Last week there was a bit of fuss in the news about whether scientists have found evidence of life on Venus. The short answer is: they haven’t. But they have found something very interesting.
Evidence of a molecule called phosphine (PH3) has been detected in the Venusian atmosphere. This came as such a surprise, that the researchers confirmed it with two different telescopes – the JCMT and ALMA – before publishing their result.
Full article here
Why is Phosphine interesting?
On Earth, the molecule Phosphine is produced primarily by microbial life. Although it can be made by other means, the amount detected is so large (20 parts per billion) that its production is difficult to explain. In their study, the researchers calculated and ruled out the origin of phosphine on Venus from:
— chemical reactions from molecules known to exist in the Venusian atmosphere
— chemical reactions from sub-surface material (i.e. volcanoes etc.)
— UV radiation causing reactions producing phosphine
— lightning causing reactions producing phosphine
— meteorites delivering phosphine to Venus
— large scale comet / asteroid impact delivering phosphine
— solar wind / charged particles interacting in the atmosphere…
None of these explanations could match the data. So the message is:
“We have detected the presence of a molecule in the atmosphere of Venus. We can’t explain by non-microbial means, but on Earth it is produced by microbial life. Can someone explain this?“
Which, with true scientific caution, is not quite the same as “We have found life!”
As Isaac Asimov once famously said:
“The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’ but rather ‘That’s funny…’ “
How was the presence of phosphine confirmed?
Slightly technical here, so feel free to skip this part.
All molecules have specific configurations of electrons occupying energy states around their atoms. When these molecules receive energy, such as from photons of light or radiation, the electrons change energy state in discrete transitions. The amount of energy corresponds to a wavelength of electromagnetic radiation. In a spectrum of light from the atmosphere, this wavelength is reduced, causing an “Absorption line” to appear.
Side note: the opposite effect of releasing energy leads to an increase in a particular wavelength, causing “Emission lines”.
Each molecule has a unique combination of possible transitions, creating a fingerprint in the electromagnetic spectrum.
The fingerprint of phosphine in the atmosphere of Venus was detected via an absorption line at 1.123 mm wavelength (i.e. infrared to radio radiation), first with the JCMT (James Clark Maxwell Telescope) and then confirmed with ALMA (the Atacama Large Millimetre / sub-millimetre Array).
The height of phosphine in the atmosphere could be determined from the width of the absorption line. As the planet is rotating, and different layers of atmosphere move at different speeds, an effect similar to the Doppler effect (why sirens change tone when they go past) causes absorption lines to broaden.
What does this mean for alien life?
We’re still looking. Venus, is a hostile place – if you were to dive through the atmosphere and had enough oxygen with you to avoid breathing in sulphuric acid, you’d still be burnt to a crisp before reaching the surface.
Nevertheless, the part of the atmosphere where Phosphine was found is the most hospitable region, with conditions most similar to those found on Earth. If life was found and confirmed on Venus, it would mean that life can survive in far more widespread conditions than previously thought. A large number of exoplanets are currently known – instead of looking for “Earth-like” exoplanets, the door would be thrown wide open for finding life in all kinds of environments.
Ultimately, we are very far from finding another home for ourselves. So in the meantime, we need to take better care of this one planet Earth that we still have.
Stay tuned, let’s see what happens next.