Asteroids Archives

January 20, 2010December 24, 2015 by Nancy Atkinson

Asteroids Zipping Too Close to Earth Can Experience Seismic Activity

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An asteroid’s orbit can be altered if it travels in the vicinity of Earth. But astronomers are finding the effects Earth has on space rocks go far beyond just orbital alterations. Richard Binzel of MIT says that Earth has considerable influence on asteroids — and from a distance much larger than previously thought. He has determined that if an near-Earth asteroid (NEA) travels within a certain range of Earth, roughly one-quarter of the distance between Earth and the moon, it can experience a “seismic shake” strong enough to bring bright, new regolith to its surface. This new finding has helped answer the question of how some asteroids appear to have fresh surfaces, as well as shedding new light on where most meteorites come from.

These rarely seen “fresh asteroids” have long interested astronomers because their spectral fingerprints, or how they reflect different wavelengths of light, match 80 percent of all meteorites that fall to Earth, according to a paper by Binzel appearing in the Jan. 21 issue of Nature. The paper suggests that Earth’s gravitational pull and tidal forces create these seismic tremors.

By hypothesizing about the cause of the fresh surfaces of some NEAs, Binzel and his colleagues have tried to solve a decades-long conundrum about why these fresh asteroids are not seen in the main asteroid belt, which is between Mars and Jupiter. They believe this is because the fresh surfaces are the result of a close encounter with Earth, which obviously wouldn’t be the case with an object in the main asteroid belt. Only those few objects that have ventured recently inside the moon’s orbital distance and have experienced a “fresh shake” match freshly fallen meteorites measured in the laboratory, Binzel said.

Binzel’s team telescopically collected information on NEAs, including a huge amount of spectral fingerprint data. Analyzing this data, the group examined where a sample of 95 NEAs had been during the past 500,000 years, tracing their orbits to see how close they’d come to Earth. They discovered that 75 NEAs in the sample had passed well inside the moon’s distance within the past 500,000 years, including all 20 fresh asteroids in the sample.

Binzel next determined that an asteroid traveling within a distance equal to 16 times the Earth’s radius (about one-quarter of the distance to the moon) appears to experience vibrations strong enough to create fresh surface material. He reached that figure based on his finding that about one-quarter of NEAs are fresh, as well as two known facts — that the space weathering process that ages regolith can happen in less than one million years, and that about one-quarter of NEAs come within 16 Earth radii in one million years.

Before now, people thought an asteroid had to come within one to two Earth radii to undergo significant physical change.

Many details about the shaking process remain unknown, including what exactly it is about Earth that shakes the asteroids, and why this happens from a distance as far away as 16 Earth radii. What is certain is that the conditions depend on complex factors such as the velocity and duration of the encounter, the asteroid’s shape and the nature of the preexisting regolith. “The exact trigger distance depends on all those seismology factors that are the totally new and interesting area for cutting edge research,” Binzel said.

Binzel also proposed a new field of study: asteroid seismology.

Further research might include computer simulations, ground observations and sending probes to look at the surfaces of asteroids. Binzel’s next steps will be to try to discover counterexamples to his findings or additional examples to support it. He may also investigate whether other planets like Venus or Mars affect asteroids that venture close to them.

Source: EurekAlert

January 19, 2010December 24, 2015 by Nancy Atkinson

Asteroid Collision May Have Created Comet-like Object

P/2010 A imaged by Dr. Robert McMillan at Kitt Peak, Arizona. Credit: LINEAR

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A strange comet-like object discovered on January 6, 2010 may actually be the result of an asteroid collision. Lincoln Near-Earth Asteroid Research (LINEAR) sky survey in New Mexico spotted an object in the asteroid belt, called P/2010 A that looked “fuzzy,” with a tail like a comet rather than a speck of light like a normal asteroid. But comets don’t normally reside in the asteroid belt, and the object’s orbit is all wrong for a comet. While the asteroid belt is made up of debris from the “leftovers” of our solar system, and like the remains of early crashes between giant rocks, astronomers haven’t witnessed a collision before.

Other comet/asteroid crossbreeds have been seen previously, such as the Comet P/1996 N2 discovered in 1996, but astronomers are keeping a close eye on this latest oddball, as they believe the best explanation is that collision took place between two asteroids deep in space, about 250 million miles away from Earth. If they are right, it will be the first confirmed high-speed crash ever witnessed between massive space rocks.

Sky and Telescope reports that the comet specialists are hoping to observe the strange goings-on with both the Hubble and Spitzer space telescopes. Neither has been given the green light yet, but if/when that happens the observations would be made within the next few days.

Sources: Skymania, Sky & Telescope, Discovery Space

January 13, 2010January 24, 2021 by Nancy Atkinson

Images and Videos of 2010 AL30

Series of 30 15" exposures tracking on 2010 AL30 between 07:18:16 and 07:27:29 GMT - Credit: Patrick Wiggins

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Amateur astronomers heeded the call of making observations of the small asteroid 2010 AL30, which whizzed by Earth today. Here are some of the great images and videos captured by the amateur astronomy community, which will help the professionals determine the exact orbit, and also perhaps what exactly this unusual asteroid is. The object, which has been estimated to be between 10-15 meters (30 -50 feet) across, is likely a natural object, but it hasn’t officially been ruled out that it might be man-made, i.e., a spent rocket booster, from perhaps the Venus Express mission. The folks who are apt to make the determination are those who work with the 70-meter radio dish at Goldstone. I corresponded with Lance Benner from the Goldstone facility, and he said, “We’re still working with the data so it’s still too early to say.”

We’ll keep you posted, but in the meantime, enjoy some of the images and videos of 2010 AL30’s flyby. Above, NASA Solar System Ambassador Patrick Wiggins in Utah took a series of exposures and combined them into a “movie.” He used a C-14 @ f/5.5 telescope and SBIG ST-10 binned 3×3 using a clear filter. The Field of View is about 18 x 26 arc minutes.

2010 AL30, on January 13, 2010. Credit: Ernesto Guido & Giovanni Sostero, Remanzacco Observatory.

This image was taken by 2010 AL30, on January 13, 2010 by Ernesto Guido & Giovanni Sostero, at the Remanzacco Observatory in Italy. Check out their website for more images.

The prospect of 2010 AL30 hitting Earth never even entered into the equation of this unusual asteroid. The problem, (if there is one) is that it was only detected two days ago. The other issue is its origin. The Italian astronomers who took the above image noted that the object has an orbital period of almost exactly one year and might be a man-made object. However, Alan Harris, senior researcher at the Space Science Institute countered by saying the object has a perfectly ordinary Earth-crossing orbit, and that its orbit doesn’t resemble any useful spacecraft trajectory. Additionally, NASA put out a press release yesterday saying the object was “a natural” asteroid.

“This object’s orbit reaches the orbit of Venus at its closest point to the sun and nearly out to the orbit of Mars at its furthest point, crossing the Earth’s orbit at a very steep angle,” the press release said. “This makes it very unlikely that 2010 AL30 is a rocket stage. Furthermore, trajectory extrapolations show that this object cannot be associated with any recent launch and it has not made any close approaches to the Earth since well before the Space Age began.”

continued below….

This is another video from Patrick Wiggins, this time with a smaller exposure time. “The target is pretty faint (not surprising for 1″ exposures) so you have to look close to see it as it moves from left to right,” he said. (Thanks to the SciBuff website for the video.)

But then, ESA mission analyst Michael Khan looked at data from the Venus Express mission, and he wrote in his blog that perhaps 2010 AL30 might be the Fregat upper stage of the rocket that sent Venus Express to Venus. Only more detailed analysis of data from the object will provide the answer.

This image was taken by Tavi Greiner, using the SLOOH robotic observatory on the Canary Islands, at 03:02 GMT. Check out SLOOH to find out how you can take your own images.

The initial word from Goldstone is that the object produced very strong radar echoes, and also that it had a very fast 9-minute rotation.

The trajectory of 2010 AL30.

2010 AL30 imaged on January 12 from the distance of 0.003 7 AU at the Nazaret Observatory at the Canary Islands – Credit: Gustavo, Muler, Schteinman – Observatorio Nazaret, J47. Click on the image or here to see a “movie” of the object.

Check out more images on Spaceweather.com, including this image from Alberto Quijan Vodniza and Mario Rojas Pereira from the University of Narino- Columbia.

There’s also this very cool animation of 2010 AL30’s approach, and what Earth would look like to anyone “riding” on the asteroid.

Also, check out the Transient Sky blog, where Carl Hergenrother lays out the details what might have happened if 2010 AL30 had been headed for impact with Earth.

And one more thing, via the Bad Astronomer, is this great graphic showing how far away this object passed by Earth.

Sources: SciBuff, Emily Lakdawalla’s Planetary Blog, Spaceweather.com, Transient Sky

December 30, 2009December 24, 2015 by Nancy Atkinson

Russia May Head Mission to Deflect Asteroid Apophis

Orbital path of Apophis. Credit: NASA NEO Program

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Russia is considering sending a spacecraft to deflect a large asteroid and prevent a possible collision with Earth, according to a radio interview by the head of the country’s space agency. Anatoly Perminov said the space agency will hold a meeting soon to assess a mission to asteroid Apophis, and said NASA, ESA, the Chinese space agency and others would be invited to join the project. Apophis is a 270-meter (885-foot) asteroid that was spotted in 2004. It is projected to come within 29,450 kilometers (18,300 miles) of Earth in 2029, and currently has an estimated 1-in-250,000 chance of hitting Earth in 2036.

A panel at the recent American Geophysical Union conference stressed that asteroid deflection is a international issue.

“There is a geopolitical misconception that NASA is taking care of it,” said former Apollo astronaut Rusty Schweickart, who is part of the B612 Foundation, which hopes to prove the technology to significantly alter the orbit of an asteroid by 2015. “They aren’t and this is an international issue. The decisions have to be world decisions.”

Perminov seemed unaware that NASA’s Near Earth Object program recently downgraded the possibility of a 2036 asteroid impact and also for a subsequent pass in 2068.

Perminov said that he heard from a scientist that Apophis asteroid is getting closer and may hit the planet. “I don’t remember exactly, but it seems to me it could hit the Earth by 2032,” Perminov said. “People’s lives are at stake. We should pay several hundred million dollars and build a system that would allow to prevent a collision, rather than sit and wait for it to happen and kill hundreds of thousands of people.”

Perminov wouldn’t disclose any details of the project, saying they still need to be worked out. But he said the mission wouldn’t require any nuclear explosions.

“Calculations show that it’s possible to create a special purpose spacecraft within the time we have, which would help avoid the collision without destroying it (the asteroid) and without detonating any nuclear charges,” Perminov said. “The threat of collision can be averted.”

Boris Shustov, the director of the Institute of Astronomy under the Russian Academy of Sciences, hailed Perminov’s statement as a signal that officials had come to recognize the danger posed by asteroids like 2036 Apophis.

“Apophis is just a symbolic example, there are many other dangerous objects we know little about,” he said, according to RIA Novosti news agency.

Sources: Associated Press/Yahoo News, AGU panel discussion

Here’s some more information on the 2036 meteor.

December 29, 2009December 24, 2015 by Nancy Atkinson

Where To Next for NASA’s Solar System Exploration?

From top to bottom, pictured are the moon, Venus, and an asteroid.From top to bottom, pictured (not to scale) are the moon, Venus, and an asteroid. These three celestial bodies from our solar system are possible candidates for NASA's next space venture.

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Where is NASA going next to probe our solar system? The space agency announced today they have selected three proposals as candidates for the agency’s next space venture to another celestial body in our solar system. The proposed missions would probe the atmosphere composition and crust of Venus; return a piece of a near-Earth asteroid for analysis; or drop a robotic lander into a basin at the moon’s south pole to return lunar rocks back to Earth for study. All three sound exciting!

Here are the finalists:

Surface and Atmosphere Geochemical Explorer, or SAGE, mission to Venus would release a probe to descend through the planet’s atmosphere. During descent, instruments would conduct extensive measurements of the atmosphere’s composition and obtain meteorological data. The probe then would land on the surface of Venus, where its abrading tool would expose both a weathered and a pristine surface area to measure its composition and mineralogy. Scientists hope to understand the origin of Venus and why it is so different from Earth. Larry Esposito of the University of Colorado in Boulder, is the principal investigator.

Origins Spectral Interpretation Resource Identification Security Regolith Explorer spacecraft, called Osiris-Rex, would rendezvous and orbit a primitive asteroid. After extensive measurements, instruments would collect more than two ounces of material from the asteriod’s surface for return to Earth. The returned samples would help scientists better undertand and answer long-held questions about the formation of our solar system and the origin of complex molecules necessary for life. Michael Drake, of the University of Arizona in Tucson, is the principal investigator.

MoonRise: Lunar South Pole-Aitken Basin Sample Return Mission would place a lander in a broad basin near the moon’s south pole and return approximately two pounds of lunar materials for study. This region of the lunar surface is believed to harbor rocks excavated from the moon’s mantle. The samples would provide new insight into the early history of the Earth-moon system. Bradley Jolliff, of Washington University in St. Louis, is the principal investigator.

The final project will be selected in mid-2011, and for now, the three finalists will receive approximately $3.3 million in 2010 to conduct a 12-month mission concept study that focuses on implementation feasibility, cost, management and technical plans. Studies also will include plans for educational outreach and small business opportunities.

The selected mission must be ready for launch no later than Dec. 30, 2018. Mission cost, excluding the launch vehicle, is limited to $650 million.

“These are projects that inspire and excite young scientists, engineers and the public,” said Ed Weiler, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “These three proposals provide the best science value among eight submitted to NASA this year.”

The final selection will become the third mission in the program. New Horizons, launched in 2006, will fly by the Pluto-Charon system in 2015 then target another Kuiper Belt object for study. The second mission, called Juno, is designed to orbit Jupiter from pole to pole for the first time, conducting an in-depth study of the giant planet’s atmosphere and interior. It is slated for launch in August 2011.

Visit the New Frontiers program site for more information.

November 26, 2009December 24, 2015 by Jon Voisey

Comets Posing as Asteroids (or is the the other way around?)

Images of known MBCs from UH 2.2-meter telescope data. Credit: Henry Hsieh

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Asteroids are rocky bodies which belong between Mars and Jupiter. Comets are icy bodies that belong way out beyond Pluto. So what are comet-like objects doing in the asteroid belt?

On the night of August 7, 1996, astronomers Eric Elst and Guido Pizarro were observing what was previously thought to be an ordinary asteroid. To their surprise, the object revealed a faint but distinct tail similar to that of a comet. Initially, this was written off as a minor impact kicking up a debris cloud, but when the tail returned in 2002, when the supposed asteroid again returned to perihelion (the closest approach to the Sun), it once again displayed a tenuous tail. The “asteroid” was then given the designation of 133P/Elst-Pizarro. In 2005, two new asteroids were discovered to sport tails: P/2005 U1 and 118401. In 2008, yet another one of these odd objects was found (P/2008 R1). This new class of objects has been dubbed “Main Belt Comets (MBCs)”.

So where are these objects coming from?

A previous article here on Universe Today explored the possibility that these objects formed like other asteroids in the main belt. After all, each of the objects has an orbit consistent with other apparently normal asteroids. They have a similar distance at with they orbit the Sun, as well as similar eccentricities and inclinations of their orbit. So trying to explain these objects as having origins in the outer solar system that migrated just right into the asteroid belt seemed like little more than special pleading.

Furthermore, a 2008 study by Schorghofer at the University of Hawaii predicted that, if such an icy body were to form, it would be able to avoid sublimation for several billion years if only it were covered with a few meters of dust and dirt thus negating the problems of these objects suffering an early death. (Keep in mind that, much like a melting snowball, the water will evaporate but the dirt won’t, so the dirt will pile up quickly on the surface making this entirely plausible!) However, if the ice were covered by such an amount of dust, it would take a collision to remove the dust and trigger the cometary appearance.

In a recent paper, Nader Haghighipour also at the University of Hawaii explores the viability of collisions to trigger this activation as well as the stability of the orbits of these objects to assess the expectation that they were formed at the same time as other asteroids in the main belt.

For the orbital range in which three of the MBCs lie, it was predicted that “on average, one m[eter]-sized object collides … every 40,000 years.” They stress this is an upper limit since their simulation did not include other, nearby asteroids which would likely deplete the number of available impactors.

When they explored the orbital stability of these objects, the discovered at least two of them were dynamically unstable and would eventually be ejected from their orbits on a timescale of 20 million years. As such, it would be unreasonable to expect such objects to have lasted for the nearly 5 billion year history of the solar system. Thus, an in-situ formation was ruled out. However, due to a similarity in orbital characteristics to a family of asteroids known as the Themis family, suggesting they may have resulted from the same break up of a larger body that created this group. This begs the question of whether or not more of these asteroids are secretly hiding water ice reservoirs and are just waiting for an impact to expose them.

Distinctly separate from this orbital family was P/2008 R1 which exists in an especially unstable orbit near one of the resonances from Jupiter. This suggests that this MBC was likely scattered to its present location, but from where remains to be determined.

So while such Main Belt Comets may not have formed simply as they are now, they are likely to be in orbits not far removed from their original formation. Also, this work supported the earlier notion that minor impacts could reliably expected to expose ice allowing for the cometary tails. Whether or not more asteroids have tails tucked between their legs will be the target of future exploration.

Haghighipour’s Paper

November 9, 2009December 24, 2015 by Nancy Atkinson

Surprise! Unknown Asteroid Buzzed Earth

Trajectory of Asteroid 2009 VA Past Earth on November 6, 2009. Credit: NASA/JPL

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A previously undiscovered asteroid came within 14,000 km (8,700 miles) of Earth last week, and astronomers noticed it only 15 hours before closest approach. On Nov. 6 at around 16:30 EST a 7 meter asteroid, now called 2009 VA, came only about 2 Earth radii from impacting our home planet. This is the third-closest known non-impacting Earth approach on record for a cataloged asteroid.

Early on Nov. 6 the asteroid was discovered by the Catalina Sky Survey and was quickly identified by the Minor Planet Center in Cambridge MA as an object that would soon pass very close to the Earth. JPL’s Near-Earth Object Program Office also computed an orbit solution for this object, and determined that it was not headed for an impact.

The two closer approaches include the 1-meter sized asteroid 2008 TS26, which passed within 6,150 km (3,800 miles) of the Earth’s surface on October 9, 2008, and the 7-meter sized asteroid 2004 FU162 that passed within 6,535 km (4,060 miles) on March 31, 2004. On average, objects the size of 2009 VA pass this close about twice per year and impact Earth about once every 5 years.

Only thirteen months ago, another asteroid, 2008 TC3 was discovered under similar circumstances, but that one was found to be on a trajectory headed for the Earth, with impact only about 11 hours away. It impacted in a remote area of Africa; no one was injured and fragments have since been recovered for study.

Source: JPL NEO office

November 9, 2009December 24, 2015 by Nicholos Wethington

Camera Network Spies Anomalous Meteorite

A network of time-lapse cameras set up in the Nullarbor Plain desert of Western Australia has allowed researchers to track a fallen meteorite to the ground, and enabled them to determine its original orbit and parent body. The meteorite has a composition different than that of other meteors, leading researchers to believe that it originates from a different parent body than most meteorites that impact Earth. The Desert Fireball Network, a project coordinated by the Imperial College of London, was able to track the meteor when it entered the atmosphere, giving researchers an impact location and information on where it originated.

The Bunburra Rockhole meteorite – so named for the location where it was discovered – fell to the Earth on July 20th, 2007. The Desert Fireball Network cameras recorded the fireball produced when the meteor passed through the Earth’s atmosphere, and by studying the entry angle of the meteor, researchers from the Imperial College were able to locate it on the ground. It was found within 100 meters (300 feet) of where they had predicted it to be.

This meteorite weighs 324 grams (12 oz), and is composed of a rare type of basalt igneous rock. More specific information on the meteorite itself can be found on the Meteorological Society’s index. Most meteorites of this composition come from one parent body, the asteroid 4 Vesta. However, the Bunburra Rockhole meteorite likely came from a different asteroid with a different orbit, which means that the formation process for the asteroid happened in a different place in the Solar System than for 4 Vesta.

The researchers determined that the Bunburra Rockhole originated from an asteroid located in the innermost main asteroid belt between Mars and Jupiter. Because the Desert Fireball Network captured images on multiple cameras of how it entered the Earth’s atmosphere, the researchers were able to triangulate the position of the rock, and model its orbit backwards in time to determine its origins.

Dr Gretchen Benedix of the Natural History Museum – where the largest fragment of the meteorite is located – analyzed the mineral content of the meteorite. She said in a press release:

“It’s vital to have a meteorite with information about where it comes from in the solar system…. We’ve known for a long time that most meteorites are from the asteroid belt, but we don’t know exactly where. This kind of information helps us fit one more piece in the puzzle of how the solar system formed and evolved. The fact that this meteorite is compositionally unusual increases it’s value even more. It helps us to uncover more information about the conditions of the early solar system.”

The Desert Fireball Network monitors the Nullarbor desert in Western Australia, and has tracked a total of 7 meteorites, three of which have been recovered. The desert is an excellent location for this type of project, as observing conditions are clear many nights out of the year, and the sparse vegetation and monotone landscape make finding the meteorites easier than in other locations.

The results of the meteorite mineral and orbital study are published in Science, and two previous papers about the Bunburra Rockhole are available on the Desert Fireball Network site.

Source: Natural History Museum, Imperial College of London

October 30, 2009April 26, 2016 by Nicholos Wethington

Asteroid Explosion over Indonesia

This has taken awhile to filter into the Western press, but an asteroid exploded over the town of Bone,Indonesia on October 8th at around 11am local time. Initially, locals called the police to report that a plane had crashed, or that an earthquake shook the ground, as reported in the Jakarta Globe. The Jakarta Post quoted Thomas Djamaluddin, head of the Lapan Center for Climate and Atmosphere Science Implementation as saying that the explosion was due to a meteorite or bit of space junk that had entered the Earth’s atmosphere. As it turns out after further analysis, the explosion was due to an asteroid about 5-10 meters (15-30 feet) in diameter exploding in the air between 15 and 20 km (nine to 12 miles) above sea level. Nobody was injured as a result of the explosion, but it evidently caused quite a scare with the local population!

In a press release from the Near Earth Object (NEO) program, the explosion was detected by many International Monitoring System (IMS) infrasound stations, five of them 10,000 km (6200 miles) away, and one 18,000 km (11,100 miles) from the blast. These stations monitor seismic waves, infrasound (low frequency soundwaves), hydroacoustic, and radionuclide emissions as part of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). They are well equipped to monitor explosions of nuclear weapons, but also detect other events such as meteorite impacts and asteroid explosions, tsunamis and earthquakes.

When analyzed, the amount and intensity of low frequency sound waves created by the explosion allowed researchers Elizabeth Silber and Peter Brown of the Meteor Infrasound Group at the Univ. of Western Ontario to determine that the explosion caused by the asteroid was on the scale of 30 – 50 kilotons of TNT. To give you an idea of how powerful of an explosion this is, the bombs dropped over Hiroshima and Nagasaki in World War II exploded with the force of 20 kilotons of TNT.

The fireball – also called a bolide – created a dusty tail upon entering the atmosphere of the Earth. It is estimated that the asteroid was traveling around 72,000 km/hour (45,000 miles/hour) when it hit the atmosphere. As an asteroid enters the thick Earth atmosphere, it slows down abruptly and heats up due to the process of ablation. If this asteroid were made of metal instead of rock, it would likely have impacted the ground causing a lot of damage. Fortunately for the residents of Bone and the surrounding area, the rock broke up in a large fireball instead. There haven’t been any reports of pieces that have touched down as of yet.

Asteroids of this size are predicted to impact the Earth about every 2-12 years, and the last one of this magnitude was a bolide over the Marshall Islands on February 1, 1994. That impactor was estimated to be between 4.4 and 13.5 meters. A full analysis of that event is available on the SAO/NASA Astrophysics Data System.

Of course, events like this always raise the question of why the object wasn’t detected before it even entered the atmosphere. The NEO program has cataloged over 600 objects in the size of 10 meters, but there are many, many more out there. The cost of a monitoring and cataloging all of the Near Earth Objects would be in the hundreds of millions of dollars, but more events like this may spur the political will and capital to further efforts at protecting human lives from the potential damage of meteorite impacts.

Source: Night Sky, Spaceweather.com, JPL Press Release

October 19, 2009December 24, 2015 by Nancy Atkinson

Giant Impact Near India — Not Mexico — May Have Killed Dinosaurs

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. The overlying 4.3-mile-tick Cenozoic strata and water column were removed to show the morphology of the crater.

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A huge, mysterious basin off the coast of India could be the largest, multi-ringed impact crater ever found on Earth. And if a new study is right, this impact may supercede the one that created the Chicxulub crater off Mexico’s Yucatán Peninsula as what may have been responsible for killing the dinosaurs 65 million years ago. Sankar Chatterjee of Texas Tech University and a team of researchers have been studying a 500-kilometer-wide (300-mile-wide) depression on the Indian Ocean seafloor which was likely created by a bolide perhaps 40 kilometers (25 miles) in diameter. Such an event would have triggered worldwide climate changes, including intensified volcanism, that led to mass extinction.

Since the 1990’s the leading candidate for what killed the dinosaurs was a ten-kilometer-wide (six-mile-wide) asteroid thought to have carved out the Chicxulub crater. This impact may have done the job, but if not, 300,000 later the impact that created the Shiva basin surely would have finished off large life on Earth.

The massive Shiva basin, a submerged depression west of India that is intensely mined for its oil and gas resources. Some complex craters are among the most productive hydrocarbon sites on the planet.

“If we are right, this is the largest crater known on our planet,” Chatterjee said. “A bolide of this size, creates its own tectonics.”

However, some geologists have disputed whether the Shiva depression was created by an impact, or if it is just a hole in Earth’s crust, possibly created by volcanism. Christian Koeberl, a geochemist at the University of Vienna in Austria, has been adamant in the past that Shiva is not an impact crater. He said not only is there no evidence of impact in the case of Shiva, there is no crater structure. He calls Shiva, “a figment of imagination.”

“There’s not even ambiguous evidence, or inconclusive evidence,” says Koeberl. “There are a couple of people that keep pushing for some crater in the Indian Ocean, but this is inconsistent not only with the regional geology and geophysics, but also with anything we know about impact cratering.”

But Chatterjee feels sure that Shiva is an impact crater and said 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.

If the huge depression was created by an impact, Earth’s crust at the point of collision would have been vaporized, 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 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.

Read the Abstract

Source: Geological Society of America