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To Bennu and Back - presented by Science@NASA
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NASA is launching a spacecraft to visit an asteroid... and return to tell the tale.
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OSIRIS-REx is scheduled to blast off from Cape Canaveral on September 8, 2016,
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on a mission to orbit, map and collect samples from the asteroid Bennu, and return to Earth 7 years later.
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Discovered in 1999 by the NASA-funded LINEAR asteroid survey, Bennu measures about 1650 feet across and weighs over 60 million tons.
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Imagine a boulder the height of the Empire State Building - that's about the size of Bennu.
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So, why Bennu? Because the asteroid is interesting due to its size and composition, and it is accessible to be sampled.
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Bennu is a primitive and carbon-rich asteroid.
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Primitive asteroids contain material that has not changed significantly since they formed over 4.5 billion years ago.
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The analysis of any organic material found on Bennu
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will give scientists an inventory of the materials present at the beginning of the solar system
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that may have had a role in the origin of life on earth, and potentially elsewhere.
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Indeed, Dante Lauretta of the University of Arizona, Principal Investigator on the OSIRIS-REx mission says
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mapping and sampling the space rock "can potentially hold answers to the most fundamental questions human beings ask, like 'Where do we come from?'"
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To get to Bennu, OSIRIS-REx will perform a series of deep space maneuvers,
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first orbiting the sun for a year and then using Earth's gravity to be slung towards the asteroid.
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The spacecraft will spend a year flying in close proximity to Bennu - its five instruments imaging the asteroid,
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documenting its lumpy shape, and surveying its chemical and physical properties.
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In July 2020, OSIRIS-REx will approach Bennu and execute its touch-and-go - or TAG - maneuver.
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A mechanical arm that functions like a combination sample scoop and pogo stick will be extended from the spacecraft.
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The spacecraft will slowly approach the asteroid until the sample head at the end of the arm gives a gentle "high five" to the surface.
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The maneuver may be executed up to three times, and OSIRIS-REx could leave Bennu with up to 4.4 pounds of sample material from the asteroid.
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Researchers will be keen to learn about Bennu for another reason.
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Bennu orbits the sun between Venus and Mars so it crosses Earth's orbit frequently and comes close to Earth every six years.
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In 2135, Bennu will make an especially close approach to Earth, just within the Moon's orbit.
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This will change Bennu's orbit, and it is more difficult to predict how much closer it may come to the Earth after that close encounter.
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Lauretta says, "We need to learn as much as about Bennu as we can."
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Predicting a small asteroid like Bennu's exact course is somewhat tricky, due to the Yarkovsky effect.
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The dark asteroid absorbs sunlight and then gives it off as heat, which serves as a gentle thruster that gradually shifts its path.
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Edward Beshore of the University of Arizona, Deputy Principal Investigator for OSIRIS-REx says,
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"We'll get accurate measurements of the Yarkovsky effect on Bennu by precisely tracking OSIRIS-REx as it orbits the asteroid."
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If all goes as planned, OSIRIS-REx will fire its main engines in March 2021 and begin its journey back to Earth.
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The samples will arrive in September 2023, when a capsule containing bits of Bennu will land at the Utah Test and Training Range.
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From there, the capsule and its precious contents will travel to NASA's Johnson Space Center in Houston, TX,
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where hands-on analysis of this ancient asteroid will begin by mission scientists and then by scientists from all over the world.
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For updates on the mission to Bennu and back, go to www.asteroidmission.org
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For more on objects in and around our solar system, stay tuned to science.nasa.gov