The Occatur Crater on the dwarf planet Ceres is home to several mysterious bright spots. New research from NASA’s Dawn mission is forcing Ceres to reveal the secrets of what the spots are and how they formed.
The mission is now reaching its lowest orbit above Ceres, just 374 kilometers (232 miles) above surface. As it descends, scientists are analyzing data collected during the approach and high-orbit phases.
“This is an exciting time in the mission when we really start to dig into the data,” says Carle Pieters, a geologist at Brown University. “We’re learning a lot, but there’s still so much about Ceres that has our heads spinning.”
A new paper published in the journal Nature describes findings from Dawn’s visible and infrared spectrometer, which has been analyzing the bulk composition of Ceres’ surface. The findings give clues—and also raise significant questions—about the dwarf planet’s origins.
The analysis shows that Ceres surface appears to be rich in ammonia-rich clays. Before the Dawn mission, Earth-based spectrometers had suggested that there were hydrated minerals on Ceres’ surface, but a key portion of the light reflected from Ceres was blocked by Earth’s atmosphere.
As a result, it wasn’t clear if those hydrated minerals were in the form of water, ammonia, or a magnesium-based compound called brucite.
“With Dawn we can finally get a look at the full spectrum,” Pieters says. “With the fitting we’ve been able to do so far, it looks like ammonia-bearing species are clearly most consistent with the new Dawn data.”
The presence of ammonia has significant implications for Ceres’ origin, and raises questions about how it came to exist in the asteroid belt between Mars and Jupiter.
“When we look at the models of the early solar system, we expect ammonia to condense much farther out—in the area of the gas giants,” Pieters says. “So the question is: How in the heck did Ceres get ammoniated material in the asteroid belt?”
Continue on to the next page, where we explore possibilities for how that happened and you can watch a beautiful flyover video compilation of images from the Dawn spacecraft…
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