Asteroid Bennu, the target of OSIRIS-REx
, NASA's first mission to a pristine carbonaceous asteroid that may hold clues to the origins of life in our solar system, took center stage on Nov. 12 at the AAS' Division for Planetary Sciences meeting in Tucson. The mission's principal investigator, Dante Lauretta,
unveiled a video animation chronicling the history and evolution of Bennu, and presented a review paper
summarizing what scientists have learned about Bennu during 12 years of astronomical observations.
The talk included the first public viewing of "Bennu's Journey
," an animation created by NASA's Goddard Space Flight Center
that highlights the asteroid and the mission for non-technical audiences. "Bennu's Journey" takes the viewer on a visually stunning exploration to the origins of asteroid Bennu and its travels that take it past the Earth every six years.
"We have taken the scientific results of the ground-based observing campaign and combined the data with results obtained through computer simulations, to make the animation," said Lauretta, a professor of planetary science in the University of Arizona's Lunar and Planetary Laboratory
The product, scheduled for public release on Nov. 18, is Goddard's first animation in the new 4k standard, providing images with four times the resolution of high-definition TV. Movie posters, wallpapers and the movie itself (after Nov. 18) can be downloaded from the OSIRIS-REx mission website
"Our review paper summarizes the results of an extensive campaign to determine the physical, geological and dynamical properties of Bennu and provides the fundamental scientific motivation for the mission and explains what we're hoping to learn," Lauretta said. "The great value of an asteroid sample return lies in the knowledge that the sample is pristine and we know exactly where it came from. This is in sharp contrast to meteorites, which come to Earth from unknown origins, are altered by their trip through the atmosphere and exposed to the elements before they are found."
Scheduled for launch in the fall of 2016, OSIRIS-REx will rendezvous with Bennu in 2018, swoop down onto the asteroid's surface, collect a sample and return it to Earth in 2023. The OSIRIS-REx mission promises to help scientists address some basic questions about the composition of the very early solar system, the source of organic materials and water that made life possible on Earth, and to better predict the orbits of asteroids that represent collision threats to the Earth.
"Our knowledge of Bennu's orbit allows us to assess its impact hazard," Lauretta said. “Bennu is one of the most Potentially Hazardous Asteroids with an approximate 1-in-2,700 chance of impacting the Earth in the late 22nd century."
In 2135, Bennu will pass 300,000 kilometers (186,411 miles) over the surface of the Earth, well inside the orbit of the moon. The highest probability for a planetary impact is with Venus, followed by the Earth. In the statistically most likely scenario, the asteroid will end its dynamical life by falling into the sun within the next 10 million years. There also is a chance that Bennu will be ejected from the inner solar system after a close encounter with Jupiter.
Bennu is a primitive carbonaceous asteroid, thought to contain organic matter and water and hold valuable clues to the formation of the solar system and the origin of life-seeding molecules on Earth.
"We infer that Bennu is an ancient object that has witnessed more than 4.5 billion years of solar system history," Lauretta said. "Its chemistry and mineralogy were established within the first 10 million years of the solar system's formation."
Bennu likely came into existence in the inner main asteroid belt between Mars and Jupiter as an individual asteroid within the past 700 million to 2 billion years, as a result of a collision shattering its parent body, an asteroid believed to be 100-150 kilometers wide (60-90 miles).
Classified as a rubble-pile asteroid, Bennu acquired its spinning-top shape — common of many near-Earth asteroids — as a result of changes in its rotational angular momentum over time, including closer encounters between Bennu and planets such as Earth or Venus that shifted rubble and smaller particles to pile up near the equator.
"These wide-scale resurfacing processes may have brought fresh material to Bennu's surface, unaltered by cosmic rays, solar wind and impacting particles, making it especially valuable scientifically," Lauretta said.
The review paper will be published as part of a special issue of the journal Meteoritics & Planetary Science dedicated to Michael J. Drake
, former head of the UA's Department of Planetary Sciences and Lunar and Planetary Laboratory and father of the OSIRIS-REx mission. Drake died in September 2011, having committed the last seven years of his life to making the OSIRIS-REx mission a reality. He established an international team, led the by the UA along with Goddard Space Flight Center and Lockheed Martin, to propose an asteroid sample return mission to NASA.