So, to start off, I am not even sure if life would develop, because I am not clear on how the mass of the planet or gravitational pull affects chemical evolution, but assuming that life did start in the oceans like it did, how would evolution look, and would the current species still exist in some form?

I understand that this is a very broad question, so feel free to go into however much depth you want to

EDIT: So, this seems to be too broad a question, so I'm trying to make this a bit more specific - let's limit evolution to its early days - i.e. from single celled organisms to multi cellular organisms with dedicated organs- how would this be different? So for instance, would certain current adaptations be faster, slower, or not appear at all in early organisms?

  • $\begingroup$ Remember that "1/3rd gravitational pull" isn't quite the same as "1/3rd the size". Mars is about half the diameter of earth but has about a third of the surface area and gravity. $\endgroup$ May 25 '19 at 10:31
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    $\begingroup$ Also, this question is waaay too broad, and therefore likely to be closed in due course. You'd do well to be more specific, asking perhaps about specific environmental niches or kinds of animals. $\endgroup$ May 25 '19 at 10:32
  • $\begingroup$ Welcome to the site. As @StarfishPrime said this question is probably too broard. We like fairly specific questiins that ca be answered in a few paragraphs. This question will probably be put on hold/closed as too broad but if you narrow it down it could get reopened. For more information visit help center and take the tour. $\endgroup$ May 25 '19 at 10:55
  • $\begingroup$ @Starfish Prime - You say " Mars is about half the diameter of earth but has about a third of the surface area" but by simple geometry if you halve the diameter of a sphere, you get 1/4 the surface area. $\endgroup$ May 25 '19 at 11:12
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    $\begingroup$ "Would the current species still exist in some form?" This is actually easy to answer: absolutely not. Evolution is not deterministic. Restarting natural evolution, even without changing any of the major environmental factors, would most certainly not result in the same current species. As S. J. Gould famously put it, replaying the tape of life will result in an entirely different show each and every time. And the question is way too broad; you should focus on one specific attribute of early multicellular organisms and ask about it. $\endgroup$
    – AlexP
    May 25 '19 at 12:55

As a starting point,


The surface gravity on Mars is only about 38% of the surface gravity on Earth...

So the reality of Mars gives a reasonably close starting point to answer your question. There are a lot of details to explore but the first major one is the extremely sparse atmosphere -- Mars just doesn't have the gravity to hold an atmosphere as dense as Earth's:


Mars...has a much thinner atmosphere, with an atmospheric volume less than 1% of Earth's.

This in turn means it "holds" less heat, and thus has much wider temperature swings between day & night. And also, obviously, earth-like mammals, reptiles, etc. would find it very hard to breathe. :)

To this point there's never been life of any kind found on Mars, and only indirect evidence as to whether life (at the microbial level) might ever have existed there:


All in all this is just a brief bit of Googling (and recalling high school science), but I hope it's a worthwhile starting point to work from.


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