New Detection Of Phosphine Deeper In Venus's Atmosphere – And Possibly Ammonia Too

Astronomers have made new discoveries in the atmosphere of Venus, adding to the compelling complexity and debate over recent discoveries of the molecule phosphine there, and what it means. The unexpected presence of phosphine continues to perplex scientists, but the idea of life in the clouds of Venus continues to be a tantalizing possibility.

From the start , the discovery of phosphine in the atmosphere of Venus has been a revolutionary (and much debated) find. The reason for the uncertainty, however, is simple. Phosphine is a biosignature, which means that its presence could indicate life (and we don't mean Missy Elliot ) – and as far as we can tell, there is no life on Venus or among its clouds. Multiple follow-up investigations have observed the presence of this molecule. Now, the team has presented new evidence for this molecule even deeper in the cloud of Venus, and possibly ammonia too.

There are a number of weirdnesses in Venus's atmosphere. Phosphine is just a new one that's come along.

Dr Dave Clements

The potential presence of this molecule deeper in the planet's clouds has been introduced before. Recent analysis of data from NASA’s Pioneer Venus Multiprobe launched in 1978 found compelling hints for the presence of phosphine at around 55 kilometers (34 miles) of altitude in the clouds. The higher the pressure a molecule experiences, the broader the line will appear in the light spectrum, and such a feature was seen on the phosphine line.

“We haven't properly sorted out the atmospheric modeling for this yet, but there are some broad lines at the level that suggest parts per million level of phosphine at around 55, 56, 57-kilometer altitude, consistent with the pioneer Venus probe data,” Dr Dave Clements , from Imperial College London, told IFLScience.

The observations come from the JCMT-Venus project , which uses the James Clerck Maxwell Telescope to detect and monitor not just phosphine but a variety of other molecules, including sulfur dioxide (SO ₂ ) and water. Dr Clement’s PhD student Wei Tang looked at the variation of water (using heavy water as a tracer) in the atmosphere of the second closest planet to the Sun.

“There are a number of weirdnesses in Venus's atmosphere. Phosphine is just a new one that's come along," Dr Clements told IFLScience. "Amongst the other strange things is the way that the amount of water and the amount of SO ₂ in the atmosphere vary over time. It's not known why. The variations haven't been monitored to a great extent, but it's known that there are variations on time scales from at least days to years."

The team is continuing the analysis of the data they have collected over three observation campaigns. There are challenges when it comes to confirming the presence of these molecules, so they are making sure that their analysis is not creating lines where it shouldn’t as well as using other independent observations to make the results very robust, including data from Pioneer Venus Multiprobe, which had also seen hints of ammonia.

In fact, ammonia might be the next big thing for Venus. The team also report the first tentative detection of ammonia up in the clouds. While ammonia can be easily produced even in a high school lab, its presence on a rocky planet is considered a good biosignature because there is no significant known source of ammonia in terrestrial worlds that does not come from life. This doesn’t mean that it is certain that there’s life on Venus – it means that we do not know yet how it came to be.

We're trying not to overstate, but yeah, it's really exciting.

Prof Jane Greaves

“There are other models coming along all the time, other explanations saying ‘Oh, you could get ammonia and phosphine and all sorts of other unexpected chemicals this way unrelated to life’ so we're trying not to overstate, but yeah, it's really exciting,” Professor Jane Greaves , from the University of Cardiff, told IFLScience.

Still, it was the possibility of life that inspired Greaves and the team to check for ammonia. Chemist William Bains has suggested the possibility for living organisms to use this chemical to counteract the acidity of the clouds of Venus, making little droplets of water livable.

“If there are any microbes in the Venus clouds, they might make certain gases that you wouldn't expect. And ammonia came up as they could use it as a way to neutralize the acid,” Professor Greaves told IFLScience. “We've detected it slightly above the region which we think is warm enough for life. Either it hasn’t got anything to do with life or the gas is perhaps produced by something living but it drifts upwards where it's a bit easier for us to detect.”

The observations come from the Green Bank Telescope in the US, however, given the brightness of Venus, it was hard to calibrate the instrument, so the team is being cautious and calling this a tentative observation of ammonia.

So no confirmation of life yet, but the work done by Greaves, Clements, and their team is extremely exciting and tells us just how complex Venus is as a planet. It is not just “ Earth’s evil twin ” but a changing world with volcanoes , bone-crushing atmospheres, hellish temperatures, and something truly bizarre going on in its clouds. There's much more to find out about this fascinating world, and luckily both NASA and the European Space Agency (ESA) are planning to go back there soon.

NASA's DAVINCI mission, which is also set to study Venus's atmosphere, is currently on schedule to launch at the end of the decade, and this mission will certainly look for phosphine as it flies through the clouds of Venus.

The goal of EnVision , the European mission, is to understand the relationship between the peculiar atmosphere and geological activity, in particular, to find out where Venus went "wrong" compared to Earth.

But we will not have to wait that long for more Venus insights. The team is continuing observation campaigns across multiple telescopes, and not just in the range to see phosphine. Currently, there is a real push to understand Venus and its atmosphere better.

In terms of close encounters, the Rocket Lab Probe , part of the Morning Star Missions, is expected to launch in January 2025 and be the first private mission to another planet. It will enter Venus's atmosphere and hopefully detect some of these intriguing molecules. On top of that, the team hopes to convince ESA's JUICE mission to turn the spacecraft instruments on as it flies by Venus next year on its way to Jupiter.

Papers on the new insights on phosphine, water, and ammonia on Venus are in preparation and the results were presented in a special session presented at the National Astronomy Meeting this week.