Life on Jupiter

Life is speculative, but it's worth considering, says Duncan Forgan, an astrobiologist at the University of St. Andrews in the United Kingdom, who did not participate in the study, but says he is close to the team. "It really opens up the field in terms of the amount of objects that we could then think, well, these are habitable regions," he says.

So far, only a few dozen cold brown dwarfs have been discovered, although statistics suggest there should be about 10 to less than 30 light-years from Earth. These dwarfs should be targeted for the James Webb Space Telescope (JWST), which is sensitive in the infrared where the brown dwarfs most standing out. After launching in 2018, JWST should reveal the climate and the composition of its atmospheres, says Jackie Faherty, an astronomer at the Carnegie Institution for Science in Washington, DC "We will begin to obtain magnificent spectra of these objects," she says. "This makes me think about it."

Proving the existence of life would require anticipating a strong spectral trace of by-products of microbes such as methane or oxygen, and then differentiating them from other processes, says Faherty. Another problem would be to explain how life could arise in an environment that lacks water-rock interfaces, such as hydrothermal vents, where life is thought to have begun on Earth. Perhaps life could develop thanks to chemical reactions on the surfaces of dust grains in the atmosphere of brown dwarfs, or perhaps it was possible to gain support after arriving aboard an asteroid. "Having tiny microbes floating in and out of the atmosphere of a brown dwarf is great. But you have to get them there first, "says Forgan.