Search For Extraterrestrial Life: Collisions In Trappist-1 System May Have Seeded Multiple Exoplanets

Emergent life on one of the closely packed TRAPPIST-1 exoplanets may have given rise to life on one or several of its sister planets via a violent transfer process, a new study suggests. The possibility exists that a large enough object — an asteroid, comet, or dwarf planet — could have impacted, dislodged, and ejected life-bearing material from one planet with enough force to propel it to another of the planetary system’s worlds.

Phys.org reported last week that University of Chicago postdoctoral scholar Sebastiaan Krijt took the idea of extraterrestrial life developing on one of the three exoplanets astronomers determined were in Trappist-1’s habitable zone and decided to conduct simulations to see if it was possible for life to make the trip from one exoplanet to another and, if so, by what means. Krijt and his team of researchers found that it was indeed possible for living organisms — life forms such as bacteria and other microorganisms — to survive the transfer process between exoplanets (a TRAPPIST-1 version of panspermia, the theory that living organisms are prevalent throughout the universe and are transferred via collisions with space objects like asteroids and comets), thereby seeding the life that had emerged on one planet on a sister world. However, not only would the initial event be violent and disruptive, the life forms would also have to be able to survive the impact, the acceleration off-planet, the trip through space, and being deposited in a totally alien environment after likely having to endure the rigors of atmospheric reentry.

According to the research, if a massive asteroid or comet could have impacted one of the TRAPPIST-1 planets and launched planetary debris into space large enough to insulate living organisms from the hardships faced during space travel. The life-bearing material, or ejecta, would have had to be expelled after impact at a rate fast enough to attain escape velocity from the planet’s gravitational pull — but not so fast that the acceleration would itself cause the destruction of the passenger life form. Once departed from its home world, the large material mass would likely have to make a relatively short journey so that its living cargo could survive.

Several simulations revealed that just such a process within the TRAPPIST-1 system in as little time as a decade. The research also indicated that the ejected mass large enough to cocoon the life it carried and still survive irradiation in space and the burning reentry process on another planet would necessarily have to be propelled from its home world at just above actual escape velocity.

“Given that tightly packed planetary systems are being detected more frequently, this research will make us rethink what we expect to find in terms of habitable planets and the transfer of life—not only in the TRAPPIST-1 system, but elsewhere,” said Fred Ciesla, University of Chicago professor of geophysical sciences and a co-author of the paper. “We should be thinking in terms of systems of planets as a whole, and how they interact, rather than in terms of individual planets.”

Ciesla noted that the search field of exoplanetology was “exploding and being considered more seriously.”

He added, “If we took the solar system as a model, we could never have imagined the things we’re finding, such as the recent discovery of a planet that orbits two suns.”

Those exoplanets with two suns — dubbed “Tatooine planets,” after the home world of Luke Skywalker in the popular science fiction film Star Wars — have not only been found to be in existence, but recent research has also shown that, given the right orbital position, some of those exoplanets could be habitable themselves. In fact, one study noted that the planets would not necessarily have to be desert worlds (like the aforementioned Tatooine, whose binary parents had deprived it of most of its water — collectors could still pull water out of the atmosphere) but could actually be waterworlds.

The TRAPPIST-1 planets have been a constant source of speculation, especially concerning the possibility of extraterrestrial life, since the announcement of its existence in February. Their relative proximity to each other prompted a quick look at the possibility of panspermia. A study released in March by Manasvi Lingam and Avi Loeb of Harvard University found that panspermia between three of the seven exoplanets of the system was 1,000 times more likely to occur than between Mars and Earth.

And it is not inconceivable that material from Earth, the one planet where we know life exists, might have been or might still be traveling through space as a potential seeding object.

“Material from Earth must be floating around out there, too,” Ciesla said, “and it’s conceivable that some of it might be carrying life. Some forms of life are very robust and could survive space travel.”

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