Rosetta captures landslide in space
Images taken by the space probe Rosetta have captured for the first time a landslide on a comet.
The collapse of the dark organic material coating a cliff face revealed that pristine water ice lies beneath the comet’s surface, scientists say in a paper published yesterday in the journal Nature Astronomy.
The landslide was the most dramatic of several geologic phenomena that Rosetta scientists have witnessed on Comet 67P/Churyumov-Gerasimenko, a lump of ice and rock. In a second paper published in the journal Science, the astronomers describe how the surface is constantly changing as a result of its rotation and the glare of the sun.
“These images are showing that comets are some of the most geologically active things in the solar system,” astronomer Maurizio Pajola said. “We see fractures increasing, dust covering areas that were not dusted before, boulders rolling, cliffs collapsing.”
The landslide, which took place sometime around July 10, 2015, would not have looked like a landslide on Earth. Comet 67P is so small it hardly has any gravity, so instead of tumbling down like an avalanche, much of the material that broke off from the fractured cliff face produced an “outburst”.
The Rosetta spacecraft had been accompanied by a lander, Philae, which was slated to take samples from Comet 67P’s subsurface. But Philae’s battery ran out just two days after landing, and scientists never got their interior samples.
Comets and asteroids are debris leftover from the early days of the solar system, when the planets were just being formed. Scientists consider them “time capsules” from that ancient time, 4.6 billion years ago. Comets like 67P, which are thought to have originated in the water-and volatile-rich outer solar system and then migrated inward, may also have delivered water and organic molecules to early Earth.
“That’s why it’s important to understand how comets behave, how they work, and what is below the surface,” Pajola said.