A UK-based mission is aiming to settle, once and for all, whether life exists on Venus. The mission plans to send a probe to the planet in search of microbial life, not on the surface, of course, but in the Venusian clouds.

Over the past half-decade, scientists have detected the presence of phosphine and ammonia—two potential signs of biological activity—in Venus’s clouds. On Earth, both gases are produced only by biological activity and industrial processes, and scientists are unsure of their origin on Venus.

Given the planet’s thick, toxic atmosphere, scorching surface temperatures, and crushing surface pressure, a booming industrial economy seems unlikely. But microbes—which can thrive in Earth’s hottest, most toxic environments—might be able to survive on Venus and produce these gases, researchers posit.

“Our latest data has found more evidence of ammonia on Venus, with the potential for it to exist in the habitable parts of the planet’s clouds,” Jane Greaves, an astronomer at the University of Cardiff, said in a statement. “There are no known chemical processes for the production of either ammonia or phosphine, so the only way to know for sure what is responsible for them is to go there.”

At this year’s Royal Astronomical Society National Astronomy Meeting, researchers from the University of Cardiff presented their plan to search for and map phosphine, ammonia, and other hydrogen-rich gases that might indicate the presence of microbial life on Earth’s twin.

The mission, called the Venus Explorer for Reduced Vapours in the Environment (VERVE), will send a CubeSat-sized probe aboard the European Space Agency’s EnVision mission—a larger mission designed to probe Venus’s surface and interior, scheduled for launch in 2031. VERVE will detach upon arrival and carry out an independent atmospheric survey.

Researchers first detected phosphine in Venus’s clouds in 2020. The finding was controversial, however, as follow-up studies failed to replicate the results.

But a subsequent project, JCMT–Venus, designed to study the molecular composition of Venus’s atmosphere using the James Clerk Maxwell Telescope in Hawaii, offered a possible explanation for these disparate findings. Researchers tracked the phosphine signature over time and found it could only be detected at night, as it was destroyed by sunlight. They also discovered that the amount of gas in Venus’s atmosphere varied over time.

Last year, at the National Astronomy Meeting, researchers also reported the detection of ammonia in Venus’s atmosphere.

Although surface temperatures on Venus reach around 450 degrees Celsius, conditions become much more reasonable about 31 miles (50 kilometers) above the surface, where temperatures range from 30 degrees Celsius to 70 degrees Celsius. Researchers believe it may be possible for extremophiles—like those found in Earth’s hydrothermal vents and deep-sea trenches—to survive in these conditions.