There are a ton of ways you’re likely to die, including heart disease, cancer, or stroke. And then there are the not-so-likely ways of being dispatched from this world, like being hit by an asteroid. But as a recent close flyby of Earth shows, there are dangers lurking out there in space that we’d never see coming, even with our advanced technology.

NASA astronomers recently discovered, to their alarm, that an asteroid named 2017 VL2 passed just 73,000 miles from Earth – or about a third of the distance between the Earth and the moon – and they found this out a day after it made its flyby. Considering the fact that this asteroid may have been more than 100 feet in diameter and could have destroyed an entire city had it struck the Earth in just the right place, that’s a sobering reality.

The good news is, asteroid strikes of that nature are rare, and even if an asteroid were to hit us, the vast, vast majority of land is unpopulated – even if it were to hit land, which is unlikely itself since two thirds of the Earth is covered by water. But when asteroids do strike, the devastation is incredible, and they’re responsible for just about every mass extinction event in Earth’s history. If humanity is wiped out at some point in the future, an asteroid strike certainly would be high on the list of probable causes.

You’d think we’d see such a huge rock coming at us, but space is so giant and these asteroids move so quickly, we’re still not at the point of being able to reliably spot them. And spotting them is one thing, avoiding them is another. NASA has set up an entire office, the Center for Near-Earth Objects, in an effort to better track asteroids. And scientists are working on technologies to help destroy these asteroids should be ever faced with one that would threaten to wipe out our species.

Until that technology matures, which may not happen in our lifetimes, we’ll just have to cross our fingers.