It's moving far too fast in the worst possible direction, and it's already far too far away.

If we'd known it was coming, we could in principle have gotten something out to its point of closest Earth approach, but the object's velocity means even that would've been a flyby with no possibility of rendezvous outside possibly an impactor.

As the matter stands today, anything we'd send after it would have to overcome a velocity disadvantage of something like 40 kilometers per second - in other words, traversing the diameter of our planet three or four times every second - on a vector pointed near as nevermind to straight away from us. That's not something our propulsion technology is so far even close to being able to do.

That doesn't make sense. If the Earth is 12,000km in diameter, surely it will take a few minutes to traverse and not multiple times per second?

Edit: Oh never mind, you meant the velocity needed to catch up with it.

Of course you're right. Evidently I cannot accurately exponentiate before coffee!

But, yes, the velocity difference is a killer. The closest we've ever come was the Apollo-Saturn stack, and even that only had ~9km/s left over after reaching escape velocity.

Probably not; we won't be able to scramble a mission fast enough.

That said, this was literally my first thought when I saw the headline on HN - that I can't wait until we have a space presence good enough that, the next time this happens, we'll be able to quickly send a probe to such an object.

It's doing ~40km/s almost directly away from us. We could launch yesterday and still never catch up. Best we could have done would be a flyby as it passed beneath the ecliptic - not nothing, to be sure, but not nearly close enough for sample return, either.