A short interview on the Russian Meteor Event

My university news service wanted to do a short interview about the Russian meteor strike last week. I’ll post a link when it’s up, but I figured I’d post my responses in full here. Enjoy!

– Dave

Q: Early reports claim that this meteor caused more than 400 injuries and damage was reported in six cities, with numbers being updated throughout the day? What is the most recent report of injuries and damage?

A: This was a staggering and dramatic event — made all the more so as it took place over a populated area. A surprising number of people had their cameras running for other reasons, which means that we’ve seen the meteor from lots of perspectives. There were shattered windows other structural damage and at last count over a thousand reported injuries. Fortunately, no deaths have been reported.

Q: Do you think there is a connection between Friday’s meteor strike and Russian news reports that the asteroid 2012 DA14 was to make the closest recorded pass of an asteroid (about 17,150 miles)?

A: People tend to forget how mind-bogglingly fast things are moving through space. Even though the meteor strike and the asteroid seem fairly closely timed, they aren’t. To put things in perspective, the Russian meteoroid was moving at at least 11 km/s (nearly 25,000 mph — and possibly faster), and hit at roughly 10:15pm EST. The Asteroid DA14 didn’t pass by the earth until 2:30pm the next day, 16 hours later. A rough estimate puts them at least 400,000 miles away from one another. What’s more, if they were related, we’d expect a large number of meteor strikes (as opposed to only one) as the asteroid was pulled apart by tidal effects from the earth’s gravity.

Q: Could the damage this meteor cause have been predicted/ prevented? How likely is something like this to happen here in the United States? What protection/ prevention methods do we have in the U.S. for something like this?

A: Likely to happen? Absolutely. The only question is when.

The Russian meteor was about 10m across, at an estimated mass of about 10 tons. Events on this scale happen about once a decade, but since most of the earth is made up of water, we don’t normally notice them. At roughly 3.8 million square miles, the U.S. makes up a little less than 2% the surface of the planet. So as an approximation, we’ll get an event like this in the U.S. every 500 years or so.

It seems unlikely that we’d be able to prevent or even really predict a meteor of this size. In part that’s because until it enters the atmosphere, meteors and other space debris don’t create their own light. They just reflect sunlight. The Russian meteor is a few times larger than a bus, and not nearly as reflective. Try to imagine catching the glint off a space-bus millions of miles away as it travels at tens of thousands of miles an hour and you’ll get some sense of the difficulty.

On the other hand, the larger the potential impactor generally speaking, the easier it is to see. The objects that could cause real damage to the earth as a whole hit much less frequently, but are much easier to see. An object the size of DA14, for instance, will hit every 1000 years or so, and obviously, we saw that well in advance of its closest approach — though this required dedicated monitoring (call your Congressperson!). Planetary events can occur on the timescale of 10’s of millions of years, and while there are large networks that are monitoring planet killers, even if we identified an impact ahead of time, we don’t currently have a way to prevent them.

Q: It’s said that most meteors burn up in Earth’s atmosphere; why did this one survive?

A: lot of it _did_ blow up in the atmosphere. As meteors (technically, they’re meteoroids at this point in their life cycle) enter the atmosphere they undergo enormous frictional forces from the air. Remember, the Russian meteor was traveling so fast — more than 30 times the speed of sound — that the loud sound you may have heard on the videos was a sonic boom.

Friction heats fast moving objects, and since many meteors have water and other materials inside them, this causes the meteors to explode. These explosions can cause much of the damage. The Russian meteor seemed to break up many kilometers above the earth. I don’t know yet whether any of the meteorites (the rocks that actually hit the ground) have even been recovered.

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2 Responses to A short interview on the Russian Meteor Event

  1. Daniel says:

    Mr. Randall Munroe’s been talking a lot in his “What If?” blog about how it’s the compression of the air that causes the rise in heat. I’m reading a lot about friction here being the source of heat.

    Help me Dr. Dave! I don’t know who to believe!

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