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. ”
Foton M3 after landing in Kazakhstan after the experiment. Samples, including Orkney sample, are screwed onto
[/caption]In an effort to understand how organic chemicals might survive after a period in the vacuum of space and then violent re-entry through the atmosphere, scientists have uncovered some interesting results. Last year, the ESA/Russian Foton-M3 mission was launched to test the effects of microgravity on various biological samples. However, a sample of Orkney rock had a harder journey than most. Attached to the outside of the craft, this sample underwent extreme heating during the descent toward the plains of Kazakhstan. Although most of the sample was vaporized, scientists have unveiled results that the sample still contains very obvious signs that it once harboured life. These exciting results set new limits on how organic chemicals may survive unaltered for long periods in space before plunging through a planetary atmosphere, plus it raises some interesting questions into how future searches for extraterrestrial life may be performed…
The principal mission objective for many planetary missions is the search for extraterrestrial life. Although many of our robotic explorers cannot detect life directly, they are able to carry out a host of mini lab experiments on samples taken from the planets surface. NASA’s Phoenix Mars Mission for example has been tirelessly slaving over its hot oven (a.k.a. the Thermal and Evolved-Gas Analyzer, or TEGA for short), dropping samples of Mars soil into its single-use kilns for the last few months. This effort is to vent any prebiotic chemicals into a gas form so instrumentation can then “sniff” the vapour. Should organic chemicals be found, there will be an improved chance that life may have evolved on the Red Planet’s surface.
But say if there is an easier (and cheaper) way to look for ET? Rather than sending hundreds of millions of dollars-worth of hardware to Mars to look for organic chemicals, why can’t we analyse all the rocky samples littered across the globe that originated from space? After all, we now know that some meteorites originate from Mars itself, surely we can perform a far more detailed analysis on these samples instead of depending on a robot millions of miles away?
The big stumbling block comes if we consider the extreme temperatures meteorites are put under during re-entry into the terrestrial atmosphere. Generally one would expect any evidence for past life (whether that be organic chemicals or fossilized remains) to be blow-torched out of existence by reentry temperatures up to 3,000°F (1,650°C). So, researchers from the University of Aberdeen, Scotland, decided to test a chunk of rock from a Scottish island by subjecting it to several days in space and then seeing if any evidence of life in the rock sample remained intact after the descent.
the Kazakhstan landing site of Foton-M3 in September 2007 (R. Demets/F. Brandstatter)
“The specially prepared piece of Orkney rock took part in the unmanned Foton M3 mission which aimed to examine the rock’s behaviour when it was exposed to the extreme temperatures involved in it’s re-entry through the Earth’s atmosphere,” Professor John Parnell, lead scientist in the study, said.
The reason why Orkney rock was used is because of the material’s robustness when exposed to extreme heat. After all, meteorites need to be made of tough stuff to make it to the ground. “Three quarters of the rock, which was about the size of a small pork pie, was burnt off in the experiment. However, the quarter which returned to Earth has shown us that if intelligent life were to have come into contact with the rock, it would have provided them with evidence that life exists on another planet.”
Now this is where the implications behind these results become abundantly clear. If this piece of rock was sent out into space, only for it to eventually encounter an alien world with intelligent life on its surface, it is conceivable that the rock would survive reentry, preserving the organic chemicals for further study by extraterrestrials. Of course, the reverse is true. If life existed (or exists) on Mars, perhaps we should take a closer look at those Martian meteorite samples…
In the case of the Orkney sample, it contains the remains of 400 million year-old algae, providing a rich chemical signature that Parnell and his team could detect. “We would be extremely excited if we found similar remains in a meteorite arriving from another world,” he added.
Although this experiment only scratches the surface of how organic chemicals may last, unaltered, in space (after all, should a meteoroid sample float in space for millions of years, could organic chemicals be altered by cosmic rays?), it does help us understand that for lower energy reentries, organic chemicals can indeed survive the burn…
Artist impression of the Asteroid Kleopatra. Credit: NASA
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Meteorites and asteroids from the inner solar system could be responsible for Earth’s store of precious metals such as platinum and iridium, brought to our nascent planet during the period of Late Heavy Bombardment, about 4,000 million years ago. Dr. Gerhard Schmidt from the University of Mainz, Germany, has calculated that about 160 metallic asteroids of about 20 kilometers in diameter would be sufficient to provide the concentrations of these metals, known as Highly Siderophile Elements (HSE), found in the Earth’s crust. “A key issue for understanding the origin of planets is the knowledge of the abundances of HSE in the crust and mantle of the Earth, Mars and the Moon. We have found remarkably uniform abundance distributions of HSE in our samples of the Earth’s upper crust. A comparison of these HSE values with meteorites strongly suggests that they have a cosmo-chemical source,” said Schmidt.
Schmidt and his colleagues have spent the last 12 years analyzing the concentrations of HSE at meteorite impact sites around the world, as well as in the samples from the Earth’s mantle and crust. In addition, he has compared the data from the Earth with data from impact breccias from the Moon brought by the Apollo missions and Martian meteorites, believed to be samples from the mantle and crust on Mars.
As the Earth formed, the heavy elements, including HSE that were present, sank to form the iron and nickel-rich metallic core. HSE were added again later by meteorite impacts, creating a veneer of material over the Earth’s surface after the core had formed, about 20-30 million years after the planet’s accretion. This could have been by the collision with a Mars-sized impactor that led to the formation of the Moon.
However, Schmidt believes that the meteorites responsible for the HSE elements on Earth are iron or stony-iron meteorites that match up with theoretical predications of asteroids formed in the Mercury-Venus region of our solar system.
Different classes of meteorites have characteristic elemental ratios of HSE that give indications where in the Solar System they formed. Chondrites are stony meteorites that represent the pristine material from the early Solar System, and iron or stony-iron meteorites, which are fragments of larger asteroids that had enough internal heat in the past to form a molten metal core. These most likely would have formed in the inner solar system.
The ratios of HSE found in Earth’s crust bear a much closer resemblance to iron or stony-iron meteorites, and Schmidt believes these meteorites came from the inner solar system.
There’s a problem, however. Of the 175 known impact craters on Earth, remains of the projectiles have been found for about 40, and none of these meteorites have been identified as being formed in the region between Mercury and Venus.
Intriguingly, some of the Martian meteorites found in Antarctica, which are probably represent samples of the Martian crust also have HSE values that resemble groups of iron meteorites and stony irons, suggesting that a similar process took place on Mars. Rock on Mars found by Opportunity rover, believed to be a meteorite. Credit: NASA/JPL
Also, the first meteorite found on Mars by the Opportunity Mars Exploration Rover in 2005 was an iron
meteorite.
Dr. Schmidt presented his findings at the European Planetary Science Congress in Muenster on Monday, 22nd September.
