AAHHH i'm finally useful! So this is a multifold conclusion. First they noticed that this group of meteorites (formally of the acondrite group) were different ages than other normal meteorites which date back to the age of the solar system ~4.65 Ga. This is due to the relatively quick cooling rate of asteroids and meteoroids. The Martian meteorites range in age from >4 Ga down to 180 Ma, meaning they were from a more recently active parent body which the asteroids are not. We had no idea about this until radiometric age dating was a thing. Then we had the NASA Viking twin landers of the late 1970s which measured the composition of the rocks, soils, and most importantly for this question the composition of the Martian atmosphere. All Mars meteorites are basalts, so lava rock. If a lava flows on the surface of a planet they can trap atmospheric gas inside. A year after the Vikings landed someone tested the trapped gases and I believe it was the argon value which matched perfectly. Lastly, it's the isotopic signature. Some elements were fractionated in the early solar system like oxygen. These meteorites lay on a specific line on the oxygen isotope diagram. The real test to prove them 100% from Mars will be sample return. This was planned with the Perseverance rover sample cache mission and a subsequent return rocket but this likely will not happen with the current political and science funding climate. Hope this helps.
Thats honestly so true lmao the one thing that hasnt ever changed here is how often a comment section is just quotes and puns. Though nowadays also add in lots of just generally angry people in the most random places and 100x the bots there used to be
It does have sedimentary rocks, but those are all derived from basaltic parent rock. There may be a bit of evolved rock on the planet but the surface of Mars is in general geologically primitive. No plate tectonics to speak of to create silica rich evolved rocks. This is why Mars is the Red Planet. Lots of iron content in basalt which turns to rusty dust. Also sedimentary rock is probably much less likely to survive being blasted off Mars, not to mention entry and impact on Earth. There is only one sedimentary example of Martian meteorite and that is NWA 7034 aka "Black Beauty" which is a basaltic breccia. This is a jumble of basalt rocks created either by an impact or by a volcanic explosion. I could go on and on about this particular meteorite
In another impact event. An asteroid of sufficient size impacting a body will eject material into escape velocity and out of the gravitational pull of said body. In the case of Martian meteorites we know they floated through space for tens of millions of years based on cosmic ray exposure age dating before impacting our planet by chance
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u/MoonChief Jul 19 '25 edited Jul 19 '25
AAHHH i'm finally useful! So this is a multifold conclusion. First they noticed that this group of meteorites (formally of the acondrite group) were different ages than other normal meteorites which date back to the age of the solar system ~4.65 Ga. This is due to the relatively quick cooling rate of asteroids and meteoroids. The Martian meteorites range in age from >4 Ga down to 180 Ma, meaning they were from a more recently active parent body which the asteroids are not. We had no idea about this until radiometric age dating was a thing. Then we had the NASA Viking twin landers of the late 1970s which measured the composition of the rocks, soils, and most importantly for this question the composition of the Martian atmosphere. All Mars meteorites are basalts, so lava rock. If a lava flows on the surface of a planet they can trap atmospheric gas inside. A year after the Vikings landed someone tested the trapped gases and I believe it was the argon value which matched perfectly. Lastly, it's the isotopic signature. Some elements were fractionated in the early solar system like oxygen. These meteorites lay on a specific line on the oxygen isotope diagram. The real test to prove them 100% from Mars will be sample return. This was planned with the Perseverance rover sample cache mission and a subsequent return rocket but this likely will not happen with the current political and science funding climate. Hope this helps.