Martian Codons of DOOOOOOM!
A Fun Romp Through Extraterrestrial Microbiology and the End of Civilization
There have been a few tantalizing hints of life on Mars. The original Viking landers saw evidence of metabolism, perchlorates, and organics. We found a Martian meteorite, ALH84001, with tiny bacterial shapes in it. There is sometimes more methane in the Martian atmosphere than there should be from geology alone (maybe), and that methane might come from life.
In my opinion, none of these individually indicate that life is currently active on Mars. The Viking experiments weren’t repeatable with other landers, the ALH84001 “microbes” were too small and not composed of chiral molecules, and NASA keeps coming up with more and more ways that methane could exist on Mars without life. Taken together, my best Bayesian estimate puts the likelihood of current Martian life at a little less than 30%, with a huge estimation uncertainty. So currently, I don’t think there is decent evidence that life probably exists on Mars.
With the commercial space race heating up, our speculation is beginning to matter less and less. In the next 5 or 10 years, we might actually have boots on Mars. If life exists under the soil within a few miles of their landing site, we will almost definitely find it.
If we do find this life, one of the most crucial questions in the history of our species is closer to being answered: Is life everywhere, or super-rare?
There are basically three high-level possibilities for the relationship between Earth life and Mars life:
Option A: Earth and Mars life arose completely independently and are unrelated. If this is the case, life is probably everywhere. Having two independent arisings of life in one solar system implies that life pops up or was created to be everywhere.
What might these differences look like? The two different trees of life might be different in thousands of fundamental ways. Mars life might be silicon based instead of carbon, or use carbon ropes as the smallest unit of life instead of cells. Mars life might store genetic information in 3D shells of metals instead of 1D strings of DNA. Earth life uses 20 specific amino acids to make its proteins. Mars life might use 10 of those and 14 different ones than Earth life uses. It could even be fundamentally electrical instead of biochemical, and exist as a network of ferrous dust tendrils spread across dozens of mile of sand, replicating via sand dune shifts. Or their microbes might just use RNA instead of DNA, or make proteins via diffusion instead of Earth-like micromachinery.
If any of those things are true, then we have evidence that life arose independently twice, and can probably expect that life will be found around many, many stars in our local neighborhood, in many of the places that certain elemental conditions and consistent energy flows coincide.
Option B: Earth and Mars life are very strongly related and are basically the same. If this is the case then from a naturalistic viewpoint, there must have been cross-contamination. Life must have started on one planet, and gotten transferred by meteorite impacts to the other planet. Philosophically, it doesn’t really matter which planet it started at. The point is that there is only one origin of life, and so we end up, philosophically, approximately in the same place.
Panspermia (life from beyond other solar systems carried by meteorites) is also congruous with this data of same life on both planets. But unlike a lot of other people, I consider extrasolar panspermia to be effectively impossible due to the timeframes involved. Even spores or DNA/RNA strands can’t survive the trip through the galactic cosmic ray environment outside stellar heliopauses without decaying into useless broken pieces. Nothing will survive those crazy, penetrating radiation fluxes for the hundreds of thousands of years such a journey would take.
But how can we tell if Earth and Mars microbial life is related? Life on Earth that is separated by billions of years of time, such as pond scum and porcupines, still share genes that are extremely similar. In many cases, those genes are unchanged, even though the common ancestors diverged 2 billion years ago. For instance, the machinery that copies information from the DNA to make cell parts (proteins) is so important and already works so well that much of it is untouched by natural selection and remains the same in algae and anteaters1. Even life that exists in VERY different environments (sulfurous deep see vent archaic bacteria and mountainous rock lichens) keep some of the same genes. And all Earth life uses the DNA—>RNA—> protein method of expressing genetic information into useful new cell parts.
These ultra-conserved elements of our genome would also very likely be conserved today if life emigrated via asteroid strike from Earth to Mars 2 billion years ago, despite the very different environments that now exist on Mars.
So if we found DNA-based life on Mars that shares even a few of the DNA sequences (genes) that Earth life uses, and it also uses almost all the same amino acids, then we would be quite confident that life only arose once in our Solar System and spread. Then we would not have any new information on the likelihood of life elsewhere, because we still would only know it happened once here.
Option C: Earth and Mars life share some similar features but are significantly different. If we find Martian microbes, this medium path is very likely to be true on the macroscopic level, in terms of structures and colors and modes of living. But what matters most is the way the cells make their own parts and store their genetic information.
So let’s assume that we find microscopic replicating metabolizers on Mars. How can we tell if Mars microbes are related to Earth life?
Just because Mars uses DNA as a storage mechanism doesn’t mean it’s related to Earth life. DNA might be a significantly better design choice than any other bioavailable storage mechanism, so Earth and Mars life might both eventually land on DNA as the answer independently. The same could even be said for using the 20 amino acids Earth life prefers. Perhaps those are simply the most useful and consistently plentiful arrangements of carbon rings to build stuff from.
So how can we differentiate origin stories, if we find on Mars life that is pretty similar to us but not completely the same?
We would look for things that chemistry says don’t matter, but are nonetheless highly conserved across all Earth life.
The best version of this is Codon Maps.
A brief bit of background is required here, but you will surely enjoy it. What I am about to explain is one of my favorite set of science facts I have every come across…the way DNA gets turned into proteins.
Human DNA contains almost 20,000 recipes for making different proteins. Proteins are amazing nanomachines constructed by our cells, thousands per cell per hour all the time. These protein nanomachines act as valves, activators, wrappers, tags, catalysts, scaffolding, signals, and watchdogs for all sorts of things. Here is what a typical protein looks like.2 It may look nondescript and lumpy, but it is a fine-tuned machine with special activation points that make it change shape to unveil other activation points. It is exquisite.
These creations are made from amino acids that get hooked together in long, single strings3, and then folded to make a very specific nanomachine shape, like that shown above.
But what are amino acids? Amino acids are very simple pieces, analogous to nuts and bolts if proteins are engine blocks. Each amino acid is made up of only about 10-30 atoms each. Here is a diagram of one of the smallest amino acids, glycine (if the R is a hydrogen atom). A good rule of thumb to remember is that proteins are very complex, and useful ones are hyper-unlikely to occur randomly. Amino acids are pretty simple and occur in lots of places.
There are 20 types of amino acids that Earth life typically uses. And here is the payoff: there are very specific DNA codes that call for which amino acid to use in which order in the making of a protein. As you probably know, each space in a DNA string can contain one of four “letters”, A, G, T, and C. These stand for certain acids in the DNA, but those are interchangeable and the sequence of those 4 letters, say, ‘AAGTCCCCCAAGTTCCCAAAAGTCATCGGA’ is how information is written.
DNA needs to efficiently encode a way to tell which amino acid is needed next in the string that makes up a certain protein. Since each place in the DNA could be one of 4 different letters, then:
in one space you could have 4 possibilities
in two spaces you could have 4x4 = 16 possibilities, because each of the two spaces could be any of the four letters.
Unfortunately, our biology uses 20 different amino acids. So the code for each amino acid needs to use three letters in order to get more than 16 possibilities. With 3 letters, you have 4x4x4 = 64 possibilities, which is way more than 20, and does the job.
So our DNA, in the sections that tell how to make proteins (each section is called a gene), the sequence of amino acids is encoded in triplet sections called codons, each made of three letters. In ALL Earth life, every single cell of every different organism uses the same codons to mean the same amino acids. Here is the table of codons for Earth life:
As you can see, we have multiple codes each for the 20 different amino acids (shaded blue) and four extra codes that tell the micromachinery of the cells that they are at the start and the stop of the gene (list of amino acids that make up one protein). All those extra codons can occur because three letter spaces gives us 64 options, but we only need 20 amino acid codons.
But here is the important part: as far as we can tell, there is no real reason that the codon code GCT should chemically be related to Arg (argine). Chemically, energetically, and physics-wise, the codon GCT could just as well code for Cys or Ser. The assignment of codons is apparently completely arbitrary. It has to be consistently maintained and always stay the same within any Earth organism, but in the beginning the codon/amino acid assignments could have been any combination.
So this gives us the PERFECT method for figuring out if Martian DNA/RNA based life is related to Earth life: If the Codon Map shown above is significantly different for Martian life, then life arose twice, because a different Codon Map means that there is no common ancestor between those trees of life.
If it’s the same, there is no chemistry or physics fundamentally driving that it should be the same. An identical (or very similar) Codon Map would mean life only arose once. Either planetary cross-contamination of life occurred, or Panspermia is true, or it’s just the way God likes it. But scientifically, it indicates that life did NOT arise twice independently in our Solar System.
But let’s say we find life on Mars, and the Codon Map is different. Besides the fun buzz of realizing that at least simple life is probably everywhere, why should this really matter to us?
The answer is that this would be the most important and dire discovery in the history of mankind.
If life is ubiquitous, then even if intelligence is fairly rare, then there should be many intelligent species in each galaxy. Every galaxy our size has over 100 billion solar systems. Even if microbial life only becomes smart beings in 1 in ten million cases, this still means 10,000 intelligent civilizations per galaxy.
But we don’t see any evidence of that. No radio signals4 or laser bursts. No UFO visitors5 or Von Neumann probes6.
And there is even better evidence we are alone, sentience-wise. We think the best, most stable source of energy upon which to build a growing intelligent society is starlight, and the best way to harness that would be to surround a star with solar panels which orbit the star. These would turn starlight into infrared light or microwaves, using that energy differential to build and drive the civilization. It would only take a few million years for any growing civilization to build out such Dyson swarms around a good percentage of the stars in a galaxy, and it seems like this is something any growing civilization would very likely do.
If any civilization did do so, it would be very obvious to us. We know what the normal colors of populations of stars in galaxies are. We would see that excess of infrared or microwave light and lack of visible light, and know it’s artificial.
The remarkable thing is that we know we can detect such deviations (of only a few percent of a galaxy’s stars being used this way) from as far as a billion light years away, and likely further. So people have looked for this, in surveys of over a million galaxies. We have not found a single galaxy with excess infrared or microwave light.
If intelligent life were anything but ultra-ultra-ultra rare, some of them would have chosen to do this Dyson Swarm strategy, and no galaxy shows it.
So then those Martian Codon Maps would foretell impending civilization death or stagnation.
You see, if life itself is super rare, then intelligent life might just be rare because ANY life is rare. And that is possible, because even the simplest life is mind-bogglingly complex. If we know of only one occurrence of simple life, then it’s possible life of any type is super rare.
But if we have TWO instances of simple life independently arising in the same solar system, then simple life must be almost ubiquitous. Yet our observations tell us intelligent life is unbelievably rare. Which means that there is some sort of Great Filter that ends intelligent civilizations before they get a chance to colonize their galaxy. Option A from earlier in this article (very different life) might mean the same thing; but if it’s super different than us, then we might be able to say it had no path to become very intelligent. But we know DNA life does have that path, because we exist. DNA life similar to us but with a different Codon Map definitely indicates that microbial life like us is common, but something unknown stops DNA life like us from going galactic.
Humans are poised to start galactic colonization in the next few hundred years; and we’d likely finish it, Dyson Swarms and all, in the next few million years. But the universe’s statistics are screaming at us that no one ever makes it there. Ever. They always get stopped and fall apart or go extinct. Interstellar-capable civilizations are, for some reason, doomed.
If the Martian Codon Map is different.
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Author’s Note: Yes, this is a little tongue-in-cheek and somewhat speculative. But the logic actually holds up, especially since we are talking about huge numbers of potential systems and civilizations and galaxies, and huge amounts of time. If we do find independently-arising Martian DNA-based life, we better start thinking carefully about what Great Filters lie ahead of us, and how to avoid them. Seriously, and soon. Because it is hard to think of something that could kill or stagnate our civilization once it becomes multi-solar, meaning the Filter has to occur before we leave our solar system.
Also, if you want to learn more about the actual mechanism of how DNA is used to make proteins, this amazing real-time, accurate video is one of my favorite things on the internet. I couldn’t find a place in the article to insert it that wouldn’t break the chain of thought, but I didn’t want to rob you of seeing it. So here it is:
Or a few single strings folded and then brought together, for some proteins.
I am aware of the WOW! signal. It’s neat, but not repeated and not convincing.
The latest Pentagon “UFO” videos do NOT show alien spacecraft. This has been thoroughly debunked by the brilliant Mick West:
Von Neumann probes are exploratory replicators that insert themselves into solar systems and then use in situ resources to self replicate, explore that solar system, then launch probes to dozens more solar systems. Such a probe system can visit and investigate all the stars in a galaxy in just a few million years using this method, even if your probes can only move at a few percent of the speed of light.