, North America is having a great meteor season with no lack of observers, eye witnesses and all-sky cameras.
Discussing last night’s Colorado fireball, astronomer Chris Peterson describes the event: “In seven years of operation, this is the brightest fireball I’ve ever recorded. I estimate the terminal explosion at magnitude -18, more than 100 times brighter than a full Moon.”
Video of the Colorado fireball (Chris Peterson)Peterson was using video recorded by Cloudbait Observatory’s all-sky camera, dedicated to meteor spotting, when the surprise magnitude -18 burst lit up the skies.
The 13 kg meteorite is roughly the size of a human head. Bruce McCurdy, Edmonton Space & Science Foundation / Royal Astronomical Society of Canada)
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Several more fragments have been found from the 10-ton asteroid that exploded over western Canada on November 20, including a head-sized piece weighing 13-kilograms (28 lbs). Imagine that landing on your house or car (or head!). University of Calgary professor Alan Hildebrand, who is leading the search estimates there could be 2,000 fragments per hectare (about 2.5 acres) in the area near where fragments were initially found. The asteroid is becoming known as the Buzzard Coulee fireball, named after the picturesque, but luckily uninhabited valley where the first pieces were located. Check out the website of Bruce McCurdy of Edmonton Space & Science Foundation and the Royal Astronomical Society of Canada, who has joined in the search for more meteorite images.
More than two dozen pieces of the asteroid have been found by researchers or members of the public. The search is focused on a 24-square-kilometer section of agricultural land along the Battle River where the scientists calculated the debris would be located. Hildebrand was appreciative all the eyewitness reports and help from the public in obtaining as much information as possible about the fireball that lit up the sky. “I was gratified that my first prediction was close,” he said of his estimate of where the fragments could be found. “We couldn’t have done this so quickly without the eyewitnesses and security camera records, and we still need the security camera records to determine the pre-fall orbit of this asteroid.”
Searchers from the University of Calgary have been joined by other members of the Canadian Space Agency-funded Small Bodies Discipline Working Group, as well as members of the public who wanted to join the search and find a chunk of history. A father and son team found the big 13 kg piece, which was given to the rancher that owned the land on which it was found.
University of Calgary graduate student Ellen Milley poses with a fragment of a meteorite in a small pond. AP Photo/The Canadian Press, Geoff Howe
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On Nov. 27, planetary scientist Dr. Alan Hildebrand from the University of Calgary and graduate student Ellen Milley brought reporters to a site where they have found numerous meteorite fragments from the bolide that streaked across the sky in Western Canada on Nov. 20. The area where the meteroite fragments were found is called Buzzard Coulee, about 40 kilometers from the town of Lloydminster, on the Alberta-Saskatchewan border. There, around a frozen pond, numerous small rocks and pebbles could be seen that the scientists said were from the meteorite. No large chunks were spotted, however, reporters said.
Fragments of a meteorite were found in a small pond at Buzzard Coulee, Sask. on Friday. (Geoff Howe/CP)
The fireball that streaked across western Canadian skies was witnessed by thousands, and Hildebrand believes it was a 10-ton fragment from an asteroid. Videos from surveillance and police cameras showed the meteor exploding before it hit the ground. Reporters were told those observations, combined with the physical evidence, give scientists a treasure trove of data that could give them a better understanding of the solar system. The reports don’t offer any indications of the type of meteorite the fragments are, but from the images they appear to possibly be iron. We’ll add more images and information as they become available.
Fragments of the big meteorite that lit up the Canadian skies across the provinces of Alberta and Saskatchewan last week have been found, according to a report in CBC online. University of Calgary scientists said they located several meteorite fragments late Thursday afternoon, and they were planning to take reporters to the site Friday. Planetary scientist Dr. Alan Hildebrand and graduate student Ellen Milley believe thousands of meteorite bits from the 10-ton bolide are strewn over a 20-square-kilometre area. The video above of the fireball was taken by a video camera in a police car in Edmonton, Alberta. Continue reading “Fragments of Canadian Fireball Found”
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The search is on for fragments of a 10-ton rock that lit the sky over western Canada last Thursday evening. Scientists estimate that at the time it hit Earth’s atmosphere, the asteroid fragment weighed approximately 10 tons and was probably about the size of a desk. It exploded with the force of 300 tons of dynamite, and hundreds of fragments of the meteorite weighing more than 50 grams (1.76 ounces) are likely strewn over a wide area. The speed of entry was relatively slow, about 14 kilometers (8.7 miles) per second, well below the average 20 kilometers (12.4 miles) per second of most meteorites, said University of Calgary researcher Alan Hildebrand. Amateur astronomers, meteorite hunters and rock hounds have been combing the prairies in western Canada for a 10-ton meteorite that lit the sky and exploded with the force of 300 tons of dynamite, according to experts from the Canadian Space Agency.
The fireball first appeared approximately 80 kilometers above and just east of the border city of Lloydminster, Alberta/Saskatchewan, and traveled SSE towards the Battle River valley fragmenting spectacularly in a series of explosions. Researchers were able to estimate it’s size and energy from infrasound recordings, said Dr. Peter Brown, Canada Research Chair in Meteor Physics at the University of Western Ontario. Infrasound is very low frequency sound produced by explosions that can travel thousands of kilometers.
“At least half a dozen infrasound stations ranging from Greenland to Utah, including Canada’s Lac Du Bonnett, Manitoba and Elgin Field, Ontario stations, recorded energy from the fireball’s explosions. The indicated energy is approximately one third of a kiloton of TNT,” Brown said.
Dr. Brown also says that a fireball this size only occurs over Canada once every five years on average. About ten fireballs of this size occur somewhere over the Earth each year.
The fireball penetrated the atmosphere at a steep angle of approximately 60 degrees from the horizontal and lasted about five seconds from 17:26:40 to 17:26:45 MST with the largest explosion at 17:26:44. The fireball was recorded on all-sky and security cameras scattered across Saskatchewan and Alberta in addition to being witnessed by tens of thousands of people who saw it streak across the sky, and may be one of the best documented meteorite falls.
But the researchers are looking for any additional information they can find.
“We are now trying to get all the transient information about the fireball before it is lost. Many motels and gas stations only keep their security recordings for one week or less, so we urge everyone to check their systems to see if they recorded the fireball or the moving shadows that it cast,” Hildebrand said. “Three gas stations and motels in Lloydminster, Lashburn and Maidstone are known to have records, but dozens of other businesses in the area probably have the fireball or its shadows recorded.”
If fireball images are found, he suggests immediately saving a copy and contacting him. “With the security camera footage we can compute the fireball’s trajectory in the sky to calculate the prefall orbit. Meteorites have only ever been recovered from known orbits nine times previously and we want to make that ten. ”
