January 7, 2020
Researchers at the Massachusetts Institute of Technology (MIT) have found that the presence of a molecule that is considered to be among the most noxious-smelling and poisonous on Earth may indicate that alien life is in residence.
Phosphine is among the most putrid and toxic gases on Earth, and is found in some of the foulest of places—among them, penguin dung heaps, the depths of swamps and bogs, and even in the bowels of some badgers and fish. Most aerobic, oxygen-breathing life forms on the planet avoid phosphine—often referred to as “swamp gas”—like the plague.
Now, MIT researchers have found that phosphine is produced by another, less abundant life form: anaerobic organisms, such as bacteria and microbes, which don’t require oxygen to thrive. The team found that phosphine cannot be produced in any other way except by these extreme, oxygen-averse organisms, making the gas what is known as “a pure biosignature”— a sign of life (at least of a certain kind).
In a paper recently published in the journal, Astrobiology, the MIT team reports that—if phosphine were produced in quantities similar to methane on Earth—the gas would generate a signature pattern of light in a planet’s atmosphere. This pattern would be clear enough to detect from as far as 16 light years away by a telescope such as NASA’s planned James Webb Space Telescope.
“Here on Earth, oxygen is a really impressive sign of life,” says lead author Clara Sousa-Silva, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “But other things besides life make oxygen too. It’s important to consider stranger molecules that might not be made as often, but if you do find them on another planet, there’s only one explanation.”
Sousa-Silva and her colleagues are assembling a database of fingerprints for molecules that could be potential biosignatures. The team has amassed more than 16,000 candidates, including phosphine.
She says that, aside from establishing phosphine as a viable biosignature in the search for extraterrestrial life, the group’s results provide a pipeline, or process for researchers to follow, in characterizing any other of the other 16,000 biosignature candidates.
“I think the community needs to invest in filtering these candidates down into some kind of priority,” she says. “Even if some of these molecules are really dim beacons, if we can determine that only life can send out that signal, then I feel like that is a goldmine.
Research contact: @MIT