This is how science works

Last time, there was a bit of excitement about the possibility of phosphine in the Venusian atmosphere. This time, I’d like to update the current status of this result and explain how science progresses in practise.


For any measurement or experimental finding to be considered true and reliable, the results must be reproducible. Independent teams must be able to reach the same conclusion with independent methods or an independent analysis. So upon the news of this exciting finding about phosphine in the Venusian atmosphere and its potential implications for life in our solar system, this is exactly what the scientific community attempted to do – to check and verify the results.

No phosphine? Mis-interpretation?

  1. 15/10/2020 Encrenaz et al. “A stringent upper limit of the PH3¬†abundance at the cloud top of Venus
    This team attempted to search for the same spectral feature using data from a different instrument – and did not detect phosphine, instead only placing a limit on the abundance.
  2. 19/10/2020 Snellen et al. “Re-analysis of the 267-GHz ALMA observations of Venus: No statistically significant detection of phosphine
    This team reanalysed the data used in the original study (from ALMA), and criticised the method used, suggesting that it could create spurious signals that seem to be significant, but are false. They conclude the original results are unreliable.
  3. 28/10/2020 Thompson “The statistical reliability of 267 GHz JCMT observations of Venus: No significant evidence for phosphine absorption
    This person reanalysed the other dataset used in the original study (from ALMA) and also has the same criticism of the original method used – finding that it can create falsely significant features and that in their reanalysis no indication for phosphine is found.
  4. 27/10/2020 Villanueva et al. “No phosphine in the atmosphere of Venus”
    Possibly the most robust refutal of phosphine detection came from the 26 member strong team claiming no detection of phosphine. The original dataset was, apparently, subject to severe calibration issues. Following their independent calibration and analysis (with different methods), they also did not find any evidence for phosphine. This team also considers that the most significant spectral feature indicating phosphine (PH3) could actually be explained by sulphur dioxide (SO2) — a far less controversial molecule to find in that environment.

Response of the original team

With criticism like that, the original team had to respond and defend their findings. On 16/11/2020, Greaves et al. did just that: “Re-analysis of Phosphine in Venus’ Clouds” in which they re-calibrate and re-analyse the data (removing the aforementioned issues). The detection of phosphine is “tentatively” recovered – at a level 7 times lower than that of their first paper. They also dispute the SO2 interpretation.
(At this point, it is worth noting that at least one independent group supported the detection of phosphine.)

reliable, reproducible, repeatable.

Scientists don’t always agree, especially when results are new. Findings must be considered reliable enough for others to trust; reproducible by independent groups and methods; and repeatable with different experiments and new data.

So far, it seems the detection of phosphine is neither reproducible, nor reliable – failing two of these tests. Repeatable with new data? Let’s wait and see.
Progress in science is made by trial and error; consensus reached by scientific debate; it’s not always black and white.

Life on Venus?

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…’

Venus in false colour from the Mariner 10, 1974

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.

Times of Change

We live in interesting times. Or at least, not many of us can remember a situation where the whole world was impacted so uniformly by the spread of a virus. The last truly global pandemic incident was probably the 1918 Spanish flu. More people died in that influenza pandemic than during the first world war.

Whilst this disruption to our usual routines is threatening, there is no need for the panic buying and extreme media hype surrounding the issue. Covid-19 is certainly a lot less deadly than many other infectious diseases. However, neither is it the time to shrug our shoulders and say “it’s just a flu”.

Global information

With so much noise and fake news circulating as well as situations changing by the hour, it is important to rely on trusted sources such as the World Health Organisation. The site does a good job of visualising the latest information.
Several countries are currently adopting an approach of only testing serious or “at risk” cases; which makes sense from a treatment perspective. Yet wider testing, where possible, will help us to get a much better understanding of this new disease.

Social distancing is one of the few measures that has been shown to effectively “flatten the curve” and slow the rate. At the time of writing, cases in most European countries are continuing to double every 2-3 days.

Many of us are now expected to work from home. Schools and universities, shops, restaurants and sports centres are closed. Travel disrupted, borders restricted and a large number of professional and social events cancelled. Research and academia, outside of lab work, is one of those jobs that can be done almost anywhere, provided there is a laptop and an internet connection. In that sense, we are very fortunate in our flexibility. Although universities are trying to continue students education, it is almost inevitable that there is a reduction in teaching hours. Many conferences and meetings have been cancelled, postponed, or replaced by remote calls. Working from home is, nevertheless, a challenge.

The positives

So, what are the best things about Covid-19?

— The reduction in commuting, travel and meetings can free up time for other things; more time for writing and research, perhaps? Certainly many people are rediscovering various pastimes.

— Globally, this has drastically improved emissions and led to noticeable improvements in the health of the environment. It shows that if politicians really wanted to act against climate change, they could.

— Something to consider – is our usual rate of travel and meetings really necessary? A reduction in the number of face-to-face meetings and improved options for remote connection could help many people who can’t always attend in person.

— If working from home emerges as a viable option for such a large portion of the population, will employers become more accepting towards the idea of flexibly working from home more often?

— On a more social level, although we no longer shake hands, many people are making more of an effort to connect with friends, family and neighbours – whilst maintaining distance, of course.

— Shared experience will perhaps make us more empathetic towards each other and, if it’s not too much to hope for, towards refugees and those who are socially isolated.

— At least people are learning how to wash their hands properly.

We are all in this together. Let’s try to collectively transfer the lessons learnt into lasting change. Now is a good time to have a serious think about what we, as a human community, want for the future.