In a press briefing today, scientists rom the Royal Astronomical Society announced a potentially revolutionary scientific discovery: They've detected the presence of phosphine in the atmosphere of Venus, which suggests the possible presence of biological life. Phosphine is a gas that's a known biosignature, which means it's only present when some form of life is also present — and more than that, it's a gas that also has no known false positives, at least when detected on Earth, that are mistaken for phosphine and not a result of biological life.
This discovery is not a sure sign that extraterrestrial life exists, despite how it may be spun by some outlets and observers. The scientists involved in the discovery all admit as much, noting that it could be the case that our understanding of how phosphine works, especially beyond the context of Earth, is actually very limited. While scientists last year determined that phosphine can only be produced by anaerobic organisms, their research was obviously limited only to its presence here on our planet, which doesn't necessarily encompass all potential cases across the galaxy. Also, until an actual extraterrestrial organic organism is observed directly and confirmed, there's no guarantee of its presence. Scientists also have to confirm that the gas detected is indeed phosphine, since a slim possibility exists that it may instead be sulfur dioxide, for instance — though scientists have verified their observations with multiple observatories so they're fairly certain it is indeed phosphine.
That said, this is definitely one of the most promising signs yet that life beyond Earth could exist, especially given how much phosphine had to be present to even trigger detection to begin with — and more important than that, the discovery was made locally here within our own galaxy. That life may exist in the Venusian atmosphere would be a strong indicator that in general, life is actually much more common and widespread throughout the galaxy than many previously believed.
Venus itself is hardly a place we'd expect to find life by traditional standards — temperatures on the surface approach 900 degrees. But the upper atmosphere could potentially support anaerobic microorganisms — not unlike swarms of algae, which is a theory that has been proposed previously to account for what appear to be UV-absorbent spots located in the clouds we can observe above Venus.
Potentially confirming the presence of microbial life in the clouds above Venus presents a number of potential challenges — and not only technical ones. There's an ethical concern, too, since any attempt to physically collect cloud material above the planet might actually disturb and affect any native lifeforms that would exist. Scientists take great care not to introduce any potential biocontaminants from Earth to extraterrestrial environments, so this would likely involve a lot of debate and ultimately, very careful collection or observation methods.