What’s the deal with methane?

[lukebl]

What with the latest successful landing on Mars, I was thinking about the excitement about the discovery of Methane in the Martian atmosphere and it being a possible indicator of organic life.

Could someone explain why that’s so exciting when the outer planets are full of the stuff and no-one’s suggesting that, say, Neptune’s methane is a sign of life. And even on earth, methane can apparently be created by chemical or geological processes. What makes Mars’s methane so special?

I was probably asleep during that particular lecture....

[Davey-T]

2 minutes ago, lukebl said:

What makes Mars’s methane so special?

I think they were speculating that  as it appeared to be seasonal it could ,might, maybe, possibly, just be a sign of life.

Dave

[billhinge]

Replenishment I believe

https://en.wikipedia.org/wiki/Methane_on_Mars

Methane (CH4) is chemically unstable in the current oxidizing atmosphere of Mars. It would quickly break down due to ultraviolet (UV) radiation from the Sun and chemical reactions with other gases. Therefore, a persistent or episodic presence of methane in the atmosphere may imply the existence of a source to continually replenish the gas.

[saac]

Two types of methane  organic and inorganic (abiogenic) - determined by their production method (pathway) ; the former would obviously be the cause of great interest if detected elsewhere in the solar system.   

https://www.sciencedirect.com/science/article/abs/pii/0009254188901015#:~:text=Methane can also form through,through bacterial or thermogenic processes.&text=Inorganic reactions%2C either surficial or,likely source of such methanes.

 

Jim 

[PEMS]

I would think that as Methane could be either organically formed or from another inorganic mechanism then the finder of such methane has two options:

Say that it is just Methane and forget it, or, say it could be from some form of microbial life.

If it is found out to be from some form of life then they were amoungst the first to identify a form of proof of life and some kudos. Otherwise they are the person to have seen what could be proof of life then ignored it.

So may as well push the "possibility of life" aspect. They have done the same for Venus and there the atmosphere is sulphuric acid, hot enough to melt lead and a pressur 90x that of the earth on its surface.

[saac]

1 hour ago, PEMS said:

I would think that as Methane could be either organically formed or from another inorganic mechanism then the finder of such methane has two options:

Say that it is just Methane and forget it, or, say it could be from some form of microbial life.

If it is found out to be from some form of life then they were amoungst the first to identify a form of proof of life and some kudos. Otherwise they are the person to have seen what could be proof of life then ignored it.

So may as well push the "possibility of life" aspect. They have done the same for Venus and there the atmosphere is sulphuric acid, hot enough to melt lead and a pressur 90x that of the earth on its surface.

To be fair the situation on Venus is a little different from Mars where Phosphine, as I understand, has no other known production pathway other than organically ( anaerobic processes) . From what I remember the team simply reported detection of Phosphine (by radio detection) in the upper atmosphere of Venus well above the cloud level.  At this altitude Phosphine molecules would ordinarily be destroyed due to ultraviolet radiation. Therefore, if its presence was confirmed then that would suggest some form of replenishment process - again not necessarily and conclusively organic !   Since their initial publication other researchers challenged the findings but the debate I believe still continues.  With the Methane on Mars there is no way to confidently declare it having been produced by life or otherwise without testing a real sample by say mass spectrometer - measuring isotope ratio of carbon 12 and carbon 14.  The notion of a simple bio signature that could uniquely and with all certainty point to life is tantalising but it must surely be fraught with difficulty. As with Venus and Mars there will always be the unknown exotic chemistry route . I can't see how any remote discovery of a bio signature anywhere could only ever result in a claim that there is a potential signature of a life process.  It's certainly an interesting area and we are going to see more discoveries as the JWT will open up atmospheric analysis of exoplanets. 

Jim

 

 

 

https://en.wikipedia.org/wiki/Biosignature