TRAPPIST-1 worlds are close enough for life to hop between them
Neat. "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."