There's new hope the Trappist-1 planets could have water
The Earth-sized planets around the nearby star may have maintained water oceans for billions of years.
In February, scientists discovered a whopping seven Earth-sized planets around nearby dwarf star Trappist-1. Now new research bolsters the prospect that the system's three habitable zone planets host water oceans that maybe, just maybe, could support alien life.
An international team used observations by NASA's Hubble Space Telescope to estimate how heat and ultraviolet radiation from the ultracool star may have affected the planets' water stores over the past eight billion years. The scientists' models suggest the system's innermost planets may have already transformed from water worlds to more parched places, losing more than 20 times the amount of ocean water on Earth.
The outer planets in the so-called "goldilocks zone," where conditions could be more favorable for life, likely lost much less water according to the models. What's more, they may have retained water on their surfaces and interiors after all those billions of years.
"In terms of habitability, this is a positive step forward to say that hopes are still high," said study co-author and MIT postdoc Julien de Wit in a release. "A few of these outer planets could have been able to hold onto some water, if they accumulated enough during their formation. But we need to gather more information and actually see a hint of water, which we haven't found yet."
In other words, no one has looked through a telescope and been able to say "look, that right there is water." But scientists believe the planets originally formed further away from their current orbits in a colder zone that allowed them to collect a lot of water ice crystals, creating massive stores of water.
"It depends a lot on their initial water content," said Geneva Observatory's Vincent Bourrier, lead author of a paper on the findings (PDF) published Thursday in the Astronomical Journal. "If they formed as ocean planets, even the inner ones would likely still harbor a lot of water. We are still a long way to determining the habitability of these planets, but our results suggest that the outer ones might be the best targets to focus our future observations."
Up next, the team will use Hubble to look for clouds of hydrogen around the planets that might further strengthen the notion that they harbor significant oceans and, perhaps, equally exciting alien beach parties.
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