Carbon-rich planets, dubbed as diamond planets may be waterless, making them incapable of supporting life.
The Sun is a carbon-poor star and hence the Earth is made up more of silicates than carbon. Stars that are rich in carbon fill their surrounding planets with carbon and even layers of diamonds. In a recent study, researchers concluded that such planets may lack oceans, making them incapable of supporting life.
"The building blocks that went into making our oceans are the icy asteroids and comets," said Torrence Johnson of NASA's Jet Propulsion Laboratory in Pasadena, Calif, who presented the results Oct. 7 at the American Astronomical Society Division of Planetary Sciences meeting in Denver. "If we keep track of these building blocks, we find that planets around carbon-rich stars come up dry," he said.
Johnson and his team found that the extra carbon in developing star systems obstruct the oxygen from forming water.
"It's ironic that if carbon, the main element of life, becomes too abundant, it will steal away the oxygen that would have made water, the solvent essential to life as we know it," said Jonathan Lunine of Cornell University, Ithaca, N.Y., a collaborator on the research.
Though many exoplanets have been discovered surrounding the Earth, scientists are still plagued with the question whether they are habitable or not. The first thing researchers look for is whether these planets are in the "habitable zone" and whether the temperatures are warm or cool enough to allow the formation of water on their surfaces. NASA's Kepler mission has found several planets within this zone, and researchers continue to scrutinize the Kepler data for candidates as small as Earth.
Even if the temperatures are right, scientists still need to determine whether there is enough water on the planet. To address this question, Johnson and his team conducted the study using planetary models based on measurements of our sun's carbon-to-oxygen ratio. During the Big Bang, the Sun inherited a pool of elements including hydrogen, helium, nitrogen, silicon, carbon and oxygen. The models used in the study measured how much water in the form of ice was locked up in our solar system when it formed billions of years ago, before the water made its way to Earth.
Though the origin of water on Earth is still a debatable topic, recent studies have suggested water first came to our planet through an asteroid impact. Despite the origin of water on our planet, researchers have established that the objects are said to have begun their journey from far beyond Earth, past a boundary called the "snow line," before impacting Earth and depositing water deep in the planet and on its surface.
In the study, when researchers applied the planetary models to carbon-rich planets, the water disappeared, suggesting no snow exists beyond the snow line.
"All rocky planets aren't created equal," said Lunine. "So-called diamond planets the size of Earth, if they exist, will look totally alien to us: lifeless, ocean-less desert worlds."
