When I was a kid, a gully was something behind someone’s house that filled up with water when it rained, and even though it seemed too gross to just walk in and swim in it, it was perfectly fine to swing into it from a rope haphazardly tied to a tree branch. There’s no app for that. Recent satellite imagery has revealed gullies on the asteroid Vesta, and researchers are now trying to figure out where they came from. Leave it to science to take all the fun out of gullies.
Mysteries are fun, though, and that’s what these eroded paths are, at least initially. NASA’s Dawn probe spent more than a year mapping Vesta’s surface from an altitude of 210 km., and finished this round of duties in September. Vesta is the second largest body in the asteroid belt between Mars and Jupiter. Jennifer Scully presented evidence at the American Geophysical Union Fall Meeting that, of the roughly 60 craters (10 km and wider) that she examined, 11 examples showed a series of complex paths cut into the rock, “They are longer and narrower. They also interconnect, branching off one another,” Ms. Scully explains. The remains of old Plinko games from extraterrestrial Price Is Right episodes?
The larger group of craters showed troughs with shapes and formations typical as the results of loose rocks or soil falling down the slope. These more detailed gullies look to be of liquid origin, even though an asteroid’s lack of atmosphere would boil any liquid on its surface immediately. Now a look beneath the surface may reveal further answers.
Dawn mission principal investigator Prof. Chris Russell says, “It would be cool enough just a few meters or even some centimeters beneath the surface that water could be preserved for a long time. So we have some mechanisms like comets that might bring water to the surface — then it could be stored for some period of time.” The Cornelia depression, near the asteroid’s equator, contains the Type B gullies forming in dark materials covering certain areas of the crater, material that has been suggested to be similar to carbonaceious chondrite meteorites, which can indeed contain water. It’s also theorized that perhaps the crater-creating impact with another flying object could have released some of this liquid upon collision, allowing for temperature fluctuations that allowed the rivulets to form before everything boiled off into the ether.
It’s only a matter of time before they find a fossil of a paper boat nearby. I bet alien boats fly.