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WWW: Searching for Signs of Subsurface Life on Mars (Extinct and Extant) - Shared screen with speaker view
Kennda Lynch
48:23
Please mute your microphone, we can hear people typing!
Kennda Lynch
48:35
If you have questons, go ahead and start posting them here
Kennda Lynch
52:30
Also, please remember to check in on the google form - https://forms.gle/EwrSp8VbyWrQjCy79
cconley
56:01
Why is it thought carotenoids are indicators only of ‘extant’ life?
pboston
58:46
I am assuming that carotenoids do not preserve particularly well?
hvgraham
59:48
is the basement rock different between the Australian and Chilean sites?
tullisonstott
01:00:04
how do you maintain acid ground water? is it just in the salt host?
Kennda Lynch
01:04:50
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.
cconley
01:05:49
Might be good to evaluate preservation potential of isoprenoids specifically in environments like those we’re discussing here...
pboston
01:06:33
I agree that this is a knowledge gap.
Kennda Lynch
01:07:29
Absolutely, this is a big area of research we need to do, I know there are some projects looking at this ...
dassarma
01:11:48
Great to hear about the use of Raman for carotenoids and isoprenoids. The references in my slide indicate their finding in ancient sediments...
dassarma
01:12:39
Breakdown products of isoprenoids are detectable, too.
tullisonstott
01:13:23
what are the cells/gram in these Permian halites?
cconley
01:13:46
Measured how?
tullisonstott
01:14:14
what do you consider the best evidence for preserved viable microorganisms in ancient salts?
dassarma
01:15:21
note sure what is best. do you meant extant?
cconley
01:16:12
need multiple independent lines of evidence
dassarma
01:17:05
whether ancient halite contains ancient halophiles is somewhat debatable.
cconley
01:20:29
Mars meteorites are quite reduced, per Steelie’s data.
pboston
01:20:38
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
Anca Selariu
01:21:15
Is anyone doing studies on the Movile Cave organisms in Romania?
Kennda Lynch
01:22:09
We have a dropbox and google repository, I will send out the links for folks to add documents too.
pboston
01:22:10
Yes, there are a number of papers out on Movile.
pboston
01:22:47
I can post what I have when we build out bibliography.
cconley
01:23:30
Plenty of biological molecules can also be produced abiotically — requiring biosignatures to be uniquely biological is a very restrictive constraint.
Anca Selariu
01:23:40
Excellent, thank you. I haven't seen but a couple pf older papers.
pboston
01:24:22
Serban Sarbu and several others are active again at the site, I believe. Serban now lives in California and we are in touch.
pboston
01:25:33
Cassie, you are correct, and clearly a focus on false biosignature biomolecules versus genuine ones is an understudied area to say the least.
cconley
01:26:27
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…).
pboston
01:26:49
Correct
tullisonstott
01:27:48
viable = extant
haley
01:30:31
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
pboston
01:31:12
I agree that the abiosignatures need a boatload more work.
hvgraham
01:36:42
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
Kennda Lynch
01:36:59
Good Point Heather!!!!
pboston
01:37:20
Yes Heather, in my mind we are looking at an n-dimensional phase space of lifeyness
pboston
01:37:44
and there is a lot of n-dimensional volume that would qualify as more alive or less alive
haley
01:37:53
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
tullisonstott
01:38:08
could be the data base, not the model
cconley
01:40:44
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…
Jen Blank
01:43:23
Gotta sign off…. have a great day, all!
Kennda Lynch
01:43:53
Thanks Jen, See you next week!
Brian Wade
01:47:50
Has the discrepancy between modelled and actual water activity been noted in the literature?
Kennda Lynch
01:51:40
Good Question Brian, this is something to look into. It sounds like Kathy’s group is on the verge of publishing on this topic
Brian Wade
01:52:43
Yes, I very much look forward to her paper pointing that out.
cconley
01:53:25
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??)
pboston
01:54:37
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.
cconley
01:55:37
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.
Brian Wade
01:55:43
I was unaware of the potentially large discrepancy between modelled and actual water activity. Very interesting!
pboston
01:56:26
My own notional opinion is that the modeling is lousy because it is leaving out the relevant physics.
cconley
01:56:49
Did anyone see the recent report of quantum tunneling being identified during photosynthesis? Physics can be complicated, too…
cconley
01:58:25
Might be easier to identify the things we *don’t* know?
Kennda Lynch
01:58:39
Please make sure to join the conversation on slack - https://join.slack.com/t/marsunderground/shared_invite/enQtNzA0NTg3MzgzNjg2LTVmN2Q1MjVlMTIyNDNlNmI2ZDBhNDBkZDVhNWM3YmJkMWFmZTFjNDA0MzJhMTM0NWY1NTcwOWMwMDQyYjA0ZjY
tullisonstott
02:02:52
so long everyone - good session -learned a lot -
pboston
02:02:57
Thanks TC
Kennda Lynch
02:03:11
Thanks TC
Kereszturi Akos
02:05:05
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).
pboston
02:05:58
Good point
Brian Wade
02:06:48
Another great meeting! Thanks, all!!
pboston
02:07:02
Thanks, I’m really enjoying this meeting of the mind.