Collision Course

When a (big enough) meteor hit the earth the last time around, the dinosaurs were its most famous casualty. But that’s not why NASA setup CNEOS to keep an eye for asteroids! Instead, it’s due to something humans saw happen, write Jorge Cham and Daniel Whitman in Frequently Asked Questions about the Universe:

“In 1994, the comet Shoemaker-Levy 9 broke into twenty-one pieces on its way toward the sun, and those frag­ments crashed into Jupiter. One of those pieces created a gigantic explosion approximately the size of Earth.”

Yes, an explosion as big as the earth.

 

As of today:

“The CNEOS team has created a pretty good database of all the biggest rocks around us, where they are, and where they will be in the near and far future.”

The good news is that the biggest rocks are rare (That’s good news since it’s the biggest ones that can cause catastrophic destruction). Even better:

“Luckily, large rocks like that are not only rare but also relatively visible. If a large rock is on a regular orbit, it's likely that we'll have seen it reflect light from the Sun.”

But of course, since these rocks only glow due to reflected sunlight, it’s entirely possible that we haven’t seen many of them yet. Either because it’s currently too far from the Sun to reflect much light; or more scarily, we missed it.

 

But there’s a bigger risk:

“While NASA has a good handle on most of the asteroids in the solar system that can kill us, it turns out that comets are much harder to spot.”

The news wrt comets gets worse. Their orbits take so long (often hundreds of thousands of years) that we’d be seeing most of them for the first time. And due to their hugely elliptical orbits, they speed up tremendously as they closer to the Sun (and thus earth).

 

Ok, let’s say we detect one of these asteroids or comets hurtling towards us. What could we do about it? Ideally, one would want to destroy it, say with a nuclear weapon or something. Another alternative is to nudge/deflect it. And how would we nudge it? One set of ideas are based on Newton’s action-reaction principle (smash a rocket into it; or land a crane on it that starts scraping pieces out of it and hurling them into space). Another one involves aiming lasers at it; or using giant mirrors in space to focus the sun’s energy onto the rock.

 

If those ideas sounds as realistic as a Hollywood movie, you’re probably right. Early detection is our best hope to have any chance. One, because the farther away it is, the smaller the nudge needed to make sure it doesn’t hit earth. And two, it would buy us more time to try a few different options. Otherwise, we’ll probably go like the dinosaurs.