Scientists Say Some of TRAPPIST-1 Planets Just Might Have Water

When it comes to the seven rocky, roughly Earth-size planets in the TRAPPIST-1 system, the question on everyone's mind is: Could they support the kind of life we find here on Earth?

An global team of researchers, led by Vincent Bourrier from Switerzland's Observatoire de l'Université de Genève, used an instrument onboard the telescope called the Space Telescope Imaging Spectrograph to search for evidence of water vapor in the atmospheres of the TRAPPIST-1 planets.

"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 Bourrier in a press release. But it's also possible that the outermost four planets (e, f, g and h - the first three of which are in the star's habitable zone) lost less than three Earth-oceans' worth of water.

This is especially true for the innermost two planets of the system, TRAPPIST-1b and TRAPPIST-1c, which receive the largest amount of UV energy, and could have lost more than twenty Earth-oceans-worth of water during the last eight billion years.

The astronomers sought to predict how much water each planet may have lost over its history. The study was led by Swiss astronomer Vincent Bourrier from the Geneva Observatory in Switzerland and colleagues.

In this NASA digital illustrationan artist's concept allows us to imagine what it would be like to stand on the surface of the exoplanet TRAPPIST-1f.

Farther away from their parent star, the planets might have formed in an environment rich in water ice, meaning the planets could have initially had very water-rich compositions.

They cautioned that their estimates remain limited by the large uncertainty on the planet masses, but said their estimates likely represent upper limits on the actual water loss.

The new research, published in The Astronomical Journal, may revive hopes somewhat.

Why do planetary astronomers continue to think these worlds may have a lot of water? "What our results show is that even if the outer planets were initially quite water-poor like the original Earth, they could still have some water on their surfaces".

It shows that "atmospheric escape may play an important role in the evolution of these planets", said Julien de Wit, co-author of the study and a researcher from the Massachusetts Institute of Technology. "This concludes that a few of these outer planets could have been able to hold onto some water, if they accumulated enough during their formation".

The level of ultraviolet energy projected onto each planet is important.

"Our results suggest that the outer planets are the best candidates to search for water with the upcoming James Webb Space Telescope", says Bourrier.

  • Joey Payne