Transient atmosphere on Ceres linked to solar activity

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NASA’s Dawn spacecraft determined the hydrogen content of the upper meter of Ceres’ surface. Blue indicates where hydrogen content is higher, near the poles, while red indicates lower content at lower latitudes.

New research suggests that Ceres’ transient atmosphere is caused by solar activity rather than the dwarf planet’s proximity to the sun.

The study, published in Astrophysical Journal Letters and conducted by scientists from NASA’s Dawn mission, challenged earlier understandings of Ceres now-you-see-me-now-you-don’t atmosphere, which attributed its production to the release of water vapour by sublimation caused by sunlight when the dwarf planet’s orbit brought it close enough to the sun.

“Sublimation probably is present, but we don’t think its significant enough to produce the amount of exosphere that we’re seeing,” explains lead author Michael Villarreal.

The research team proposed an alternative hypothesis, placing the emphasis on solar activity rather than distance.

The study suggests that when energetic particles from the sun collide with ice on or near Ceres’ surface, a transfer of energy occurs which releases the water molecules and generates the weak, transitory atmosphere.

The novel theory is strengthened by the fact that past observations of Ceres’ transient atmosphere coincided with the detection of higher concentrations of energetic protons from the sun, while the lack of observations aligned with low detection of these particles.

While Ceres is presently growing closer to the sun, the sun is currently in a particularly quiet period. Villareal and colleagues predict that the dwarf planet will have no detectable atmosphere for some time, but recommend that observatories continue monitoring Ceres for future emissions.

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