Distant planets could harbor water — and life

Several planets in a distant solar system have temperatures that could sustain liquid water, thought to be a key for life, a series of studies reported Monday.

The planets, which scientists say are the best-studied worlds outside our solar system, “remarkably resemble Mercury, Venus, our Earth, its moon and Mars,” said Amaury Triaud, a University of Birmingham astronomer who cowrote one of the studies.

The worlds circle a dim star called TRAPPIST-1, which shares its name with the Belgian-operated telescope (Transiting Planets and Planetesimals Small Telescope) in Chile.

Astronomers peering through the scope first discovered the system two years ago and continue to uncover more details about the star and its worlds.

The new studies say that, as had been theorized, all of the planets are rocky and not gaseous. The planets’ densities suggest some planets could contain up to 5% of their mass in water — 250 times more than the oceans on Earth.

According to the research, the fourth planet in the system, known as TRAPPIST-1e, is the most Earth-like. Of the known planets outside our solar system, 1e is the one most similar to the Earth in size, density and the amount of radiation it receives from its star, according to researchers at the University of Bern in Switzerland.

It’s the only one of the seven that is denser than Earth, and it is not ruled out that liquid water exists on its surface.

“Densities, while important clues to the planets’ compositions, do not say anything about habitability,” said BriceOlivier Demory of the University of Bern, a study co-author. “However, our study is an important step forward as we continue to explore whether these planets could support life.”

The star and its planets are less than 40 light-years away, NASA said. Yet the star is too dim to be seen with the naked eye or with a large amateur telescope.

NASA’s James Webb Space Telescope, scheduled for launch in 2019, will delve into the question of if the planets have atmospheres. The studies are published in Nature

Astronomy and Astronomy and Astrophysics.