Scientists Say TRAPPIST-1 Worlds Are Close Enough for Life to Hop Between Them

The newly discovered planets of the TRAPPIST-1 system could be a playground for rock-riding microbes.

Three of the small, dim star’s seven planets orbit firmly within its habitable zone – the region with the right temperature to retain liquid water, thought to be a requisite for life. They keep close to each other, only a few times the distance between Earth and the moon, looming large in one another’s sky.

At such short distances, when a meteorite hits the surface of one of the planets, the resulting debris could make its way between them.

If bacteria or other forms of life stowed away on a piece of debris, they could hitch-hike between worlds in a process called panspermia. Some scientists believe life on Earth may have started this way, as microbial stowaways from Mars.

Now, Manasvi Lingam and Avi Loeb at Harvard University have determined that this sort of transfer is 1000 times more likely to occur between the TRAPPIST-1 planets than between Earth and Mars.

Bringing life to another planet is more complicated than just flinging rocks. Any stowaways would have to survive the vacuum and harsh radiation in space, which few known organisms can do. But the quick commute between TRAPPIST-1’s habitable planets – about 100 times quicker than between Earth and Mars – should help.

“Because these distances are so close, a lot more different kinds of species, microbial or otherwise, could migrate from one planet to another,” says Lingam.