Space Probe Will Search Venus for Life in Fortuitous Flyby
Tags: Venus, Space, Science, Aliens, Solar System

by Joel Hruska

It’s a storybook meet-cute that transcends culture: She’s a toxic hellstew with a surface temperature that could melt lead. He’s a half-European, half-Japanese satellite on his way to somewhere else entirely. Despite the promises he’s made, despite his previous feelings, that “somewhere else” suddenly feels very far away. Together, they fight crime could prove the existence of life — or at least phosphine — in Venus’ atmosphere.

A few days ago, news broke that phosphine has been detected in Venus’ atmosphere (just in case you missed that bit). Phosphine is an unusual chemical signature to detect on Venus because, on Earth, it’s only produced in two ways: Man-made chemical reactions and via decaying organic matter. Off-planet, we only know of one other source: Deep inside gas giants.

There’s a distinct lack of humans performing advanced chemical engineering on our sister planet, which seems to knock out #1. Venus, as you are likely aware, is also not a gas giant. The presence of decaying organic matter on the surface also seems unlikely, given that Venus’ atmosphere is so thick, there are no asteroid craters smaller than 3km. Incoming objects less than 160 feet /50m in diameter burn up before reaching the ground. Venus’ atmospheric pressure is so high, it creates types of lava flows not seen on Earth: so-called “pancake domes.” Toss in the balmy 880F (471 C) temperatures, and the surface isn’t what you’d call “friendly” to life. In short, we don’t have a good explanation for where the phosphine could be coming from, or even confirmation that it exists at all.

But that’s where BepiColombo might be in a position to do the world a favor. The Mercury-bound probe is about to slingshot past Venus on October 15, 2020. The first time it flies past, it’ll be fairly distant, at 10,663km above the surface. In August 2021, however, BepiColombo will be much closer — as close as 550km.

Image by the ESA

There’s an instrument on BepiColombo called MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer). It’s designed to study the surface composition of Mercury by measuring the content of the light reflected off the surface. In theory, BepiColombo might be able to use this instrument to check for phosphine in Venus’ atmosphere.

“There actually is something in the spectral range of MERTIS,” says Jörn Helbert from the German Aerospace Center, co-lead on the MERTIS instrument. “So we are now seeing if our sensitivity is good enough to do observations.”

The second flyby next year is expected to have a much better chance of detecting phosphine than the first will. “We possibly could detect phosphine,” ESA’s Johannes Benkhoff, BepiColombo’s Project Scientist, told Forbes. “But we do not know if our instrument is sensitive enough.”

According to the scientists, this detection attempt will be at the very limit of what MERTIS is designed to do, meaning even a negative result won’t necessarily mean phosphine isn’t present. But BepiColombo is the only spacecraft in the area that’s equipped to attempt to check for phosphine, and it can do so before any probe we could launch from Earth.

If BepiColombo verifies that there’s phosphine in Venus’ atmosphere, it wouldn’t automatically mean the phosphine was coming from an organic source. But it would be confirmation that a chemical reaction we can’t easily explain is occurring in a place it shouldn’t be. If the cause turns out to be the results of a previously unknown chemical process — possibly one unique to the environment of Venus — that would be exciting. If it turned out to be caused by some kind of life, it would mean we weren’t alone in the universe.

The chances that we’ll find microscopic life living in the clouds of Venus is remote, but it’s not zero. A lot of eyes are going to be trained on BepiColombo as it shoots past Venus in October, and again when it returns on August 10, 2021.

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