Images of known MBCs from UH 2.2-meter telescope data. Credit: Henry Hsieh
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Back in 1996, astronomers discovered a strange object in the asteroid belt. They decided it was either a “lost” comet or an icy asteroid, as it ejected dust like a comet but had an orbit like an asteroid. No one had ever seen anything like the object, called 133P. Ever since it was found, astronomers have wondered if it was just an oddity — one of a kind. We now know it is not, and the discovery of more of these half asteroids/half comets means there is a new class of objects in our solar system.
One of these new objecst, 176P/LINEAR is also emitting dust as it orbits in the asteroid belt. It was found by Henry Hsieh at Queen’s University, Belfast in Northern Ireland. Hsieh has been working to figure out the unusual behavior of 133P. He hypothesized that either one of two things could explain the existence of the comet-asteroid: “(1.) 133P is a classical comet from the outer solar system that has evolved onto a main-belt orbit, or (2.) 133P is a dynamically ordinary main-belt asteroid on which subsurface ice has recently been exposed,” Hsieh wrote in his paper. “If (1) is correct, the expected rarity of a dynamical transition onto an asteroidal orbit implies that 133P could be alone in the main belt. In contrast, if (2) is correct, other icy main-belt objects should exist and could also exhibit cometary activity.”
Hsieh thought it was unlikely a comet could have been kicked around enough to end up in orbit in the asteroid belt, so he followed the assumption that 133P was a dynamically ordinary, yet icy main-belt asteroid. He set out to prove the hypothesis that 133P-like objects should be common and could be found by an well-designed observational survey.
Hsieh made 657 observations of 599 asteroids in the asteroid belt and found 176P/LINEAR. He also determined the asteroid is partially made of ice, which is being ejected following a collision with another object, thus the comet-like attributes.
Additionally, since there is evidence for past and even present water in main-belt asteroids, Hsieh says statistically there should be around 100 currently active Main Belt Comets (MBCs) as these objects are called, among the kilometer-scale, low-inclination, outer belt asteroid population.
The Technology Review blog offered suggestions for what to name these new objects that are half comet and half asteroid: “Comsteroids? Asteromets? Hsiehroids?”
With the recent impact on Jupiter, a lot of people out there have asteroids on their mind and wonder if one could possibly hit Earth. Now, NASA and JPL have a new website called “Asteroid Watch” which will keep everyone updated if any object approaches Earth. They’ve also created an Asteroid Watch Twitter account that Tweet updates on NEOs, plus there’s a downloadable widget as well.
“The goal of our Web site is to provide the public with the most up-to-date and accurate information on these intriguing objects,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office at JPL.
“This innovative new Web application gives the public an unprecedented look at what’s going on in near-Earth space,” said Lindley Johnson, program executive for the Near-Earth Objects Observation program at NASA Headquarters in Washington.
Information is garnered from surveys and missions that detect and track asteroids and comets passing close to Earth. The Near-Earth Object Observation Program, commonly called “Spaceguard,” also plots the orbits of these objects to determine if any could be potentially hazardous to our planet.
There’s also another non-NASA Twitter feed called lowflyingrocks that lets you know about every Near Earth Object that passes within 0.2AU of Earth.
California's Channel Islands, where heat-shocked soot and diamonds are suggesting a killing comsic impact. Courtesy NOAA and UC Santa Barbara
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Archeologists have been divided about whether an extraterrestiral impact blasted North America about 12,900 years ago, wreaking havoc on Earth’s surface and sending scores of species — including a pygmy mammoth and the horse — into oblivion.
New clues from California’s Channel Islands should put any doubt to rest, says an international team of researchers.
This transmission electron microscopy close-up shows a single lonsdaleite crystal, left, and associated diffraction pattern. Credit: University of Oregon
The 17-member team, led by University of Oregon archaeologist Douglas J. Kennett, has found what may be the smoking gun.
The team has found shock-synthesized hexagonal diamonds in 12,900-year-old sediments on the Northern Channel Islands off the southern California coast.
The tiny diamonds and diamond clusters were buried deeply below four meters (13 feet) of sediment. They date to the end of Clovis — a Paleoindian culture long thought to be North America’s first human inhabitants. The nano-sized diamonds were pulled from Arlington Canyon on the island of Santa Rosa, which had once been joined with three other Northern Channel Islands in a landmass known as Santarosae.
The diamonds were found in association with soot that forms in extremely hot fires, and they suggest associated regional wildfires, based on nearby environmental records.
Such soot and diamonds are rare in the geological record. They were found in sediment dating to massive asteroid impacts 65 million years ago in a layer widely known as the K-T Boundary. The thin layer of iridium-and-quartz-rich sediment dates to the transition of the Cretaceous and Tertiary periods, which mark the end of the Mesozoic Era and the beginning of the Cenozoic Era.
“The type of diamond we have found — Lonsdaleite — is a shock-synthesized mineral defined by its hexagonal crystalline structure. It forms under very high temperatures and pressures consistent with a cosmic impact,” Kennett said. “These diamonds have only been found thus far in meteorites and impact craters on Earth and appear to be the strongest indicator yet of a significant cosmic impact [during Clovis].”
The age of this event also matches the extinction of the pygmy mammoth on the Northern Channel Islands, as well as numerous other North American mammals, including the horse, which Europeans later reintroduced. In all, an estimated 35 mammal and 19 bird genera became extinct near the end of the Pleistocene with some of them occurring very close in time to the proposed cosmic impact, first reported in October 2007 in PNAS.
Source: University of Oregon, via Eurekalert. The results appear in a paper online ahead of print in the Proceedings of the National Academy of Sciences.
Celestial impacts can bring life as well as wipe it out, say the authors of a new study out of the University of Colorado at Boulder.
A case in point: the bombardment of Earth nearly 4 billion years ago by asteroids as large as Kansas would not have had the firepower to extinguish potential early life on the planet and may even have given it a boost.
In a new paper in the journal Nature, Oleg Abramov and Stephen Mojzsis report on their study of impact evidence from lunar samples, meteorites and the pockmarked surfaces of the inner planets. The evidence paints a picture of a violent environment in the solar system during the Hadean Eon 4.5 to 3.8 billion years ago, particularly through a cataclysmic event known as the Late Heavy Bombardment about 3.9 billion years ago.
Although many believe the bombardment would have sterilized Earth, the new study shows it would have melted only a fraction of Earth’s crust, and that microbes could well have survived in subsurface habitats, insulated from the destruction.
“These new results push back the possible beginnings of life on Earth to well before the bombardment period 3.9 billion years ago,” Abramov said. “It opens up the possibility that life emerged as far back as 4.4 billion years ago, about the time the first oceans are thought to have formed.”
Because physical evidence of Earth’s early bombardment has been erased by weathering and plate tectonics over the eons, the researchers used data from Apollo moon rocks, impact records from the moon, Mars and Mercury, and previous theoretical studies to build three-dimensional computer models that replicate the bombardment. Abramov and Mojzsis plugged in asteroid size, frequency and distribution estimates into their simulations to chart the damage to the Earth during the Late Heavy Bombardment, which is thought to have lasted for 20 million to 200 million years.
The 3-D models allowed Abramov and Mojzsis to monitor temperatures beneath individual craters to assess heating and cooling of the crust following large impacts in order to evaluate habitability. The study indicated that less than 25 percent of Earth’s crust would have melted during such a bombardment.
The CU-Boulder researchers even cranked up the intensity of the asteroid barrage in their simulations by 10-fold — an event that could have vaporized Earth’s oceans. “Even under the most extreme conditions we imposed, Earth would not have been completely sterilized by the bombardment,” said Abramov.
Instead, hydrothermal vents may have provided sanctuaries for extreme, heat-loving microbes known as “hyperthermophilic bacteria” following bombardments, said Mojzsis. Even if life had not emerged by 3.9 billion years ago, such underground havens could still have provided a “crucible” for life’s origin on Earth, Mojzsis said.
Geologic evidence suggests that life on Earth was present at least 3.83 billion years ago, said Mojzsis. “So it is not unreasonable to suggest there was life on Earth before 3.9 billion years ago. We know from the geochemical record that our planet was eminently habitable by that time, and this new study sews up a major problem in origins of life studies by sweeping away the necessity for multiple origins of life on Earth.”
The results also support the potential for microbial life on other planets like Mars and perhaps even rocky, Earth-like planets in other solar systems that may have been resurfaced by impacts, said Abramov.
The Solar System often throws up surprises for astronomers, but the recent discovery of a 2- to 3-km wide asteroid called 2009 HC82 has sent observers in a spin. A retrograde spin to be precise.
This particular near-Earth asteroid (NEO) should have already been spotted as it has such a strange orbit. It is highly inclined, making it orbit the Sun backwards (when compared with the rest of the Solar System’s planetary bodies) every 3.39 years. What’s more, it ventures uncomfortably close (3.5 million km) to the Earth, making this NEO a potentially deadly lump of rock…
2009 HC82 was discovered on April 29th by the highly successful Catalina Sky Survey, and after independent observations by five different groups, it was determined that the asteroid has an orbit of 3.39 years and that its orbit is very inclined. So inclined in fact that the asteroid’s orbit takes it well out of the Solar System ecliptic at an angle of 155°. Inclined orbits aren’t rare in themselves, but if you find an asteroid with an inclination of more than 90°, you are seeing a very rare type of object: a retrograde asteroid.
The last time I wrote about a retrograde asteroid was back in September 2008 (Kuiper Belt Object Travelling the Wrong-Way in a One-Way Solar System), when a University of British Columbia researcher spotted a rather unique retrograde Kuiper belt object (called 2008 KV42) that had a large looping orbit with an inclination larger than 90°. It was nicknamed “Drac” after Dracula’s ability to walk on walls.
2009 HC82 is therefore not only rare, it is also very strange. It orbits the Sun the wrong way (therefore making it very inclined), it is a potentially hazardous NEO (it is smaller than the 10 km asteroid that is attributed to wiping out the dinosaurs, but it would cause significant devastation on a global scale if it did hit us) and it is very eccentric.
The orbit of 2009 HC82 (NASA)
All these orbital components have led to speculation that 2009 HC82 is in fact a “burnt out” comet. Comets originate from the Oort Cloud, a theoretical region cometary nuclei that occasionally gets nudged by gravitational disturbances when stars pass by. The Oort Cloud is not restricted to a belt along the ecliptic (like the asteroid belt or the Kuiper belt), it encapsulates our Solar System. Therefore, this may explain 2009 HC82’s bizarre trajectory; it was a comet, but all the ice has vaporized, leaving a rocky core to fling around the Sun on a death-defying orbit, buzzing the inner Solar System.
Brian Marsden of the Minor Planet Center agrees that some retrograde asteroids could be burnt-out comets. The size and shape of the new asteroid’s orbit “is very like Encke’s comet except for inclination,” he said, but the only difference is the fact that 2009 HC82 has no cometary tail.
More observations are needed before a definitive conclusion can be made, but Marsden is confused as to why this object has not been discovered before now. “It should have been easily observable in 2000,” says Marsden. “Why wasn’t it seen then?”
It is hoped further investigation may answer this question…
The black arrows indicate the orientation of chevrons along the southern coast of Madagascar, but the white arrows indicate what computer models say should have been the orientation if they were caused by the impact of a space body in the Indian Ocean. Credit: Robert Weiss
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Coastal formations called chevrons, large U- or V-shaped features found on coastlines around the world were originally thought to be evidence of ancient “megatsunamis” caused by asteroids or comets slamming into the ocean. However, new research using Google Earth and computer models to recreate large wave action refutes that school of thought.
The theory of chevrons being created by tsunamis was proposed in 2006 after the structures were found in Egypt and the Bahamas. Some were, at places, between several hundred meters- and a kilometer-wide. Since they were also found to exist in Australia and Madagascar, some geologists formed the hypothesis that they were sediment cones left behind by large tsunamis, perhaps up to ten times stronger than the devastating tsunami in the Indian Ocean in December 2005.
The theory propsed the only source for such a megatsunami was a meteor impact, occurring about 5,000 years ago.
But a new study, led by Jody Bourgeois, a geologist and tsunami expert at the University of Washington, argues that this theory is simply “nonsense. For example, she said, there are numerous chevrons on Madagascar, but many are parallel to the coastline. Models created by Bourgeois’ colleague Robert Weiss show that if they were created by tsunamis they should point in the direction the waves were travelling, mostly perpendicular to the shore. Landsat image of the Fenambosy Chevrons in Madagascar by USGS. The open side of these chevrons point directly at a crater at the bottom of the Indian Ocean. They suggest a gigantic meteor impact occurred about 4800 years ago. But new research says chevrons were likely formed by wind.
“And if it really was from an impact, you should find evidence on the coast of Africa too, since it is so near,” she said.
By using Google Earth, Bourgeois and her team searched for chevrons and surprisingly they found some in desert areas, well inland and away from the shores.
“The extraordinary claim of ‘chevron’ genesis by megatsunamis cannot withstand simple but rigorous testing. There are the same forms in the Palouse in eastern Washington state, and those are clearly not from a tsunami,” Bourgeois said.
She believes the structures were formed by wind.
The discovery of marine fossils in some chevron formations seems to support the idea that a wave created the deposit, but Bourgeois discounts that evidence also.
“Marine fossils can get into non-marine deposits. It’s not uncommon. You only have to change sea level a little bit or have them wash up on a beach in a storm,” she said. “And some marine organisms can be carried by the wind. I am convinced these are largely wind-blown deposits.”
She noted that similar deposits have been seen on the Kamchatka Peninsula on Russia’s east coast, where she has conducted research for more than a decade.
“Those are made of volcanic ash, and they are not near the coast at all, yet they look very similar to these coastal chevrons,” Bourgeois said.
In 1979, the huge Chicxulub crater, measuring about 180 km (112 miles) in diameter, was discovered on the northern Yucatan Peninsula, Mexico. Scientists made the obvious conclusion that something rather large had hit the Earth in this location, probably causing all kinds of global devastation 65 million years ago. At around the same time, 65% of all life on the face of the planet was snuffed out of existence. The dinosaurs that roamed the planet up to that point were no more.
The timing of asteroid impact and the time of the mass extinction was too much of a coincidence to be ignored. When particles from the asteroid impact were discovered just below the Cretaceous-Tertiary (K-T) boundary, there was a strong causal link: the effects of the asteroid impact had driven the dinosaurs to extinction.
However, a problem with this theory has come to light. It turns out the Chicxulub impact may pre-date the K-T boundary by 300,000 years…
A number of scientists have disagreed with the theory that the Chicxulub impact caused the death of the dinosaurs 65 million years ago, and this newest research appears to show the two events may not be linked after all.
Gerta Keller of Princeton University in New Jersey, and Thierry Adatte of the University of Lausanne, Switzerland, are set to publish this new work in the Journal of the Geological Society today, using data from the analysis of sediment from Mexico to prove the asteroid impact pre-dated the K-T boundary by as much as 300,000 years.
“We know that between four and nine meters of sediments were deposited at about two to three centimeters per thousand years after the impact,” said Keller. “The mass extinction level can be seen in the sediments above this interval.”
This means that the mass extinctions appeared to take place a long time after the impact. However, impact-extinction advocates point out that this inconsistency in sediment data is probably down to sediment disruption by tsunamis and geological upheaval immediately after the impact.
According to Keller, there is no indication that this could be the case. Deposition of impact sediment occurred over a huge time period, not the hours or days deposition would have taken if a tsunami affected sedimentary records.
Another problem with the impact extinction theory is that the Chicxulub impact may not have had the radical extinction effect on plants and animals as we previously thought. The researchers found a total of 52 fossilized species that appeared to be happily living before the layer of impact sediment… and the same 52 species appeared to by happily living after the layer of impact sediment.
“We found that not a single species went extinct as a result of the Chicxulub impact.” — Gerta Keller
Although this is some very interesting research, sure to turn dinosaur extinction theory on its head, if an asteroid didn’t kill the dinosaurs, what did?
Keller points the finger at volcanic activity. Massive amounts of dust and gas was released from eruptions at the Deccan Traps in India 65 million years ago, possibly plunging the planet into a prolonged period without Sun.
Update: With any scientific debate, there are details behind new research that may not be immediately apparent. As Ethan Siegel highlights in a recent ScienceBlogs article (What Wiped Out The Dinosaurs?, April 27th), the evidence for an asteroid impact wiping out the dinosaurs is overwhelming. Just because there appears to be a discrepancy in the location of impact sediment and K-T boundary does not mean the impact-extinction theory is wrong in any way. Keller’s research is an interesting investigation, worthy of further study, but this doesn’t change the fact that huge global damage would have been caused by the Chicxulub impact. This remains the prime candidate as to why the dinosaurs were suddenly made extinct 65 million years ago.
If Earthlings discovered a large asteroid heading towards our planet, how would we react? But more importantly would the space agencies and/or world governments be prepared for such an event? “Mankind is now technically able to predict, sometimes several decades in advance, the trajectory of Near Earth Objects (NEOs),” said Frans von der Dunk, professor of space law at the University of Nebraska-Lincoln. “Additionally, existing space technology could deflect the vast majority of threatening asteroids.” But even if a threatening object is discovered, von der Dunk said no mechanism exists for effective international decision-making on how to deal with a threat. To examine these issues, UNL hosted a conference on April 23 & 24, “Near-Earth Objects: Risks, Responses and Opportunities,” to look at the legal and institutional challenges of creating an international protocol of dealing with NEOs.
NEOs are an increasing area of concern among the world’s space scientists. Many experts believe that over the next 15 years, advances in technology will allow for the detection of more than 500,000 NEOs – and of those, several dozen will likely pose an uncomfortably high risk of striking Earth and inflicting local or regional damage.
Concept for a possible gravity tractor. Credit: JPL
Right now, if an Earth-bound asteroid were discovered, we have the technology today to send a spacecraft to an asteroid to act as a gravity tractor, or to impact the asteroid to alter the space rock’s trajectory. Other current options are to use a mass driver, rocket engines or a solar sail to push the asteroid on a different course.
But, von der Dunk told Universe Today, completely lacking is an official structure for preparation, planning and timely decision-making in the event of a potential collision, as well as what country or entity would have the authorization and responsibility to act, or take care of the financial implications.
Von der Dunk hopes the conference will shed more light on these issues.
“We hope to accomplish two things,” he said. “One is to generate more attention to this problem and make sure it will remain on people’s agenda, even though we recognize there are more immediate pressing global concerns, such as climate change or economic issues.” But even in terms of economic concerns von der Dunk said making decisions now about asteroid deflection is worthwhile because we can develop a proper process which could save millions or billions of dollars.
Instead of using scenarios like the movies “Deep Impact” or “Armageddon” – the typical Hollywood approach, von der Dunk said, we could take action early in the game. “Gravity tractors only require a couple of million dollars in cost.”
The other goal of the conference is to shed more insight into the protocols and legal issues of an Earth-bound asteroid. “What protocols should be followed to tackle the problem, what threshold would be sufficient to start taking action, who should take the action, who should pay for it, and who would be liable if something goes wrong? Those are the types of issues that we are putting on the table.”
While the actual capacities to take action against an NEO are still limited to a few space-fairing nations, von der Dunk said there’s also the possibility of global political fallout if there is a divergence between them. “One country may decide at a certain point not to bother about it, while another country with a greater chance of being hit, might want to take action,” he said. “The idea is to create a protocol and procedure of how we deal with these things to try to avoid the worst political fallout from happening, so if tomorrow, or ten years or hundred years from now and we know we have an asteroid heading in our direction we know we can actually do something about it and have a general legal understanding of how things will work.”
Von der Dunk specializes in space law and is a member of a panel created by the Association of Space Explorers, chaired by Apollo astronaut Rusty Schweickart. Von der Dunk has looked at what current protocols could be used in the event of an impending asteroid hit, but says nothing really exists. “I have looked at this issue and it quickly became clear to me that the current international treaty dealing with liability simply never foresaw the possibility of something going wrong in a case such as if the asteroid were deflected and then hit a different part of Earth than where it originally was going to hit,” he said. “And then a lawyer would be faced with taking some existing clauses which come closest and stretching them beyond what they were ever meant to be. We need to consider drafting a new international treaty agreement for this. At the conference we will discuss what such a treaty should look like, how should we phrase it, what particulars should be targeted.”
A number of members of Schweickart’s panel will be presenting at the conference, as well as “speakers from outside the community to broaden the issue,” von der Dunk said. “We will take stock of what is happening now, is it going in the right direction, discuss in more detail some of the legal issues such as liability, and add to that something in a more positive tone. Asteroids are not only about ‘deep impact,” but also about the possibilities of creating access to potentially very valuable minerals. If someone is going to mine an asteroid, we need the appropriate legal framework for that.”
Von der Dunk said attendees of the conference are lawyers, policy makers, members of think-tanks, and government representatives. Other speakers include former NASA astronaut Tom Jones, and Vice-Chairman of the United Nations Committee on the Peaceful Use of Outer Space (COPUOS), Ciro Arevalo.
The conference ends today with a simulation led by Dr. Eligar Sadeh of the Eisenhower Center For Space & Defense Studies of what actions and decisions would need to be made in the event of the discovery of an Earth-bound asteroid. “From this we may come to an understanding of why certain decisions have to be made at a certain point in time and how the consequential logic of a process like that flows,” von der Dunk said.
Von der Dunk is the leading academic expert on space law, and UNL’s College of Law is has the only master of laws program in space and telecommunications law offered in the United States.
Young asteroid tanning is big business in the Solar System (ESO)
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If you stay out in the Sun too long, you’ll eventually get a suntan (or sunburn); your skin will also get damaged and it will show signs of ageing faster. This might sound like a sunblock ad, but the same principal holds true for the small chunks of rock floating around in the Solar System. Yes, a young asteroid’s surface will age prematurely, but it’s not caused by the Sun’s ultraviolet rays, it’s caused by the solar wind…
Within a million years, an asteroid can turn from lunar grey to Martian red when left out in the solar wind. A million years is a tiny amount of time in relation to the Solar System’s lifetime. Why is this important? European Southern Observatory (ESO) researchers have realized that this finding will not only help astronomers relate an asteroid’s appearance with its history, but it can act as an indicator for after effects of impacts with other asteroids.
It turns out that the study of “space weathering” is fairly controversial, scientists have been mulling it over for a long time. Central to the problem is the fact that the appearance of the interior of meteorites found on Earth are remarkably different to the asteroids we see in space; asteroids are redder than their meteorite cousins. So what causes this redness?
“Asteroids seem to get a ‘sun tan’ very quickly,” says lead author Pierre Vernazza. “But not, as for people, from an overdose of the Sun’s ultraviolet radiation, but from the effects of its powerful wind.”
Although this is an interesting discovery, the speed at which the “tanning” occurs is astonishing. After an asteroid collision, fresh asteroid chunks are created with new surfaces. Within a million years these young asteroid surfaces will turn a dirty shade of red as the surface minerals are continuously battered by ionizing solar wind particles. “The charged, fast moving particles in the solar wind damage the asteroid’s surface at an amazing rate,” Vernazza added.
Naturally, a lot depends on the mineral composition of an asteroid’s surface, influencing how red its surface will become, but most of the tanning effect occurs in the first million years. Afterwards, the tanning continues, just at a slower rate.
Asteroid observations also reveal that the high proportion of “fresh surfaces” seen on near-Earth asteroid probably isn’t down to asteroid collisions. The frequency of collisions is far lower than the sun-tanning timescales, meaning that there shouldn’t be any “fresh surfaces” to be seen. It is far more likely that the upper layers of asteroids are renewed through planetary encounters, where the gravitational field of planets “shake off” the tanned dust.
It may not look like much, but that drawing could save a life someday — or 7 billion.
David French, a doctoral candidate in aerospace engineering at North Carolina State University is proposing a new tool for the anti-asteroid arsenal.
French said his PhD advisor Andre Mazzoleni, an associate professor of mechanical and aerospace engineering at the university, were not beholden to grant funds and “we just decided to go off on a direction that’s interesting and exciting.”
Mazzoleni has worked with tethers in other applications, and the two have now come up with a way to effectively divert asteroids and other threatening objects from impacting Earth by attaching a long tether and ballast to the incoming object.
By attaching the ballast, French explains, “you change the object’s center of mass, effectively changing the object’s orbit and allowing it to pass by the Earth, rather than impacting it.”
NASA’s Near Earth Object Program has identified more than 1,000 “potentially hazardous asteroids” and they are finding more all the time. “While none of these objects is currently projected to hit Earth in the near future, slight changes in the orbits of these bodies, which could be caused by the gravitational pull of other objects, push from the solar wind, or some other effect could cause an intersection,” French explains.
He said it’s hard to imagine the scale of both the problem and the potential solutions — but he points out that some asteroid impacts on Earth have been catastrophic.
“About 65 million years ago, a very large asteroid is thought to have hit the Earth in the southern Gulf of Mexico, wiping out the dinosaurs, and, in 1907, a very small airburst of a comet over Siberia flattened a forest over an area equal in size to New York City,” he said. “The scale of our solution is similarly hard to imagine.”
The idea is to use a tether somewhere in length between 1,000 kilometers (621 miles; roughly the distance from Raleigh to Miami) to 100,000 kilometers (62,137 miles; you could wrap this around the Earth two and a half times).
Other ideas that have emerged sound no less extreme, French notes. Those include painting the asteroids in order to alter how light may influence their orbit, a plan that would guide a second asteroid into the threatening one, and nuclear weapons.
“They probably all have their merits and drawbacks,” he said. “Nuclear weapons are already accessible; we’ve already made them. I can look at my own idea and say it’s long duration and very trackable.”
A tether effort could last in the ballpark of 20 to 50 years, he said, depending on the size and shape of the asteroid and its orbit, and the size of ballast.
French acknowledges there are “technical barriers that have to be surpassed.”
“First, you would have to mitigate the rotation of the asteroid,” he said, adding that the crescent-shaped piece connecting the poles on a globe might make a good conceptual model for a tether anchor, because it would allow for the asteroid’s rotation.
Another problem is the composition,” he added. “Some asteroids are just rubble piles.”
French said his idea was never to have all the kinks worked out on his model before presenting it; he just hoped to add another option to the asteroid-preparedness table.
“We’re opening up the concept, and we invite the broader scientific community to help us solve the issues,” he said.
Source: An NC State press release, via Eurekalert, and an interview with David French.
