Artist’s concept of building planets through collisions – planetary
accretion in the Solar Nebula 4.56 billion years ago. Credit: NASA
that of the latter’s rocky surface,
even at the relatively low temperatures (130K-200K or -73°C
to -143°C) found at Ceres.
Given the surprising evidence
of activity in some of the outer
icy moons of the solar system,
there is even speculation that
liquid water could exist in
pockets deep beneath Ceres’
surface, although much of the
necessary radiogenic heat in its
core has probably long since
been lost to space, and there
is no large body nearby to produce tidal heating. There has
recently been evidence, however, from the Herschel Space Observatory of very small amounts
of water vapour emanating
NASA’s Dawn spacecraft took this image on approach to
Ceres on Feb. 4, 2015 at a distance of about 90,000 miles
(145,000 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
from the surface of Ceres, so
cryovolcanism is not ruled out,
even if the water vapour may
be the result of sublimation of
ice caused by solar radiation.
Whatever surprises lie in store
at Ceres, the Dawn team will be
ready. Marc Rayman says “We
are expecting