TimeLeopard t1_it15igf wrote on October 20, 2022 at 4:25 AM

Reply to comment by Pluto_and_Charon in Curiosity Mars Rover Reaches Long-Awaited Salty Region by Pluto_and_Charon

In your opinion, and assuming life did in fact exist on mars, what are the odds that curiosity or another rover would just stumble upon a fossil out in the open?

Like the rover is driving a long and boom just in frame in a rock or in the Martian soil is a fish fossil or something.

My assumption would be because of wind and sand erosion it's super unlikely. We would have to dig to find anything. But the thought a fossil just showing up in one of these photos makes me so excited. Especially considering where Curiosity is now.

canyonstom t1_it1tykg wrote on October 20, 2022 at 9:53 AM

I'm not OP but it's probably just short of impossible it could chance upon a fossil of any sort of multicellular organism. Based on Earth history, we have evidence of microbial life from approximately 3.7 billion years ago.

The first evidence of multicellular organisms don't appear until circa 600 million years ago, so evolution took 3 billion years to advance from single to multicellular life.

From our observations of Mars, it is believed the last water would have dried up around 3.7 billion years ago. Its approximate age is 4.6 billion years, or around the same age as Earth.

Taking what we know about our own planet it is fair to say that any single celled organisms on Mars didn't have long enough to evolve to become multicellular, assuming there ever were any single celled lifeforms there in the first place.

TimeLeopard t1_it29c13 wrote on October 20, 2022 at 12:39 PM

Well also consider that even if Earth and Mars are the same age, we can factor in that most models predict the moon slaming into earth during its early formation. If the same event didn't happen until much later in Mars formation, it could be possible Mars had a head start. Granted didnt Phobos slam into Mars too? I don't really know when that was supposed to have happened.

But yeah I'm getting way into speculation here than actually any science.

danielravennest t1_it3nyy6 wrote on October 20, 2022 at 6:21 PM

> Granted didnt Phobos slam into Mars too? I don't really know when that was supposed to have happened.

50 million years from now, if we don't mess with it. By then we could have mined it for raw materials, or turned it into an anchor for a space elevator.

We don't know how Phobos and Deimos came to be, but one idea is debris kicked up by an asteroid collision, that then came together by gravity. There are plenty of big craters on Mars that could have been a source.

Pluto_and_Charon OP t1_it32d0s wrote on October 20, 2022 at 4:02 PM

So something like a fish is definitely out the question, because the period when Mars was habitable was only like 500-1000 million years after the solar system formed. Complex life like simple animals (jellyfish,sponges) didn't evolve until 3700 million years into Earth's history and fish didn't evolve until 4100 million years into Earth's history. Mars never had the time to evolve something so complex as a fish.

So instead of fish we're looking for much simpler microbial life. An individual fossil microbe is far too small for the rover to spot. Fortunately though, even simple microbes can group into larger colonies leaving behind rock structures called stromatolites which are really distinctive and are known from rocks of similar age on Earth. So that's the kind of thing we're hoping the rover just stumbles on.

It's worth adding though that Curiosity has been exploring lake-bottom sediments for 10 years now and nothing remotely like a stromatolite has yet been found. Perhaps that's telling us something. Maybe there were microbes but they didn't form into colonies for some reason, maybe the water conditions were wrong. Maybe there was life on Mars but it never reached this lake. Or maybe there was no life at all. OOOOor maybe there are stromatolites in Gale Crater and we just landed in the wrong place ;)