Trappsit-1 Planets hold a lot of water. How much? It could be 250 times Earth's Oceans.

TRAPPIST-1 Planets Could Harbor 250 Times More Water Than Earth's Oceans

The seven Earth-size planets around the distant star TRAPPIST-1 are "tugging" on each other as they travel around their parent star.By carefully observing those tugs, scientists were able to gather information about the planets' composition, and found that some of the TRAPPIST-1 worlds could have as much as 250 times more water than the amount in all of Earth's oceans, according to a new study.

From article, ("In the TRAPPIST-1 system, the planets are so close together that they perturb each other," Grimm said in a statement from the University of Bern. "This causes a slight shift in the times of each transit." (A "transit" refers to when the planet appears to pass in front of its parent star as seen from Earth. Thousands of exoplanets have been detected and studied using the transit method.) By simulating the planetary orbits of TRAPPIST-1 with an algorithm until the computational model matched what astronomers had observed in the TRAPPIST-1 system, the team could estimate the masses of the planets. From the mass data, the team could then deduce the planets' individual densities and compositions.

Intriguingly, they found that each of the five lightest planets could have about 250 times more water than the amount in Earth's oceans according to a statement from NASA. Up to 5 percent of their composition could be water, whereas only 0.02 percent of Earth is water.

TRAPPIST-1c, d and e lie close to the star's "habitable zone," or the region where a star receives enough radiation that water might be able to exist as a liquid on its surface. TRAPPIST-1b, the innermost planet, and TRAPPIST-1c likely have rocky interiors and atmospheres denser than Earth's, according to the study. Of all the TRAPPIST-1 exoplanets, TRAPPIST-1d is the lightest, at about 30 percent Earth's mass. This may mean it has a large atmosphere, an ice layer or an ocean, but scientists cannot yet discern that. TRAPPIST-1e is likely a rocky planet with a thin atmosphere. TRAPPIST-1f, g and h are so distant from their parent star that their surfaces are probably covered in ice.

"We were able to measure precisely the density of exoplanets that are similar to Earth in terms of their size, mass and irradiation, with an uncertainty of less than 10 percent, which is a first and a decisive step in the characterisation of potential habitability," said Brice-Olivier Demory, a professor at the Center for Space and Habitability and co-author of the study, which was published in late January 2018 in the journal Astronomy and Astrophysics.

The exoplanet TRAPPIST-1e yielded another interesting finding: It is the most similar to Earth in the amount of radiation it receives from its parent star, its size and its density. And liquid water could exist on its surface.)

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