Dawn captures detailed image of Ceres's Occator Crater

Region contains largest deposits of carbonates beyond Earth and Mars.
By Laurel Kornfeld | Nov 09, 2018
From its lowest ever orbit around dwarf planet Ceres, NASA's Dawn spacecraft has captured detailed images of Occator Crater, the enigmatic region of bright deposits first discovered by the probe three years ago.

On June 14, the spacecraft imaged a region of the crater named Vinalia Faculae from an altitude of just 24 miles (39 km), revealing a dark background with a structure somewhat similar to that seen at sites of lava flow on Earth. In Ceres's case, scientists believe these features were created by flowing ice.

Bright areas visible in the bottom center and upper left of the image are composed of a salt known as sodium carbonate, identified by Dawn's visible and infrared mapping spectrometer. These likely originated within a liquid source.

The center of this photograph is at 21 degrees north latitude and 241.3 degrees east longitude.

On June 22, Dawn imaged a large mound on the west side ofCerealia Facula, another interesting region of Occator Crater, and the largest region of sodium carbonate deposits, from an altitude of around 21 miles (34 km).

Shaped like a mesa with steep slopes and a flat top, Cerealia Faculae is an area of significant contrast, with bright salt deposits scattered between dark surface material. This area is located at 19.5 degrees north latitude and 239.2 degrees east longitude.

To observe this region up close, Dawn had to fire its ion engines, possibly for the last time. Prior to this close flyby, the lowest altitude ever flown by the spacecraft was 240 miles (385 km) above Ceres's surface.

"Acquiring these spectacular pictures has been one of the greatest challenges in Dawn's extraordinary extraterrestrial expedition, and the results are better than we had ever hoped. Dawn is a master artist, adding rich details to the otherworldly beauty in its intimate portrait of Ceres," said mission chief engineer and project manager Marc Rayman of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

Scientists are still uncertain as to the origins of these salt deposits, specifically, whether they were exposed from a shallow underground source of water and minerals or from a deeper ocean of salty water that rose up through surface fractures.

Even sharper detail of Ceres's surface composition will be obtained by other Dawn instruments, including a gamma ray and neutron detector and a visible and infrared mapping spectrometer.

The mission team also plans to learn more about a possible subsurface ocean through closeup gravity measurements.

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