> are we safe forever on Earth ?

and that's why Mars exploration is more important than curing cancer. Cancer is unlikely to kill everyone of us all at once.

There's almost nothing we could do to this planet which would make Mars a more attractive option. I guess there's always a meteor/comet risk, but practically anything else still leaves Earth as a better option.

Even if we all had to live in bio-domes because the planet was so polluted, it would _still_ be a better option than Mars, just by virtue of the fact that we have gravity and an atmosphere. On Mars, a cracked bio-dome means everybody dies. On Earth, you could probably just go fix it.

Earth has:

  - Gravity
  - Much better temperatures compared to Mars
  - A moderately-pressurized atmosphere
  - Water (even if it's salty/polluted)

A thermonuclear war and the ensuing nuclear winter would shift the situation quite a bit. Which is not that far-fetched, we have the capability and have been dangerously close a couple of times. Earth might still have stronger fundamentals, but it is good to have options. And, perhaps more importantly, technology developed in pursuit of becoming a multi-planetary species might very well help here on earth too - both in our current development path and in case of disaster.

I generally agree (and I'd add: magnetic field, more sunlight - not just for temperature, but also power generation), but come on, Mars does have gravity :).

Its not that Mars would be better or even equal, but that it would be a second chance, just in case.

So are planetary risks. They give the name to "astronomically unlikely". But while cancer might not kill everyone at once, it's going to kill billions of us.

We're all going to die. And if we don't get killed by something else, we die of cancer, eventually. Death, taxes and cancer are as close to a trinity of certainty as you can get, and I'm not sanguine about finding a "cure" for conditions that represent the terminus of a lifetime of wear and tear on the body, at least on actionable timescales.