9 replies to this topic

[lanndonkane]

https://www.astronom...a-sign-of-life/

It looks like more studies have been done on this exoplanet to confirm the presence of this “biosignature”. Previously, it was debated that maybe its detection was simply an artifact. Now, its presence seems essentially confirmed.

However, that doesn’t necessarily mean it’s from life. But at least this time, it seems like there’s a reasonable chance it IS from life.

Do you all think this is “it”?

[SimonTelescopium]

problem is we have been here before - NASA Alan Hills meteorite, the Venus debacle etc... The BBC news was saying it will be another couple of years before the detection levels can be considered as a scientific discovery, whey they are currently saying is the signal strength is still growing so possibly on the path to discovery status, and once there is consensus they have made a detection, there will no doubt be years of debate on if there are non-biological means of producing Dimethyl sulphide. So for me, no this isn't 'It' yet

[Phil Perry]

It's one of those things that can be produced by life, but it's no guarantee that life actually produced it. Methane is frequently produced by living organisms on Earth, but there's plenty of CH4 in the gas giants that formed abiotically. Even amino acids have been found in meteorites, but no one is claiming that life produced them. It would not be surprising to find a way (without life being involved) to produce dimethyl sulfide, so don't get excited about it.

[12BH7]

The galaxy is filled with pre-biotic clouds. I'm hoping for more advanced detection techniques myself. 

[mikemarotta]

"... because the models assume that biogenically emitted DMS and DMDS do not have a return sink to the ocean, allowing the abundance to build up over time."
 
After this paragraph, Section 4.2 does address False Positives.
 
Recent photochemical modeling of K2-18 b suggests that large quantities of DMS and DMDS, with mixing ratios up to 10−2 can accumulate in the atmosphere for assumed biogenic oceanic fluxes of these gases of ≳20× Earth levels (Tsai et al. 2024). Such quantities are con- sistent with our current MIRI results for DMDS and DMS and with previous abundance constraints of DMS (Madhusudhan et al. 2023b). These otherwise photo- chemically fragile molecules survive in the Tsai et al. (2024) models under high surface-flux emission condi- tions: (1) because of the favorable ultraviolet spectral energy distribution of M-dwarf stars (see also Segura et al. 2005; Domagal-Goldman et al. 2011a; Seager et al. 2013a), (2) because DMS and DMDS can eventually self- shield, as well as shield molecules such as CO2 from photolysis when their column density is high enough, significantly cutting down on their photochemical de- struction pathways (Tsai et al. 2024), and (3) because the models assume that biogenically emitted DMS and DMDS do not have a return sink to the ocean, allow- ing the abundance to build up over time.
 
"New Constraints on DMS and DMDS in K2-18 b using JWST MIRI," page 14.
Draft version April 17, 2025
Typeset using LATEX twocolumn style in AASTeX631
arXiv:2504.12267 [astro-ph.EP]
  (or arXiv:2504.12267v1 [astro-ph.EP] for this version)
https://doi.org/10.4...rXiv.2504.12267

 
 

problem is we have been here before - NASA Alan Hills meteorite, the Venus debacle etc... 

It's one of those things that can be produced by life, but it's no guarantee that life actually produced it. Methane is frequently produced by living organisms on Earth, but there's plenty of CH4 in the gas giants that formed abiotically.Even amino acids ... 

The galaxy is filled with pre-biotic clouds.

 

 

It depends on your definition of "life." If "life" must be capable of reproduction, then the "domestic equine hybrid between a donkey and a horse" is not alive. We say that DNA is not "alive" on its own but it can edit itself and repair itself. I think that "life" is a gradient of organization. Roger Penrose (primarily) and Stuart Hammeroff (in collaboration) believe that such organization is demanded by quantum mechanics. I remain skeptical and interested.

We will find out when we get there.

 

Thanks and Clear Skies,

Mike M.

Edited by mikemarotta, 19 April 2025 - 06:38 PM.

[JWolf_21]

 
 

It depends on your definition of "life." If "life" must be capable of reproduction, then the "domestic equine hybrid between a donkey and a horse" is not alive. We say that DNA is not "alive" on its own but it can edit itself and repair itself. I think that "life" is a gradient of organization. Roger Penrose (primarily) and Stuart Hammeroff (in collaboration) believe that such organization is demanded by quantum mechanics. I remain skeptical and interested.

We will find out when we get there.

 

Thanks and Clear Skies,

Mike M.

DNA doesn't edit itself and doesn't repair itself. But finding it would certainly be a sign of high probability of finding life.

 

But yes, the definition of life is tricky, and I guess it will be twisted a lot in future, when it will be convenient for press and researchers to label as "life" whatever finding they want to publish.

Edited by JWolf_21, 20 April 2025 - 07:11 PM.

[bunyon]

If they find a donkey on Europa, I’ll celebrate.

[Russell Swan]

 
 

It depends on your definition of "life." If "life" must be capable of reproduction, then the "domestic equine hybrid between a donkey and a horse" is not alive. We say that DNA is not "alive" on its own but it can edit itself and repair itself. I think that "life" is a gradient of organization. Roger Penrose (primarily) and Stuart Hammeroff (in collaboration) believe that such organization is demanded by quantum mechanics. I remain skeptical and interested.

We will find out when we get there.

 

Thanks and Clear Skies,

Mike M.

“I think that "life" is a gradient of organization.”

 

Just like is everything else which is a complex system of interdependent parts. Or a continuous spectrum. Where exactly does green become blue? 
 

Such evidence will never “prove” life. It can build the case to a very high degree of confidence however. That’s what scientific investigation results in. A level of confidence. In a case like this we seek 5 Sigma likelihood. 

Edited by Russell Swan, 21 April 2025 - 11:21 AM.

[JWolf_21]

If they find a donkey on Europa, I’ll celebrate.

This will be my new definition of life from now on, the presence of a donkey   My students will love it

[Andrew_L]

If they find a donkey on Europa, I’ll celebrate.

I think the donkey might be quite pleased too.