Pallas: The Asteroid Belt’s Most Cratered Object
A Violent Past Revealed
Pallas, one of the most infamous asteroids in our solar system, has been captured in stunning detail by astronomers using the SPHERE instrument at the European Southern Observatory’s Very Large Telescope. The images reveal a remarkable sight: Pallas is the most cratered object in the asteroid belt, a title it has likely earned through countless collisions with its neighbors.
“These first detailed images of Pallas suggest that the asteroid has had a violent past,” said Franck Marchis, a planetary scientist at MIT and co-author of a study published in Nature Astronomy.
An Unusual Orbit
While most asteroids in the belt travel along a similar path around the sun, Pallas takes a more rogue approach. Its tilted orbit brings it crashing through the belt at an awkward angle, increasing the likelihood of collisions.
“Pallas experiences two or three times more collisions than Ceres or Vesta,” the two largest objects in the asteroid belt, said Michaël Marsset, a planetary scientist at MIT and co-author of the study.
A Golf Ball Asteroid
The constant bombardment has left Pallas heavily pockmarked, earning it the nickname “golf ball asteroid.” An analysis of images captured by SPHERE showed that craters make up at least 10% of the asteroid’s surface.
Severe Impacts
The impacts that Pallas experiences are particularly severe. Computer simulations revealed that the impactors responsible for the craters were traveling at speeds over 25,000 miles per hour, nearly twice as fast as is typical for asteroid belt collisions.
A Family of Followers
At least 36 of the depressions on Pallas span at least 18 miles in diameter, including one massive crater that stretches 250 miles across. This crater is likely the result of a collision with an object up to 25 miles wide.
The impact that created this crater may also be responsible for the group of smaller objects that trail Pallas. After smashing into the asteroid some 1.7 billion years ago, the impactor may have shattered into fragments that drifted into space and now follow their leader.
A Window into the Past
“Because we are now able to see the surface of large asteroids in the main-belt, we have access to a fictive book on the history of our solar system,” said Marsset. “We are in the process of learning how to read it, and each page is a surprise to us, including Pallas.”
By studying Pallas and other asteroids, scientists are gaining a better understanding of the violent and chaotic early days of our solar system. These celestial bodies hold clues to the processes that shaped our planet and the potential hazards that still exist in space.