Is there really life on Venus?

Last year, scientists from the Royal Astronomical Society of the United Kingdom detected the presence of phosphine in the atmosphere of Venus, and the concentration of phosphine in the atmosphere exceeded the amount that could be produced by non-biological mechanisms, so this may represent the existence of some unknown form of life in the atmosphere of Venus. So, is there life on Venus? Why is phosphine used as evidence of the existence of life?

Today I will talk to you about this. My personal opinion: It can only be said to be a possibility, not an absolute. Why? Please read on.

01. What exactly is phosphine?

What exactly is the PH3 (phosphine) discovered on Venus this time? In fact, it is a life gas based on Earth's cognition.

Phosphine is a colorless, highly toxic, flammable liquefied compressed gas stored in cylinders with the chemical formula PH3.

However, this gas is not ordinary because it is generally not easy to generate. In other words, it is generally difficult to generate in the natural environment.

In contrast, this gas is easily produced in biological metabolism, especially in the absence of oxygen, by anaerobic organisms. This toxic gas is well known in natural anaerobic environments as well as in sewage and landfill gases.

For example, the following figure shows the PH3 produced by the fermentation of pig manure (the other CH4 is also the main component of biogas that everyone is familiar with - methane)

The fungi that can produce it are also anaerobic organisms

However, if it is a purely natural environment without any living organisms, it would be a bit troublesome to generate PH3.

For example, in the industrial preparation of PH3, the reaction is as follows:

3 KOH + P3 KOH + p4+ 3 H+ 3 h2O → 3 KHO →3 KH2PO+ PH+ PH 3

However, in the known natural environment, there is a lack of strong enough reducing agents to directly convert phosphate into phosphine. Because of this, people believe that this gas should be a trace of life activities, or simply a product of anaerobic organisms.

In fact, phosphine does exist in the Earth's atmosphere, albeit in very low concentrations.

For example, the figure below shows the content of phosphine in the atmosphere detected by multiple studies [1].

As for why other gases are not used, it is mainly because the PH3 spectrum is relatively special and can be easily separated from other life characteristic spectra.

02. Are there anaerobic organisms on Venus?

So can we conclude that there are anaerobic organisms on Venus? The answer is no.

1. First, we have no direct evidence of the existence of anaerobic life on Venus.

In fact, so far, we have not obtained any evidence of the existence of any life on any extraterrestrial body, so to be truly sure, we need to capture the microorganisms of Venus.

2. Can phosphine be used as the gold standard for life? I think this is debatable.

Although we generally believe that the Earth lacks sufficient reducing agents to produce PH3, the chain of evidence to infer that this must be the case on Venus is incomplete.

3. Not just Venus

In fact, PH3 has also been found in Jupiter's turbulent atmosphere.

But as we all know, Jupiter is a balloon, and Jupiter's PH3 is formed in its hot interior and reacts with other compounds in the upper atmosphere.

03. Why is it possible that there is life on Venus?

So why do we say that there might be life on Venus? This is based on our understanding of Earth. We believe that PH3 should be the product of anaerobic organisms. The discovery on Venus seems to be consistent with this speculation [2].

The following figure is the core evidence of this article:

10 ppb of phosphine. Of course, the authors also ruled out some other factors, such as whether gas reactions, light/geochemical reactions or exogenous non-equilibrium inputs could produce PH3 on Venus, etc., and believed that biological production was more likely.

Of course, the environment on Venus is not as bad as everyone thinks. For example, the atmospheric conditions on Venus are good, the temperature is also acceptable, 0-60°C, and the pressure is also acceptable, 0.4-2 atmospheres[3].

For example, sulfide, carbon dioxide and water. If we must compare, assume that there is life on Venus.

Then life on Venus may be in the same period as Earth - 3.5 billion years ago.

At that time, there may have been a large number of anaerobic bacteria on the earth. It was not until 3.2 billion years ago that photosynthesis began to appear in large numbers on the earth and release oxygen.

04. Research on the existence of life on Venus

I was reminded of another study from 2018, which was also very interesting and more detailed than this Nature article [4].

They first compared the atmospheric spectra of Venus and Earth and found that they were opposite. Because Earth's atmosphere is 21% oxygen, Venus and Earth are opposite.

Images of clouds on Venus(A–H)and Earth(I–N)demonstrating the relationships of contrast with wavelength.

Next, we discovered that the atmosphere of Venus has spectral absorption of unknown substances (especially between 330-600 nanometers), which is also the core starting point.

FIG. 2.Venus' spectra as measured by Morozet al.(1985), Irvine (1968), Travis (1975), Wallaceet al.(1972) (scaled geometric albedo), MESSENGER (Perez-Hoyoset al.,2013; Pérez-Hoyoset al.,2017), and Barkeret al.(1975), including the unexplained absorption, as calculated from the difference between the VIRA cloud model and the MESSENGER spectra. The real Venus spectrum varies with location and time, so the residual curve is illustrative and not definitive.

How about comparing it with the frequency spectra of some known creatures on Earth?

Comparison of catalase spectra from E. coli and the Fe–S proteins of Acidithiobacillus ferrooxidans and Acinetobacter gyllenbergii (A) and various cofactors and biochemical molecules, including biopterins, carotenoids, and chlorophylls a, b, and f (B).

Well, there are similarities, and if Venus's clouds do harbor life, then that would be a good explanation for these spectral overlaps.

In the author's words, it is very similar (tantalizingly).

tantalizingly similar to the absorption properties of terrestrial biological molecules

So, let's continue to fly towards the hypothesis that there are organisms on Venus, and further calculate how anaerobic organisms produce PH3 if there are anaerobic organisms on Venus.

Diagram of iron- and sulfur-focused metabolic redox reactions that could occur in the Venus clouds, where Fe3+/2+ complexes refer to inorganic and organic ligands and dotted arrows refer to possible redox cycles.

1. The concentration of phosphine on Venus is not low, which means that this is not an accidental phenomenon, and such a high concentration should be produced by a large number of anaerobic organisms.

2. According to the movement trajectory of Venus, in theory, there should be continuous anaerobic organisms producing phosphine to maintain the phosphine concentration in its atmosphere.

3. Venus’s atmosphere is conducive to the generation of life.

As early as 1967, researchers proposed the habitability of Venus, and in 1999 Cockell proposed that the conditions in the middle and lower atmospheres are suitable for biological survival. Although the high altitude may freeze, it does not necessarily kill microorganisms.

Venus itself has some objective physical and chemical conditions that can give rise to life, such as sulfide, carbon dioxide and water.

So they made a hypothetical inference: Venus may have anaerobic organisms that continuously produce PH3.

Finally, searching for extraterrestrial life has always been an important meaning of looking up at the stars. The universe is so big, we should not be alone.

1. Glindemann, Dietmar, Ulrich Stottmeister, and Armin Bergmann. "Free phosphine from the anaerobic biosphere." Environmental Science and Pollution Research3.1 (1996): 17-19.

2. Greaves, JS, Richards, AMS, Bains, W. et al. Phosphine gas in the cloud decks of Venus. Nat Astron (2020).

3. Irwin, Louis N., and Dirk Schulze-Makuch. "The Astrobiology of Alien Worlds: Known and Unknown Forms of Life." Universe6.9 (2020): 130.

4. Schulze-Makuch, Dirk, et al. "A sulfur-based survival strategy for putative phototrophic life in the Venusian atmosphere." Astrobiology4.1 (2004): 11-18.