From Scientific American:
Observations by NASA’s Ceres-orbiting Dawn spacecraft indicate that “ice volcanos” have erupted on the dwarf planet in the recent past and that Ceres’ crust is an odd ice-rock mixture that has never been observed before, scientists reported in a series of six new studies published online today (Sept. 1) in the journal Science.
“When we got to Ceres, we were expecting to be surprised, and we have been in many ways,” Dawn principal investigator Chris Russell, a professor of geophysics and space physics at the University of California, Los Angeles (UCLA), told Space.com. [Watch: An Ice Volcano on Ceres]
“Ceres has been active during its history inside; the interior has been changing, evolving, much like the Earth’s interior changes with time,” added Russell, lead author of one of the new Science papers and co-author on the other five. “It’s in the transition between the smaller asteroids and the Earth, in that it changes, and has changed, over the years from the time that the material initially came together.”
Dawn launched in September 2007 on a $467 million mission to study the two largest objects in the main asteroid belt between Mars and Jupiter — the 330-mile-wide (530 kilometers) protoplanet Vesta and Ceres, which is about 590 miles (950 km) across.
Dawn orbited Vesta from July 2011 through September 2012, when the probe departed for Ceres. The spacecraft arrived at the dwarf planet in March 2015, in the process becoming the first probe ever to orbit two different bodies beyond the Earth-moon system.
Scientists already knew a bit about Vesta, based on analyses of rocks that were blasted off the object long ago and have fallen to Earth as meteorites. Dawn’s work confirmed suspicions that Vesta is basically “frozen in time,” Russell said.
“It formed early and cooled off rapidly, and has just been a …