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Starts With A Bang

Ceres bright spots are salts!

And are likely due to subsurface water, geysers and an incredible process.


“Have you entered the springs of the sea? Or have you walked in search of the depths?” –Job 38:16

When NASA’s Dawn spacecraft visited Ceres, the largest world in the asteroid belt, its brightest feature was a huge surprise.

In the center of Occator crater, a large (but not the largest) feature on Ceres’ moon-like surface exhibits a series of bright, white spots along the crater floor.

Occator Crater is 57 miles (92 kilometers) wide, with a central pit around 6 miles (10 kilometers) wide. This enhanced-color view highlights subtle color differences on Ceres’ surface. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI/LPI.

As Dawn flew closer, it was able to perform a distant chemical analysis, determining that this wasn’t ice or aliens, but rather salts that were so reflective.

Occator Crater, measuring 57 miles (92 kilometers) across and 2.5 miles (4 kilometers) deep, contains the brightest area on Ceres. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI.

The dome-like structure is at a depth of 4 km (2.5 miles) below the surface, deeper than anything else known.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, converted from Nature Publishing Group press’s YouTube channel.

But the big surprise, as new analysis shows, is that the salts are sodium carbonates, not magnesium sulfates, indicating that at least the surface contains icy, Kuiper-belt like materials.

The center of Ceres’ mysterious Occator Crater is the brightest area on the dwarf planet. The inset perspective view shows new data on this feature: Red signifies a high abundance of carbonates, while gray indicates a low carbonate abundance. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/ASI/INAF.

This represents the largest concentration of carbonate materials in the Solar System outside of Earth. An impacting asteroid could not have delivered them, indicating a recent hydrothermal origin from within Ceres itself.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, from A. Natheus et al. (2015), Nature 528, 237–240.

At the pressures interior to Ceres, liquid, briny water could have existed, depositing salts and then sublimating, leaving the reflective, bright carbonates behind.

These carbonates may be abundant across the surface, as future Dawn data will reveal.


Mostly Mute Monday tells the story of a single astronomical phenomenon or object primarily in visuals, with no more than 200 words of text.

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