I remember seeing a show awhile back that talked about ways the World Could End, and GRBs were one of the things discussed. I know that it would basically kill all higher lifeforms, but would it wipe out all life on Earth? I guess it would depend on how far away it was, but I’ve heard they could be extinction events even half a galaxy away.
Also, it mentioned the ozone layer would be wiped out - is it possible that one close enough might destroy the whole atmosphere? It would be purely academic of course, but I wondered if the planet might be left with nothing but preserved human civilizations in a vacuum, which might last for millions of years basically untouched without weather to erode buildings, etc.
Without an ozone layer, the unfiltered UV light would put a lot of wear on manmade structures. I don’t know about underground ones but the above ground ones certainly wouldn’t last centuries, let alone millennia. I was just reading about the flags on the moon, which have all apparently been bleached white by the unrelenting UV radiation and the temperature extremes, and are very likely starting to disintegrate. Buildings would obviously take longer but they would not be “preserved in a vacuum”; unprotected space is far harsher than life on Earth.
As for life, well…it takes a lot to kill all the bacteria on Earth and there are certainly anaerobic ones. Who knows?
Something that gets overlooked a lot with GRBs is that they’re very, very quick. Even the “long-duration” ones only last tens of seconds. So you’re only going to insta-fry half of the planet, at worst. This will still have dire indirect effects on the other half, of course, but life, and probably humans, would survive.
I was under the impression that even being on the other side of the planet wouldn’t protect from the radiation effects because of the intensity of the blast…?
A nearby GRB isn’t going to be intense enough to penetrate or irradiate through 8 thousand miles of rock (at the thickest diameter).
The atmosphere, as the OP mentions, will get a huge dose of radiation and do some serious damage to the stratosphere and ozone layer. But I doubt this would still be enough to totally wipe out humanity. Though it wouldn’t be no picnic.
Imagine a massively energetic event that produces gamma rays, channeled into a very tight beam. The exact mechanism isn’t known but could be caused by certain supernovas, merging binary stars or other massively powerful events in space.
The burst will cause nitrogen and oxygen in the atmosphere to react and create nitrous oxide; this destroys ozone, darkens the sky and rains out as nitric acid. Paradoxically this fixes nitrogen then proceeds to fertilise the soil, so you will get deaths and diebacks from the acid rain, increased UV and darkened sky, but then you might get increased growth in some areas.
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Anything that could destroy the atmosphere wouldn’t leave much behind of the surface of the planet; that would take an enormous amount of force. I expect that all human structures would be reduced to powder in the process.
As you might realise, I really meant NOx; this also includes nitric oxide and nitrogen dioxide as well. The mixture would be highly toxic and not all that useful as an anaesthetic or euphoric agent.
