So in case you've been living under a rock (that's an asteroid joke), we had a close fly by of a medium-ish asteroid the other day. It's been labeled the 2019 OK asteroid and it came much closer to Earth than the moon.
What changes this from an interesting scientific fact to a terror-inducing fact is nobody knew it was coming until it was already here.
2019 OK is estimated to be about 100 meters wide and moving at 24,000 km/s. As far as asteroids go, it's medium sized and moving fast.
Asteroids like this are very dark, so detecting them is very difficult.
Meteor Showers Aren't Just Pretty Lights
Meteor showers come from fragments of comets and asteroids that are left behind as these bodies move about the solar system. In school, you probably saw models of the solar system that had all the planets and the asteroid belt neatly organized. While those are the major bodies, there are countless pieces of rock, ice, and frozen gasses tumbling, spinning, and moving about out there. Space is big, but the sun tends to pull everything in eventually.
For comets and asteroids, they tend to break apart as they get closer to the gravity and heat of the sun. So they leave behind space junk (technical term). When the orbit of the Earth passes through one of these junky trails, the rocks and debris enter our atmosphere from our perspective. They burn up and make for pretty lights in the sky.
Except when they are big enough to survive penetrating the atmosphere and do some (or a lot) of damage.
Think of a meteor shower like a beach ball. If your friend throws some sand in the air and the beach ball is thrown through the sand, no big deal. If there are some pebbles in the mix of sand, you get a much different result as the beach ball hits the pebble.
Right now we are in the Perseid meteor stream. It's unclear at the moment if 2019 OK is in the Perseid group or if is an independent body.
2019 OK is in the pebble or "city killer" category.
Estimates are that if it impacted Earth, the impact would be equivalent to the same energy released by a 10 megaton nuclear device. That is an enormous amount of energy. If you want to get a visual of what that looks like, head over to https://nuclearsecrecy.com/nukemap/
Here's the map of what 10 MT looks like dropped on Miami:
An asteroid impact isn't going to have the same radioactive fallout issues that a nuclear weapon will, but if you are in the red zone you'll still be vaporized. As you get farther from the impact site, you'll have blast waves, ejecta, and such to deal with depending on what part of the world it actually hit. In the Tunguska explosion a century ago of what is believed to be a similar-sized object, large trees were flattened for hundreds of miles. And that one didn't even hit the ground.
Aside from being academically interesting and frightening, what can you do to prepare for an event like this?
If you are in the direct impact area, nothing. You're toast.
If you are nearby and survive the impact, you are likely to experience similar effects as other natural disasters: fires, power outages, earthquakes, complete disruptions of water and gas service, destroyed roads, etc.
Even if the impact is in the ocean, which is a best-case scenario, you still will have tsunamis near the coasts and incredible rainfalls as vast amounts of seawater are vaporized into the atmosphere.
I think we are at an interesting time in history. We have the capability to alter an asteroid's orbit somewhat. Enough to turn a devastating collision into a near-miss. If we see it years ahead of time.
But like we just saw with 2019 OK, detecting them can be very difficult. It is hypothesized by some that even large bodies that have very low-density, low-reflectivity surfaces will be almost impossible to detect until it is far too late.
Or, just try not to think about it.