Assuming that Mars held an atmosphere capable of supporting life (and always has), what would a martian bird look like when compared to it's earthen counterpart?

  • The gravity difference remains the same between planets.
  • The atmosphere is roughly half of what it is on Earth.
  • The ecosystem of the planet is similar to earthen deserts and tundras.
  • You can pick any bird that you feel would best illustrate the differences.

https://en.m.wikipedia.org/wiki/Bird - This will serve as the definition. If the specifics of evolution/biology cause too many problems, then assume that Mars came to posess creatures that share the many qualities that we associate with birds. Also, an exact scientific answer is hardly necessary, approximations based on our current understanding of these things will suffice.

While this question certainly requires the use of opinion and guestimations to some extent, it is rooted in logical conclusions. In what ways would a Martian bird be different based on the necessary adaptations to the Martian environment. For example...

  • Would they be overall larger/smaller.
  • Would wings be bigger/smaller.
  • Would the tail be longer/shorter.
  • Would feathers be longer/shorter.
  • Would bones be thicker/thinner.
  • Would muscles be more/less developed.
  • Would legs be longer/shorter.
  • Would beak shape be effected.
  • Would eye size be effected.
  • Would lung capacity increase/decrease.
  • etcetera

These are all very simple ways of describing the appearance of something as it pertains to biological adaptations.

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    $\begingroup$ What is a bird? On Earth, birds are by definition those dinosaurs which are still extant; for example, a commonly used definition is that birds are all animals descended from the common ancestor of Archaeopterix litographyca and Passer domesticus. This definition is obviously not applicable to Mars. Hence the question, what is a bird? Please provide a definition which works both on Earth and on Mars. $\endgroup$
    – AlexP
    Commented May 4, 2017 at 21:49
  • $\begingroup$ What a bird looks like is highly dependent upon it's environment. Look at the number of different birds we have on earth. As it's currently written this question is too broad and opinion based to get good answers. $\endgroup$
    – sphennings
    Commented May 4, 2017 at 21:49
  • 2
    $\begingroup$ We don't and can't know. Birds are all descended from a specific set of ancestors that never existed on Mars. Mars with it's lower gravity could obviously have bigger flying creatures but that's about the only concrete thing we can say. $\endgroup$
    – Mormacil
    Commented May 4, 2017 at 21:57
  • $\begingroup$ Echo of Mormacil, birds are a long evolutionary chain that has been heavily influenced by the evolution of Earth through hundreds of millions of years. Flight has evolved on Earth independently atleast 4 times...to suggest that Martian evolution would result in a 'bird' is to suggest hundreds of millions of years of mysteriously convergent evolution despite many possibilities. Could martian birds originate as insects? Or, for the point of this question, are we to assume Mars somehow followed the exact evolutionary path as dino's on Earth have (extinction events et al)? $\endgroup$
    – Twelfth
    Commented May 4, 2017 at 22:48
  • 1
    $\begingroup$ What do you mean by "slightly thinner atmosphere"? $\endgroup$
    – Karl
    Commented May 4, 2017 at 23:07

3 Answers 3


Basically you're making earth smaller and asking what birds would be like. They would be able to be much bigger because of the lower gravity. They would also be slightly more muscular in both the wings and legs to be able to take off fast and maintain that speed in the lower atmospheric pressure; but not insanely more.


I'm not sure how much thinner the atmosphere of mars is, but it seems that the less dense the air, the less efficient flapping would become as a means to power flight, and the more effiecient means such as catching updrafts coming off ridges, thermal vents, ect to power flight, so birds would as a whole tend to be adapted to this, having, having have large wingspans/high glide ratios to capitilse on height gained. So trending towards birds build like this: https://web.stanford.edu/group/stanfordbirds/text/essays/Soaring.html Jet propulsion also comes to mind as becoming more/and not less efficient with a thinner atmosphere, but as you've specified a Martian "bird", it might not be something you'd want.

  • $\begingroup$ The real-world Mars has a surface atmospheric pressure of about 0.00628 atm according to Wikipedia. Compared to Earth, that's barely more than a hard vacuum. (In fact, I did read somewhere -- forgot where, though -- that Mars is the worst of both worlds in terms of atmosphere: Not sufficient atmosphere to get any significant aerobraking capability on entry, but at the same time sufficient atmosphere that aerodynamics have to be taken into account for an entry-capable craft.) $\endgroup$
    – user
    Commented May 5, 2017 at 16:48

Flight on mars in the atmosphere currently there would be hard, if not impossible. While Mars has a lower gravity than earth, it als has a much thinner atmosphere (1% of earth), meaning birds would have barely anything to "push" against.

However, if Mars had an only slightly thinner atmosphere than earth, things would change. The best analogue for this would be Titan. xkcd gives a good rundown of how flight mechanics would work on other planets, and Titan would be the best analogue for the situation you're describing (although Titan has even lower gravity than mars (Mars: 0.376 g, Titan: 0.14 g, where 1 g is the gravity on Earth), and an atmosphere four times as thick as earth). In lower gravity, but under simular atmospheric conditions, it would require less energy to fly than on earth. Birds could be larger, but which traits are selected will not only depend on the atmosphere and gravity but also on the ecosystem.

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    $\begingroup$ The question supposes that there is an earthlike atmosphere on Mars. $\endgroup$
    – sphennings
    Commented May 4, 2017 at 22:22
  • $\begingroup$ @sphennings "... but slightly thinner". Now on a logarithmic (linear makes no sense at all) range from todays Mars (6 mbar) to 1000mbar, where is "slightly" thinner? 200? 500? $\endgroup$
    – Karl
    Commented May 4, 2017 at 23:05
  • $\begingroup$ @Karl if you think question is not precise enough, comment on question. Also, xkcd.com/1162 $\endgroup$
    – Mołot
    Commented May 4, 2017 at 23:10
  • 1
    $\begingroup$ It quite isn't. I like that XKCD, btw. I tried guessing at it before clicking the link, and this one sprang to my mind: xkcd.com/169 ;-) $\endgroup$
    – Karl
    Commented May 4, 2017 at 23:21

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