LEILA FADEL, HOST:
A 1,000-pound metal ring fell from the sky and crashed into a Kenyan village this week. Kenya Space Agency says it was part of a rocket used to launch objects into space. There were no casualties or damage reported, but there's growing concern about all the satellites, rocket parts and other junk in space that could potentially crash back into Earth. Marlon Sorge is executive director of the Aerospace Corporation's Center for Orbital and Reentry Debris Studies. Good morning, Marlon.
MARLON SORGE: Good morning, Leila.
FADEL: So this was wild to me, that debris from space fell out of the sky, just crashed into a village on Earth. How common is this?
SORGE: There are decent-sized objects coming out of orbit every few days, typically, but the chances of it actually hitting somebody are extremely small.
FADEL: OK. So people don't need to be worried that they'll be walking around and, boom, get hit by some junk falling from space?
SORGE: No, no. You're way, way more likely to get hit by lightning than this. So far as we know, nobody's ever been killed by something falling out of space before.
FADEL: Now, you work with the federal government to track objects in orbit. How many objects are you keeping an eye on?
SORGE: Right now, the Space Force is tracking something like 40,000 objects on orbit. These are things that are 10 centimeters - 2.5 inches - across and larger kind of down in the low orbits. But there are somewhere between half a million and a million objects smaller than that but are still dangerous. If they hit your satellite, it would be a bad day. And there are well over 100 million objects that are even smaller than that.
FADEL: Now, there is an ongoing lawsuit about a chunk of space debris that crashed into a house in Florida. Who is responsible when that happens?
SORGE: That's actually discussed in the Outer Space Treaty that the U.N. put into effect back in 1967, actually, that the country who launches an object is responsible for it. They have ownership of it past the time that it's operating even when it falls back to Earth. We had actually a clear example of that situation back in the late 1970s with the Soviet satellite Cosmos 254 - crashed into Canada. It had radioactive material on it. And although the Canadians cleaned it up, it was the Soviet Union that was actually responsible for - in principle, for paying for that.
FADEL: Now, you mentioned how unlikely it is that you'll get hit by something falling out of the sky. But what is done to protect against that debris hitting or hurting people and things?
SORGE: So many of the satellite operators are very conscious about making sure that their satellites will burn up. Certainly, the U.S. government, with their upper stages, the big vehicles that take things up there, they actually frequently will do what's called a controlled reentry. They'll target it to go into the middle of the ocean, where there are no people, to make sure that there isn't a risk.
FADEL: Marlon Sorge is executive director of the Aerospace Corporation's Center for Orbital and Reentry Debris Studies. Thank you for being on the program.
SORGE: Thanks.
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