WWW: Searching for Signs of Subsurface Life on Mars (Extinct and Extant) - Shared screen with speaker view
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If you have questons, go ahead and start posting them here
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Why is it thought carotenoids are indicators only of ‘extant’ life?
I am assuming that carotenoids do not preserve particularly well?
is the basement rock different between the Australian and Chilean sites?
how do you maintain acid ground water? is it just in the salt host?
regarding carotenoids and isoprenoids - in general they are not very good at preserving over geological time unless they are in fluid inclusions, so they are subject to diagenesis. Some of the side chains can preserve well, but then it can be hard to determine if the compound was produced by biology or otherwise.
Might be good to evaluate preservation potential of isoprenoids specifically in environments like those we’re discussing here...
I agree that this is a knowledge gap.
Absolutely, this is a big area of research we need to do, I know there are some projects looking at this ...
Great to hear about the use of Raman for carotenoids and isoprenoids. The references in my slide indicate their finding in ancient sediments...
Breakdown products of isoprenoids are detectable, too.
what are the cells/gram in these Permian halites?
what do you consider the best evidence for preserved viable microorganisms in ancient salts?
note sure what is best. do you meant extant?
need multiple independent lines of evidence
whether ancient halite contains ancient halophiles is somewhat debatable.
Mars meteorites are quite reduced, per Steelie’s data.
Yes, the slow plastic nature of halite over geological time is a often discussed caveat. Perhaps rounding up the available literature on this would be helpful. i have quite a bit of it. I think it may be time to start a group bibliography in different categories
Is anyone doing studies on the Movile Cave organisms in Romania?
We have a dropbox and google repository, I will send out the links for folks to add documents too.
Yes, there are a number of papers out on Movile.
I can post what I have when we build out bibliography.
Plenty of biological molecules can also be produced abiotically — requiring biosignatures to be uniquely biological is a very restrictive constraint.
Excellent, thank you. I haven't seen but a couple pf older papers.
Serban Sarbu and several others are active again at the site, I believe. Serban now lives in California and we are in touch.
Cassie, you are correct, and clearly a focus on false biosignature biomolecules versus genuine ones is an understudied area to say the least.
Assuming anything that could be abiotic must be abiotic is quite susceptible to false-negative interpretations (e.g., Viking assuming that chlorinated methane was cleaning fluid, when SAM just showed it’s from Mars organics…).
viable = extant
a biosignature must be exclusively attributed to biological processes, the concept of an ‘abiosignature’ is starting to gain attraction in terms of a negative control. Unfortunately it may not be possible to find a true abiosignature on Earth
I agree that the abiosignatures need a boatload more work.
I would also chime in to say that life detection isn’t necessarily a yes/no activity and we should think of signals with uncertainty to accommodate novel or nascent life
Good Point Heather!!!!
Yes Heather, in my mind we are looking at an n-dimensional phase space of lifeyness
and there is a lot of n-dimensional volume that would qualify as more alive or less alive
Yes - I agree - I think there may be a continuum between prebiotic and biotic in terms of origin of life and that becomes magnified when looking for the byproducts of life that may be recorded in the rock record
could be the data base, not the model
Regarding Penny’s comment about water activity and microstructure vs. bulk measurement — temporal cycling of things like temperature and pressure also makes a huge difference. To get pure water on Mars, just wait for frost to fall…
Gotta sign off…. have a great day, all!
Thanks Jen, See you next week!
Has the discrepancy between modelled and actual water activity been noted in the literature?
Good Question Brian, this is something to look into. It sounds like Kathy’s group is on the verge of publishing on this topic
Yes, I very much look forward to her paper pointing that out.
Use of water ‘vapor’ also has a whole lot to do with physics of surfaces and micro-scale environments, and how they change over time — a hygroscopic salt crystal on a surface will grab water from the air and deliquesce, and the liquid may flow somewhere else. (Also - how do I get Zoom to stop mis-correcting my typing??)
I don’t think you can talk Zoom out of its spell correcting. And yes, the deliquescence and chaotropicity issues are critical. Someday someone will actually explain chaotropicity to me that actually makes sense….I’m still waiting.
I don’t really think ‘chaotropicity’ is a real thing, Hallsworthy to the contrary — but there’s definitely a lot more going on with charged macromolecules than people currently understand.
I was unaware of the potentially large discrepancy between modelled and actual water activity. Very interesting!
My own notional opinion is that the modeling is lousy because it is leaving out the relevant physics.
Did anyone see the recent report of quantum tunneling being identified during photosynthesis? Physics can be complicated, too…
Might be easier to identify the things we *don’t* know?
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so long everyone - good session -learned a lot -
One more ergument "not to loose" motivation to search for life below the Martian surface: on Mars much larger mass of hypothetic population could have witnessed mutations, than on Earth (here "evolved life" does no allow this).
Another great meeting! Thanks, all!!
Thanks, I’m really enjoying this meeting of the mind.