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takyon [soylentnews.org] writes:

Scientists theorize that Ceres's [wikipedia.org] cryovolcanoes slowly flatten over time [agu.org]:

A recently discovered solitary ice volcano on the dwarf planet Ceres may have some hidden older siblings, say scientists who have tested a likely way such mountains of icy rock – called cryovolcanoes – might disappear over millions of years. NASA's Dawn spacecraft discovered Ceres's 4-kilometer (2.5-mile) tall Ahuna Mons cryovolcano in 2015. Other icy worlds in our solar system, like Pluto, Europa, Triton, Charon and Titan, may also have cryovolcanoes, but Ahuna Mons is conspicuously alone on Ceres. The dwarf planet, with an orbit between Mars and Jupiter, also lies far closer to the sun than other planetary bodies where cryovolcanoes have been found.

Now, scientists show there may have been cryovolcanoes other than Ahuna Mons on Ceres millions or billions of years ago, but these cryovolcanoes may have flattened out over time and become indistinguishable from the planet's surface. They report their findings in a new paper accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

[...] Ceres has no atmosphere, so the processes that wear down volcanoes on Earth – wind, rain and ice – aren't possible on the dwarf planet. Sori and his colleagues hypothesized that another process, called viscous relaxation, could be at work. Viscous relaxation is the idea that just about any solid will flow, given enough time. For example, a cold block of honey appears to be solid. But if given enough time, the block will flatten out until there is no sign left of the original block structure. On Earth, viscous relaxation is what makes glaciers flow, Sori explained. The process doesn't affect volcanoes on Earth because they are made of rock, but Ceres's volcanoes contain ice – making viscous relaxation possible. On Ceres, viscous relaxation could be causing older cryovolcanoes to flatten out over millions of years so they are hard to discern. Ceres's location close to the sun could make the process more pronounced, Sori said.

The vanishing cryovolcanoes of Ceres [wiley.com] (open, DOI: 10.1002/2016GL072319) (DX [doi.org])

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