Is there microbial life floating around in the clouds of Venus? Scientists have long pondered this question and soon we may get some answers. A new report outlines the Venus Life Finder Missions, starting with a cloud-skimming mission in 2023 to search for signs of life.
At a glance, Venus hardly seems like a promising place to find life. Surface temperatures soar to 464 °C (867 °F) – hot enough to melt lead – under a smothering atmosphere almost entirely composed of carbon dioxide, with pressures up to 92 times higher than at sea level on Earth.
But many scientists speculate that there could be a hidden oasis in the clouds, at altitudes between 48 and 60 km (30 and 37 miles). Up there the pressure is less intense, it’s much cooler and there’s more water in the air, which could all help microbial communities thrive. Sure, they’d have to deal with concentrated sulfuric acid, but cloud particles could provide some shelter, according to the hypothesis.
Adding more fuel to the fire, in September 2020 a team of scientists reported the detection of a gas called phosphine in the Venusian atmosphere. This molecule is rare on Earth and is usually only produced by anaerobic microbes, meaning it’s considered a potential biosignature to look for on other planets. Nobody expected to find it right next door though.
Alas, the bubble burst a few months later, as another team re-examined the data and found that the most likely culprit behind the signal wasn’t phosphine but sulfur dioxide, one of the most common components of Venus’s atmosphere. Either way, it seems like the only way to find out for sure is to go back – and that’s where the Venus Life Finder Missions come in.
“There are these lingering mysteries on Venus that we can’t really solve unless we go back there directly,” says Sara Seager, principal investigator for the Missions and a team member on the phosphine detection study. “Lingering chemical anomalies that leave room for the possibility of life.”
The Venus Life Finder Missions will do exactly what it says on the tin – send missions to Venus to find signs of life. The project involves three missions over the next decade, each one building on the findings of those before it. The team involves scientists from MIT, Georgia Tech, Purdue University, Caltech and the Planetary Science Institute, and was privately funded by Breakthrough Initiatives and Rocket Labs.
The first mission is set to launch as soon as May 2023, atop Rocket Lab’s Electron launch vehicle. Electron will release a spacecraft called Photon to head towards Venus, before releasing a small probe that will enter the planet’s atmosphere.
The probe will contain an instrument called an autofluorescing nephelometer, which will shine a laser through a window onto the clouds. If there are any organic or complex molecules out there, they’ll fluoresce in response to the laser light.
“If we see fluorescence, we know something interesting is in the cloud particles,” says Seager. “We can't guarantee what organic molecule it is, or even be certain it's an organic molecule. But it's going to tell you there's something incredibly interesting going on.”
The nephelometer can also figure out what shape the droplets are, by measuring the pattern of light that’s reflected back. If it’s pure sulfuric acid, the droplets should be perfect spheres, so any other type of signal would be further evidence of other chemistry.
The instrument won’t have long to gather data though – the extreme sulfuric acid content in the clouds will destroy the probe in as little as three minutes.
The second mission is set to follow in 2026. This would include a balloon that would float for a week or two at an altitude of 52 km (32 miles), deploying four mini probes to measure acidity and water vapor content. And finally, in 2029 an ambitious third mission would attempt to capture about one liter of Venusian atmospheric gases and return the sample to Earth for more rigorous analysis.
The Venus Life Missions report has been published online.
Source: MIT