Planets rich in carbon
may be waterless worlds
Planets rich in carbon, inseveral planets within this zone,
cluding so-called diamond
and researchers continue to
planets, may lack oceans, acscrutinize the Kepler data for
cording to NASA-funded theocandidates as small as Earth.
retical research.
But even if a planet is found
Our sun is a carbon-poor star,
in this so-called “Goldilocks”
and as result, our planet Earth
zone, where oceans could, in
is made up largely of silicates,
theory, abound, is there actunot carbon. Stars with much
ally enough water available
more carbon than the sun, on
to wet the surface? Johnson
the other hand, are predicted
and his team addressed this
to make planets chock full of
question with planetary modcarbon, and perhaps even
els based on measurements
layers of diamond.
of our sun’s carbon-to-oxygen
By modeling the ingredients
ratio. Our sun, like other stars,
in these carbon-based planinherited a soup of elements
etary systems, the scientists
from the Big Bang and from
determined they lack icy waprevious generations of stars,
ter reservoirs thought to supply
including hydrogen, helium,
planets with oceans.
nitrogen, silicon, carbon and
“The building blocks that
oxygen.
went into making our oceans
“Our universe has its own
are the icy asteroids and com- This artist’s concept illustrates the fate of two differ- top 10 list of elements,” said
ets,” said Torrence Johnson of ent planets: the one above is similar to Earth, made up Johnson, referring to the 10
NASA’s Jet Propulsion Labora- largely of silicate-based rocks with oceans coating its most abundant elements in
tory in Pasadena, Calif, who surface. The one on the left is rich in carbon and dry. our universe.
presented the results recently. Chances are low that life as we know it, which requires
These models accurately
Johnson, a team member of liquid water, would thrive under such barren conditions. predict how much water was
Image: NASA/JPL-Caltech locked up in the form of ice
several NASA planetary missions, including Galileo, Voyearly in the history of our solar
ager and Cassini, has spent decades studying the system, billions of years ago, before making its way to
planets in our own solar system.
Earth. Comets and/or the parent bodies of asteroids
“If we keep tra