Impacts From Twin Asteroids Underestimated, Dinosaur Killer Comet Re-evaluated

In what amounts to an until now overlooked great danger to our planet, double impacts caused by binary asteroids, and among them the extinction-level event (ELE) that likely eradicated the dinosaurs, could be more common than previously assumed. This assumption could be drawn from a new study with the hypothesis that only a fraction of twin impact craters on Earth have been identified until now, which also means that there have been some more super disastrous impacts than thought.

Interesting enough to take a look at the study, titled "Morphology and population of binary asteroid impact craters," and published in Earth and Planetary Science Letters. The discrepancy at the root of the study lead by Katarina Miljkovic from the Institute of Earth Physics in Paris is that about 15 percent of the numerous asteroids spotted around Earth are so called binary, pairs orbiting each other, but only 2 to 4 percent of craters on Earth have been identified as binary impacts. Miljkovic therefore assumes this number to be under-reported, which is possible because the craters from the twin asteroids can easily overlap.

The study shows likely shapes of such double crash site, which can range from craters that are peanut-shaped to ones that look like a pair, for example. The key is to look for abnormalities in known impact craters and measuring them for such asymmetrical features to discover more binary impacts throughout history than previously noted.

And one candidate for such a re-evaluation is actually the crater of the asteroid that many scientists credit with the extinction of the dinosaurs, which is located Chicxulub in Mexico and has a diameter of 180 kilometers. "The Chicxulub crater shows some important asymmetries. It is worth considering that it was formed by a binary asteroid," Miljkovic told New Scientist.

The researchers ran computer simulations of twin impacts with the result that most binary asteroids hit the same spot and thus form a single crater. The binary asteroids that hit two separate spots are the exception and are assumed to be smaller rocks orbiting each other at a greater distance. One example for such a crater pair are the Clearwater Lakes near Hudson Bay in Canada, twin craters that formed about 290 million years ago.

One issue is that binary asteroids are possibly harder to deflect if they are found to be on a collision course with our planet. A well aimed nuclear missile might still do the trick though, according to a NASA asteroid researcher. A smaller single asteroid is going to chart a near miss in just one week, when 2012DA14 will pass the earth so close that it will enter inside the ring of geosynchronous weather and communications satellites on February 15, 2013.