Humans would clearly bring other life with them to Mars just as we have to almost every part of the earth.
In contrast to this worldview that humans are the agents of mass-extinction, it's much more likely that humans are the only ticket to survival for every species on earth. No other species has been able to escape Earth's massive gravity well, nor has come anywhere close to harnessing the energy required to do so.
> just as we have to almost every part of the earth.
Do you have an idea of the ratio between the species human has been moving around vs the number of species in existence?
> In contrast to this worldview that humans are the agents of mass-extinction
Wait wait wait. This is a fact. We are living a mass extinction now, it is acted. We, human, have removed 2/3 of trees, 2/3 of mammals, and 2/3 of insects from Earth. Mostly because of the loss of habitat (not Climate Change, this still has to come as a bonus, and definitely won't help).
It is not hypothetical, it is not a worldview. It is a fact. Of all the species that lived on Earth at the same time as humans, the number of species that got decimated because of humans is so much higher than the number that humans may bring to space (should we ever succeed, which is far from certain) that it feels absolutely wrong to consider that "humans are the only ticket to survival for every species on earth". Pretty much every species on Earth would be better off without humans.
And again: preserving life on Earth is much easier than bringing it to space (and we are failing at it right now). The asteroid scenario is completely ridiculous: again it's far easier to prevent the asteroid from colliding with Earth than to send a few species to survive in space.
Do you realise that the Sun "threat" is not for another few billions of years (with a "b")? Dinosaurs appeared what, 250 millions years ago (with an "m")?
And there's more: the closest star, Proxima Centauri, is more than 4 light-years away. It means that if you want a chance to survive the Sun, you don't need engineering; you need theoretical physics. You need a fundamental discovery in physics to make that kind of travel realistic. At which point the engineering you will have put to go to Mars will possibly don't apply at all.
Again: there is no planet B unless you make a fundamental discovery in theoretical physics. People need to stop pretending that going to Mars is a need. It is an artistic performance. It is cool, but mostly useless.
In contrast to this worldview that humans are the agents of mass-extinction, it's much more likely that humans are the only ticket to survival for every species on earth. No other species has been able to escape Earth's massive gravity well, nor has come anywhere close to harnessing the energy required to do so.