NASA's Osiris-Rex meets asteroid Bennu for cosmic pickpocketing

The spacecraft's mission? To learn more about an asteroid that could potentially hit Earth in the next century.

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Eric Mack
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Osiris-Rex will now spend a year and a half scanning and mapping Bennu.


NASA's Osiris-Rex spacecraft officially rendezvoused on Monday with Bennu, an asteroid with a tiny chance of hitting Earth in the distant future.

"We have arrived," communications system engineer Javi Cerna called out in the mission control center at Lockheed Martin outside Denver at about 10 minutes after 9 a.m. PT.

Osiris-Rex, which stands for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, launched from Earth on Sept. 8, 2016, and has taken more than two years to link up with its target. 

The goal of the mission is to become the first US spacecraft to return a sample from an asteroid to Earth. Japan's Hayabusa mission successfully brought back particles of an asteroid in 2010 and the follow-up, Hayabusa-2, is currently preparing for the sequel at the space rock Ryugu.

Enlarge Image

The 360-degree view of Bennu.


Osiris-Rex is equipped with a fancy robotic arm tipped with the equivalent of a super premium Shop-Vac called the Touch-And-Go Sample Arm Mechanism, or Tagsam. Tagsam will reach out and literally tag the surface of Bennu. Then, while touching the ancient rock, it'll blow a burst of nitrogen gas to loosen up bits of debris that'll be sucked up and transported home. 

This cosmic pickpocketing won't take place until 2020. Until then, Osiris-Rex will be orbiting, scanning and mapping its host to help pick just the right "tag" site.

In a way, asteroids are like time capsules that provide a look at the solar system billions of years in the past and scientists hope the mission will yield a more detailed history of our corner of the universe and perhaps even reveal the origins of life on Earth. Some astronomers theorize that the building blocks of life were first delivered here by an asteroid.

In addition to looking deep into the past, there's also a chance Osiris-Rex will help us plan for the future.

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"Bennu is a potentially hazardous asteroid," says Rich Burns, Osiris-Rex project manager for NASA. "There's a very small chance that it will impact Earth in the next century."

With a diameter of about 500 meters (1,600 feet), Bennu is wider than the height of the Empire State Building. 

The mission will investigate something called the Yarkovsky effect, in which heat from the sun is absorbed by an asteroid and then radiated back out into space, acting as a sort of mini-thruster that affects its movement. Better understanding of this effect could help scientists predict the flight paths of asteroids, particularly those that might pose a threat to Earth in the future. 

On Monday, the mission team performed a burn to transition into operating around the asteroid, a challenging task given the minute gravity of an object that's the smallest to ever be orbited by a spacecraft. 

Explore asteroid Ryugu with Japan's Hayabusa 2 spacecraft

See all photos

During NASA's press event for the arrival at Bennu, navigation engineer Coralie Adam explained that the first close flyby of Bennu (at a distance of about 5 miles or 8 kilometers) will take place Tuesday. 

Osiris-Rex will start its residency in the asteroid's orbit by flying over its poles and equator to begin mapping the rock's gravity and also identifying landmarks on the surface that'll be used for navigation during the mission.

"Looking at Bennu in more and more detail is going to help us identify all the areas that we shouldn't go to sample from," said Dani Della-Giustina of the University of Arizona, the image processing lead for the mission.

The sample Osiris-Rex collects will be flown back to Earth, where mission planners aim to land it in the Utah desert in 2023. 

According to the mission's deputy principal investigator, Heather Enos, we can expect to see some of the first science data and perhaps some new close-up images from Bennu next week.

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