One way astronomers plan to hunt for life on worlds orbiting other stars is to sniff out compounds in a planet’s atmosphere that might have been produced by living organisms. But some recent studies of worlds in our own solar system show just how tough that’ll be.

Last year, a team said it detected phosphine in the atmosphere of Venus. Most of the phosphine on Earth appears to be associated with microscopic organisms. That suggested that the phosphine on Venus could be produced by microbes in the clouds.

But other scientists disagreed with that conclusion. This summer, one team said the phosphine could have been produced by volcanoes — no life required.

Another disagreement concerns methane on Mars. Methane is another compound that, on Earth, is produced mainly by life. On Mars, the Curiosity rover has measured several outbursts of it. But a Mars orbiter has detected almost none. That could mean that any methane at the surface is destroyed as it climbs into the atmosphere, leaving nothing for orbiters to find.

Another team recently reported finding methane in plumes of ice from Enceladus, one of the moons of Saturn. The ice probably comes from an ocean of liquid water below the moon’s crust. So the methane could be produced by organisms living in the ocean. But that detection hasn’t been confirmed, either.

So finding life beyond our own planet isn’t easy — whether it’s on a sister world, or out among the stars.
 

Script by Damond Benningfield