If I was to ask you which object in our Solar System was likely to have alien life, what answer would you give?
Maybe Mars, or some of the moons of Jupiter or Saturn?
I'd wager that you probably wouldn't have answered Venus, our similar sized, next-door neighbour closer to the sun.
Venus, while looking spectacular in the evening sky over the past few months, is in fact a hellish world that you would want to stay far away from.
Due to the runaway greenhouse effect (the same process that is currently causing our own planet to warm up), the temperature on Venus is the highest of any planet in the solar system - a blistering 450 degrees.
The atmosphere is made of oppressive carbon dioxide, causing a pressure of about 90 times that of Earth.
If that isn't enough, Venus' clouds rain sulphuric acid - a very corrosive substance commonly found in car batteries.
Surely there can't be life on our planetary twin!
However, that was exactly the claim of a number of UK astronomers a couple of years ago.
Using the ALMA radio telescope, they analysed the atmosphere of Venus and found traces of the molecule phosphine.
There are trace amounts of phosphine in our atmosphere, and it is widely thought to be produced by life.
This discovery upended the astrobiology community overnight - perhaps there is life on Venus after all, people wondered.
Of course, though, extraordinary claims require extraordinary evidence.
Other astronomers from around the world obtained and reanalysed the data, wanting to make sure that the detection was real.
With all the attention on this one dataset, the ALMA observatory itself realised that the data had been incorrectly processed.
After re-uploading a fixed version, the detection of phosphine was found to be much weaker than the original claim.
As such many astronomers began to dispute the result; instead, the phosphene was more likely explained by sulphur dioxide in the upper atmosphere.
Sulphur dioxide is the third most common molecule in Venus' atmosphere, and not evidence for alien life.
This did not deter the original team and their supporters though, and to this day there is still a debate on whether the phosphine detection is real.
Until new, more precise observations are made, the question on whether there may be life on Venus remains open.
This whole story is also a wonderful example of how modern science is done.
A group of scientists obtain some data and analyse it, working to see if it confirms or rejects a hypothesis (in this case, that there is phosphine on Venus).
Once publishing this result, however, other scientists then scrutinise and re-analyse the same data to see whether they reach the same conclusion.
This process is known as peer-review, and is one of the reasons we can be sure about many scientific facts.
So, if you see extraordinary scientific claims out there without proper scientific scrutiny, take them with a grain of salt.
And as for life on Venus?
Well, for now it remains one more mystery for astronomers to ponder.
- Jonah Hansen is a PhD student specialising in space interferometry at Mount Stromlo Observatory, at the Australian National University.
