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To Venus and beyond: how close are we to finding life on another planet?

sky, star, moon

We could be closer than we think to finding life on another planet… literally. Earth’s nearest neighbour, Venus, is showing signs of life, while the search continues on Mars and beyond.

Dr Tana Joseph

Given how 2020 is unfolding, would it really be surprising if this was the year we found life on other planets? We’ve been searching for life on Mars for quite a while, and, as we explain below, we could be heading to Jupiter and Saturn’s moons to look for life in a few years’ time. But Venus, our closest neighbour and the second planet from the sun, is starting to look promising. 

The idea that we might find some form of life on Venus soon might sound crazy, but it’s actually not that far off. A few weeks ago, a team of astronomers announced that they had discovered some “anomalous and unexplained chemistry” on Venus that could take us one step closer to that reality.

This group of researchers, led by Prof. Jane Greaves from the University of Cardiff, have discovered a stinky gas called phosphine in the clouds that make up the upper atmosphere of Venus. Phosphine, a molecule consisting of one phosphorus atom and three hydrogen atoms, is manufactured on Earth for use in industries like agriculture. It can also be produced naturally by certain kinds of bacteria here on Earth. So, the presence in the Venusian atmosphere could be a sign that there’s life on our nearest planetary neighbour!

But what if the detection was a mistake? Prof. Greaves’ and her team checked that out too. They initially collected data using the James Clerk Maxwell Telescope in Hawaii in 2017. They were so surprised to find phosphine that they took more data using the Atacama Large Millimeter Array telescope, based in Chile, in 2019 to double check what they were seeing. The data from these telescopes agreed with each other. So the discovery was real. 

Could  something else have produced the phosphine in the clouds around Venus? The researchers ran tests and did calculations on almost 100 chemical reactions that could lead to the production of phosphine in the clouds of Venus. But, given the temperatures, pressure and chemical makeup of Venus’ atmosphere, none of these processes could produce as much of the smelly gas as they had detected. They also checked to see if the gas could have come from on or below the surface of the planet. No dice. They even looked into whether volcanic activity, lightning strikes or meteorite impacts could account for the phosphine, and they couldn’t. So for now, a biological origin is the leading contender for the production of phosphine in Venus’ atmosphere.

Seeing the potential signs of life on Venus might seem rather unexpected. After all, this planet has surface temperatures of over 400 ℃, not to mention an atmosphere that’s nearly 100 times denser than the Earth’s and extremely acidic to boot! But finding life on Venus would be a surprise only if we think inside the box of what constitutes a cosy environment for living organisms. Just because we can’t readily picture life in these harsh conditions doesn’t mean that there aren’t life forms that could thrive on Venus. 

In fact, there are life forms right here on Earth that live quite happily in extreme conditions. They’re called extremophiles: organisms that live in boiling hot water, acid lakes or the deepest trenches in the ocean. Some are even resistant to radiation levels up to 3000 times stronger than what we can handle as humans. Studying these freaky-deaky creatures has given scientists a lot of insight into what kind of lifeforms we could expect to find living in our Solar System.

So, where else are we looking for alien life? Well, there’s always Mars. Mars is a close neighbour that has been explored extensively compared to the other planets that orbit the Sun. To date,  14 spacecraft have been sent to the Martian surface from Earth. And so far, we’ve mapped 90% of the Martian surface. We’ve been searching for life on Mars since 1971, but we haven’t turned up any conclusive evidence yet.

The latest spacecraft making its way to the red planet is Perseverance. Launched in July, Perseverance is expected to land in February 2021. Like its predecessors, Perseverance will take soil and rock samples, looking for signs of ancient life on the planet. Unlike its predecessors, Perseverance will also listen for sound on Mars and the samples it collects might actually return to Earth! If this return is successful, we will be able to study soil and rock samples from Mars using the most sophisticated laboratories on Earth. And who knows what we could uncover then?

But wait, there’s more! What if we told you scientists were looking for life on moons? Because that’s exactly what they’re planning to do. Europa (a moon of Jupiter), Enceladus and Titan (two of Saturn’s moons) are considered by astrobiologists as some of the most likely places to harbour some type of life. And we could be sending missions to these far-flung moons as early as 2026. So, watch this space for more details. We may be saying hello to some aliens sooner than we think.

Dr Tana Joseph is the founder and director of AstroComms (Science, Technology, Engineering and Mathematics (STEM) Consulting and Communications)