Hubble delivers hints of water in Earth-like TRAPPIST-1 system

Earlier this year, NASA announced the discovery of seven Earth-sized planets orbiting an ultra-cool dwarf star, called TRAPPIST-1.

The find meant that TRAPPIST-1 was among the star systems with the largest number of Earth-sized planets.

Now, an international team has used the Hubble space telescope to estimate the chances of water on the planets — and the results are encouraging.

“The results suggest that the outer planets of the system might still harbour substantial amounts of water. This includes the three planets within the habitable zone of the star, lending further weight to the possibility that they may indeed be habitable,” read a release on the Hubble website.

The team of scientists used tools aboard Hubble to take a closer look at ultraviolet radiation from the planets in question.

“As in our own atmosphere, where ultraviolet sunlight breaks molecules apart, ultraviolet starlight can break water vapour in the atmospheres of exoplanets into hydrogen and oxygen,” explained team lead Vincent Bourrier. Hydrogen escaping from the atmospheres can thus be detected by Hubble.

A new study tackles the question of water on the Earth-like TRAPPIST-1 star system

The team found that the planets within TRAPPIST-1 “could have lost gigantic amounts of water over the course of their history”. Just how much is “gigantic” then?

“The inner planets could have lost more than 20 Earth-oceans-worth of water during the last eight billion years,” read an excerpt of the press release. Of course, the inner planets are closer to the star and thus receive the most ultraviolet energy.

Fortunately, there’s still some hope for the outer planets in the system.

“…the outer planets of the system — including the planets e, f and g which are in the habitable zone — should have lost much less water, suggesting that they could have retained some on their surfaces. The calculated water loss rates as well as geophysical water release rates also favour the idea that the outermost, more massive planets retain their water.”

In fact, the team suggests that the outer planets lost “less than three Earth-oceans of water”.

Featured image: ESO/N. Bartmann/spaceengine.org