Tag Archives: asteroid impact

It isn't hyperbole to say, the survival of our species may depend on a sucessful method of preventing an asteroid impact. (Robert Lea)

Playing Asteroids is No Game: Humanity’s Future Could Depend on Diverting Asteroid Impacts

Earth is surrounded by thousands of Near-Earth Objects, a few of these are potentially hazardous, and fewer still which are classified as planet killers. An impact from the latter carries implications as severe the name suggests. Clearly, we need a method of diverting such objects. In fact, it isn’t hyperbole to say, the survival of our species may depend on it. 

News stories about massive objects skirting close to Earth are pretty common in the media, as a timely example, in April news organisations across the globe reported a mile-wide asteroid passing with just 3.9 miles of our planet. Fortunately, the rock identified as (52768) 1998 OR2, posed no real impact threat. 

 (52768) 1998 OR2 passed within 3.9 miles of Earth last month. A near miss, but it no-means the only NEO out there. @AreciboRadar/Twitter/PA
(52768) 1998 OR2 passed within 3.9 miles of Earth last month. A near miss, but it no-means the only NEO out there. @AreciboRadar/Twitter/PA

Yet, our planet is scarred with the evidence of previous collisions with such objects. The most frequently thought of example is the impact that wiped out the dinosaurs 66-million-years-ago, the scale of which can be seen by examining the Chicxulub crater centred on the Yucatán Peninsula in Mexico. 

The dinosaur destroying asteroid is estimated to have been around 10–15 km in width, but the crater it created was 150 km in diameter and the debris in threw into the atmosphere blacked out the Sun for months as well as triggering massive tidal waves which battered the entire continent of America and other deadly secondary effects. 

Even looking beyond the surface of our own planet, the Moon’s geology is strongly shaped by a history of asteroid impacts, as are the faces of other planets in the solar system.

 Animation depicts a mapping of the positions of known near-Earth objects The animation depicts a mapping of the positions of known near-Earth objects (NEOs) at points in time over the past 20 years and finishes with a map of all known asteroids as of January 2018. Asteroid search teams supported by NASA’s NEO Observations Program have found over 95 per cent of near-Earth asteroids currently known. There are now over 18,000 known NEOs and the discovery rate averages about 40 per week.  (NASA/JPL-Caltech)
Animation depicts a mapping of the positions of known near-Earth objects The animation depicts a mapping of the positions of known near-Earth objects (NEOs) at points in time over the past 20 years and finishes with a map of all known asteroids as of January 2018. Asteroid search teams supported by NASA’s NEO Observations Program have found over 95 per cent of near-Earth asteroids currently known. There are now over 18,000 known NEOs and the discovery rate averages about 40 per week. (NASA/JPL-Caltech)

The truth is the Earth exists within the vicinity of thousands of Near Earth Objects (NEOs), many of which carry the risk of colliding with our planet. If one of these asteroids — referred to as Potentially Hazardous Objects (PHOs) —did strike our planet, it could cause devastating effects including massive property and infrastructure damage, as well as significant loss of life. Within the population of PHOs is a smaller population of objects which could, much like the asteroid that wiped out the dinosaurs and 75% of all other animal life, trigger a major extinction event. 

It should be abundantly clear that developing a method of mitigating the impact of one of these objects by knocking off its collision course is imperative. Asteroid mitigation has been identified as one of NASA’s ‘Space Technology Grand Challenges’ — problems that require cutting -edge scientific solutions.  Indeed, many other institutions across the globe are working on their own mitigation strategies, each of which comes with its own unique pros and cons.

Should the possibility of an asteroid impact arise, the governments of Earth will be faced with a stark choice. Depending on a number of factors and characteristics they will have to choose between an instantaneous approach or a more gradual method .

Some of these methods and their potential successes and failures are listed below, starting with the more extreme, blunt solutions to asteroid mitigation.

The direct approach

There is probably nothing that constitutes ‘direct approach’ more than tossing a nuclear explosion at a problem. Thus, it may come as no surprise that many research hours have been devoted to devising a scheme in which an asteroid can be diverted with the aid of a nuclear weapon. 

The stark truth of the matter is, if the NEO is spotted on a collision course with Earth with less than 10 years warning, direct intercept with such a device may well be our only hope of diversion. Further to this, these ‘short lead time’ encounters are currently the most likely probable scenarios involving Earth and an encounter with a PHO. 

(NEOSheild 2/ EU Horizons)

Hitting an asteroid with a nuclear weapon obviously provides mitigation by imparting energy to the object to divert it, even if only slightly. Another way of doing this is by slamming the PHO with another object. Instead of imparting nuclear energy, this kinetic impactor is a spacecraft that hits the PHO at a high velocity transferring momentum to it changing its velocity and hopefully diverting its course. 

Interestingly, this method requires the use of a reconnaissance craft to first map the characteristics of the PHO, such as its orbit, size, shape and rotation, even its chemical make-up so that the impact can be perfectly calibrated. One kinetic impactor system currently being researched is the NEOShield-2, which involves the reconnaissance craft launching together with the impactor. The two craft, initially stacked together, will separate with the reconnaissance craft hopefully reaching the asteroid first, and the impactor following through when details are collected.

In March last year, NASA unveiled early plans for a ‘best of both worlds’ mission that unites a kinetic impactor and nuclear device for the purpose of asteroid diversion. The Hypervelocity Asteroid Intercept Vehicle (HAIV) mission craft consists of a fore-body kinetic impactor which smashes into the asteroid, and an aft-body which when deposits a nuclear charge. The beauty of this arrangement is that if the impactor can create a crater in the asteroid, the nuclear blast will occur beneath the surface of the NEO, imparting more energy than a glancing blow could. 

An artist's interpretation of how the  Hypervelocity Asteroid Intercept Vehicle (HAIV) will divert an asteroid (EADS)
An artist’s interpretation of how the Hypervelocity Asteroid Intercept Vehicle (HAIV) will divert an asteroid (EADS)

Both of these missions are still at least ten years from reaching a viable testing-stage. And there is another, deeper problem.

The danger of any direct impact mission is that it could fragment the asteroid in question, especially as some asteroids are merely a loose conglomeration of smaller bodies. This could result in Earth being bombarded with a multitude of meteors — each causing untold destruction. Even worse, if the NEO in question has a core of pure iron, even a nuclear device/ kinetic impactor double-punch is unlikely to divert it.

This is the case if we have little notification of an asteroid’s impact — less than ten years, what if space agencies are granted more time to divert the PHO? 

Diverting asteroids — the gentle way

Methods that require a long lead time tend to be more gentle than short-lead time techniques, and interestingly, also tend to exploit our understanding of physics and energy way beyond that of kinetic energy alone. 

Perhaps the most well-known long-lead-time diversion method involves using gravitational energy to alter the orbit of a NEO. It’s also the most ‘gentle’ of even the long-lead-time methods, not even requiring contact with the asteroid. 

A gravity tractor slowly influences the orbit of a NEO. It is a method that requires a long-lead-time. (NASA)

The idea is to place a spacecraft in orbit alongside a PHO over a period of many years or even decades. The gravitational influence of the gravity tractor gradually pulls the asteroid off course, thus preventing a close encounter with the earth. The gravity tractor method would work on asteroids of all compositions, and shapes, even if they are collections of smaller bodies, loosely gravitationally bound. There is a limit to the size of an asteroid that could be gravitationally pulled, however, making this a technique that is unlikely to tug a planet killer.

The theory behind gravity tractors is so robust and the control it allows is so precise, that it has even been suggested that the method could be used to place asteroids in positions where they could be beneficial for humanity — allowing them to be used for research or even commercial purposes. 

A less ‘contactless’ version of the gravity tractor approach, involves using an actual physical tether to divert the asteroid to a higher orbit. The tethered object would be smaller than the NEO and could either be a spacecraft launched from earth, or another NEO. The concept behind this method is that attaching the larger body to a smaller one changes the centre of mass of the body and thus adjusts its orbit. 

One potential drawback of the system is that is likely to require some pretty intensive surface operations, especially if the tether is to be attached to two NEOs. It also carries the risk of the tether becoming tangled, meaning before any operation was undertaken the motion of the PHO would have to be known precisely.

Though the message is clear if the paint method is going to work, researchers may want to consider a more even coating. (Robert Lea)

One of the most ‘out there’ ideas to divert an asteroid on course to strike the Earth involves spraying a thin layer of powdered paint on one side of an asteroid and allowing radiation from the Sun to alter the asteroid’s orbital path. The paint coating changes the amount of radiation reflected by the asteroid’s surface. This leads to unequal heating within the body, and thermal particles being ejected more strongly on one-side than the other. As a result, a strong net force is created which over the course of several years can shift the asteroid’s orbit. 

Again, these methods which are just the tip of the iceberg in terms of mitigation strategies, are still very much in the developmental phase, and moving them into the test stages could be a matter of some urgency. 

It’s a matter of ‘when’ not ‘if’

“An asteroid collision would be something against which we have no defence… This is not science fiction; it is guaranteed by the laws of physics and probability.” 

— Stephen Hawking, Brief Answers to Big Questions, [2018].

If 2020 teaches humanity nothing else it should impart the lesson that we are simply not ready to deal with some of the hazards that nature can and will throw at us. If the strategies put in place to deal with a potential pandemic strike us as slap-shot, underwhelming and inadequate, the provisions taken thus far to prevent an asteroid strike fall considerably short of even this. 

The only real hope we have of diverting a PHO as things currently stand is spotting it well in advance and getting a satisfactorily long-lead time. But still, there is very little in the way of infrastructure in place to deal with such an eventuality.

Just as historians may one day look back at the MERS and SARS outbreaks as stark warnings of a coronavirus pandemic that governments around the world failed to take heed of, so too they may consider the close brush with 99942 Apophis as a warning to prepare for asteroid incursion.

The NEO with a diameter of 370 meters caused concern in December 2004 when observations indicated there was a 2.7% chance that on a future sweep past our planet in April 2029, it would strike the planet. Estimations changed between 2004 and 2006, first appearing that 99942 Apophis would miss both the Earth and the Moon, with the possibility that during the 2029 encounter it would pass through a gravitational keyhole, that would result in it impacting the planet in 2036. 

Fortunately, by 2008 it had been determined that the asteroid would both miss the Earth and the 1km gravitational keyhole that would shift it onto a collision course in 2036. As it currently stands, 99942 Apophis has a 1 in 150,000 chance of colliding with our planet in 2068. Pretty slim. But, unfortunately, 99942 Apophis is hardly the only PHO out there, and there are many that we have yet to discover. 

The trail in the key over Russia left by the Chelyabinsk Meteor. ( Alex Alishevskikh/ CCbySA2.0)

The Chelyabinsk meteor provides a stark example of such an unknown object. The object with a 20-meter diameter entered Earth’s atmosphere over Russia on 15th February 2013. Due to its high velocity and shallow entry angle, the meteor broke apart in an airburst at around 30 km over the Chelyabinsk Oblast. The energy it released was so potent that the airburst was brighter than the Sun, and could be seen from a distance of 62 miles away.

Over 1,500 people were injured as a result of the blast. 

Should it have actually hit the surface of our planet, impacting in a region with a population of 3.5 million people, it would have been the equivalent of the detonation of around 500 kilotonnes of TNT — around 33 times the energy released by the detonation of the atomic bomb that devastated Hiroshima. 

We had literally no idea it was there. We still don’t know where it came from.

The real key to asteroid mitigation is increased investment in space science and infrastructure. Developing mitigation strategies isn’t enough, as Chelyabinsk shows, we need to also focus on detection methods.

Hopefully, this is a lesson that won’t be learned in hindsight, because as Hawking predicted in his final work shortly before his death in 2018, this is inevitable. And as estimates made using Earth’s history as a guide, collisions with an object of the size of 99942 Apophis occur roughly once every 80,000 years. That means we are currently well-overdue. 

Sources and Further Reading 

Sugimoto. Y, Radice. G, Ceriotti. M, et al, Hazardous Near-Earth asteroid mitigation campaign planning based on uncertain information on fundamental asteroid characteristics, Acta Astronautica, [2014]

Foster. C, Bellerose. J, Mauro. D, et al, Mission concepts and operations for asteroid mitigation involving multiple gravity tractors, Acta Astronautica, [2013]

Lu. E, The Project B612 Concept, ARC, [2012]

Dearborn. D, 21st Century Steam for Asteroid Mitigation, ARC, [2012]

Spitale. J. N, Asteroid Hazard Mitigation Using the Yarkovsky Effect, Science, [2012]

Belton. M. J. S, Morgan T. H, Samarasinha N. H, Yeomans D. K, Mitigation of Hazardous Comets and Asteroids, Cambridge University Press. 

Hawking. S, Brief Answers to Big Questions, Hodder & Stoughton, [2018].

Kinetic impactor
The principle of the kinetic impactor mitigation method is that the NEO or Asteroid is deflected following an impact…www.neoshield.eu


NASA – National Aeronautics and Space Administration
By providing strategic guidance, the Strategic Integration (SI) Office in collaboration with Stakeholders from the…www.nasa.gov


An Innovative Solution to NASA’s NEO Impact Threat Mitigation
An Innovative Solution to NASA’s NEO Impact Threat Mitigation Grand Challenge and Flight Validation Mission…www.nasa.gov

Fossil Friday: paleontological trove shows how mammals took over from the dinosaurs

More than 40 mammal skulls have been dug out of Corral Bluffs, a fossil site in Colorado. Credit: HHMI TANGLED BANK STUDIOS

One gloomy day about 66 million years ago, disaster struck our planet. That day, an asteroid hit offshore Mexico’s Yucatan peninsula with the force of 10 billion Hiroshima bombs. As a result of the devastating impact, 75% of all animal and plant species became extinct — including all non-avian dinosaurs.

But, in the wake of the dinosaurs’ downfall, a new lineage was ready to fill in the ecological void and dominate the globe’s surface. How exactly mammals swept in during these chaotic times, however, has always been somewhat of a mystery since the fossil record in the first million years after the asteroid impact is rather poorly documented.

The discovery of a trove of exceptionally preserved fossils might change all that. Paleontologists have recently described the remains of 16 mammalian species, as well as turtles, crocodilians, and plants, encased in hundreds of fossils unearthed in Colorado.

Corral Bluffs, near Colorado Springs. Credit: HHMI TANGLED BANK STUDIOS

The unlikely find comes from a site at Corral Bluffs, an outcrop in the Denver Basin, just east of Colorado Springs, not famous at all for fossils. But Tyler Lyson, a paleontologist at the Denver Museum of Nature and Science, struck gold there, finding an array of mammalian species that lived from a couple of thousand years to a million years after the killer asteroid impact.

“I split open a concretion and saw a mammal skull smiling back at me,” Lyson said. “And then I looked around and saw concretions just littering the landscape and was like, ‘oh man, here we go.’ Sure enough, we found like four or five mammal skulls within a few minutes. That was one of the most remarkable moments in my life.”

These fossils showed the remarkable growth spurt that mammalians went through after they were free to occupy ecological niches previously dominated by dinosaurs. While the biggest mammal that escaped the mayhem weighed no more than a pound (0.5kg), just 100,000 years later there were 13-pound (6-kg) specimens. Another 200,000 years later, the largest mammals had triple that weight.

Pictured: Loxolophus, a raccoon-sized omnivorous mammal that thrived only 300,000 years after the asteroid impact. HHMI TANGLED BANK STUDIOS

And it wasn’t just the demise of dinosaurs that helped mammals. The asteroid impact also changed the plant landscape, with trees from the walnut family becoming more common, replacing the previously palm tree-dominated landscape. This was very advantageous to early omnivorous mammals, who could now supplement their insect diet with more nutritious plant-based protein.

The largest mammal from this time period was Carsioptychuswhich is a distant relative of today’s hoofed mammals.

“Its premolars were very large and flat, with many weird folds, so there has always been speculation they may have fed on hard objects, such as the nuts trees in this family produce,” Lyson told National Geographic.

Another 400,000 years later, some mammals could weigh over a hundred pounds (45 kg). This period, the researchers noted, coincides with the appearance of the first plants from the bean family, whose leaves and protein-rich seed pods helped many herbivores thrive.

Besides free ecological niches and new nutritional sources, the rise of the mammals may have also been accelerated by three periods of significant warming in the million years after the mass extinction.

The idea that mammals quickly recovered after the most recent mass extinction and grew rapidly in size is not new. Where this new study shines, however, is in the fine details that describe how this transition went about. What’s more, this may just be the beginning. The newly described fossils come from a single geographical site, but there’s much to learn by including more diverse sites. Finding specimens that lived close to the post-asteroid period is not easy, but there is now a new impetus to look for them.

The findings appeared in the journaScience. A one-hour documentary produced by NOVA about the discovery, called “Rise of the Mammels” will also be available to stream on the PBS site and will air on PBS the evening of October 30.

The giant asteroid impact that wiped out dinosaurs made the rock beneath behave like a liquid

Artist rendering of Chicxulub impact. Credit: NASA

Artist rendering of Chicxulub impact. Credit: NASA

Around 66 million years ago a 6-mile wide asteroid hit the planet near the town of Chicxulub, Mexico. The impact resulted in a huge explosion and created a 100-mile crater. Debris was flung in the air at a height twice that of Mount Everest, and a plume of dust and ash engulfed the whole planet, shielding the sun and causing nuclear winter-like effects. Countless species were eradicated, among them all the dinosaurs (except birds).

Among scientists, there’s a debate as to how all of this mayhem played out. There are two trains of thought. The first suggests that once the asteroid hit Earth, the immediate subsurface melted, moving material from side to side. The material then moves towards the center and becomes uplifted creating the familiar ‘peak rings’ we can see to this day at the Chicxulub crater. The other hypothesis is far more dramatic, proposing that fluid-like material was propelled from deep beneath the Earth’s crust.

Sean Gulick, a geophysicist at the University of Texas, Austin, and colleagues, traveled to Chicxulub and drilled the crater. Immediately after they recovered the first cores, there was no doubt in the researchers’ minds that the impact physics were described by ‘hypothesis #2’.

The Cretacious Period, the geological timeframe during the asteroid impact, is characterized by abundant limestone. However, the cores were made of pink granite which is typically found deeper beneath the Earth.

“And it was just plain as day,” he says, “and everybody staring at it went, ‘Wow, there’s the answer. It’s from deep,'” said Gulick.

Here’s how Gulick describes the mass extinction triggering event, liking it to a rock hitting a water pond.

“It makes a hole initially as the rock penetrates into the pond. And the sides will sort of collapse inward toward the hole while the center kind of rebounds up like a big water droplet rising up.”

“If you picture all of this happening in a slightly slower-moving fluid than water would be, you can envision that the center that rebounds upwards and splashes upwards would kind of collapse outwards. So just as the sides are falling in, this rebounding center is sort of collapsing outwards to create … this ring of mountains, made from material that ultimately came from fairly deep.”

And it all took no more than 10 minutes.

That’s not to say that all the physics behind the impact are solved. Many questions remain unanswered. For instance, although the rocks behaved like a fluid, they remained solid. The huge energy from the impact altered the rocks’ cohesion causing them to move like a slow-moving fluid, though.

Next, the researchers plan to analyze in greater detail the pink granite which came from 6 miles beneath the surface. They think it might provide hints as to how life rebounded after the unfortunate event.

Findings appeared in Science.

The Permian extinction – caused by “lemon juice” acidic rain ?

  • The Permian extinction was the biggest extinction ever, killing 96% of all marine species and 70% of terrestrial vertebrates
  • Possible causes include: impact, loss of oxygen and volcanic eruptions
  • Researchers tested the validity of the last hypothesis, finding it likely

The biggest extinction – ever

Artistic representation of the Permian plants, affected by acidic rain. Via MIT.

Artistic representation of the Permian plants, affected by acidic rain. Via MIT.

MIT Researchers believe that rain as acidic as undiluted lemon juice may have contributed to massive extinction that took place at the end of the Permian, 252 million years ago. These acidic rains may have played a part in killing off plants and organisms around the world during what is regarded as the most severe extinction the world has ever gone through.

It was so severe that it killed 96% of all marine species and 70% of terrestrial vertebrate species – and it took life about 10 million years to recover from it!

Pin-pointing the exact cause (or causes) of the Permian–Triassic extinction event is a difficult undertaking because it took place so long ago that most of the evidence was destroyed, eroded or buried away. There’s a major scientific debate, centering on several potential causes:

– an asteroid impact, similar to what wiped off the dinosaurs at the end of the Mesozoic
– a gradual, global loss of oxygen in the oceans
– a host of environmental changes caused by massive volcanic eruptions in today’s Siberia.

Now, researchers at MIT have simulated the final possibility. They created a climate model for a Permian world in which massive eruptions took place, ejecting volcanic gases (including sulfur) into the atmosphere. They found that if this were the case, then sulfur emissions were significant enough to create widespread acid rain throughout the Northern Hemisphere, with pH levels reaching 2 — as acidic as undiluted lemon juice. These acidic rains alone would have been enough to maim virtually all living plants, halting their growth and development, ultimately leading to the massive extinction.

“Imagine you’re a plant that’s growing happily in the latest Permian,” says Benjamin Black, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “It’s been getting hotter and hotter, but perhaps your species has had time to adjust to that. But then quite suddenly, over the course of a few months, the rain begins to sizzle with sulfuric acid. It would be quite a shock if you were that plant.”

Volcanoes in Siberia

The world at the time of the Permian extinction. Highlighted are the biggest igneous provinces - notice Siberia.

The world at the time of the Permian extinction. Highlighted are the biggest igneous provinces – notice Siberia. Source

It’s hard to wrap your mind around such a dramatic event as this one, and in a way, it’s hard to believe that it was just a single cause – it seems pretty likely that at least a couple of separate, unfortunate elements converged towards this extinction. Geologists analyzing the rocks in Siberia found evidence of immense volcanism that came in short bursts beginning near the end of the Permian period and continuing for another million years. The volume of the magma was several million cubic kilometers, enough to put a thick cover over all the United States. But even so, were these eruptions enough on their own?

The group simulated 27 scenarios, each approximating the release of gases from a plausible volcanic episode, including a wide range of gases in their simulations, based on estimates from chemical analyses and thermal modeling. They then modeled the interaction between these gases and the atmosphere, ultimately, how they were absorbed and then came down as low pH rain.

They found that with repeated bursts of volcanic activity, the acidic rains had a dramatic effect on land plants, probably going way past the point they could handle.

“Plants and animals wouldn’t have much time to adapt to these changes in the pH of rain,” Black says. “I think it certainly contributed to the environmental stress which was making it difficult for plants and animals to survive. At a certain point you have to ask, ‘How much can a plant take?’”

Now, Black hopes paleontologists and geochemists will consider his own results and compare them with their own observations of the Permian extinction, in order to paint a more accurate picture.

“It’s not just one thing that was unpleasant,” Black says. “It’s this whole host of really nasty atmospheric and environmental effects. These results really made me feel sorry for end-Permian organisms.”

Asteroid that wiped out the dinosaurs may have been a set of binary asteroids

The (still debated) asteroid that slammed into the Earth 65 million years ago and played a crucial role in wiping dinosaurs out, may have actually been a binary system- 2 asteroids engaged in an orbit around each other.

Double trouble

binary asteroid

The surprising claim comes from analyzing the proportion of asteroid craters on Earth that were formed from binary impacts; the results also add to the concern of those who fear catastrophic collisions in future. Here’s the deal: our planet bears the scars of twin-asteroid impacts just like single impact craters; a good example is the Clearwater Lakes near Hudson Bay in Canada, formed 290 million years ago. However, examples like this are pretty rare: 98% of all craters are single impact, with only 2 in 100 coming from a binary system.

“It’s been known for 15 years that about 15 per cent of near-Earth asteroids are binary,” says Katarina Miljković at the Institute of Earth Physics in Paris, France.

So, all things being equal, if 15 percent of all asteroids are binary, why aren’t 15 percent of craters binary ? Miljković and her colleagues believe they have found the answer: they ran computer simulations and found that even binary systems often form a single crater, mimicking a single asteroid impact.

Considering that the crater is typically 10 times bigger than the asteroid, this seems intuitive. The team found that only unusual cases involving two small, widely separated asteroids are guaranteed to form a pair of distinct craters. Their simulations confirmed that such situations are just rare enough to explain why paired craters account for only 2 per cent of all Earth’s craters.

Symmetry and non-symmetry

crater_c

The next step was, of course, seeing if single craters caused by single asteroids could be differentiated by single craters caused by binary asteroids. What they found is that it is possible to identify which of Earth’s single craters had binary origins – these craters should be subtly asymmetrical – a feature displayed by the crater near Chicxulub in Mexico – thought to lead to the extinction of the dinosaurs.

“The Chicxulub crater shows some important asymmetries,” says Miljković. “It is worth considering that it was formed by a binary asteroid.”

Geophysical research is key to studying such impact craters – gravity measurements are a great indication for this, especially for asteroids which are still buried. Studying the gravity anomalies supported this theory, as Petr Pravec at the Academy of Sciences of the Czech Republic in Ondrejov explained.

“The signatures also suggested that the Chicxulub crater might have been formed by a binary asteroid impact,” he says.

So what did Chicxulub looked like? Most likely, if it was indeed a binary, the 180 km radius of the crater suggests the combined diameter of the two asteroids being somewhere around 7 to 10 km – the same diameter as the single rock previously imagined to be the culprit.

Twice the asteroid – twice the problem?

If this is true, what does it mean for future impact mitigation and preparation? Even with today’s technology, we have what it takes to totally avoid the dangers posed by an asteroid, but what happens with a binary?

“I am not sure if any of the proposed asteroid deflection techniques could deflect both binary components with a single weapon,” says Katarina Miljković at the Institute of Earth Physics in Paris, France, who led the new study.

However, researchers seem prepared for this possibility as well. Don Yeomans of NASA’s Near Earth Object Program thinks that won’t be a problem for a future asteroid-deflecting spacecraft.

“There is a slim chance that the autonomous navigation camera might be confused with two images in its field of view, but I should think these issues would be easily overcome,” he says.

Source

Doomsday part 6: asteroid strike

mayan-doomsday-special-zmescience

You’ve seen it on the news, so you know it’s true. Your 8 o’clock special news report showcases in a Mayan Apocalypse special a computer simulation of a massive meteor or asteroid impacting Earth causing world doom. There’s no mention anywhere in any Mayan records or myths that the end of the Mayan calendar is associated with an impact from a cosmic body, still the media seems to be obsessed with imagery of asteroid impacts whenever world annihilation is  mentioned. Still would it be possible?

Reality check

Thanks for government and private agencies that monitor bodies on a possible collision course with Earth, for the year of 2012 there aren’t any reported marginally real threats of an asteroid impact. In fact, scientists are capable of predicting threatening orbits with plenty of time in advance, a number of preventive measures can then be taken to avoid any kind of catastrophe  The most threatening asteroid set to come nearby Earth is Apophis in 2036 when it will flyby our planet at a mere 18,300 miles (30,000 kilometers). There’s a  1 in 250,000 possibility the asteroid might hit Earth, even then however the damage would affect a surface roughly the size of Germany, not worldwide.

NASA reports:

The Earth has always been subject to impacts by comets and asteroids, although big hits are very rare. The last big impact was 65 million years ago, and that led to the extinction of the dinosaurs. Today NASA astronomers are carrying out a survey called the Spaceguard Survey to find any large near-Earth asteroids long before they hit. We have already determined that there are no threatening asteroids as large as the one that killed the dinosaurs. All this work is done openly with the discoveries posted every day on the NASA Near-Earth Object Program Office website, so you can see for yourself that nothing is predicted to hit in 2012

 

Read about other popular Mayan doomsday “prophecies” from our debunking series:

Artist impression of the Apophis asteroid.

Forget about nukes, dangerous asteroids could be deflected with paintball pellets

Artist impression of the Apophis asteroid.

Artist impression of the Apophis asteroid.

No, this isn’t one of those misleading headlines. A MIT graduate student has recently proposed that bombarding an asteroid’s surface with paintballs could throw it off course from a possible collision orbit with our planet, by harnessing solar pressure.

The paintball cloud would hit the targeted asteroid and cover it in paint – white paint to be more specific. The pellets would cover the space rock’s surface as much as possible, doubling the amount of reflected sunlight. This, coupled with the slight orbit deviation from the pellet impact, would avert the threat of an asteroid impact, according to Sung Wook Paek’s computations.

Paek tested out his theory and ran a simulation on the asteroid Apophis, a 270 meter wide space rock often cited as a possible Earth colliding body sometime in the following decades. The next time it will pass Earth is 2029, and again in 2036. Apparently, 5 tones of paint would be required to roughly cover all of Apophis’ surface. Don’t imagine, however, that this method would immediately nudge such a huge asteroid. According to Paek, it would take 20 years for solar radiation pressure to successfully pull it off its Earth-bound trajectory.

It sounds like an interesting, maybe even viable option, if follow-up studies confirm the results, for pulling asteroids that might end up on a potentially threatening collision orbit with Earth in the following decades. It’s a lot safer than using nukes, like some papers and Hollywood proposed in the past. Other proposed solutions include gravity tractors, laser beams or impactors.

Paek says that other substances could be used for the pellets, besides paint, like aerosols that would “impart air drag on the incoming asteroid to slow it down,” he said in a statement. “Or you could just paint the asteroid so you can track it more easily with telescopes on Earth. So there are other uses for this method.”

Check out this MIT video below to see how this tactic would work:


Lindley Johnson, program manager for NASA’s Near Earth Objects Observation Program, believes Paek’s proposal is ‘an innovative variation’ on a method already used by others to exploit solar radiation pressure, like the Messenger spacecraft,  which is currently orbiting Mercury. The spacecraft is equipped with solar sails that propel the craft with solar radiation pressure, reducing the fuel needed to power it.

“It is very important that we develop and test a few deflection techniques sufficiently so that we know we have a viable ‘toolbox’ of deflection capabilities to implement when we inevitably discover an asteroid on an impact trajectory,” he says.

How to deflect an asteroid with today’s technology

An asteroid threat to Earth seems like something we are going to have to face, sooner or later – and people are starting to aknowledge this fact; take Apollo 9 astronaut Rusty Schweickart for example. He is among a group of people that are championing the need to be prepared in case of such an event. According to him, we are on the right path:

“Our report and recommendations are a necessary, but not sufficient element of a sequence of actions which hopefully will lead to humanity being able to prevent future asteroid impacts with Earth,” Schweickart explained. “Assuming positive action by OSTP (Office of Science and Technology Policy) and the Congress, we’ll be well on our way to preventing future impact disasters.”

In a phone interview he gave Universe Today, he expains there are two possible approaches to such a deflection:
– either send a mission to the asteroid in an attempt to move it, or
– somehow change its orbit, so that it would become harmless.

Rusty Schweickart

These two strategies would have to be used together: a kinetic impact would “push” and somewhat deflect the asteroid, while a gravity tractor would “tug slowly” on the asteroid. These two methods are the best thing we’ve got at the moment.

“In a way, the kinetic impact was demonstrated by the Deep Impact mission back in 2005,” said Schweickart. “But that was a very big target and a small impactor that had relatively no effect on the comet. So, we haven’t really demonstrated the capability to have the guidance necessary to deflect a moderately sized asteroid.”

Artist depiction

Actually, things would be slightly different; the gravity tractor would have to arrive first, to observe the orbit and estimate how big the kinetic impact would have to be. It would also have to be there after the kinetic impact, and if required, “trim” the asteroid’s orbit even more.

“You want to know what happens when you do a kinetic impact, so you want an ‘observer’ spacecraft up there as well,” Schweickart explained. “You don’t do a kinetic impact without an observation, because the impactor destroys itself in the process and without the observer you wouldn’t know what happened except by tracking the object over time, which is not the best way to find out whether you got the job done.”

So you would need to know with at least 10-15 years in advance – 50 would be great, in order to send a spacecraft to observe what’s going on.

“This, in fact, would also be a gravity tractor,” Schweickart said. “It doesn’t have to be real big, but bigger gets the job done a little faster. The feature you are interested in the outset is not the gravity tractor but the transponder that flies in formation with the asteroid and you track the NEO, and back on Earth we can know exactly where it is.”

Even the most precise and lucky estimation of the asteroid‘s orbit wouldn’t be as good as an estimation made at by a spacecraft located close to it. It will also estimate what kind of a kinetic impulse is required, if required at all.

“You may launch at the latest possible time, but at that time the probability of impact may be 1 in 5 or 1 or 2,” Schweickart said. “So the first thing you are going to do with the observer spacecraft is make a precise orbit determination and now you’re going to know if it really will impact Earth and even perhaps where it will impact.”

After the orbit is calculated, the required action has to be calculated too.

“So now, if needed you launch a kinetic impactor and now you know what job has to be done,” Schweickart said. “As the impactor is getting ready to impact the asteroid, the observer spacecraft pulls back and images what is going on so you can confirm the impact was solid, –not a glancing blow — and then after impact is done, the observer spacecraft goes back in and makes another precision orbit determination so that you can confirm that you changed its velocity so that it no longer will hit the Earth.”

The thing is, calculating the impact would be even harder, because the asteroid might go through what is called a “keyhole” – meaning that it will first avoid Earth, but then our planet’s gravity would pull it back again. That is the case with the Apophis asteroid, who will miss Earth in 2029, but might ome back to “visit” us in 2036.

“So if it does go through that keyhole,” said Schweickart, “now you can use the gravity tractor capability of the spacecraft to make a small adjustment so that it goes between keyholes on that close approach. And now you have a complete verified deflection campaign.”

via Universe Today