From: Planetary Science Institute
Posted: Thursday, December 15, 2016
Ceres’s surface globally contains materials that were altered by the action of liquid water within the interior of the dwarf planet, nuclear spectroscopy data from NASA’s Dawn spacecraft shows.
Dawn’s Gamma Ray and Neutron Detector (GRaND) instrument measured the concentrations of Fe (iron), H (hydrogen) and K (potassium) on the surface of Ceres. The elemental data show that materials were processed by liquid water within the interior, said Thomas H. Prettyman of the Planetary Science Institute.
Prettyman, a Senior Scientist at PSI, is lead author of the Science paper “Extensive water ice within Ceres’ aqueously altered regolith: Evidence from nuclear spectroscopy” that was published today and was the topic of a press conference at the American Geophysical Union Fall Meeting in San Francisco.
Ceres’ uppermost surface is rich in hydrogen, with higher concentrations at mid-to-high latitudes, which is consistent with the presence of vast expanses of near-surface water ice. The ice table is closest to the surface at high latitudes.
"On Ceres, ice is not just localized to a few craters. It's everywhere, and nearer to the surface with higher latitudes," said Prettyman, principal investigator of the GRaND instrument.
“These results confirm predictions made nearly three decades ago that ice can survive for billions of years within a meter of the surface of Ceres. The evidence strengthens the case for the presence of near-surface water ice on other main belt asteroids.”
The elemental composition of Ceres’ surface was compared with the CI and CM carbonaceous chondrite meteorites, which were also altered by water. The elemental data suggest Ceres is different from the parent body(s) of these meteorites, which were likely much smaller than Ceres. Within Ceres, large-scale convection may have resulted in the separation of ice and rock components, resulting in the surface having different elemental composition than the bulk. Alternatively, Ceres formed in a different location in the solar system than the meteorite parent bodies.
Visit www.psi.edu/news/cereshydrogen to see video animations depicting the distribution of hydrogen on Ceres.
Paper co-authors include PSI scientists Yuki Yamashita, William C. Feldman and Hanna G. Sizemore.
The project was in part funded by a subcontract from the NASA Jet Propulsion Laboratory and by subcontract from the University of California, Los Angeles, which leads the Dawn mission under the auspices of the NASA Discovery program. This work was also funded by a grant to PSI from the NASA Dawn at Ceres Guest Investigator program. GRaND is managed by the Planetary Science Institute.
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