> A Special Region is defined as a location where the temperature could exceed -28° Celsius (-18.4° Fahrenheit) and water activity is at least 0.5. Water is key to life as we know it, and water activity considers the availability of water and water vapor as a potential support for life processes.
> The Mars 2020 mission is restricted from landing in, entering, or creating, a Special Region on Mars
[...]
> Thus, the Mars 2020 mission is also restricted from landing in sites where scientists suspect water, brine, or water ice could be present, or could be induced, within 5 meters (about 16.4 feet) of the surface
It takes them seven months to fly a rover to mars. They could potentially devise a way to expose the rover to space during these months to sterilize it.
Rovers are assembled in a clean room and space doesn't sterilize all life. It is impossible to know with certainty that a rover is sterile. Even autoclaving the whole rover doesn't guarantee sterility.
There has to be some limit on radiation resistance for these microorganisms. At the end of the day, DNA is a fragile molecule and it can be degraded. Maybe the rover could be overbombarded with radiation on this journey, if the background radiation in space is insufficient.
Radiodurans probably still has some limit where the rate of radiation is higher than its ability to repair fragmented DNA, at which point things snowball and the DNA is quickly broken down to its constituent bases and there would be no template at all in which to initiate any repair.
They haven't bothered with labeled release or adding water to soil. Curiosity does have a similar oven+GCMS setup to Viking, which has indeed found funny organic chemicals in some soil samples: https://en.wikipedia.org/wiki/Sample_Analysis_at_Mars
Please. We live on a planet that has been bombarded by space rocks for billions of years and that's home to all sorts of viruses and bacteria that have been evolving to kill us for as long as we've been around.
If Mars were covered in gray goo we would have noticed by now.
This just reinforces my point. The germs that killed the native Americans grew up in an environment where humans were living in close proximity to a variety of animals (cows, chickens, rats) for thousands of years. (cf. https://en.wikipedia.org/wiki/Guns,_Germs,_and_Steel)
Not that your point is invalid, but I wouldn't be linking Guns, Germs, and Steel. Quite a few historians have heavily criticized the claims in that book for being overly reductive pop history.
This is argumentum ad verecundiam in a debate that is theoretical back-and-forth. I think it's at least worthy of examination, especially if you want to understand the points being made by those historians to which you allude. By all means link to their counterarguments, but don't chill the sharing of other work like that.
Well, I actually think it would make sense, to test it somewhere in space first, see how it reacts with earth life.
(it likeley would just die, I think and not become parasitic)
But I rather think it won't happen soon, because it is not a priority to most funding parties.
Please take the divisive interjections to some other site. I know they might seem funny or insightful to you, but they're not adding anything to this discussion.
I think you're too confident in this assumption, then, and there are way less nutjobs that would be freaked out by a Mars sample return mission than you are concerned about.
You were not allowed to go to restaurants, hotels, cinemas or theatres. Or work in sensitive areas like hospitals (in my country this was even only true for new hires, not for people who were already on the job).
They are talking about cells, but must every form of life be built from cells?
It seems like all life on earth descended from one species, that was a cell. So all our life on earth is made out of cells. But couldn't life be completely different somewhere else?
A cell is just literally an organic unit. It’s something organized that is alive. Any living thing would have to have cell’s otherwise it’s just not organized in any way which doesn’t make sense in the context of our universe
It is very likely that some kind of life that doesn't require cells must be possible, because it must have existed before the appearance of cells.
Cells are much too complex to appear spontaneously, without evolving from an acellular form of life. Cell membranes can form spontaneously from fatty substances, but no cell can live without complex molecular pumps that are embedded in the cell membrane and which bring in some substances from outside and which expel some other substances from inside. Such pumps must be the result of a long evolution that preceded the first cells.
Nevertheless, any form of life that is not made of cells cannot live free in a fluid like water, but it must be attached to the surface of some suitable rocks, where a flow of nutrients must exist.
The most plausible hypotheses about the appearance of life on Earth suppose that before the appearance of cells, life was restricted to pores inside rocks from hydrothermal vents, where a flow of dihydrogen and of alkaline ions could provide the energy, and metallic sulfide minerals could provide the catalysts for organic syntheses.
The biggest issue is that life has to perform some sort of chemical process. Any lacking any clear delineation of an inside the life in question and the outside, would make continuous chemical processes impossible.
A stray breeze blowing away chemicals would effectively kill life. A "cell" having a barrier would allow that chemical process to happen.
Life may not require cells in the way cells on Earth evolved, but they'll require cells of some sort.
I'm trying to imagine some wacky living polymer or protein that wiggles around and grabs whatever molecules it needs to force localized reactions without a protected cell environment.
But then I start to wonder if evolutionary pressure would encourage ones that form colonies and eventually closed topologies and cells. And then others might specialize to hijack those colonies...
Maybe the planet, or locality on the planet, has resources that permit continuous chemical processes to happen without cell (maybe no breeze). Maybe it doesn't need to be continuous.
I think that no matter what definition one comes up with, it is possible to have counter examples (i.e., is fire alive, seeing as how it reproduces, consumes food (fuel), etc).
One of the indicators of life I like to use, that seems to be useful in the general sense is that life is good at decreasing (fighting against) entropy at a local level. So fire for example increases entropy. A living being takes in raw materials plus energy, and produces a lower entropy (higher organization) of those inputs. Like plants making sugar, and pulling apart CO2 to make free oxygen. Or animals taking in sugar and oxygen, the output is higher entropy (CO2) but you have higher organization of material (lower entropy) locally within that organism.
This also means that life doesn't necessarily need to reproduce (although that is how life that we know of works). You could theoretically have a living being that kept evolving its own form but never developed the ability to copy itself. It just keeps consuming energy and environmental items, and maintaining its own internal complex structures.
No, it actually can't. Fire will burn as hot and quickly as it has fuel and oxygen to sustain, because it's a chemical reaction, it doesn't maintain any kind of steady-state in order to extend it's survival.
If you take away my food, I will still have energy to find more. If you take away my air, I will still have air (albeit quite time-limited) to find more. That gradient is how we understand something to be alive.
You can indeed argue it does maintain certain states to help extend its survival. Think of how fire tends to burn wood into charcoal. Now a big wind may blow out the primary flame, yet it actually lives on through the charcoal for a period of time, which when the right conditions are met, are able to reignite the blaze. Think of how fire tends to fragment matter, and send it up in the updraft. Sparks of this nature are able to ignite more fires further than the primary fire could reach on its own, beyond firebreaks even. This is akin to clonal propagation to ensure survival that we see in many species, or the release of many progeny over an area banking on the reality that most will not survive, but some will.
I think if we go further down the logic hole and start questioning that by virtue of it being something you can start yourself with a tinderbox, that fire is not life, we question the entire premise of ideas like abiogenesis which argue life is inevitable when certain chemical conditions being met.
> You can indeed argue it does maintain certain states to help extend its survival.
Not really. Everything you described is a property of chemistry and physics, not biology. Coals smolder under high residual heat and a lack of oxygen, not because of gated ion channels, osmotic barriers or any other evolved structure.
> This is akin to clonal propagation to ensure survival that we see in many species, or the release of many progeny over an area banking on the reality that most will not survive, but some will.
It's really not. Fire has no genome, nor a biological urge to reproduce. Cinders are a result of physics - pieces of organic matter fragment, heat causes rising air, some fragments are light enough to rise on hot air. If they are still hot when they land, fire can start at a new location.
There is a critical point between high and low entropy where life exists: You can increase or decrease entropy, but on either end you seem to have death. High entropy at least has more information.
Homeostasis seems to be important.
Reproduction seems important, but that's "just" a survival strategy. It doesn't necessarily seem like a requirement for something to be "alive".
A system that in some context has an inheritable genotype that influences its phenotype.
I add the context part so we can say a virus is alive if the context of host cells is present, and otherwise not. Similar to how we are alive in the context of being on the Earth's surface, but not on the Sun.
Its very easy to say something like that, but impossible to provide any sort of examples, even in a fantasy context.
Like what a gas cloud with intelligence?
We live in a universe with distinct rules, saying life doesnt have to have cells is basically fantasizing about other dimensions where we're made out of hot dogs or something. Saying life doesn't require cells is just redefining what words mean, since a cell literally means the smallest functional unit of life.
> We live in a universe with distinct rules, saying life doesnt have to have cells is basically fantasizing about other dimensions where we're made out of hot dogs or something.
That comparison is ridiculous.
We live in a universe for which many of the rules are unclear and we have only grasped some small subset of the possibility space dor emergent structures those rules enable.
We have a hard enough time coming up with a clear definition of which of the emergent structures that we do know about qualify as "life". You seem to accept it as settled that viruses are not alive and are mere chemistry but it seems to me like drawing a line in the sand between two similar processes.
When we're talking about cells, that seems like an easier thing to define, but I would posit that is another definition that could prove to be slippery if an alien biology without a common ancestor is discovered.
We have to be careful about how we define life and cells in relation to each other to avoid just creating tautologies rather than useful definitions.
For example, how sure can we be that by defining life to exclude viruses, we haven't defined life in such a way that we have excluded processes that can support consciousness?
I think it is pretty easy to imagine life which has "cells" that we fail to recognize as such because they serve a similar function but with a sufficiently different form that we would fail to see or recognize them in a microscope.
Now, many of those imaginings may be scientifically impossible but that doesn't justify comparing all of them to "a dimension where we are made of hotdogs."
Technically yes, but I think many people would say it seems likely that all life would have some sort of "exterior layer" like a cell membrane. Realistically this falls into the "unknown unknown" category of knowledge, where we have to speculate with very little concrete evidence.
It makes sense to think about an organisms like that.
But it would be really interesting, if there were other possibilities too we could think of.
A hundred years ago nobody thought something like quantum entanglement could be possible. Maybe there will be a similar eye opening surprise in extra terrestrial life.
But off course it’s reasonable to start looking for all the things we can already imagine, and make observations in a way we already know of.
Sure, I'd love to learn that some sort of inscrutable aliens on the surface of a neutron star (https://gwern.net/doc/science/1973-drake.pdf) or gasbags on Jupiter (1. Sagan, C., and Salpeter, E. E. "Particles, Environments and Possible Ecologies in the Jovian Atmosphere," Astrophysical Journal Supplement, 32, 737 (1976).) to creatures that leave in witch space.
We simply don't have a framework other than basic physics and chemistry to speculate in this area. The possibility space is too large and we don't know the fitness function.
That was my the point, these conversations are linguistically phrased as trying to estabilish if something is alive but are actually structured as a debate on what "alive" means
Its a semantic argument. People agree on how these things work, they don't agree on defining it as one way or another. I'm in favor of viruses being a form of life. The argument against them being a form of life is that they can't replicate themselves without a host. To that I say, neither can us humans. Go on, sit in a field and try and replicate yourself without a host. It can't be done. Ergo, according to some virologist, you are not alive. Whether that host is a cell or another parent is semantics, since its the same situation just at a different level of abstraction essentially (whole organism vs microbe).
Still viruses are very specifically adapted to life on earth, everything contains DNA and RNA. Maybe this is the only form of life that is chemically possible, maybe there are many alternatives.
If you define 'life' as "any process that sits at the boundary between low to high entropy to make more of itself, and is subject to natural selection and evolution to produce diversity" then I'm sure there's all sorts of things that can be described that way. Maybe even things as "mundane" as the cloud patterns of Jupiter, or some internal processes inside a star? And would we even recognize these things if we saw them, most of the time?
... But the kind of thing people mean by "life" colloquially is really multicellular or at least eukaryotic life, which only arose on earth like 600 million years ago, which is only like 15% of the time that life in the more strict sense (bacteria/archae) has existed here.
Folks, I don't usually do popularity contests, but I'm trying to figure out why I'm being downvoted into oblivion here. Earlier today I was upvoted a bunch, now I'm -3, and..
I don't really see much of controversy in what I said here?
Cells (as in the bit that makes it a contained volume) are both a thing that forms spontaneously without biology, and very useful for isolating one blob of chemistry from others right next to it.
All the cells that can form spontaneously without biology are dead.
More precisely, they are just cell membranes, not cells. Cell membranes form spontaneously from many fatty substances, the root cause being that oil and water do not mix, i.e. fatty substances are hydrophobic.
A dead cell or cell membrane does not exchange chemical substances with the environment (except passively, i.e. when molecules or ions diffuse from high concentration towards low concentration).
A living cell has not only a cell membrane that separates the interior from the exterior, but it also has molecular pumps and ionic pumps embedded in the membrane, which selectively pump some substances in and other substances out. Without this controlled exchange between interior and exterior, the growth and multiplication that define life are impossible.
What is characteristic for life are the molecular pumps and ionic pumps. The cell membranes have only the passive role of preventing the substances that have been pumped in one direction to come back to the place from where they had been taken by the pump.
If extraterrestrial life were silicon-based, it may instead of cells have ceramic and metallic structures (like filaments) that grow via crystallization. I think that is what the parent is getting at - cells are part of our carbon/water based biology but maybe not all possible forms of life
Anything is possible, obviously, but in the current way we understand life, it's not likely.
I am unaware of any understanding of evolution or early life on Earth which supports an idea of some giant contiguous life-form.
That said, Mars is not Earth, and our definition of life is ever evolving (is a virus alive? is fire alive?) so, again anything is possible, but not everything is likely.
I recall hearing this explicitly stated by a member of the current rover team. They said that we need to begin imagining completely different forms of life from our own - like completely outside the box thinking.
Thankfully plenty of hard sci-fi writers have done that for us.
It's something that I've been very interested in for a long time, especially the idea of "scale of life" - could there be a brain the size of a solar system? How would we even understand it? What about life which operates on a different time scale (in the solar-system brain example, it would operate on a different scale on two axis - space and time).
The timescale issue is fun to think about. Even in my own life, there have been times that I've responded to a message within a second and other times that I've taken multiple years.
Our lifespan also seems quite arbitrary. Some sophisticated animals live quite a bit longer than us and others live a tiny fraction of a percent as long. One would imagine that between solar systems there is a much greater degree of variance.
It would be difficult to understand the time horizons of a collectively intelligent swarm of fruit flies or a serene pod of whales, but imagine if interstellar life has a geologic component to its life cycle?
I'd still consider all sci-fi stories and images quite inside the box thinking. The idea is that our brains are hard-wired to think the way they do. So we can't really think outside of our small subset of reality.
I believe, In the slim chance we encounter some kind of 'life', it wouldn't be even considered as life by our standards.
Just a simple quiz to exercise the brain:
- should life move at all?
- what's the maximum distance between molecules we can still consider as one entity?
- can a state of matter be 'life'. Not a matter itself, but just a state of it?
Sci-fi writers often tend to percolate interesting ideas from biologists, chemists, and physicists into interesting stories. I wouldn't discard them so easily.
The box needs to be defined at some point, lest you start realizing you've defined it so broadly that natural phenomenon like fire, the wind, or the tides qualify.
A cell is fundamentally a structural division between an inside and an outside. This creates an energy gradient that does work. So a cell is simply a structure that maintains a gradient for the purpose of doing work.
It's a very simple object--kind of a thermodynamic primitive for resisting entropy. The organelles within cells are themselves cells. I'm not sure what life would look like without cells but it would probably rely on some type of otherwise naturally occuring gradient like a tide pool or mineral formation.
So, one the one hand all Earth life depends on proton gradients over membranes in some form or other for energy, as in the mitochondria powering us. But because prokaryotes and archea seem to share a common ancestor but use radically different cell membranes it looks like their common ancestor might not have generated its own membranes but used naturally occurring lipid membranes. And we'd probably want to call that common ancestor alive.
Prokaryotes are archaea. The nature of the difference between their cell walls and other single cell organisms is not fully explored, and whether they formed from convergent evolution or not is still up for debate: https://en.m.wikipedia.org/wiki/Pseudopeptidoglycan
> Archaea (/ɑːrˈkiːə/ (listen) ar-KEE-ə; SG: archaeon /ɑːrˈkiːən/ ar-KEE-ən) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes.
One feature of living things is that, in a metaphysical sense, the whole precedes the parts (you might get away with calling them simultaneous in some simple cases, but it isn't the case with complex organisms). To call a collection of things incidentally arranged "living" is to either pass the buck and assign "life" status to the thing doing the "using", or to adopt a mechanistic view of reality that renders the notion of "life" meaningless.
mechanistic view of reality that renders the notion of "life" meaningless.
Correct. All notions are tools constructed by and for human minds for their own purposes. It's possible to hypothesize a definition-breaking example for nearly everything that isn't a mathematical abstract. What counts is useful definitions. In the case of "life" we already have many examples of things that don't perfectly fit the definition, like viruses and prions.
There's an interesting theory that suggests Martian and Earth life have a common ancestor, and have exchanged life through material kicked up out of atmosphere due to asteroid or meteor impact.
I think the implication was that it's kind of putting the cart before the horse. "Scientists hypothesize that Martian life and Earth life had a common ancestor" is pretty bizarre given that no Martian life has been found.
You have to separate low entropy volume from high entropy volume to do life. Btw cell internals are also full of membranes for the same reason. https://en.wikipedia.org/wiki/Organelle
That doesn’t mean your idea is wrong, but if we assume regular cold chemistry (i.e. not stellar insides or other exotic states/physics), membranes are just the sane and obvious default. Which conditions could make them less effective than something else?
Exactly. Earth life requires organization (low entropy) to generate usable biological energy. Absent a division, that low entropy state reverts to the environmental mean.
I'm struggling to imagine what usable energy generation in a high entropy environment would look like.
> You have to separate low entropy volume from high entropy volume to do life
That's what I believed too, but I have doubts now after reading another comment that defines it as energy gradients. As far as I understand the concept, a crystal is low entropy as well. Or is it the same thing? Or the combination of the two (Use energy to keep entropy low)?
> membranes are just the sane and obvious default
The less sane one could be... Magnetic confinement fields I guess?
If you want to understand crystals thermodynamically, in terms of entropy, you should be using a more rigorous notion of entropy. When crystal formation is thermodynamically favorable, the process causes entropy to increase, not decrease. So if you have a crystal which exists in-situ, in the conditions which caused it to form, you don’t increase entropy by un-creating it.
The main problem with crystals and solid-phase life in general is that, being solid, it tends to just sit there and be solid. It's why silicon life is nominally appealing if you just look at the periodic table, but when you look out into the real world and see what the characteristics of the compounds it actually forms look like, you see an awful lot of solids and it isn't really plausible as a basis for life.
It helps to look at how biology actually works; we get these images of things like DNA copying where the next amino acid is just sitting there, all but busting in the door to be copied. It gives a very false image of how biology works. In reality it's an insane world down there with a whole bunch of the cell just jiggling around thermally all the time, and the mechanisms all work by waiting to be bashed into by the right thing. Everything is so fast and the rate of jiggling is such that it all ends up working out. But it's nothing like anything we'd design or even very easily wrap our head around. I've sometimes wondered if we were somehow otherwise the same, but not biological, how long it would take for us to ever invent biology. We are certainly nowhere near it now.
Crystals and solid-phase in general doesn't have an obvious route to chemistry occurring anything like the way it does in biology, and indeed, it doesn't have an obvious route to chemistry occurring at all at any scale.
Maybe solid-phase life wouldn't mainly depend on what we normally think of as chemistry, but instead some other physical processes. Perhaps radiation making patterns in a crystal that somehow manage to utilize an energy gradient in the material to self-reproduce, with the radiation causing imperfections, or mutations, in the patterns. Or some completely different physical process we can't even conceive of because we haven't observed anything like it on earth.
I like to distinguish between "science fiction theories" and science we actually understand.
In science fiction, anything goes. If you want to talk about physical processes we've never even heard of, hey, go nuts. I've got my own pet theories.
If we want to stick to science, we can in fact use science to put some bounds on things. We don't have to know everything. Physical reproduction in the case you are talking about would have to be incredibly, incredible slow, plural orders of magnitude slower than Earth life. Reproduction of some energy signature might be possible, but without the ability to increase the physical substrate it can run on, that's all it would be. We actually have examples of that today; basically a laser fits the bill here, a crystal (in at least some cases) that can give a particular energy pattern the ability to reproduce. Clearly not life, though.
It actually reminds me of theories about life arising on Pluto or something. While we can't necessarily prove it is impossible, I've seen theories about using superfluid Helium as a base liquid for life, we can say it would have to be by necessity excruciatingly slow by Earth standards by the obvious ways the temperature affects chemistry speed. I can't prove a solid is completely impossible to be alive, but it is so, so much slower that it has some serious problems with its sun burning out in the metabolic equivalent of just a few thousand years of Earth metabolism.
I like both modes of thought. I do not like people mixing them willy-nilly. It wrecks them both and you very much get a worst of both worlds.
I don't think the speed of the process is really relevant, outside of the pace (or risk) of change of the environment. In animal life as we know it, lifespan ranges from a few days to centuries.
The point wasn’t that what I came up with is necessarily likely or possible though, just that maybe it will turn out there's life, i.e. some self-reproducing evolving thing that doesn't store its instructions for self-reproduction in a molecule in a solution. As for physical processes we haven't heard of, I was thinking of things that's not chemistry, but could reproduce some patterns. Some examples we have in technology is photography or photolithography.
OK, headline is more worrying that it needs to be - makes it sounds like we accidentally killed ALL life on Mars. It's actually referring to possible life in the soil sample the Viking lander poured water on.
Also, the part where they heated all (?) the samples before testing sounds more problematic than pouring water on some (especially since parts of mars hit 100% humidity, per the article).
I've said this before and I'll say this again: Space is not a amateur game.
I see a lot of young SV types thinking they want to build a deep tech space company. And they can. But it requires a couple years of deep training in of aeronautics and physics before you even know what's going on.
Elon for instance spent years studying space on his own before launching SpaceX. Elon's at a different level, but we can at least learn a few things from him and SpaceX.
I'm not sure what strawman you are talking about, but every space company in SV I have seen has been started by domain experts, mostly aerospace and hardware engineers.
There are also a lot of space companies focusing on a narrow niche that doesn't involve rockets — sometimes imagery (Planet, other satellites), sometimes 3D printing, etc. It's not like deep training in aeronautics will make you an expert in 3D printing in space - there's not a 101 guide to the space, it's novel tech.
Buddy elon doesn't even understand basic physics, like classical motion and energy equations. Or do you not remember the time he was talking about "compressed gas thrusters" on Teslas? Such a system would be laughably ineffective and all it takes to understand that is a high school physics equation.
Elon’s arguably the greatest founder in history. Either him, or JP Morgan. He doesn’t need to be more like a physician, physicians need to be more like him.
Ah yes, person is great because they started off with resources other people don't, and were able to leverage those resources to get even more resources. Truly, we should all emulate that.
Oh, most people don't start off rich? Oh what a shame.
Elon bought Tesla, Elon is only vaguely a part of SpaceX, and every single other venture he has been involved with has either gone nowhere, been a scam/grift/lie (boring company, hyperloop, neurolink though it shouldn't be judged just yet) or even classic nepotism with Solar roofing.
Elon is such a good businessman, which is why he bought Twitter at the peak of it's valuation, continually flakes on all it's bills, publicly admits to losing half of that peak value, saddled it with a billion dollar a year debt, erased any brand recognition it might have to replace it with a stupid domain name he has been obsessed with for twenty years, lost half of the advertising revenue, blocked it off from public access, fired anyone who isn't a sycophant, and repeats really dumb conspiracy theories about fucking everything.
How wealthy were his parents and family? How many other people have parents and family that wealthy, or wealthier? How many of them end up being $100+ billionaires?
To be fair he made most of his initial wealth during the dot.com psychosis...
Not saying he isn't one of the greatest businessmen in history (well... assuming he's running Twitter to the ground for shits & giggles anyway) but selling a company for hundreds of millions back in those days does not necessarily was not necessarily that different from winning the lottery (being at the right time and the right place was enough).
Tesla is pretty legit though, SpaceX too. Whatever I might think about him as a person I don't see how can someone deny that Tesla is running circles around all traditional car manufacturers.
They falsify so much, I don't know what is happening there. All I know they get lot of funding, which has happened with complete scams (everyone says it can't be a scam, until they knew it all along) and successes, and everything in between.
There are tons of people that start off rich and do nothing with it. There are tons of people who start poor and go nowhere with that, or start poor and become rich, and still do nothing with it.
Yes, he was fortunate to be born above an arbitrary rich/poor line that many other people weren't. How about instead of judging him based on something he had no control over (the irony in that judgement is palpable), judge him for what he has done, regardless of where he started from.
I'm not at all a Musk fanboy but he is undeniably a "great" person. He's got ~several~ achievements that would make him a great person, which reinforces the point even more.
Elon probably knows more engineering than Jim Farley or Dave Calhoun. I don't think you have a good handle on CEO competence in this industry. Musk is running circles around these guys.
I remember reading (probably from one of his books) that Sagan's idea for a life-detecting experiment on Mars was never actually sent there (apparently this experiment went instead). IIRC, it was basically to put a sample in a box and just watch it to see if anything changed at all in a way that indicates that some chemical process is happening.
Microscopy could also be a good route. Microbial life should look pretty distinct from inorganic matter, even if everything in the soil sample were dead by the time it was imaged. As far as I know, we have not sent a microscope up capable of resolving even a large mammalian cell, let alone resolve 1 micron bacteria (if these microbes are even to be similar in size as those on Earth). I suspect the vibrations during launch make it especially challenging to actually get a powerful microscope out to Mars unharmed.
It's very important to NASA to never send anything to Mars that could definitively rule out the presence of life or water.
Something I noticed a few years ago is that NASA publishes a press release every month or so with the title "possible hint of water found on Mars". There are literally thousands of such web pages on their site:https://www.google.com/search?q=site%3Anasa.gov+"hint"+"wate...
Nobody ought to be this obsessed with something, unless there's an agenda. It's like cigarette companies going on and on about how their latest product is "more healthy".
What's going on is that NASA has had a lot of trouble in recent decades maintaining their funding. There's not a lot in space that excites US senators. There's no oil, no resources that can be practically mined, etc...
So they have to have some sort of goal, something they have to get funding for so that they can go "look for it".
Some NASA administrator picked "water on Mars". Now it has morphed into a reason for the agency to exist, which means if it was ever shown not to exist, then NASA would face a real existential risk itself.
So they'll drag their feet as long as possible, sending every possible instrument they can pack into a rover, except for the one that could definitively rule out life and/or water.
This is why they didn't send a microscope, and most likely won't send one on the next mission either.
No planet you can land on, so that leaves the moons and pluto and the cost is much higher. Not the little extra fuel and hardware requirements, but the mission time alone...
Venus is extremely dense and hot that it melts all the equipment pretty quickly, Mercury is hard to reach. Probably very hot too on the very long and sunny days and the nights are too cold. It also require the most fuel to visit without space brakes.
I'm talking about a big headline mission to survey everything in the vicinity of the outer 2 smaller gas giants. Think Cassini or Galileo (too bad about that antena). Sure these missions take a long time. Means we have to start today so our kids can see the results.
All 4 gas giants have plenty of moons with places to land. But I'm not even talking that far out in the future. I just want a suite of scientific instruments in a wide orbit around a gas giant surveying every moon they can get near.
Grvity assist slingshot opportunities to get to the outer giants don't come along every decade and yet when one does come up the proposed mission opportunity and it's budget gets instead allocated to yet another damn mars rover.
What discrete realistic experiment would “definitively rule out” life or water on the entire planet?
How many samples would need to be microscopically analyzed to prove the negative?
> As I have argued before, we need a new mission to Mars dedicated primarily to life detection to test this hypothesis and others. It should explore potential habitats on Mars like the Southern Highlands, where life could persist in salt rocks close to the surface
On a quick scan, I'm not seeing anything in your linked article that counters either your selected quote, or the thrust of the OP. Can you help me out by pointing to a section or summarizing the argument?
"It should explore potential habitats on Mars like the Southern Highlands, where life could persist in salt rocks close to the surface" is basically saying that we should throw away planetary protection guidelines in favor of studying places with potential for extant life, an argument that the author has been making repeatedly for a long time, and what the article I linked counters.
The discussion about Viking lander results was just build-up for that final paragraph making the argument for new life-searching mission.
I see. The OP article doesn't say anything about throwing away planetary protection guidelines... are you saying that there is no way to do the mission discussed in the article without relaxing or eliminating these guidelines?
I feel like I'm wading into the middle of a lover's quarrel, where the words have nothing to do with the actual fight...
Actually finding life vs is there actually life makes no difference. There is almost zero chance that we only have life here on earth and exponentially high chance the detection method give false positives
This seems a bit hyperbolic. I suppose there is a tiny chance that we caused the extinction of the last vestiges of microscopic life on Mars. I doubt it though.
Science is about trying things and learning from our mistakes.
how desperate do you have to be to write this headline? endless experiments fail to find life (as any reasonable person would expect) and then you justify your undying belief in extraterrestrials by conjecturing that maybe there was life all along but we killed it accidentally! this is one of the most cringe headlines I've ever read in my entire life. you didn't find life at any point. this is not in dispute.
I hope this is actually just brain dead clickbait and not genuine simping for aliens by claiming xenocide based on literally nothing. hey, maybe one of the scientists accidentally farted on all the moon rocks too. we can't rule this out. better alert the media and make it seem like we're actually on the case
alien hunters can't get a life here where it's warm so why would they get any out there? the real aliens are truly the friends we made along the way
The article is not claiming xenocide; it is saying that the probe may have killed the life in the sample when it added water. Yes the headline is a little ambiguous, but I assume most readers have built up a filter for that by now.
walking through sewage does indeed strengthen the immune system. at least as much as water filters out the weak aliens.
there was no life. the only fluid anywhere near the planet surface is a weak amount of carbon dioxide. there are no billion-year-old organisms still alive from when there was liquid water. I've heard of child-like wonder but this is just embarassing. i hope none of my taxes go to this
"if elvis is alive, he lives on the moon" is a true statement only because elvis is not alive. if life was in the sample, it was killed by water is a true statement only on the technicality that the premise is impossible. the author either deeply misunderstands propositional logic or it's intentional clickbait. probably both.
The best way to conduct a proper experiment is to either send a human, or a robot that is as adaptable as a human. This will let us run an effective experiment, react to intermediate results and continue based on that. Anything else is a waste of time, we'll never get anything conclusive.
176 comments
[ 3.7 ms ] story [ 230 ms ] threadMaking a lander where we know there are no earth microbes on it is quite difficult and certainly important for testing for life.
https://marsnext.jpl.nasa.gov/scieng_plantary.cfm
> A Special Region is defined as a location where the temperature could exceed -28° Celsius (-18.4° Fahrenheit) and water activity is at least 0.5. Water is key to life as we know it, and water activity considers the availability of water and water vapor as a potential support for life processes.
> The Mars 2020 mission is restricted from landing in, entering, or creating, a Special Region on Mars
[...]
> Thus, the Mars 2020 mission is also restricted from landing in sites where scientists suspect water, brine, or water ice could be present, or could be induced, within 5 meters (about 16.4 feet) of the surface
https://www.sciencealert.com/a-bunch-of-earth-organisms-were...
https://en.wikipedia.org/wiki/Deinococcus_radiodurans
If Mars were covered in gray goo we would have noticed by now.
I’ve certainly not seen a refutation of the fact that the natural attributes of living in one place provide advantages over other places.
I haven’t looked into this in a while though, so if you’re aware of some more comprehensive rebuttals, I’d like to see them.
But I rather think it won't happen soon, because it is not a priority to most funding parties.
We have brought extraterrestrial samples to Earth before.
https://mars.nasa.gov/msr/#Facts
EU, Japan and China have plans for Mars and they're not worried about religion.
That's why we don't have one.
It seems like all life on earth descended from one species, that was a cell. So all our life on earth is made out of cells. But couldn't life be completely different somewhere else?
Cells are much too complex to appear spontaneously, without evolving from an acellular form of life. Cell membranes can form spontaneously from fatty substances, but no cell can live without complex molecular pumps that are embedded in the cell membrane and which bring in some substances from outside and which expel some other substances from inside. Such pumps must be the result of a long evolution that preceded the first cells.
Nevertheless, any form of life that is not made of cells cannot live free in a fluid like water, but it must be attached to the surface of some suitable rocks, where a flow of nutrients must exist.
The most plausible hypotheses about the appearance of life on Earth suppose that before the appearance of cells, life was restricted to pores inside rocks from hydrothermal vents, where a flow of dihydrogen and of alkaline ions could provide the energy, and metallic sulfide minerals could provide the catalysts for organic syntheses.
A stray breeze blowing away chemicals would effectively kill life. A "cell" having a barrier would allow that chemical process to happen.
Life may not require cells in the way cells on Earth evolved, but they'll require cells of some sort.
But then I start to wonder if evolutionary pressure would encourage ones that form colonies and eventually closed topologies and cells. And then others might specialize to hijack those colonies...
https://en.wikipedia.org/wiki/Biomolecular_condensate
One of the indicators of life I like to use, that seems to be useful in the general sense is that life is good at decreasing (fighting against) entropy at a local level. So fire for example increases entropy. A living being takes in raw materials plus energy, and produces a lower entropy (higher organization) of those inputs. Like plants making sugar, and pulling apart CO2 to make free oxygen. Or animals taking in sugar and oxygen, the output is higher entropy (CO2) but you have higher organization of material (lower entropy) locally within that organism.
This also means that life doesn't necessarily need to reproduce (although that is how life that we know of works). You could theoretically have a living being that kept evolving its own form but never developed the ability to copy itself. It just keeps consuming energy and environmental items, and maintaining its own internal complex structures.
If you take away my food, I will still have energy to find more. If you take away my air, I will still have air (albeit quite time-limited) to find more. That gradient is how we understand something to be alive.
I think if we go further down the logic hole and start questioning that by virtue of it being something you can start yourself with a tinderbox, that fire is not life, we question the entire premise of ideas like abiogenesis which argue life is inevitable when certain chemical conditions being met.
Not really. Everything you described is a property of chemistry and physics, not biology. Coals smolder under high residual heat and a lack of oxygen, not because of gated ion channels, osmotic barriers or any other evolved structure.
> This is akin to clonal propagation to ensure survival that we see in many species, or the release of many progeny over an area banking on the reality that most will not survive, but some will.
It's really not. Fire has no genome, nor a biological urge to reproduce. Cinders are a result of physics - pieces of organic matter fragment, heat causes rising air, some fragments are light enough to rise on hot air. If they are still hot when they land, fire can start at a new location.
Homeostasis seems to be important.
Reproduction seems important, but that's "just" a survival strategy. It doesn't necessarily seem like a requirement for something to be "alive".
I add the context part so we can say a virus is alive if the context of host cells is present, and otherwise not. Similar to how we are alive in the context of being on the Earth's surface, but not on the Sun.
Like what a gas cloud with intelligence?
We live in a universe with distinct rules, saying life doesnt have to have cells is basically fantasizing about other dimensions where we're made out of hot dogs or something. Saying life doesn't require cells is just redefining what words mean, since a cell literally means the smallest functional unit of life.
That comparison is ridiculous.
We live in a universe for which many of the rules are unclear and we have only grasped some small subset of the possibility space dor emergent structures those rules enable.
We have a hard enough time coming up with a clear definition of which of the emergent structures that we do know about qualify as "life". You seem to accept it as settled that viruses are not alive and are mere chemistry but it seems to me like drawing a line in the sand between two similar processes.
When we're talking about cells, that seems like an easier thing to define, but I would posit that is another definition that could prove to be slippery if an alien biology without a common ancestor is discovered.
We have to be careful about how we define life and cells in relation to each other to avoid just creating tautologies rather than useful definitions.
For example, how sure can we be that by defining life to exclude viruses, we haven't defined life in such a way that we have excluded processes that can support consciousness?
I think it is pretty easy to imagine life which has "cells" that we fail to recognize as such because they serve a similar function but with a sufficiently different form that we would fail to see or recognize them in a microscope.
Now, many of those imaginings may be scientifically impossible but that doesn't justify comparing all of them to "a dimension where we are made of hotdogs."
But it would be really interesting, if there were other possibilities too we could think of.
A hundred years ago nobody thought something like quantum entanglement could be possible. Maybe there will be a similar eye opening surprise in extra terrestrial life.
But off course it’s reasonable to start looking for all the things we can already imagine, and make observations in a way we already know of.
We simply don't have a framework other than basic physics and chemistry to speculate in this area. The possibility space is too large and we don't know the fitness function.
But the only life we know... is cells. Unless you count viruses. Which most biologists don't.
That is we are not trying to discover whether a thing is alive or not, we are trying to decide what Alive means.
This confusion creates the illusion that terms like Life, consciousness, emotions, reflexes, etc. are well defined while they in practice are not.
I hope it wouldn’t be a huge breakthrough for the virus
... But the kind of thing people mean by "life" colloquially is really multicellular or at least eukaryotic life, which only arose on earth like 600 million years ago, which is only like 15% of the time that life in the more strict sense (bacteria/archae) has existed here.
I don't really see much of controversy in what I said here?
Cells (as in the bit that makes it a contained volume) are both a thing that forms spontaneously without biology, and very useful for isolating one blob of chemistry from others right next to it.
There is however life on earth with huge cells and multiple nucleuses: https://en.wikipedia.org/wiki/Plasmodium_(life_cycle)
But also, the Viking test was more general than "cells", it would have ben positive with anything that could, to simplify, eat the food it was given.
More precisely, they are just cell membranes, not cells. Cell membranes form spontaneously from many fatty substances, the root cause being that oil and water do not mix, i.e. fatty substances are hydrophobic.
A dead cell or cell membrane does not exchange chemical substances with the environment (except passively, i.e. when molecules or ions diffuse from high concentration towards low concentration).
A living cell has not only a cell membrane that separates the interior from the exterior, but it also has molecular pumps and ionic pumps embedded in the membrane, which selectively pump some substances in and other substances out. Without this controlled exchange between interior and exterior, the growth and multiplication that define life are impossible.
What is characteristic for life are the molecular pumps and ionic pumps. The cell membranes have only the passive role of preventing the substances that have been pumped in one direction to come back to the place from where they had been taken by the pump.
https://en.wikipedia.org/wiki/Micelle
I am unaware of any understanding of evolution or early life on Earth which supports an idea of some giant contiguous life-form.
That said, Mars is not Earth, and our definition of life is ever evolving (is a virus alive? is fire alive?) so, again anything is possible, but not everything is likely.
Okay? People have no idea what pre-cellular life looked like so the entire earth being a giant cell is not out of the question.
It's something that I've been very interested in for a long time, especially the idea of "scale of life" - could there be a brain the size of a solar system? How would we even understand it? What about life which operates on a different time scale (in the solar-system brain example, it would operate on a different scale on two axis - space and time).
Our lifespan also seems quite arbitrary. Some sophisticated animals live quite a bit longer than us and others live a tiny fraction of a percent as long. One would imagine that between solar systems there is a much greater degree of variance.
It would be difficult to understand the time horizons of a collectively intelligent swarm of fruit flies or a serene pod of whales, but imagine if interstellar life has a geologic component to its life cycle?
I believe, In the slim chance we encounter some kind of 'life', it wouldn't be even considered as life by our standards.
Just a simple quiz to exercise the brain: - should life move at all? - what's the maximum distance between molecules we can still consider as one entity? - can a state of matter be 'life'. Not a matter itself, but just a state of it?
The reality might be very boring. Way too boring for a good story.
Life? Don't talk to me about life.
I think the only wiggle room there is "nontrivial".
It's a very simple object--kind of a thermodynamic primitive for resisting entropy. The organelles within cells are themselves cells. I'm not sure what life would look like without cells but it would probably rely on some type of otherwise naturally occuring gradient like a tide pool or mineral formation.
I don't doubt there is some relationship, but that isn't the definition of domain. Otherwise we'd have 1 domain.
> Archaea (/ɑːrˈkiːə/ (listen) ar-KEE-ə; SG: archaeon /ɑːrˈkiːən/ ar-KEE-ən) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes.
https://en.m.wikipedia.org/wiki/Archaea
The three-domain system divides life in Archaea, Bacteria, and Eukarya. In this system, Archaea and Bacteria can be grouped together as prokaryotes.
In the two-domain system, the division is between Archaea and Bacteria. In this case, eukaryotes are seen as a subgroup of Archaea.
Hope to have cleared up some of the confusion.
Correct. All notions are tools constructed by and for human minds for their own purposes. It's possible to hypothesize a definition-breaking example for nearly everything that isn't a mathematical abstract. What counts is useful definitions. In the case of "life" we already have many examples of things that don't perfectly fit the definition, like viruses and prions.
The local star, especially if close enough, creates lots of gradients.
Martian isn't a broad synonym for alien or extraterrestrial. It just means life on mars
That doesn’t mean your idea is wrong, but if we assume regular cold chemistry (i.e. not stellar insides or other exotic states/physics), membranes are just the sane and obvious default. Which conditions could make them less effective than something else?
I'm struggling to imagine what usable energy generation in a high entropy environment would look like.
That's what I believed too, but I have doubts now after reading another comment that defines it as energy gradients. As far as I understand the concept, a crystal is low entropy as well. Or is it the same thing? Or the combination of the two (Use energy to keep entropy low)?
> membranes are just the sane and obvious default
The less sane one could be... Magnetic confinement fields I guess?
It helps to look at how biology actually works; we get these images of things like DNA copying where the next amino acid is just sitting there, all but busting in the door to be copied. It gives a very false image of how biology works. In reality it's an insane world down there with a whole bunch of the cell just jiggling around thermally all the time, and the mechanisms all work by waiting to be bashed into by the right thing. Everything is so fast and the rate of jiggling is such that it all ends up working out. But it's nothing like anything we'd design or even very easily wrap our head around. I've sometimes wondered if we were somehow otherwise the same, but not biological, how long it would take for us to ever invent biology. We are certainly nowhere near it now.
Crystals and solid-phase in general doesn't have an obvious route to chemistry occurring anything like the way it does in biology, and indeed, it doesn't have an obvious route to chemistry occurring at all at any scale.
In science fiction, anything goes. If you want to talk about physical processes we've never even heard of, hey, go nuts. I've got my own pet theories.
If we want to stick to science, we can in fact use science to put some bounds on things. We don't have to know everything. Physical reproduction in the case you are talking about would have to be incredibly, incredible slow, plural orders of magnitude slower than Earth life. Reproduction of some energy signature might be possible, but without the ability to increase the physical substrate it can run on, that's all it would be. We actually have examples of that today; basically a laser fits the bill here, a crystal (in at least some cases) that can give a particular energy pattern the ability to reproduce. Clearly not life, though.
It actually reminds me of theories about life arising on Pluto or something. While we can't necessarily prove it is impossible, I've seen theories about using superfluid Helium as a base liquid for life, we can say it would have to be by necessity excruciatingly slow by Earth standards by the obvious ways the temperature affects chemistry speed. I can't prove a solid is completely impossible to be alive, but it is so, so much slower that it has some serious problems with its sun burning out in the metabolic equivalent of just a few thousand years of Earth metabolism.
I like both modes of thought. I do not like people mixing them willy-nilly. It wrecks them both and you very much get a worst of both worlds.
passive aggressive subtitle vs. headline wars ftw
I see a lot of young SV types thinking they want to build a deep tech space company. And they can. But it requires a couple years of deep training in of aeronautics and physics before you even know what's going on.
Elon for instance spent years studying space on his own before launching SpaceX. Elon's at a different level, but we can at least learn a few things from him and SpaceX.
There are also a lot of space companies focusing on a narrow niche that doesn't involve rockets — sometimes imagery (Planet, other satellites), sometimes 3D printing, etc. It's not like deep training in aeronautics will make you an expert in 3D printing in space - there's not a 101 guide to the space, it's novel tech.
Oh, most people don't start off rich? Oh what a shame.
Elon bought Tesla, Elon is only vaguely a part of SpaceX, and every single other venture he has been involved with has either gone nowhere, been a scam/grift/lie (boring company, hyperloop, neurolink though it shouldn't be judged just yet) or even classic nepotism with Solar roofing.
Elon is such a good businessman, which is why he bought Twitter at the peak of it's valuation, continually flakes on all it's bills, publicly admits to losing half of that peak value, saddled it with a billion dollar a year debt, erased any brand recognition it might have to replace it with a stupid domain name he has been obsessed with for twenty years, lost half of the advertising revenue, blocked it off from public access, fired anyone who isn't a sycophant, and repeats really dumb conspiracy theories about fucking everything.
How rich did Elon start off?
His payoff from paypal is not something most people will have access to. The dot com boom was basically a lottery.
Compaq managed to sell AltaVista for $2.3 billion 6 months later and not long before the crash so maybe it wasn't the stupidest move on their side.
Elon family riches is uncertain: https://futurism.com/elon-musk-dad-emerald-mine
Not saying he isn't one of the greatest businessmen in history (well... assuming he's running Twitter to the ground for shits & giggles anyway) but selling a company for hundreds of millions back in those days does not necessarily was not necessarily that different from winning the lottery (being at the right time and the right place was enough).
And now make money in another, partly self-created psychosis
>They falsify so much
What do you even mean by that? Whom did Tesla scam?
Yes, he was fortunate to be born above an arbitrary rich/poor line that many other people weren't. How about instead of judging him based on something he had no control over (the irony in that judgement is palpable), judge him for what he has done, regardless of where he started from.
I'm not at all a Musk fanboy but he is undeniably a "great" person. He's got ~several~ achievements that would make him a great person, which reinforces the point even more.
What does being a founder have to do with being a doctor?
Or a physicist for that matter?
So you're saying that the people who designed and launched the Viking lander back in the 70s (it landed on Mars when Musk was about 5) were amateurs?
Well as far as Mars exploration is concerned they achieved much more than him with basically stone age tech compared to what's available now...
Here are some interesting slides I found while trying to figure out what his actual experiment idea involved: https://www.vanderbilt.edu/olli/archive/Life_On_Mars_Session...
Something I noticed a few years ago is that NASA publishes a press release every month or so with the title "possible hint of water found on Mars". There are literally thousands of such web pages on their site:https://www.google.com/search?q=site%3Anasa.gov+"hint"+"wate...
Nobody ought to be this obsessed with something, unless there's an agenda. It's like cigarette companies going on and on about how their latest product is "more healthy".
What's going on is that NASA has had a lot of trouble in recent decades maintaining their funding. There's not a lot in space that excites US senators. There's no oil, no resources that can be practically mined, etc...
So they have to have some sort of goal, something they have to get funding for so that they can go "look for it".
Some NASA administrator picked "water on Mars". Now it has morphed into a reason for the agency to exist, which means if it was ever shown not to exist, then NASA would face a real existential risk itself.
So they'll drag their feet as long as possible, sending every possible instrument they can pack into a rover, except for the one that could definitively rule out life and/or water.
This is why they didn't send a microscope, and most likely won't send one on the next mission either.
I agree that mars has been over explored to the detriment of all other planets, especially the outer ones.
Venus is extremely dense and hot that it melts all the equipment pretty quickly, Mercury is hard to reach. Probably very hot too on the very long and sunny days and the nights are too cold. It also require the most fuel to visit without space brakes.
All 4 gas giants have plenty of moons with places to land. But I'm not even talking that far out in the future. I just want a suite of scientific instruments in a wide orbit around a gas giant surveying every moon they can get near.
Grvity assist slingshot opportunities to get to the outer giants don't come along every decade and yet when one does come up the proposed mission opportunity and it's budget gets instead allocated to yet another damn mars rover.
Asteroid mining would at least have a huge economic payout if achieved.
And the refutations to the authors original pleas are still as valid as they were then: https://www.liebertpub.com/doi/10.1089/ast.2017.1749
The discussion about Viking lander results was just build-up for that final paragraph making the argument for new life-searching mission.
I feel like I'm wading into the middle of a lover's quarrel, where the words have nothing to do with the actual fight...
Science is about trying things and learning from our mistakes.
I hope this is actually just brain dead clickbait and not genuine simping for aliens by claiming xenocide based on literally nothing. hey, maybe one of the scientists accidentally farted on all the moon rocks too. we can't rule this out. better alert the media and make it seem like we're actually on the case
alien hunters can't get a life here where it's warm so why would they get any out there? the real aliens are truly the friends we made along the way
there was no life. the only fluid anywhere near the planet surface is a weak amount of carbon dioxide. there are no billion-year-old organisms still alive from when there was liquid water. I've heard of child-like wonder but this is just embarassing. i hope none of my taxes go to this
"if elvis is alive, he lives on the moon" is a true statement only because elvis is not alive. if life was in the sample, it was killed by water is a true statement only on the technicality that the premise is impossible. the author either deeply misunderstands propositional logic or it's intentional clickbait. probably both.
https://www.wolframalpha.com/input?i=truth+table+%28p+implie... https://www.wolframalpha.com/input?i=truth+table+%28p+implie...