underground tunnels on earth the day after an asteroid strike would still be more hospitable than tunnels on mars mars is an insurance policy for essentially a

underground tunnels on earth the day after an asteroid strike would still be more hospitable than tunnels on mars mars is an insurance policy for essentially a 100% extinction event (save maybe a bio-weapon targeted against humanity). Anything much less than 100% and I imagine a pocket of humanity would survive. That would be like the entire surface of the planet getting liquefied or a gamma ray burst directly hitting Earth.