[mbreese]

Humans, as a species, have a very low bus-factor in planetary terms...

[dllthomas]

I think we're fine if a bus hits the planet.

[bronson]

Not if it's doing 0.999c.

obwhatif https://what-if.xkcd.com/20/

[dllthomas]

That sphere of diamond weighs about 3000x as much as a typical bus. So presumably we'd wind up with 1/60th of Chicxulub, rather than 50x. It'd suck (a lot) - and yeah, "we're fine" wouldn't hold - but I think we'd survive.

Edited to add: I don't know if I mis-read it or if you edited it, but the above was a response to 0.99c.