The TRAPPIST-1 system has totally entranced Earthlings since NASA announced its discovery last month. For both astronomers and tinfoil hat believers (*raises hand*), TRAPPIST-1 is a sign of hope for finding alien life, since three of its planets are located in the habitable zone which supports liquid water. With water comes life, and with life comes alien conspiracy theories — at least that's the idea.
Artist's rendition of a TRAPPIST-1 planet. (Image: NASA)
A new study from Manasvi Lingam and Avi Loeb at Harvard University makes the question of life in TRAPPIST-1 even more compelling: The researchers suggest that the TRAPPIST-1 planets are close enough to each other that microbes could travel from one world to another, via rocks. According to the team's hypothesis, when an object collides with a TRAPPIST-1 planet, it will send material into space, which could wind up on a neighbouring planet. This idea of travelling life is known as the theory of panspermia, and some scientists have suggested that life on Earth could have started in this way — by microbes from Mars hitchhiking their way to Earth after a large impact.
Last month, the solar system lost its collective chill when NASA announced the discovery of a seven-planet system called TRAPPIST-1, just 39 light-years from our Sun. The system is particularly exciting, not only because of its proximity to our planet, but because it has three planets within the habitable zone, where liquid water (and potentially life) could be supported. There's already a website dedicated to these mysterious planets, filled with stunning art and literal fan fiction. In short, TRAPPIST-1 is already getting the One Direction treatment.
"The rocks are driven into space," Harvard astronomer Avi Loeb, who is a co-author on the paper, told Gizmodo. "If there is life on one of them, life may be preserved inside these rocks and be transferred to another planet."
To test their idea, the team created models based on the way certain species on Earth have immigrated between neighbouring islands. They found that between the habitable planets, the likelihood of transfer of life is 1000 times greater than between Earth and Mars, since the planets are tidally locked in a tightly stacked orbit around their star. If one planet contains microbes, it's very likely the others will have life as well.
"These planets are similar to islands on the surface of the Earth, and there are studies of the immigration of species from one island to another," Loeb explained. "We used the same model to illustrate that the likelihood is very high for transfer of life."
Of course, this idea can only work if the TRAPPIST-1 planets in the habitable zone have atmospheres — after all, liquid water cannot exist without one. Loeb said that the next step is to observe the way the three planets pass in front of their star and measure the fraction of light that could indicate an atmosphere. After that, it will be crucial to study the composition of the planets' atmospheres to find out if they have oxygen and other so-called "building blocks of life".
At least in TRAPPIST-1, we have quite a few chances to find microbes, which would change our perception of life as we know it.
"We can roll the dice three times in this system compared to Earth, which is the only planet where we know life exists in the solar system," Loeb said. "So at least you have three chances."