

Chelyabinsk Meteorite Collided With Asteroid Before Hitting Earth - suprgeek
http://blogs.discovermagazine.com/d-brief/2014/05/22/chelyabinsk-meteorite-collided-with-asteroid-before-hitting-earth

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pyre
> While more research is needed, the proposed timeline suggests that asteroids
> — including NEOs that pose a potential threat to Earth — may have much
> greater longevity than previously estimated.

The phrasing here is a little confusing. Is it just new that NEOs can be this
old? What was the thinking before? That no asteroids could be that old? Or
that no asteroids that old would ever come near Earth (if so, why)?

Am I missing some information (e.g. said meteorite was in some sort of
unstable orb around Earth / the Sun for a long time)?

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jameskilton
I believe the common thinking is that the giant gravity wells of Jupiter,
Saturn, and the Sun are often considered a shield for the inner Solar System
planets. Thus, given enough time (10 million years per the article) these
wells attract and destroy a vast majority of free rocks, preventing them from
threatening Earth.

But (my conjecture) if there's far more random junk flying around out there,
that's going to force a re-think of how we guarantee the safety of space
travel past the Moon.

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Florin_Andrei
> _The team estimated the massive collision happened up to 290 million years
> ago._

The title seemed to imply a different timescale.

