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Occator Crater on Ceres
The bright central spots near the center of Occator Crater are shown in enhanced color in this view from NASA’s Dawn spacecraft. Such views can be used to highlight subtle color differences on Ceres’ surface. The view combines high-resolution images of Occator from February with lower-resolution color data acquired in September 2015. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / PSI / LPI)

The scientists behind NASA’s Dawn mission today showed off their latest, greatest pictures of the dwarf planet Ceres, including close-up views of curious bright spots on the surface.

The car-sized Dawn spacecraft has been circling Ceres, the biggest mini-world in the solar system’s asteroid belt, for just more than a year. In Dawn’s distant views, the bright spots looked like alien headlights. The latest images, captured from a height of just 240 miles, reveal that the brightest spot is a fractured dome sticking up from 57-mile-wide Occator Crater.

Other bright areas appear to be highly reflective deposits, crisscrossed by linear features and fractures.

Dawn’s scientists discussed their latest data today at the Lunar and Planetary Science Conference in The Woodlands, Texas.

“Before Dawn began its intensive observations of Ceres last year, Occator Crater looked to be one large bright area. Now, with the latest close views, we can see complex features that provide new mysteries to investigate,” Ralf Jaumann, a planetary scientist at the German Aerospace Center, said in a news release.

He said “the intricate geometry of the crater interior suggests geologic activity in the recent past, but we will need to complete detailed geologic mapping of the crater in order to test hypotheses for its formation.”

Last December, Dawn’s scientists said they were leaning toward the view that the bright areas marked places where salty water ice was exposed on the surface, due to cosmic impacts or volcanic activity.

In this scenario, the ice turns into vapor through a process known as sublimation, leaving the bright salt behind. What kind of salt? Scientists suspect it’s mainly a type of hydrated magnesium sulfate known as hexahydrite. Similar bright patches and streaks have been spotted in other craters, including Haulani Crater and Oxo Crater.

Fresh readings from Dawn’s Gamma Ray and Neutron Detector, or GRaND, support the view that deposits of water ice lie beneath the surface, particularly in the polar regions of the 590-mile-wide world. Additional data gathered during Dawn’s close-in orbits should help tell the tale definitively.

“Our analyses will test a longstanding prediction that water ice can survive just beneath Ceres’ cold, high-latitude surface for billions of years,” said the Planetary Science Institute’s Tom Prettyman, who heads the GRaND research team.

Neutron readings on Ceres
This color-coded map shows neutron distribution data from Dawn’s GRaND instrument. Blue denotes relatively low neutron counts, and red denotes relatively high counts. Lower neutron counts near the north pole suggest the presence of water ice within about a yard of the surface at high latitudes. (Credit: NASA / JPL-Caltech / UCLA / ASI /INAF)

Dawn was launched in 2007 and spent 14 months mapping the asteroid Vesta before moving on to Ceres. The spacecraft is due to orbit Ceres indefinitely, even after its primary mission ends in June – and the data analysis is likely to continue for months and years to come.

Scientists say Ceres and Vesta are worthy of study because they preserve material from the beginnings of the solar system. Some have even suggested that Ceres’ subsurface could have supported life.

“Now that we can see Ceres’ enigmatic bright spots, surface minerals and morphology in high resolution, we’re busy working to figure out what processes shaped this unique dwarf planet,” deputy principal investigator Carol Raymond, who’s based at NASA’s Jet Propulsion Laboratory, said in today’s news release. “By comparing Ceres with Vesta, we’ll glean new insights about the early solar system.”

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