The prospect of discovering alien life on any one -- or several -- of the Trappist-1 planets has captivated the imaginations of the people of Earth since NASA broke the news of the red dwarf star's treasure trove of Earth-sized worlds, not to mention the fact that three -- and later four -- of the seven planets were located within the star's habitable zone. And now, a study has emerged presenting the probability with which alien life might have prospered within the Trappist-1 planetary system through panspermia (that is, moving from world to world via collision and or ejecta transference).
The newly discovered Trappist-1 planets could be a veritable "playground for rock-riding microbes," New Scientist reported this week, noting that a recently published study from 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. (Note: Mars meteorites have been discovered on Earth. There is a theory that life on Earth began via a Mars meteor carrying microbial hitchhikers billions of years ago.) This is due to a trio of the Trappist-1 habitable zone planets being far closer to each other than Earth and Mars. All three can be observed in each other's skies.
Lingam said of the proximity: "Because these distances are so close, a lot more different kinds of species, microbial or otherwise, could migrate from one planet to another."
It is likely, the study suggests, that if there is life on one of the Trappist-1 planets, there will be life on all three. Not only that, the life found on the planets will likely have analogous organisms on all three.
Said Loeb, "It would not be surprising to find the same forms of life on all three habitable planets near Trappist-1."
Lingam and Loeb compared the Trappist-1 system to a string of islands, then used island ecology mathematical methods to describe migration and extinction between the chain.
Still, the presence of alien life on a Trappist-1 world is not as simple as organisms just taking a ride and getting off on a nearby planet. The microbes would also have to survive the ordeal of space travel (the vacuum, the radiation), perhaps even the burn of entering an alien atmosphere, then a possible second burn, not to mention the force of impact, as the meteor slams into its new home world. And yet, survival by micro-organisms, at least during the space travel portion of the trip, is possible.
The study has its detractors. Biologist Valeria Souza at the National Autonomous University of Mexico said of the probability of panspermia, "This work is interesting, but no, planets are not islands, even if they are close." She added that migration between islands is still a difficult process -- even on Earth. Regardless, she concluded, evolution would take different paths upon arrival.
Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University in Ithaca, New York, noted that theory of panspermia has yet to be validated. She suggested it would be a "fascinating story in science really would be that life evolved on all of these planets individually and you could see the diversity of what nature could come up with."
All this is presupposing that the volatility of Trappist-1, a young red dwarf star that fires off radiation bursts every two hours, hasn't left the planets in the system barren and irradiated and without atmospheres.
This is the second controversial study presented by the Harvard duo in less than a month. At the end of February, Lingam and Loeb posited that it was feasible for a technologically advanced alien civilization to build a transmitter to fire off an energy beam directed at a massive light sail that could be powered to drive a craft through space. They suggested that it could be the "leakage" of this energy beam spilling out around such a sail that astronomers are picking up as "fast radio bursts," the mysterious milliseconds-long bursts that have been detected emanating outside our galaxy.
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