Forgive the vagueish title, inspired by this story about the hypothesis that Earth’s life may have originated on the Red Planet. What intrigued me is the line “Meteorites from Mars have been arriving on Earth throughout our planet’s history”, which was news to me - I’d have thought that the odds of that were, no pun intended, astronomical.
So I was thinking does it work the other way round - is it possible there any pieces of Earth on Mars (other than the probes and rovers) and could any known lifeform from Earth survive on Mars?
One of the hypotheses for the moon’s formation is that it’s the result of a collision between a primitive (moonless) earth and a mars-sized body early in the development of the solar system. In such a case, the “splash” would likely result in some Earth materials making it to Martian orbit, although it’s extremely unlikely that life existed at that point.
Over–what’s the solar system equivalent of “geologic?” sollogic?–time, there’s plenty of collisions, debris, and whatnot to get mixed. However, it’s easier for things to fall “into” the solar system than be pushed out of it, so most transfer is going to be from the outermost planet (Mars, in this case), to the innermost one (Earth).
Which immediately causes me to wonder: how much material, if any, from Pluto (or similar large outer-solar objects) exists on the Earth? I assume the gas giants don’t transfer materials over such distances, but maybe their moons do.
A million to one, he said.
Mars meteorites have been known for a while. I think the problem with the transfer is that they’re coming in at such a velocity that it would be hard for any microbial life to survive the fiery crash landing.
How does Mars eject this matter at escape velocity in the first place, that it’s incoming on Earth? Are you talking about matter from the Martian surface? What accelerates it *that *much?
As for Sun science, I think the term is “heliological.” Greek roots here.
So what impels the Martian “stuff” to leave the Martian soil, achieve escape velocity, and bee-line for Earth?
Asteroid slams into Mars…stuff spews out really far, beyond orbit, and that violent asplosion and trip through space DOESN’T kill the life on board?
*ETA: Damn you Johanna…Ninja chopped.
Life is really, really, really resilient, and rocks are pretty good containers. If you’re a life-form that’s single-celled, can survive being frozen, and doesn’t need any particular atmosphere to survive (and there are lots of such things on Earth), the transfer itself isn’t particularly unbelievable.
Mostly, as always, it comes down to whether there is/was any life there in the first place to transfer, and then Occam’s razor: the life is here now and isn’t there; in the absence of competing evidence, the safer bet is that it started here.
No, the odds are heavily against there being Earth rocks on Mars. However, the odds are good that there are Earth rocks on Venus and Mercury.
As the article mentions, some collisions are so large that pieces of the planet are launched into space. At that point they go into an orbit around the sun. If the orbit is elliptical and crosses Earth’s orbit then collisions become possible. The reason that Earth rocks aren’t likely going out to Mars orbit is that the collision to launch debris into such a higher orbit around the sun would likely have destroyed the entire planet in the process.
There are many examples of Martian rocks that we have discovered. If you recall a few years ago there was some hype around a rock we found in Antarctica that appeared to have martian microbes in it. Since then there’s a lot of controversy around that discovery but I bring it up to illustrate that the idea of Martian life seeding Earth isn’t a completely new idea.
That has two implications - first, Mars throws more stuff out of its own gravitational well (at least, it did when it was volcanically active) than Earth does.
Second, Mars pulls in less stuff than the Earth does, because it has a smaller gravitational well.
So, are there Earth rocks on Mars? Hard to say, but there probably are. However, Earth has a lot more Martian rocks.
It’s neat to think there may be some fairly complex Terran fossils on Mars. Mars used to have plesiosaurs! Loch Ness Monster lovers would have a field day.
The early solar system was analogous to a pinball machine. It’s thought that about 4 billion years ago there was a period of heavy bombardment. All of the inner solar system objects would have been struck by multiple, very large, comets and asteroids many times a year. As mentioned above, this is when a planet sized collision impacted Earth and created the moon. The solar system has quieted down quite a bit since then - but in those early days there were many collisions large enough to send debris into space.
The issus isn’t whether the rocks are going up or down in the solar gravity well; it’s the delta v required to get them on a path that crosses another planet’s orbit. Getting to either Mars or Venus from Earth (once the rock is out of Earth’s gravity well) requires similar amounts of extra push.
Volcanoes aren’t necessary; meteor impacts will eject material into space.
Another factor: Earth has a fairly thick atmosphere, which makes it harder for rocks that get blasted upward to 1)maintain escape velocity and 2)stay in one piece.
So, it seems that if we find evidence of life on Mars (or Europa), we must consider the strong possibility that it had the same origin as life on Earth.
If we find live life, it won’t be too hard to determine if it uses DNA, and if it does, if it uses the same genetic code we do. If it does, it’s a slam-dunk that we have a common origin. If it doesn’t use DNA, it’s no kin to us. If it uses DNA but a substantially different genetic code… Well, that’d be a head-scratcher.
Unfortunately, if we just find fossils, we’ll know much less, and might not even be able to agree whether they’re remnants of life at all (I don’t know whether the “Martian microbes” in the Antarctic meteors were ever completely resolved).
Bumping this because I realize I don’t understand what you mean by ‘uses the same genetic code we do.’
Is DNA comparisons of humans, to, say, ferns, close enough that anybody could recognize they have a common ancestor?
The only argument I’ve heard of for the ‘one (or very few)’ origins of all life on earth is that all DNA happens to coil in the same direction (clockwise, I want to say).
The “genetic code” refers to which DNA base triplets code for each of the 20 amino acids used in building proteins. This code is, as far a we know, essentially arbitrary.
Yes, it uses the same genetic code.
Because there is no necessary relationship between a codon and an amino acid, the odds are astronomical that two codes would be the same by pure chance. It would be like finding that the Roman alphabet had been independently developed on Alpha Centauri. The fact that all life on Earth uses the same code makes it certain that it shares a common descent.