Mars rover detects carbon signature that may hint at past life source | Hacker News Reader

Mars rover detects carbon signature that may hint at past life source

science.org

165 pointsjnord89 comments

As Harrison noted, the authors are appropriately conservative.

The team found that the carbon trapped in a handful of rocks probed by the rover is dramatically enriched in light isotopes of carbon. On Earth, the signal would be seen as strong evidence for ancient microbial life...

...however, the researchers are reluctant to make any grand claims, and they have worked hard to concoct alternative, nonbiological explanations involving ultraviolet (UV) light and stardust. But those alternatives are at least as far-fetched as a scenario in which subterranean microbes emitted the enriched carbon as methane gas. The team concludes the study does “inch up the plausibility” that microbes once existed on the planet...

I'm curious if we do if we do find evidence for life on another planet would we explain it away with non-biological theoretical phenomenon before realizing its significance?

The DNA would be sequenced, compared to Earth's life forms, and if no relation is found then it should be explained. For me it would exponentially increase the probabilities of more life in the Universe.

If DNA is found, it almost certainly indicates a common ancestor. The likelihood of DNA evolving twice from whatever separate self-reproducing protolifeforms came before it has to be unbelievably low.

We only have a single sample of a life encoding mechanism such as DNA. We can't know if it's one of many possibilities, or the naturally emergent phenomenon for life, like stars and quartz crystals that would form the same way anywhere from the same basic components of our physical universe.

Silcon is another possible mechanism similar to DNA. I forget the research on this.

EDIT: Found this https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...

Sure, I wouldn't be surprised if it's possible, but the chances DNA emerging elsewhere aren't necessarily "unbelievable low".

The AI in this computer agrees ;D

Or this speculation:

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

Silicon is a post-ferrous element. There may be silicon-based life in the universe. But abundance of carbon and hydrogen, together with the superior stability of hydrocarbons relative to silanes, sort of seals the deal for everything but theoretical edge cases.

It's more complicated than that. A few of the considerations:

* DNA/RNA are not the only options. Other nucleobases potentially exist and artificial ones have certainly been created (1)

* A completely unique sequence would indicate no shared ancestor even if it was DNA.

* We're not sure how life started on Earth either. It could've been more than once in more than one way. We don't know.

* Earth and Mars shared material as asteroid impacts ejected material that eventually landed on the other. Some microorganisms could potentially survive the journey.

(1) https://en.wikipedia.org/wiki/Nucleobase

Why is this DNA/RNA/polynucleotide chauvinism so prevalent? It's one complex molecule in an infinite space of complex molecules, some of which might be more suitable as basis of life on other planets with other chemistries. Life does not equal chain of heterocycle-sugar-phosphates.

Based on the current sample size of one life bearing planet, DNA/RNA is the most durable example we have that produces results at this time. As soon as a second nucleotide is discovered as functional, this will be up for discussion.

"Based on the current sample size of one writing system having civilization, hieroglyphs are the most durable example we have that produces results at this time. As soon as a second way of record keeping is discovered as functional, this will be up for discussion."

But we can infer that life could exist without DNA. It could be similar to our machines, made of different materials and replicating through other ways.

There is a definition of life that comprises any mechanism that controls its own entropy. Maybe there are energy-based interactions that fit this description like systems with no matter involved, or very high-scale/long-term systems.

Maybe I'm a DNA chauvinist, but I think this is one of the most important questions in the universe, but incredibly difficult to answer without massive-scale space travel.

Unless there is life not based on DNA.

Assuming there's no current life on Mars (which seems likely), any past DNA would have been obliterated over the millennia. We'd find base pairs, possibly short oligos. Jurassic Park doesn't exist for a reason.

Why do we assume life on other planets will have DNA?

> if we do find evidence for life on another planet would we explain it away with non-biological theoretical phenomenon before realizing its significance?

Do you mean, will scientists carefully verify the accuracy of their claims? Would it be better if they shortcut that process when the question is exciting?

That's not what I mean at all. On Viking 2's LR experiment; "Our experiment was a definite positive response for life, but a lot of people have claimed that it was a false positive for a variety of reasons. One of the reasons was because there wasn't any water found"

We didn't even attempt to verify the accuracy of the LR experiment despite to-date nobody coming up with a non-biological explanation.

Everytime news like this comes up, I'm more certain that if we ever find life outside our planet, it would take years to be announced

6 hours tops

I had the same thought after the phosphine gas discovery at Venus was announced. It will take so long to be certain about a claim like this, and evidence will mount so gradually, that by the time the confirmation is made it will be unsurprising. Sort of like the discovery of ancient liquid water on Mars - it took so long to prove it that by the time proof was certain, it had become a joke (NASA announces discovery of water on mars for Nth time! haha).

On the down side, we're less likely get a world-wide event to collectively celebrate; on the up side, we're less likely to panic subgroups of society.

Makes me think of how there is a huge hesitation to ever use the "F" word with any Mars photos. F - as in fossil.

There are definitely natural mineral formations that can mimic fossils, but then there are fossils too that aren't always obviously such.

Likely context of parent regarding fossils: https://en.wikipedia.org/wiki/Allan_Hills_84001

And seconds to be destroyed.

It will be interesting to see if all life uses DNA in four pairs or if every planet evolves a system for encoding life differently.

My entirely uninformed guess is that life on Earth is probably fairly representative of how life forms on any similar planet. Throughout evolution there are endless ways life could have formed, and we're the product of whatever method worked best against billions or trillions or more possibilities. I wouldn't be surprised to find plants and animals on other planets that are not dissimilar to ones on Earth, especially considering the sheer number of types of animals and plants and how much they vary in structure and appearance.

It would be so exciting if they find life there

I'm glad they're careful not to oversell this finding, but it's a little discouraging how far we are from the phrase we want to hear:

"Mars has life"

"We've found past life on mars"

"Rover finds past life on mars"

"Rover finds hints of past life on mars"

"Rover detects hints of past life on mars"

"Rover detects carbon signature that hints of past life on mars"

"Rover detects carbon signature that may hint of past life on mars"

You would have to look for evidence of life in the first place if you wanted to find it. None of the rovers we have on Mars right now have the right instruments to do so. Exomars' Rosalnd Franklin will be the first.

https://solarsystem.nasa.gov/missions/viking-1/in-depth/

    Viking 1
    
    July 20, 1976: Lander touched down
    
    Scientific Instruments
    
    Lander
    1. Imaging System (2 facsimile cameras)
    2. Gas Chromatograph Mass Spectrometer (GCMS)
    3. Seismometer
    4. X-Ray Fluorescence Spectrometer
    5. Biological Laboratory
    6. Weather Instrument Package (Temperature, Pressure, Wind Velocity)
    7. Remote Sampler Arm

Not for me. Behind all those hedges is where the intrigue lies! I'd rather that than overselling a thrice-maybe as a positive.

>"Rover detects carbon signature that may hint of past life on mars"

If you expand the list to include all the geological stuff Spirit/Oportunity, Pathfinder and Viking found then slap a "you are here" on it we are much closer to the "earth" end of things than the "dead rock" end of things.

I hope they don't. It would be a very bad indicator for our future in the cosmos, making it far more likely that whatever great filter is out there, is in front of us still.

Not necessarily. Before the great filter, there's the jump to multi-cellular life. As far as we know, the symbioses with mitochondria bacteria only happened once, and is the progenesis of all multi-cellular life on earth.

So single-celled life may not be terribly uncommon throughout the cosmos.

> Before the great filter, there's the jump to multi-cellular life.

Well, the filter may exist prior to the jump to multi-cellular life. Finding early life on Mars would necessarily be bad because we would now be able to mostly eliminate that possibility, which means that the probability that the filter is ahead of us increases.

I disagree. While finding dead life on other planets decreases the probability of some filters, it also increases the probability of other filters.

For example, if we go to every planet in the solar system and see evidence of extinct multi-cellular life, but no sapient life, this would suggest that the filter is indeed behind us, and not in front of us.

I don't think this is right. It moves the filter forward from "no life" to "no intelligent life" (If we have a TON of examples – remember, we are also a data point. so even if we find 200 planets with dead multicellular life, we still have 1/200 making it to spacefaring — that's a huge % when extrapolated out to a galactic scale! It's a large enough % that I don't even find this to be a meaningful prior adjustment).

It also adds no information as to which, if any, filters are in front of us. How would "lot of dead fish" help us understand "do civilizations destroy themselves with nuclear weapons"?

I agree with the first part, but not the second. Agreed it would rule out some early filters. But for the second part, the ratio doesn't go to 1 in 200. That's not how the anthropic principle works. You're already assuming that the Earth is extraordinary oh, so you can't just put it in the data set. Instead you would look at 199 out of 199 planets where sapient life capable of making an observation failed to develop.

Agreed that it provides no data on future filters ahead of us

> Agreed that it provides no data on future filters ahead of us

This was my instinct, too, after reading both of your posts, but on reflection I think that it's unlikely to be no information.

If we instead found 199 examples of extinct complex life (say, fossilized rodent-like creatures), instead of extinct simple life, we all probably agree that this would increase the odds of the filter being in front of us.

Now, imagine gradually changing the example from extinct complex life (rodent-type creatures) and going down to extinct simple life. At what point in this thought experiment does it become "no data"?

I guess I agree that discovering extinct life is information about probabilistic filters in earths future. I But, it does have to be weighed against the newly observed data supporting filters humans have already past.

To take your example, as we keep finding rodent fossils, we become more confident that a filter exists between rat and rocket-men. As we go from 0 planets with rodent fossils to 1 trillion planets, the probability that this is the filter keeps going up.

That is to say, we are not only decreasing the chance of pre-rat filters, but simultaneously increasing the chance that the filter is in the rat stage.

Isn't that backwards? The great filter is meant to explain why we don't see extraterrestrial life, so finding it would be counterevidence for a great filter

It's correct. There is still a filter somewhere that explains the Fermi Paradox. So finding evidence of primordial life on Mars would just mean that the filter exists somewhere between that primordial life and somewhere ahead of us. That is bad, because it increases the probability that the filter is ahead of us by eliminating the possibility that the filter was behind that primordial life.

If we assume that the great filter is ahead of us, then we were already a better lower bound. If it's behind us, then who cares?

If it's at all possible that it's behind us (which I believe it is), then this finding would be bad, because it necessarily shifts probability density into our future. Probability density must sum to 1. So eliminating one large chunk of possibility will necessarily increase the odds that the filter is in our future.

Yes, thank you for fleshing out what I meant.

Unless, for example, we were to find Mars had and has single cellular life. That might increase the likelihood that the filter is at the single to multicellular phase by enough to offset the bad news that the filter is not the abiogenesis step.

> it necessarily shifts probability density into our future

why? if the filter is "move from unicellular to multicellular" it would have wiped out life on Mars but Earth somehow made it. It shows there's at least one step behind us which is "hard" (while showing there's another one which is "easy").

I think one thing to keep in mind is that we haven't been here for very long. And as a technological society that is able to be detected or detect something we have been here for something between 70 or 5 years or 0 years depending on the definition. So the great filter is something that hinders us to detect detectable civilizations. But we are at the moment not totally sure if we are already detectable.

So per definition the great filter has to be in front of us as long as we wouldn't be able to find ourselves.

"Dissolving the Fermi Paradox": https://arxiv.org/abs/1806.02404

>The expectation that the universe should be teeming with intelligent life is linked to models like the Drake equation, which suggest that even if the probability of intelligent life developing at a given site is small, the sheer multitude of possible sites should nonetheless yield a large number of potentially observable civilizations. We show that this conflict arises from the use of Drake-like equations, which implicitly assume certainty regarding highly uncertain parameters. We examine these parameters, incorporating models of chemical and genetic transitions on paths to the origin of life, and show that extant scientific knowledge corresponds to uncertainties that span multiple orders of magnitude. This makes a stark difference.

This paper seems to get posted in most Great Filter discussions now. I don't find it very convincing - or I'm not sure why it is worded so strongly. It seems ultimately like just another opinion piece dressed with a bit more math than the topic usually gets.

My statistics chops might just not be up to snuff, but the authors are ultimately just choosing their own numbers (probability distributions in this case) and plugging them in like everyone else.

We still don't know the values of those parameters. The Fermi paradox exists only given "optimistic" guesses for those parameters. The authors choose "pessimistic" distributions and declare the problem "dissolved".

Sandberg and Ord are based at the same institute as Bostrom who popularized the Great Filter, if that has any effect on your opinion of the piece. They tend to work on pretty wacky things mind you, I had a discussion with Sandberg on whole brain emulation once and Ord champions donating to fairly sci-fi sounding charitable organizations (including his own, the future of humanities institute).

The problem I personally have with the Fermi paradox is that it essentially works if you assume that every non-zero probability is one, and justify that with there being enough chances for life to get going that it's bound to happen. Except... there really isn't all that much slack.

Another point that I don't see addressed much is the possibility that interstellar travel may just simply be impossible: that building machines that can travel to other stars, let alone ones that are capable of hosting a colonization process, are just simply not within the realm of materials that can actually exist.

FTL travel may well be impossible but what could possibly make sub-light-speed interstellar travel impossible?

Only if it had evolved independently during this step. Which is not certain either because we know big asteroid impacts can transfer material to other planets.

But I think the whole Fermi Paradox is a bit chauvinistic. It's assuming all life is like us, and ending in a colonisation explosion. Like our way is the only possible way.

Maybe other aliens do manage to reach a balance with their environment instead of screwing it all up like we are doing? After all, never-ending growth is simply impossible. It always reminds me of Agent Smith's speech from the matrix :)

But we as humanity have a habit of defining things around us in our own terms. We thought earth had to be the centre of the universe. Perhaps here we're also wrong and most life is just not like us?

How do we know never-ending growth is impossible?

I don't think there's just one great filter.

I imagine there are various filters depending on the particular environment and circumstances.

Several are behind us already. Several are ahead.

The filter might also not be one in which a civilization goes extinct but one in which the civilization goes dark to any outside observers. What if the ultimate fate of any sufficiently sophisticated species is to harness their sun's energy to create and enter a pocket universe where the stars are still close enough together to travel between them at light speed?

This isn’t an original opinion, it’s taken from this paper:

https://www.nickbostrom.com/extraterrestrial.pdf

I hadn't seen this post, but I'm glad he agrees. It's not a hard opinion to reach independently when you work through the math.

And I believe Bostrom was just summarizing the Fermi Paradox

https://en.m.wikipedia.org/wiki/Fermi_paradox

Beresheet Tardigrades floated over and are setting up camp to enact their revenge would be my bet.

it would be super ironic if it turned out earth life came from Mars or something :P

Is anyone else having problem accessing the paper? The link on Science isn't working, and the DOI I managed to find in the rest of the coverage doesn't seem to exist. I can't find the paper anywhere.

Same. The reference appears to be "Depleted carbon isotope compositions observed at Gale crater, Mars, Proceedings of the National Academy of Sciences(2022). http://doi.org/10.1073/pnas.2115651119" DOI is not working yet but this is normal, however the link to PNAS seems broken indeed: https://www.pnas.org/content/119/4/e2115651119

I wonder - if you would build a dome over one of the water-ice-swamps in the canyons and allowed atmosphere to build up- if we would see something grow..

We are finding Mars originated rocks here, so it can be pieces of Earth on Mars too. Probability is low due to relatively thick Earth atmosphere, but still...

It astonishes me anew every time they land one of these things on Mars with exactly zero microscopes on board.

Microscopes are expensive and you need to hire a martian to look at the samples. Last i looked on Linkedin there were not many martians with this qualification.

Don't we have microscopes that generate jpegs?

JPEG was patent encumbered up until 2009

It is impossible to imagine JPL unable to get a license for a Mars probe. Never mind JPL using lossy compression on science data.

Curiosity rover already used jpeg compression: https://www.design-reuse.com/news/34583/jpeg-encoder-ip-core...

I heard that we had sent robots to Mars. (Some people don't believe that, but I do.) Some of these robots have been equipped to do a variety of sample preparations and science observations, and even to report some of their results back to Earth scientists.

Thankfully the smart people of NASA listened

https://mars.nasa.gov/mer/mission/instruments/mi/

A microscope that cannot resolve smaller than 0.1 mm will not be very useful for seeing bacteria.

As it says in the blurb, "magnifying glass views".

Sorry, I willfully risked Poe's law, and the results were to be expected.

Have you considered that the people that design, develop, transport and operate autonomous robots on other planets in order to perform science have not "forgotten" to include a microscope?

Whenever you think you've got a great idea, try asking your question to Google. For example, when you type "microscope mars rover", the first link is what I sent. The third link is a StackOverflow thread explaining why there is not a better resolution:

  https://space.stackexchange.com/questions/39525/why-is-there-no-microscope-on-the-mars-2020-rover

The reason suggested? For high magnification you get shallow depth-of-field. Hence, samples must be prepared, and that's not easy.

Like any engineering issue it could be done in theory. But there are constraints and budgets, and choices have to be made, based on science priorities and the likelyhood of mission success. I'm not a rocket scientist, but that's the likely reason that there is not a high-power microscope on rovers.

I've got good news for you though. The second result on Google says that the current Mars mission will test for microbial life by using chemical analysis. Not in-situ, but using a sample return.

Viking 1 also did chemical analysis. Canonically inconclusively.

SHERLOC/WATSON instruments on board Perseverance rover can image with 10-15um resolution. Not super impressive in terms of microscopy, but it's getting there.

"Damn it J355ie, i told you not to shit outside".

TLDR; "Still, the rover has seen no physical traces of ancient microbes"

Or just the subtitle:

> Dramatically “light” carbon could also be explained by atmospheric reactions or cosmic dust

Not a pro but AFAIK the threshold for anyone saying "yup we found life" would be very high and probably that the instruments currently deployed on Mars wouldn't possibly suffice to convince someone at NASA to make that call. That is, because (every?) experiments out there can be explained by a multitude of phenomenons that could be non-life based.

I wouldn't be surprised if life turns out to be abundant over there and we've just been very hard-nosed on the evidence we'll accept.

At least that's my understanding, when looking at summaries like https://www.youtube.com/watch?v=YwXSEP3_Rwk.

The problem is that there is so much noise regarding life on other planets (we found life on Venus, we found life on Mars ) that when we will really will be finding something will be something like "Another clickbaity title".

I dont think we would expect physical traces, but rather chemical traces.

Considering the 1996 "Life on Mars Hoax" was recently debunked, a bit of patience and caution would serve our planet.

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