Pallas asteroid
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Watch out, Avengers: This asteroid has a more violent track record than Thanos

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Feb 23, 2020, 2:51 AM EST (Updated)

When you hear the word “asteroid,” you probably think of something hurtling toward Earth at unfathomable speeds, ready to take us out like Thanos snapping his fingers — but the asteroid Pallas has experienced violence in a whole other way.

Pallas is named after Pallas Athena. She was the ancient Greek goddess of wisdom, but what you might not know is that Athena was also a martial deity who was often portrayed with a helmet, shield, and spear. Pallas the asteroid looks like it’s been through endless cosmic battles, and all the impact craters punched into it say it’s really taken a beating. A strange orbit that takes it crashing through the asteroid belt is to blame. Now a research team led by Pierre Vernazza of the Laboratoire d'Astrophyisque de Marseille in France has been able to observe the asteroid like never before to reveal its violent history.

Just to give you an idea of what kind of chaos Pallas has been through, Vernazza and his team found 36 craters that exceeded 18 miles in diameter. That’s just a fifth of the diameter of the fateful Chicxulub asteroid that trashed the dinosaurs 65 million years ago.

“Pallas is the largest main-belt object not yet visited by a spacecraft, making its surface geology largely unknown and limiting our understanding of its origin and collisional evolution,” Vernazza and colleagues said in a study recently published in Nature Astronomy, explaining why they needed some help from computers here on Earth to start understanding it.

Pallas has a weirdly tilted orbit that has long been suspected, but finally studied using images of its pockmarked face from the Very Large Telescope’s SPHERE instrument — an array of four telescopes situated with 8-meter-wide mirrors that the team reserved for two years to see if they could catch Pallas orbiting as close to Earth as possible.

Vernazza and the other astronomers used the 11 images they were able to grab to generate a 3D reconstruction of what the asteroid should look like up close — meaning its shape, its poles, and all its craters. The level of violence it had been through was gauged by its reputation for butting heads with everything else floating around in the asteroid belt over the past 4 billion years. Asteroids Ceres and Vesta were used as comparisons in simulations that showed every collision.

Pallas was found to have been bombarded with crashes that left behind craters on at least 10 percent of its surface, which the team said was “suggestive of a violent collisional history.” Something odd the team found about Pallas when compared to Ceres and Vesta was that it didn’t take as much force to put a dent in Pallas. The same size of crater on either of the other two asteroids, about 25 miles in diameter, could be made by a much smaller object hitting Pallas at a high velocity. If you think about how many smaller objects are zooming through the asteroid belt compared to larger ones, you can probably imagine what Pallas goes through.

As if all that weren't enough, Pallas was also discovered to have a monster crater thought to be caused by its chemical composition, and a mysterious bright spot in its southern hemisphere whose origin remains unknown.

The Avengers don’t have to put themselves at risk again to find out more — but NASA might send out satellites in the future.

(via Phys.org/Nature Astronomy)


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