This also would mean that there's no opportunity for any other form of life to develop in the same conditions - dna based life probably has a monopoly on water based planets throughout the galaxy
Bacterial cells in one adult human body: ~100 trillion
Stars in observable universe: ~1 billion trillion
You're off by seven orders of magnitude.
I'm not saying it couldn't have happened, but even on a cosmic scale it sounds like it would have to be an exceedingly rare outcome.
Not only is their original habitat 420 K and 1 K (absolute zero) they’re described as “colony” species.
Quite interesting.
In space, your temperature may range from 0.01K to over 2000K depending on solar radiation levels over the spectrum.
You're exposed to higher levels of radiation and vacuum will tear at organic structures.
A tradigrade can probably survive a trip to mars if they're very lucky. Better to send a huge amount of them, maybe one makes it.
But interstellar distances are too vast and the time taken is too long. The DNA within tradigrades, even when hibernating, will have been torn to shreds and with no energy to repair there is no way back to life from that.
I will quote form the article:
> Back on Earth, over 68% of the subjects protected from solar UV radiation were reanimated within 30 minutes following rehydration, although subsequent mortality was high; many of these produced viable embryos.
And that is after 10 days of exposure. If it was 400 years, it's unlikely that even 1 is able to reanimate.
The hydrates species fared much worse and hydrated is more likely the state of the tardigrade when they are blown into space, rather than carefully dehydrated.
> Some of them can withstand extremely cold temperatures down to 1 K (−458 °F; −272 °C) (close to absolute zero), while others can withstand extremely hot temperatures up to 420 K (300 °F; 150 °C)[36] for several minutes, pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space.[37] Tardigrades that live in harsh conditions undergo an annual process of cyclomorphosis, allowing for survival in sub-zero temperatures.
It's certain we still don't have enough data to make any conclusions about how easy it's for life to spread. I'd wager it's less than expected yet in our galaxy, my guess would be that either hundreds or dozens of planets/moons contain life. Depends on the statistical distribution of the occurrence of life.
Yeah but likely not for tens of thousands of years in the void between space + cosmic radiation?
You can take a country as deadly as Australia and introduce something as innocuous as 24 rabbits, and it can have an absolutely devastating effect on the ecosystem.
Frankly it's beyond hubris to suggest that we'd be fine just because of the way we've evolved.
Something that represented a danger to us from another planet would have to be an issue in how simplistic it was...like mad cow disease style prions, or a parasite that happens to attack us in a novel way. Something virus like just wouldn’t be an issue.
Based on? Rabbits didn't co-evolve with australia's deadly fauna, and yet...
We are talking compatibility on a protein level.
They are not analogous and depend on completely different factors.
(not that I find any such scenario to be even remotely likely)
Edit: well, that's basically what's being said in a parent comment
It's super unlikely that a virus that evolved outside of Earth would (on its own) have a mechanism to infect cells they hadn't encountered before in order to propagate. Again, nothing is impossible, but physics, chemistry and biology would all have to line up in a very specific way for that virus to infect a human cell.
So alien viruses could directly and initially interface with Earth based life-froms cells (humans,the biota inside the humans, etc.), with probably also, somewhat predictable results. Or at least novel coronavirus like outcomes.
Entirely possible, but COV-19's novel spike protein was developed through brute-force trial and error. An alien virus would need to do so via happenstance.
That's just another nice way to describe evolution. It's just a storm of probabilistic biochemistry. I think if you read about how fast and crowded biochemical interactions in the cell are [1], you will quickly appreciate that's it's basically just quadrillions of hypersonic processes doing what you describe as "brute-force trial and error".
For example, that's how a good number of drugs work that attempt to bind to some protein, like Aspirin. They don't go and find it. The drug molecules enter the cell space and just bang around at incredible speeds until they finally just jam into the protein they need to. Brownian motion and similar effects and not some taxi service to the target protein. It's basically just probability which is where concentration comes from. Increasing the probably of the drug molecule hitting the target.
That's also why I really dislike the personification of things. SARS-CoV-2 didn't consciously do anything. I know most people know, but the language constantly insinuates just that.
[1] http://www.righto.com/2011/07/cells-are-very-fast-and-crowde...
Now if some otherworldy life had billions of years of evolution similar to ours or exceeding it, well, it might present some threat.
But if life doesn't readily emerge, then we don't have any evidence one way or another. However, the likelihood of encountering extraterrestrial life is also diminished.
"But", someone replies, "I'm talking about life forced to evolve under extreme and alien circumstances." But Earth has plenty of extreme environments, both now and especially early on, and scientists optimistic about the likelihood of spontaneous life are constantly equivocating those environments to others in our Solar system and beyond. Plus, let's not forget that the modern, biologically created Earth atmosphere is something of an extreme environment of it own. So no matter how you spin it (I'm too lazy to put down several other scenarios I've had in mind), the more likely we are to encounter extraterrestrial life, the more robust Earth life likely is.
> I think it's unlikely we'd find an bacteria or virus that could successfully infect Earth based organisms in a way that threatens us.
Expecting the opposite would be like betting on a random path in a graph with millions of edges to be faster than a path that was optimized by billions of computers for billions of years.
It's not that old life optimized for killing the new life (it probably didn't because it doesn't seem to be a common enough occurence). It's that the new life would be very likely very bad at everything.
Between human species on Earth. Humans in the Americas were not genetically distinct from their European cousins, thus a European virus could readily infect an American human and vice versa (Europeans were not wiped out because the diseases they acquired were not as deadly, such as syphilis).
Our immune systems are adaptive, but a bacteria/virus will be limited in it's ability to adapt. As such, it's pretty unlikely to be able to infect a complex, multicellular organism that it's never encountered before. The most likely vector for an attack is an alien bacteria that is able to rapidly transpose genetic code with earth-evolved bacteria and create a novel hybrid. Then you are dealing with a COV-19 type scenario.
That's not to say we couldn't inadvertently pick up a bioengineered complex organism from an advanced alien species - that would be a completely different story.
Martian life, if any, should simply be "trained" to pry on the particularities of its own environment, not ours. There's a extremely low chance that it could survive and thrive on our warm planet. Add to the fact that lots of precautions will be in place, Martian life exploration can be considered very safe for Earthlings.
However... since life evolves to be successful in (almost) any environment, Martian life could just as well be trained exactly for these rare moments: to be dormant then suddenly pry on unsuspecting alien visitors that come snooping around... But then that would be the argument of a successful Ridley Scott movie franchise.
That said, it would be prudent to take anything that may be living to the ISS first.
Maybe some kind of invasive organism could exist that spreads like kudzu and plain outcompetes existing life -> however this sounds like something that could be controlled by brute force.
What could still be very dangerous, is otherworldly defence mechanisms like toxins. Plant and fish toxins are commonly deadly to all higher life forms
Alternatively, it is probably far more likely that life from Earth would rapidly evolve to kill or replace any extant life on other worlds, especially microscopic life. We know that Terran life is tenacious. It readily thrives in hostile environments and has evolved under extreme adversarial pressures on Earth. It’s not a stretch to imagine that it could become the apex predator in an ecosystem devoid of such extreme evolutionary pressure.
we know quite a lot about this, most life-forms on Earth almost continously try to kill humans or at least to mine its biological resources for its use.
We should be careful about what we send to Mars. Something like candidas aureous could just wipe out the life on the planet.
Some people on the net says that the current coronavirus situation could be an alien-species. I know it is FAR FAR from anything related to what we already know about the virus.
But it gives an idea about what could have looked an encounter with a new alien-patogen which just landed on Earth at some point at history and got to survive and thrive in the local ecosystem.
One school of thought is that extraterrestrial pathogens could pose limited risk. Earthbound pathogens have co-evolved with humanity in order to harm us better, but xenobiological pathogens would not have this advantage and might not pose much of a threat.
On the other hand, it's entirely possible that the random chances of evolution could create a xenovirus that's airborne in humans and bootstraps a fatal prion disease in everyone it infects.
A virus wound be absolutely shocking.
Indeed, it would imply coming from an origin with reproducing DNA.
I'd even be surprised, though less so, if they can even survive here.
Of course we have zero empirical observations of such life, so predictions are guesswork.
That said, if something managed to survive and multiply on Earth, I can imagine it could be a a huge nuisance without attacking our bodies directly.
And I think terrestrial immune systems can handle microorganisms, whether they're DNA based or not. It hunts based on shape, as I understand it.
I was thinking microorganisms, since anything big we can just kill on sight. But when you mention it, something insect size could be very hard to fight.
It's very very very unlikely it will even be able to run at all. It would use a different machine code, even if it was by crazy accident the same it would use some long forgotten binary format instead of elf and depend on different directory structure. It wouldn't be adapted to modern protection schemes like stack randomization.
We know that if we apply an energy gradient through a soup of ammonia, methane, and water vapour, we get the fundamental building blocks of Earth life.
If we discovered these same blocks on another planet, that has all of these pre-conditions, what would it tell us?
Random link from Google https://www.astrobio.net/news-exclusive/possibility-silicon-...
I mean we have a definition of life and it’s building blocks, and we don’t consider a rock having a life, even though it does have a lifecycle.
I hope it's really different. I don't want to be that special.
Doubtful, given that we've been able to recreate multicellularity evolving in the lab. The initial jump to life, not so much.
Yes and?
1) DNA based life with genetic overlap (potentially indicating that Mars life seeded earth life, or vs.vs).
2) DNA based life with no genetic overlap (possibly indicating original life on mars, or a common seed source for Earth and Mars)
3) Radical, non DNA based life (indicating original life on mars)
4) E. coli (indicating that NASA needs to fire their sterilization team).
I'm sure there are more fascinating possibilities that I'm not aware of!
Both of those would likely be a "more interesting" thing to study.
The most boring part would likely be finding DNA life which is quite similar, I'm not sure it would point to any specific origin and if it's metabolically going to be quite similar to some life we can find on earth the overall new science from it might be fairly limited.