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 Using the European Space Agency's Herschel infrared space
telescope, researchers spotted plumes of water vapor periodically
spewing from Ceres, the largest object in the asteroid belt residing
between the orbits of Mars and Jupiter.
The discovery comes just over a year before the scheduled arrival of
NASA's Dawn spacecraft for a closer look at Ceres, a round body
measuring about 590 miles in diameter — less than a third of the
size of the moon.
"This is the first time water vapor has been unequivocally detected
on Ceres or any other object in the asteroid belt and provides proof
that Ceres has an icy surface and an atmosphere," Michael Küppers of
the European Space Agency in Spain, who led the research published
in the journal Nature, said in a statement.
The question is what is causing these plumes of water vapor from two
locations on Ceres. One idea, according to scientists, is that the
sun sometimes warms parts of the icy surface enough that water vapor
emerges.
Another possibility, they say, is that there is liquid water under
the frozen surface of Ceres and that vapor is shooting out of
geysers or icy volcanoes. Dramatic geysers have been spotted on
Enceladus, one of the innermost moons of the giant ringed planet
Saturn.
Scientists think Ceres holds rock in its interior and is wrapped in
a mantle of ice that, if melted, would amount to more fresh water
than is contained on Earth.
Ceres was discovered in 1801, more than a century before the
discovery in 1930 of the more famous — and more distant — dwarf
planet Pluto. It is one of the few places in the solar system aside
from Earth where water has been located. A big question about the
discovery of the water vapor on Ceres is what it means regarding the
possibility of life.
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"One of the things that's intriguing here is the possibility of
there being liquid water as opposed to ice," Marc Rayman of NASA's
Jet Propulsion Laboratory, Dawn's chief engineer and mission
director, said in a telephone interview.
"Certainly all life that we know depends on water. And so this is
part of the larger question of where can life exist."
He said it is too early to declare that Ceres a good candidate for
possible microbial life.
"I think that's a stretch," Rayman said. "Rather, I would say this
indicates Ceres might be a good place to look to understand more
about the places life could form — and perhaps places that life has
formed.
"There's a lot more than just water that's required for life. And
whether Ceres has those other ingredients — which include, for
example, a source of energy and all of the nutrients that life
requires, the rest of the chemistry — it's too early to say."
Rayman said scientists plan to use instruments aboard Dawn to map
the surface of Ceres, measure its surface elevations, catalogue its
minerals and study its interior structure. Dawn is due to arrive at
Ceres in March or April 2015.
(Editing by Eric Walsh)
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