One of the hypothesis for the Late Ordovician mass extinction event, which killed off about 85% of all marine species at the time, is an unfortunate burst of gamma rays, about 10 seconds long, from regions of space at least thousands of light years away. [1] One star goes boom and blanks out life on a planet thousands of light years away. The brutality of our universe cannot be overstated.
It's one of the many reasons life being multiplanetary is so important. There's no reason this, a giant asteroid, supervolcano, or any other of the million possible ways the universe can think up to kill us all off won't happen. In fact it will happen, sooner or later - and we're overdue. Of course the odds of it happening tomorrow are near zero, but that will be just as true the day before it happens. And the number of things that can wipe out two wildly different planets simultaneously is a small subset of all things that can wipe out 1. And the same is true as we expand on outward to new star systems, eventually even new galaxies, and perhaps further yet beyond that.
Given that ~14 feet of water attenuates gamma rays by a factor of a billion[1], and it had to reach earth from 6,000 light years away, that's an absolutely gobsmacking amount of energy.
With the factors of power involved I don't think being on another planet would have helped that much. Even if we were a few light years away the hypothesized burst travelled thousands of light years to get here and we don't know what direction the next killing bolt will come from (I suppose we could go further away from the galactic core to reduce the highest odds, but still). And it still had enough power to cause decimation a billion times over if we weren't underwater.
It really shows how it is a massive waste to colonize Mars compared to stuff like preserving Earth and maybe researching ways of shielding from all sorts of radiation (that would also make interplanetary space travel possible without dying quickly after arrival, by the way, and living on planets without magnetosphere).
Sure, if you're only concerned with this one specific hypothetical cosmic event. If we open the floor to, say, asteroid impacts (which I'd guess is much more likely, given we're pretty sure we've seen one in the past), then colonizing Mars would be a benefit.
Put differently, events that can destroy life on a multiple planets are much less common than those than can destroy life on one.
> Put differently, events that can destroy life on a multiple planets are much less common than those than can destroy life on one.
That doesn't strike me as intuitively true. More numerous perhaps, but I don't know that gamma ray irradiation isn't 1000x more likely than an asteroid impact. Light waves would seem, intuitively, more far reaching than a solid mass.
As mentioned elsewhere, even from this event Mars would have been safe. The main hypothesis for what the gamma ray burst did was basically wreck the atmosphere and ozone, exposing everything to massive radiation and starting a domino effect.
But on Mars you're already ambiently exposed to high levels of dangerous radiation, and the atmosphere (for what there is) is highly toxic. So life will have to develop in a way such that it cannot depend on the atmosphere, and protection from ambient radiation is a daily part of life.
In all probability a gamma ray burst event on a Mars colony would be relatively harmless.
You don't go to Mars because life support is easier (than even a catastrophe-damaged Earth.) You go to Mars so the starving mass of human survivors can't reach you to steal, and probably inadvertently destroy, whatever habitat you're living in. That's the only way Mars makes any sense as a backup plan.
I'm not sure. You're saying instead of protecting Earth from outside threats like gamma burst they work to create a backup place to go when Earth is destroyed from inside.
Result: still no protection from outside threat or radiation but more contamination of Earth adding up to its destruction.
I’m saying there are plenty of places on Earth that will still be more hospitable than Mars after a GRB or even a massive asteroid/comet impact. You could operate multiple colonies underground or underwater for a fraction of the cost of a Mars colony. Mars is so inhospitable that the only conceivable reason for using it as a backup plan is (1) you’re planning for events that completely destroy the Earth’s surface and oceans to a depth of hundreds of meters on all sides (this is not GRBs) or (2) you’re correctly worried about eight billion starving and well-armed humans trying to get in.
For the preservation of life in this single case it would be a waste but there as so many other scenarios where it would work. Plus there are so many other reasons to have a human civilization and terrestrial life spread to Mars. Humanity can do more than one thing at a time.
Even in this event Mars would have been a safe haven. Unlike Earth, the atmosphere on Mars is completely toxic with the planet exposed to dangerously high levels of radiation. Not exactly what one would call benefits, but in this case they would be, because human settlement on Mars would already entail the sort of lifestyle and technology that would render this sort of catastrophe relatively harmless.
Nonsensical argument, this shielding has to exist on Earth first (we are rolling the dice otherwise), deciding to colonize Mars adds nothing except a colossal waste of time and effort on other things.
Shielding isn't some distant future technology. Many simple compounds work as great shields, including water. That's been proposed as one of the ways to deal with extreme space weather events when traveling to Mars - using the water storage as an emergency shield. But of course you can't just put some giant shield up over the entire Earth for many reasons that I think should be pretty clear?
Unfortunately, Earth will literally never be safe from extinction. Nor will any planet. The first thing that should happen once we set foot on Mars is planning for the settlement of the next planet, or moon, to follow. That doesn't mean we should neglect any planet, most obviously including Earth, but the benefit of having 8 billion people is we're more than capable of doing more than one thing at a time.
> Shielding isn't some distant future technology. Many simple compounds work as great shields, including water
Wasn't it your own comment that there was a burst that killed 85% of marine species at the time. Water did not help did it?
> Unfortunately, Earth will literally never be safe from extinction. Nor will any planet. The first thing that should happen once we set foot on Mars is planning for the settlement of the next planet
Gamma bursts don't distinguish between planets or even entire solar systems. You'd need to go way further to be safe. So if you choose to colonize Mars, you are trading off the work that could allow that for a bunch of unrelated effort associated with colonizing Mars.
The gamma ray burst didn't just fry things (or at least half the planet would have been completely untouched), rather it fried the atmosphere. That set in stage a domino effect. If you strip the ozone introducing ultra high UV radiation everywhere, and then life starts dying from that including plants/animal in shallow water, creatures that depend on those creatures start dying, oxygen levels start shifting, and you get this lengthy domino effect everywhere. The 15% that survived were primarily from sea life that was deep enough to not just be shielded (which doesn't need to be that deep at all), but also to have a self sustainable cycle of life untouched by the life that was affected.
And this zero sum notion of work is a bit off. Nearly all work is spent doing completely pointless to harmful tasks. Unimaginably vast sums of money and manhour are spent doing things like trying to make people watch ads they don't want to see, or far worse. Yet, somehow, this sort of 'optimization of labor' only seems to come up when talking about doing petty things like make humanity a multiplanetary species. I find it to be neither compelling nor made in particularly good faith.
That was 6000 ly away. If another one happens 3000 ly away, whatever water thickness you cover your entire Martian base may easily not be enough. Or 1000 ly. Or 100 ly. You can hope but you are still rolling dice wherever you are in solar system or out.
If you want to protect humanity's survival from gamma rays, you can add the same protection on Earth more easily. The rational reason to colonize Mars is so that you can escape there when things go bad on Earth. Which is especially funny because the 1% who escape there are the ones responsible for most of the pollution right here.
Again, the rays themselves did not directly cause the death and destruction. Rather they messed up the atmosphere. On Mars, where the atmosphere is already toxic, this would be irrelevant. And there's no way to shield Earth against this at all. And nobody's going to be escaping to Mars. The wealthy and powerful already have their doomsday bunkers and hideouts; even a post-apocalyptic (such as after WW3) Earth would generally be a much more hospitable place than Mars will be.
It (is hypothesised that) wasn't that gamma radiation that directly killed the plankton, it damaged the ozone layer so that normally-blocked solar UV killed the plankton.
It's one of the many reasons life being multiplanetary is so important. There's no reason this, a giant asteroid, supervolcano, or any other of the million possible ways the universe can think up to kill us all off won't happen. In fact it will happen, sooner or later - and we're overdue. Of course the odds of it happening tomorrow are near zero, but that will be just as true the day before it happens. And the number of things that can wipe out two wildly different planets simultaneously is a small subset of all things that can wipe out 1. And the same is true as we expand on outward to new star systems, eventually even new galaxies, and perhaps further yet beyond that.
[1] - https://en.wikipedia.org/wiki/Late_Ordovician_mass_extinctio...