Well a meteorite the size of the Chelyabinsk meteor, 20 meters, that's every 60 years or so. Impact event - Frequency table
As for a big 10 km scale one like the one that made the dinosaurs extinct, that's a chance of about 0.0001% to be hit by it before 2100. And humans wouldn't go extinct as we have enough technology to survive a fire storm, at least some of us, and probably also save a lot of species of plants and animals - and may be able to deflect it given enough warning.
There's pretty much zero chance of being hit by something large enough to make humans extinct, as there is no impact crater large enough in the geological record.
The largest one we know about is a 300 km crater in S. Africa which formed about 2 billion years, probably created by an impactor between 5 and 10 km in diameter. Vredefort crater
So impactors of up to 10 km or so in diameter are possible, but there have probably never been any larger impacts since the Hadean period 4 billion years ago.
See also What is the probability of a significant asteroid impact event by 2100?
As for a big 10 km scale one like the one that made the dinosaurs extinct, that's a chance of about 0.0001% to be hit by it before 2100. And humans wouldn't go extinct as we have enough technology to survive a fire storm, at least some of us, and probably also save a lot of species of plants and animals - and may be able to deflect it given enough warning.
There's pretty much zero chance of being hit by something large enough to make humans extinct, as there is no impact crater large enough in the geological record.
The largest one we know about is a 300 km crater in S. Africa which formed about 2 billion years, probably created by an impactor between 5 and 10 km in diameter. Vredefort crater
So impactors of up to 10 km or so in diameter are possible, but there have probably never been any larger impacts since the Hadean period 4 billion years ago.
See also What is the probability of a significant asteroid impact event by 2100?
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Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
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