2 weeks ago

Only one possibility, not absolute. 

What is PH3 (phosphine) discovered by Venus? Why are you so excited? 

 _1_ . _life_gas_based_on_earth_cognition_
Phosphine is a kind of colorless, highly toxic, flammable liquefied compressed gas stored in steel cylinder, the chemical formula is PH3. 

 however, this kind of gas is not common because it is not easy to generate. In other words, it is generally difficult to generate through natural environment. 

In contrast, this kind of gas is easy to generate in biological metabolism, especially in the case of hypoxia, anaerobic organisms will generate. 

In the well-known natural anaerobic environment, as well as sewage and landfill gas, the existence of this toxic gas. 

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

 and the fungus that can produce it is also anaerobic

 however, it would be a bit troublesome to generate PH3 in a pure natural environment without living things

For example, PH3 is prepared in industry, and 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 agent to directly convert phosphate to phosphine. 

Because of this, people think that this kind of gas, 
 should be the trace of life activities, or simply the product of anaerobic organisms 

 in fact, phosphine is actually present in the earth's atmosphere, although the concentration is very low. 

For example, the following figure shows the levels of phosphine in the atmosphere detected by several studies [1]. 

 as for why other gases are not used, the main reason is that PH3 spectrum is relatively special and easy to be separated from other life characteristic spectrum. 

Secondly, why do we think that there may be life on Venus. 

Based on the understanding of the earth, we believe that PH3 should be the product of anaerobic organisms. 

The discovery of Venus seems to conform to this conjecture. 

The following is the core evidence of this article:

 10 ppb phosphine. Of course, the author also excluded some other factors, such as whether gas reaction, photo / geochemical reaction or exogenous non-equilibrium input could produce PH3 on Venus, and so on, and thought that biological production was more likely. 

Of course, Venus's environment is not as bad as people think. 

For example, the atmospheric conditions of Venus are good, the temperature is OK, the pressure is OK at 0-60 ℃, and the pressure is 0.4-2 atmospheres [3]. 

 for example, sulfide, carbon dioxide and water, if necessary, assume that Venus has life. 

So Venus's life may be at this time on earth - the Earth 3.5 billion years ago. 

 at that time, there might be 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 quantities, releasing oxygen. 

 3. The conclusion is still early

So can we conclude that Venus is anaerobic? 

The answer is No. 

 1. First of all, we have no direct evidence of anaerobic organisms on Venus. 

In fact, so far, we haven't acquired any extraterrestrial objects, and there are any creatures, so to be sure, we need to capture the microbes of Venus. 

 2, can phosphine be used as the gold standard of life? 
 I think this is questionable. 

Although we generally believe that there is not enough reducing agent on earth to generate PH3, the evidence chain is incomplete to speculate that Venus must be like this. 

 3, not just Venus

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

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

 -- a more interesting article 2 years ago

I think of another 
 study in 2018 
, which is also very interesting and more detailed than this one [3]. 

They first compared the atmospheric spectra of Venus and the earth, and found that they were opposite. 

Because the earth's atmosphere has 21% oxygen, Venus is the opposite of the earth. 

 images of clouds on Venus (a – h) and earth (I – n) demonstrating the relationships of contrast with wavelength. 
 next, we found that 
 the atmosphere of Venus has spectral absorption of unknown substances (
 especially 330-600 nm 
 _this_is_also_the_core_starting_point_ ._ 

FIG. 2.
Venus' spectra as measured by Moroz
et al.
), Irvine (
), Travis (
), Wallace
et al.
) (scaled geometric albedo), MESSENGER (Perez-Hoyos
et al.
; Pérez-Hoyos
et al.
), and Barker
et al.
), 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 spectrum of some known organisms on earth? 

The catalase spectra (a) and cofactors and biochemical molecules of E.coli and 
 Acidithiobacillus ferrooxidans 
 Fe – s protein and 
 Acinetobacter gyllenbergii were compared, including Biopterin, carotenoids and chlorophylls a, B and f (b)

 well, there are similarities. If Venus clouds do contain organisms, then these spectral overlap characteristics can be well explained. 

In the author's words, it's tantalizingly similar. 

tantalizingly similar to the absorption properties of terrestrial biological molecules

So, we continue to fly toward the hypothesis that Venus has organisms, and further calculate the way in which Venus produces PH3 if anaerobic organisms exist

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 lives and dotted arrows refer to possible redox cycles. 
 1, the phosphine concentration of Venus is not low

This means that this is not an accidental phenomenon, and the formation of such a high concentration should be produced by a large number of anaerobic organisms. 
2_ . _according_to_the_trajectory_of_venus_ , _theoretically_ , _there_should_be_continuous_anaerobic_organisms_producing_phosphine_in_order_to_maintain_the_concentration_of_phosphine_in_the_atmosphere_ ._ 

 3, the atmosphere of Venus is conducive to the formation of life. 

As early as 1967, researchers proposed the habitability of Venus. In 1999, cockell proposed that the conditions of low and middle atmosphere were suitable for living things. Although it may freeze at high altitudes, it doesn't necessarily kill microbes. 

Venus itself has some objective physical and chemical conditions for the birth of life, such as sulfide, carbon dioxide and water. 

 so they made a hypothesis that Venus may have anaerobic organisms that continue to generate PH3. 


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