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TRAPPIST-1 Exoplanets May Have Too Much Water to Support Life

Accepted submission by takyon at 2018-03-21 07:44:37
Science

TRAPPIST-1's exoplanets appear to have migrated closer to TRAPPIST-1 [wikipedia.org] over time until they reached their current orbits. This migration appears to have allowed them to retain too much water to support life [asu.edu]:

What [the ASU-Vanderbilt team] found through their analyses was that the relatively "dry" inner planets ("b" and "c") were consistent with having less than 15 percent water by mass (for comparison, Earth is 0.02 percent water by mass). The outer planets ("f" and "g") were consistent with having more than 50 percent water by mass. This equates to the water of hundreds of Earth-oceans. The masses of the TRAPPIST-1 planets continue to be refined, so these proportions must be considered estimates for now, but the general trends seem clear.

"What we are seeing for the first time are Earth-sized planets that have a lot of water or ice on them," said Steven Desch, ASU astrophysicist and contributing author.

But the researchers also found that the ice-rich TRAPPIST-1 planets are much closer to their host star than the ice line. The "ice line" in any solar system, including TRAPPIST-1's, is the distance from the star beyond which water exists as ice and can be accreted into a planet; inside the ice line water exists as vapor and will not be accreted. Through their analyses, the team determined that the TRAPPIST-1 planets must have formed much farther from their star, beyond the ice line, and migrated in to their current orbits close to the host star.

[...] "We typically think having liquid water on a planet as a way to start life, since life, as we know it on Earth, is composed mostly of water and requires it to live," Hinkel explained. "However, a planet that is a water world, or one that doesn't have any surface above the water, does not have the important geochemical or elemental cycles that are absolutely necessary for life."

Called it [soylentnews.org].

Also at Phys.org [phys.org].

Inward migration of the TRAPPIST-1 planets as inferred from their water-rich compositions [nature.com] (DOI: 10.1038/s41550-018-0411-6) (DX [doi.org])

Related: Powerful Solar Flares Found at TRAPPIST-1 Could Dim Chances for Life [soylentnews.org]
TRAPPIST-1 Older than Our Solar System [soylentnews.org]
Hubble Observations Suggest TRAPPIST-1 Exoplanets Could Have Water [soylentnews.org]
Induction Heating Could Cause TRAPPIST-1 Exoplanets to Melt [soylentnews.org]
Another TRAPPIST-1 Habitability Study [soylentnews.org]


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