Scientists have spotted the ghosts of nearly two
dozen ice volcanoes on dwarf planet Ceres.
When NASA’s Dawn spacecraft arrived at the
small world in the asteroid belt in 2015, researchers found just one cryovolcano: Ahuna Mons, a
4-kilometer-high mountain that formed at most
240 million years ago (shown above in Dawn
images). Cryovolcanoes spew water, not magma,
though it’s unclear if Ahuna Mons is still active.
But why Ceres didn’t seem to have any other
volcanoes was a mystery.
Now, using data from the probe, the remains of
21 more ice volcanoes have been located (all 22
sites marked with diamonds in the topographical
map at right), researchers report September 17 in
Nature Astronomy. The newly identified volcanoes
formed hundreds of millions to about 2 billion
years before Ahuna Mons, scientists estimate.
Only one, called Yamor Mons (No. 1 in the images
at right), is similar to Ahuna Mons ( 2) in size and
steepness. The rest have slumped into shorter,
wider domes over time (one example, 3).
The team calculates that the volcanoes, now
inactive, should have spewed out an average of
10,000 cubic meters of water per year. Volcanoes on
rocky planets, such as Earth, that erupt molten rock
spew thousands of times as much material as that,
even when taking the worlds’ relative sizes into
account. So icy volcanism seems less important to
Ceres’ history than rocky volcanism has been to
other places, planetary scientist and study coauthor
Michael Sori of the University of Arizona in Tucson
and colleagues conclude. — Lisa Grossman
Found: Ceres’ missing
0° 90° E 270° E 180°
– 3 1 0
– 2 2 – 1 3