TRAPPIST-1 planets could have water (and oceans of it), says Hubble

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Sep 4, 2017

If there’s any hotbed for seeking out extraterrestrial life besides Mars, which is really turning into more of a search for fossils if anything, it’s the TRAPPIST-1 system. Now something Hubble just saw makes water even more likely to exist on at least some of these seven planets.

An international team of scientists used Hubble’s Space Telescope Imaging Spectrograph (STIS) to determine how much radiation beams down on each planet and analyze what effects this radiation may have on the hypothetical water supply. While it turns out that the two planets closest to the ultracool dwarf star are probably desert wastelands, the other five may have oceans’ worth of water.

TRAPPIST-1 has an expansive habitable zone, with an unusually high potential for inter-planetary microbial contamination, meaning that any of the planets orbiting in that region could be crawling with micro-aliens. High-powered gravitational interactions are also believed to raise immense ocean tides that could further the chance of life spawning—or having been spawned—on one of the possibly habitable planets. Just watch out for solar flares that could vaporize the atmosphere and keep life from ever emerging.

What scientists realized in the new study is that the hydrogen floating around the TRAPPIST-1 planets could indicate atmospheric water vapor. Hydrogen is light enough to easily escape a planet’s atmosphere, and Hubble is hypersensitive enough to identify that hydrogen, which could have broken off from molecules of atmospheric water vapor. The space telescope’s measurements of UV light that radiates onto these planets also tell scientists how fast the atmospheres of these planets are vanishing.

“As in our own atmosphere, where ultraviolet sunlight breaks molecules apart, ultraviolet starlight can break water vapor in the atmospheres of exoplanets into hydrogen and oxygen,” said astronomer Vincent Bourrier, who led the study recently published in The Astronomical Journal.

Could the hydrogen escaping from some TRAPPIST-1 planet’s atmospheres mean water vapor and even liquid water?

Much of the TRAPPIST-1 planets’ atmospheres disappeared as they evolved. TRAPPIST-1b and TRAPPIST-1c, which orbit closest to their star and are hit by the most UV radiation, continue to bleed out water into space and are thought to have lost as much as 20 oceans’ worth in the past 8 billion years. The outermost planets in the habitable zone have supposedly lost only a fraction of that and are thought to be environments more ideal for sustaining liquid water. The only issue is that without knowing precise planetary masses, the team can only offer estimates of how much liquid water could be on each planet.

“While our results suggest that the outer planets are the best candidates to search for water with the upcoming James Webb Space Telescope, they also highlight the need for theoretical studies and complementary observations at all wavelengths to determine the nature of the TRAPPIST-1 planets and their potential habitability,” Bourrier said.

We might have to wait a while before we know for sure, but the sooner we find water, the sooner we can look for something swimming in it.

(via Gizmodo)