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Today, the space agency NASA will try to land a spacecraft on an asteroid, a hunk of rock in space that is roughly the size of a large building on Earth. The spacecraft only needs to stay there for five to 10 seconds, just long enough to collect some dust and rocks, which is pretty cool if it works, which it might not. Here's NPR's Nell Greenfieldboyce.
NELL GREENFIELDBOYCE, BYLINE: The asteroid is named Bennu. It's about 200 million miles away, and it's a potentially dangerous asteroid.
DANTE LAURETTA: Our most recent calculations suggest that it has about a 1 in 2,700 chance of impacting the Earth.
GREENFIELDBOYCE: Dante Lauretta of the University of Arizona is the principal investigator for a NASA mission called OSIRIS-REx. He says the good news is this asteroid wouldn't hit Earth for at least 150 years.
LAURETTA: And part of the OSIRIS-REx mission is to better understand that impact probability.
GREENFIELDBOYCE: What's more - asteroids are like pristine relics of the early solar system, undisturbed leftovers from when the planets first formed. So NASA isn't the only space agency interested in asteroids. Japan's has already collected a tiny amount of asteroid material that's on its way back to Earth. It will get here in December. Lori Glaze is head of NASA's planetary science division. She says the agencies have been collaborating.
LORI GLAZE: And, of course, we'll be exchanging portions of each other's samples so that we can maximize the science.
GREENFIELDBOYCE: Assuming NASA's effort goes off without a hitch. Its probe arrived at Bennu a couple years ago, giving researchers their first up-close view of this asteroid. Lauretta says they were expecting a smooth, sandy surface.
LAURETTA: Immediately, I was struck by how rough and rugged and rocky the surface was.
GREENFIELDBOYCE: It's been a real challenge to find a relatively rock-free spot where the probe can be ordered to briefly touch down. Later today, operators will send the go command. As the spacecraft leaves orbit and ventures down, the scientists will only be able to watch a trickle of data coming back.
LAURETTA: There's nothing we can do to change the course of events. In fact, by the time we get the data, everything that happened was 18 1/2 minutes in the past because that's how far away the spacecraft is from the Earth.
GREENFIELDBOYCE: The spacecraft, which is about the size of a big passenger van, will head to a crater that's about the size of a tennis court, but it's filled with boulders.
LAURETTA: So we're actually targeting a site about half that size, about 10 meters across. This is roughly the size of a few parking spaces in a parking lot.
GREENFIELDBOYCE: If the spacecraft's onboard systems decide that it's likely to hit a dangerous rock, it might call off the attempt. If everything goes just right, the research team will know right away if they've touched the surface. Knowing if they've got a sample will take longer. Beth Buck is the mission operations program manager at Lockheed Martin Space.
BETH BUCK: Our first imagery will start coming in on Wednesday, and that will give us a much better feel for whether we have a sample or not and how the spacecraft is actually performing.
GREENFIELDBOYCE: With luck, they'll have collected everything from tiny grains to stones nearly an inch across. Heather Enos of the University of Arizona is the deputy principal investigator for the mission.
HEATHER ENOS: The best outcome would be that we would collect a massive sample. I mean, we say we have a requirement of 60 grams or two ounces, so we have the capability of collecting up to two kilograms. And I would love for that capsule to be completely full.
GREENFIELDBOYCE: By October 30, the team will decide whether or not to try another sample collection attempt in January. And in March, the spacecraft will start its two-year journey back home.
Nell Greenfieldboyce, NPR News.
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