Bennu is among the thousands of so-called Near-Earth Asteroids, one or more of which may prove to be hazardous to Earth in the future. Scientists with the upcoming Osiris-Rex mission hope to learn more about how heating and pressure from sunlight impart motions into an asteroid. The information one day may be critical for diverting an asteroid that is on a collision course with Earth.
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The $800 million Osiris-Rex spacecraft is expected to spend between 18 months and two years slowly circling Bennu so its science instruments and cameras can collect data for global, three-dimensional surface maps and catalog chemicals and minerals on the asteroid's surface.
Scientists expect to find Bennu rich with chondrules, which likely formed when bits of dust in the solar nebula were flash-heated to become molten rock that later solidified. Over time, chondrules clumped together to become the building blocks of asteroids and planets.
"On planets like Earth, the original materials have been profoundly altered by geologic activity and chemical reactions with our atmosphere and water. We think Bennu may be relatively unchanged," mission deputy scientist Edward Beshore, also with University of Arizona, said in a NASA interview.
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Scientists suspect Bennu also contains organic material from the solar system's early years. Carbon-rich organics are key to life on Earth, and perhaps elsewhere as well.
NASA says an analysis of any organic material found on Bennu will give scientists an inventory of the materials present at the beginning of the solar system that may have had a role in the origin of life.
"By bringing this material back to Earth, we can do a far more thorough analysis than we can with instruments on a spacecraft, because of practical limits on the size, mass, and energy consumption of what can be flown," Beshore said.
Osiris-Rex is designed to collect a minimum of 60 grams – 2 ounces -- of soil and crushed rock from Bennu's surface. However, preflight tests of the probe's sample collection system have scientists optimistic the spacecraft can collect as much as 70 ounces, or 4 pounds.
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Osiris-Rex will descend to the asteroid's surface for only the briefest of time and come only as close as what is need to place its 11-foot long robot arm on the ground. The arm is designed to fire off a burst of nitrogen gas and then collect small rocks and soil that have been stirred up.
Once scientists confirm they have at least 60 grams of material aboard, Osiris-Rex has just one task left: Get home.
If all goes as planned the spacecraft will put itself into orbit around Bennu in 2018, collect the sample in 2020 and fly back to Earth in September 2023.
Launch aboard a United Launch Alliance Atlas 5 rocket is scheduled for at 7:05 p.m. EDT Thursday at Cape Canaveral Air Force Station in Florida.
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