Should We Terraform Mars?

...or should we breed Martians.

Science fiction loves the idea of terraforming Mars. (I only touch on it in Transpecial, where Martians continue to live in shielded domes).

But there's also the idea of breeding Martians.

Or more precisely, gene-tweaking colonists using traits from other animals or specific human groups (for example, there are distinct blood differences between the people living in the Himalayas than those of us adapted to sea level). Is this ethical?

One scientist, Christopher Mason, argues that it's unethical not to...because any attempt to terraform will destroy any surviving life on Mars. If there is an ecosystem there, no matter how small or marginal, aren't we bound to protect it?

So, yeah. So many ethical arguments on both sides, but maybe one day we'll breed Martians, genetically tweaked to have higher resistance to radiation, lower need for oxygen, and some protection from dust...maybe even something like a Gallifreyan's respiratory bypass system (I headcanon that THAT is an evolution for dust protection given how dry Gallifrey is shown to be).

Thoughts?