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Ceres Has Lots of Bright Spots

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Posted June 18, 2015

Those bright mystery spots aren’t the only ones on Ceres. Recent photos posted on JPL’s Photojournal site  feature a spectacular rayed crater resembling the familiar lunar craters Kepler and Copernicus.

Fresh material is exposed in a rayed crater on Ceres. Taken on June 6 from 2,700 miles (4,400 km), it has a resolution of 1,400 feet (410 meters) per pixel, Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Fresh material is exposed in a rayed crater on Ceres. Taken on June 6 from 2,700 miles (4,400 km), it has a resolution of 1,400 feet (410 meters) per pixel, Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Lunar rays are bright because they contrast with their older surroundings which have been darkened by exposure to solar and cosmic radiation. Impacts expose fresh material from below the surface that settles into a spider web of rays around the newly excavated crater. Huge boulders lofted above the Moon’s surface during the impact slam back into the crust to create secondary craters also crowned with bright dust and rock.

Unique view of the lunar crater Proclus showing an extension system of bright rays taken from Apollo 15. Credit: NASA

Unique view of the lunar crater Proclus showing an extension system of bright rays taken from Apollo 15. Credit: NASA

Most models of Ceres depict a rocky crust,  mantle of ice and a rocky inner core.  This makes us wonder if the bright material unearthed might be ice. If so, it would gradually vaporize on the virtually air-free dwarf planet.

Bright dots and patches of material are seen in this photo taken by Dawn on May 22, 2015 from 3,200 miles (5,100 km) away. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Bright dots and patches of material are seen in this photo taken by Dawn on May 22, 2015 from 3,200 miles (5,100 km) away. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dawn will spend through early 2016 at Ceres during its primary mission and then remain in orbit there perpetually. We should be able to cipher the composition of the white material during that time with the spacecraft’s Gamma Ray and Neutron Detector and Visible and Infrared Mapping Spectrometer, but a lengthy stay might allow us to see changes in the extent of any ice exposures as they gradually vaporize away.

Taken back on May 4 from 8,400 miles (13,600 km), this photo shows the rayed crater (bottom) and another bright spot above center. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Taken back on May 4 from 8,400 miles (13,600 km), this photo shows the rayed crater (bottom) and another bright spot above center. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

One thing we know for certain about Ceres are its dimensions. Dawn observations have revised the size to be about 599 miles (963 km) across at the equator with a polar diameter of 554 miles (891 km).

Based on Ceres’ density, it contains a large fraction of low density materials including clays, water ice, salts and organic compounds. This schematic gives a general idea of the dwarf planet’s makeup. Credit: NASA/ESA/STScI

Based on Ceres’ density, it contains a large fraction of low density materials including clays, water ice, salts and organic compounds. This schematic gives a general idea of the dwarf planet’s makeup. Credit: NASA/ESA/STScI

Like Earth and other planets, Ceres is a slightly flattened sphere wider at the equator than from pole to pole. The temperature there ranges from about -100°F (-73°C) during the day and dips to -225°F (-143°C) at night. That makes its daytime high about 28° warmer than coldest temperature ever recorded on Earth.

Uncropped, untoned view of the rayed crater seen in the earlier image. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Uncropped, untoned view of the rayed crater seen in the earlier image. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Source: Universe Today, written by Bob King

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