A massive ice volcano towers over the surface of the dwarf planet Ceres, researchers report today in Science1.
Dubbed Ahuna Mons, the volcano stands 4 kilometres tall, roughly half the height of Mount Everest. Although scientists have spotted potential cryovolcanoes elsewhere in the Solar System — most notably on Pluto2 — the study’s authors say that their evidence is the strongest yet.
“This huge mountain was a surprise,” says lead author Ottaviano Ruesch, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. ”We were expecting to see just fluid plains of lava.”
Ruesch and his colleagues based their analysis on images and other observations collected by NASA’s Dawn spacecraft, which began orbiting Ceres in March 2015. Those data demonstrate that the dwarf planet is more than just a cratered ball of rock and ice: it seems to be geologically active, with processes other than crater-forming impacts shaping its surface.
The Dawn images, which have a resolution of 35 metres per pixel, reveal steep slopes covered in debris, and crags and pits on the summit of Ahuna Mons. The mound-like cryovolcano appears to be only a few hundred million years old, making it a relatively recent addition to 4.5-billion-year-old Ceres.
Ceres’s cryovolcano could be a frozen analogue to some volcanoes on Earth — its shape is consistent with that of a spreading volcanic dome such as Mount St Helens in Washington. Such volcanoes do not typically spew lava into the sky; instead, it oozes slowly to the surface, where it forms a dome. The researchers think that Ahuna Mons was formed by the same mechanism, but with slushy ice …