Cryovolcanism on Ceres
The presence of what appear to be recent, bright salt deposits at
Ceres’ surface raises the question of question of whether hydrothermal
activity may still be still active. Could it have been responsible for forc-
ing these salts up to the surface? The fractured dome at the heart of
Occator’s bright central region looks like it could well be of volcanic
origin, forced upwards by material rising from the interior.
One piece of evidence which might support the idea of active re-
plenishment of ice or water at Ceres’ surface is a haze that appears
occasionally in Occator, above some of the bright spots found inside
the crater. This haze reoccurs at local ‘noon-time’, when the Sun would
be high in the sky, enhancing any process of sublimation. The bright
spots could be creating a transient local atmosphere in this particular
region of Ceres. This is the first body in asteroid belt upon which such a
process has been observed directly, and would support observations
from Earth, made by ESA’s Herschel Space Observatory in January
2014, of water vapour being emitted from several mid-latitude sources
on Ceres. As yet, this is the only location so far where such a phenom-
enon has been observed, despite there being many other such spots
on the dwarf planet’s surface.
Hydrothermal activity is a form of volcanism, and there is other evi-
dence to suggest that cryovolcanism - cold volcanism involving vola-
tiles such as water ice – has occurred on Ceres at least in recent geo-
logical time. For instance, besides the salt deposits and their associated
surface fractures, a large number of craters have central pits on their
floors which may be due to cryovolcanism, marking places where wa-
ter may reach the surface from deep below.
AHUNA MONS: a volcanic dome on Ceres?: Left: Imaged by Dawn from its High-Altitude Mapping Orbit. Right: Ceres’ lonely mountain, Ahuna Mons, is seen in this simulat-
ed perspective view. The elevation has been exaggerated by a factor of two. The view was made using enhanced-colour images from Dawn’s Low-Altitude Mapping Orbit. It
shows the mountain’s sharp, bright, unaltered features which would imply that it is a relatively young feature. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The most spectacular evidence for volcanic activity on Ceres is the
discovery of a lone mountain, Ahuna Mons, which stands 5km (3 miles)
above the surrounding area on its steepest side near the dwarf planet’s
equator. It resembles a volcanic dome and probably formed as a ‘salty
mud’ volcano. It would appear to be unique so far in the Solar system,
being the first cryovolcano observed which has been produced by a
mixture of brine and clays, as opposed to rock or ices. Although the
volcano is not active now, Ahuna Mons’ appearance indicates that it
is a surprisingly young feature geologically-speaking. It is bright, sharp,
steep-sloped and unmarked by craters, and also has fine features like
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