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NASA charts course of risky Bennu asteroid

Marcia Dunn, August 12, 2021 7:00PM AP

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An artist’s depiction shows the Osiris-Rex spacecraft descending towards Bennu to collect samples of the asteroid’s surface. Image: NASA/Goddard/Arizona State University/ AFP media_cameraAn artist’s depiction shows the Osiris-Rex spacecraft descending towards Bennu to collect samples of the asteroid’s surface. Image: NASA/Goddard/Arizona State University/ AFP

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NASA’s Osiris-Rex spacecraft is on its way back to Earth after its mission to collect asteroid samples has helped scientists better predict the path of the space rock.

The data collected by the spacecraft has given scientists a better idea of asteroid Bennu’s whereabouts for the next 200 years, including the remote chance it will collide with Earth.

The data shows there is a slightly greater chance of the asteroid hitting Earth than previously thought. But don’t be alarmed: the chances are still very low.

“We shouldn’t be worried about it too much,” said Davide Farnocchia, a scientist with NASA’s Center for Near Earth Object Studies at the Jet Propulsion Laboratory in the US, who served as the study’s lead author.

This undated image made available by NASA shows the asteroid Bennu from the OSIRIS-REx spacecraft. After almost two years circling the ancient asteroid, OSIRIS-REx will attempt to descend to the treacherous, boulder-packed surface and snatch a handful of rubble on Tuesday, Oct. 20, 2020. (NASA/Goddard/University of Arizona/CSA/York/MDA via AP) media_cameraA view of asteroid Bennu from the Osiris-Rex spacecraft. Image: NASA/Goddard/University of Arizona/CSA/York/MDA via AP

While the odds of Bennu striking Earth have risen from a 1-in-2700 chance to a 1-in-1750 chance over the next century or two, Mr Farnocchia said it was good that scientists had been able to make a more precise* calculation of its orbit and its closeness to Earth.

“So I think that overall, the situation has improved,” he said.

Osiris-Rex is headed back to Earth on a long, roundabout loop after collecting samples from Bennu, a large, spinning rubble pile that is considered one of the two most hazardous* known asteroids in our solar system. The samples are due here in 2023.

Before Osiris-Rex arrived at Bennu in 2018, telescopes provided solid insight into the asteroid, which measures about 500m in diameter.

But the spacecraft collected even more data over 2.5 years and this information has helped scientists better predict the asteroid’s orbital path well into the future.

Their findings, published in the journal Icarus, should also help in charting the course of other asteroids.

media_cameraAn artist’s impression of the Osiris-Rex spacecraft descending towards asteroid Bennu to collect a sample. Picture: AFP/University of Arizona/NASA Goddard Space Flight Center

Before Osiris-Rex arrived on the scene, scientists put the odds of Bennu hitting Earth by the year 2200 at 1-in-2700. Now it’s 1-in-1750 by the year 2300. The single most menacing* day is September 24, 2182.

Bennu is also expected to have a close encounter with Earth in 2135 when it passes within half the distance of the moon. It was feared that Earth’s gravity could change the asteroid’s future path and put it on a collision course with Earth in the 2200s, but this is less likely now based on Osiris-Rex observations.

If Bennu did slam into Earth, it wouldn’t wipe out life, dinosaur-style, but rather create a crater roughly 10 to 20 times the size of the asteroid, according to NASA’s planetary defence officer, Lindley Johnson.

Mr Johnson said finding threatening asteroids like Bennu, which was discovered in 1999, in advance increased the chances and options for pushing them out of our way.

“One hundred years from now, who knows what the technology is going to be?” he said.

This November, NASA plans to launch an experimental mission* to knock an asteroid offcourse by hitting it. The target will be the moonlet of a bigger space rock.

GLOSSARY

  • precise: exact, accurate
  • hazardous: risky, dangerous
  • menacing: threatening, suggesting danger
  • experimental mission: a mission designed as a test
  • moonlet: small moon

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Big asteroids zooming ‘close’ by Earth

QUICK QUIZ

  1. What is the name of the asteroid in this story?
  2. What is the diameter of the asteroid?
  3. When did the Osiris-Rex spacecraft arrive at the asteroid?
  4. What is the chance the asteroid will strike Earth?
  5. What year is the asteroid expected to have a close encounter with Earth when it passes within half the distance of the moon?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. Design a Poster
Younger kids could be worried by this story. Design a poster. Your purpose is to help other kids to understand that we are safe from Bennu and to encourage them to see how amazing asteroids are.

Time: allow 30 minutes to complete this activity
Curriculum Links: English, Science, Personal and Social Capability

2. Extension
Imagine that it is 2182. Design a system or some technology that will stop Bennu from hitting Earth. Remember that you will be more scientifically advanced than we are today, so use your imagination!

Time: allow 40 minutes to complete this activity
Curriculum Links: English, Science, Critical and Creative Thinking

VCOP ACTIVITY
I Spy Nouns
Nouns are places, names (of people and objects), and time (months or days of the week).

How many nouns can you find in the article? Can you sort them into places, names and time?

Pick three nouns and add an adjective (describing word) to the nouns.

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