It’s a sweet storybook that transcends culture: She’s a toxic hell with a surface temperature that can melt lead. He is a semi-European, semi-Japanese satellite on his way to somewhere else entirely. Despite the promises he has 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 came the news that phosphine has been discovered in the atmosphere of Venus (only if you missed that bit). Phosphine is an unusual chemical signature to be discovered on Venus because it is produced on Earth in only two ways: artificial chemical reactions and by decaying organic matter. Off the plane, we only know of another source: Deep inside the gas giants.
There is a clear shortage of people performing advanced chemical engineering on our sister planet, which seems to knock out # 1. Venus, as you are probably aware, is not a gas giant either. The presence of decaying organic matter on the surface also seems unlikely, given that Venus’ atmosphere is so thick that there are no asteroid craters smaller than 3 km. Incoming objects that are less than 50 meters in diameter burn up before they reach the ground. Venus’ atmospheric pressure is so high that it creates types of lava flows that are not seen on Earth: so-called “pancake domes”. Throw in the mild temperatures of 880F (471 C), and the surface is not what you would call “friendly” to life. In short, we do not have a good explanation for where the phosphine may come from, or even confirmation that it exists at all.
But it’s there BepiColombo may be able to do the world a favor. The mercury-bound probe is about to throw past Venus on October 15, 2020. The first time it flies past, it will be quite distant, 10,663 km above the surface. In August 2021, however, BepiColombo will be much closer – as close as 550 km.
There is an instrument on BepiColombo called MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer). It is designed to study the surface composition of mercury by measuring the content of the light reflected from the surface. In theory, BepiColombo could use this instrument to control phosphine in Venus’ atmosphere.
“There is actually something in the spectrum area for MERTIS,” says Jörn Helbert from the German Aerospace Center, co-leader of the MERTIS instrument. “So we’ll see now if our sensitivity is good enough to make observations.”
The second flyby next year is expected to have a much better chance of detecting phosphine than the first will. “We could possibly discover phosphine,” ESA’s Johannes Benkhoff, BepiColombo’s project researcher, told Forbes. “But we do not know if our instrument is sensitive enough.”
According to the researchers, the detection attempt will be at the limit of what MERTIS is designed to do, which means that even a negative result does not necessarily mean that phosphine does not exist. But BepiColombo is the only spacecraft in the area that is equipped to try to control phosphine, and it can do so before any probe we can launch from Earth.
If BepiColombo verifies that there is phosphine in Venus’ atmosphere, it would not automatically mean that the phosphine came from an organic source. But it would be a confirmation that a chemical reaction that we can not easily explain takes place in a place that it should not be. If the cause turns out to be the result of a previously unknown chemical process – possibly unique to the Venus environment – it would be exciting. If it turned out to be caused by some kind of life, it would mean that we were not alone in the universe.
The chances that we will find a microscopic life living in the clouds of Venus are slim, but it is not zero. Many eyes will be trained on BepiColombo as it shoots past Venus in October, and again when it returns on August 10, 2021.