TRAPPIST-1 exoplanets may have a lot of water, and other new clues about potential habitability

Artist’s conception of the TRAPPIST-1 system, which contains seven Earth-sized exoplanets. Image Credit: NASA

I missed posting this before, but there are some very interesting updates about the TRAPPIST-1 exoplanets (seven Earth-sized planets orbiting a red dwarf star 40 light-years away). There are two new science papers, which indicate that all seven could have water in some form, ranging from vapour to liquid to ice, depending on their distance from the star and other factors. Some of the planets could have up to 5% of their mass composed of water, compared to 0.02% for Earth! Some probably have thick atmospheres while others have thinner atmospheres. The two related articles and two new papers are linked below.

TRAPPIST-1 Planets Probably Rich in Water

Hubble delivers first insight into atmospheres of potentially habitable planets orbiting TRAPPIST-1

The nature of the TRAPPIST-1 exoplanets

Atmospheric Reconnaissance of Habitable-zone Earth- sized Exoplanets

“A new study has found that the seven planets orbiting the nearby ultra-cool dwarf star TRAPPIST-1 are all made mostly of rock, and some could potentially hold more water than Earth. The planets’ densities, now known much more precisely than before, suggest that some of them could have up to 5 percent of their mass in the form of water – about 250 times more than Earth’s oceans. The hotter planets closest to their parent star are likely to have dense steamy atmospheres and the more distant ones probably have icy surfaces. In terms of size, density and the amount of radiation it receives from its star, the fourth planet out is the most similar to Earth. It seems to be the rockiest planet of the seven, and has the potential to host liquid water.”

From the Grimm et al paper:

“Our new masses result in a five to eight-fold improvement on the planetary density uncertainties, with precisions ranging from 5% to 12%. These updated values provide new insights into the bulk structure of the TRAPPIST-1 planets. We find that TRAPPIST-1 c and e likely have largely rocky interiors, while planets b, d, f, g, and h require envelopes of volatiles in the form of thick atmospheres, oceans, or ice, in most cases with water mass fractions less than 5%.”

It will be interesting to see what follow-up observations, such as with the upcoming James Webb Space Telescope, find out about the atmospheres of these planets. As we learn more about them, the potential habitability of at least some of them seems to be increasing.

“Spectroscopic observations of the TRAPPIST-1 planets with the next generation of telescopes – including the James Webb Space Telescope – will allow us to probe deeper into their atmospheres,” concludes Michael Gillon, from the University of Líege, Belgium. “This will allow us to search for heavier gases such as carbon, methane, water, and oxygen, which could offer biosignatures for life.”

 

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