Artist concept of OSIRIS-REx. Image credit: NASA Goddard/University of Arizona Artist concept of OSIRIS-REx. Image credit: NASA Goddard/University of Arizona

Mission to return an asteroid sample to Earth

Sen— NASA is planning a mission to capture an asteroid sample and return it to Earth.

The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, and Regolith Explorer) spacecraft is being planned for a launch in 2016 and would return a sample in 2023.

The aim of the mission is to return sample for analysis which could give scientists a greater understanding of planet formation and the origin of life, as well as improving our knowledge of asteroids that could impact Earth.

We currently know of over 500,000 asteroids, over 8,000 of which can come close to Earth. There are only 74 objects that have relatively easily accessible orbits and are large enough to be sample return targets for OSIRIS-REx. 5 of those 74 objects are carbonaceous including the target asteroid, 1999 RQ36.

Asteroids move at an average of 12 to 15 kilometers per second (about 27,000 to 33,000 miles per hour) relative to Earth. A large fraction of asteroids with diameters less than 200 meters rotate as quickly as once every 1 to 60 minutes, greatly increasing the risk to spacecraft operations, but also centrifugal forces can eject regolith from the surface. As a result, small asteroids may not possess any loosely bound material for sample return.

Asteroid 1999 RQ36 measures 575 meters (one-third of a mile) in diameter. Scientists have classified it as a B-type asteroid, a rare subgroup of the dark, carbonaceous C-type asteroids, which are called “primitive” having undergone little processing from their time of formation. 1999 RQ36 is a time capsule from the early solar system rich with organic compounds that may have seeded life on Earth.

OSIRIS-REx is scheduled to arrive at its destination asteroid in 2018, orbiting the asteroid for up to 505 days, until 2021.

The spacecraft will map the surface from a distance of between 5 km and as a close as 0.7 km to characterize its geologic and dynamic history and global properties, chemistry, and mineralog.

The mission's big challenge is then to bring back a sample (at least 60 grams or 2.1 ounces) to Earth. The sample would be sent back to Earth aboard a Sample Return Capsule. The sample would be analysed for the nature, history, and distribution of its constituent minerals and organic material.

OSIRIS-REx will also measure the asteroid's orbit deviations produced by the Yarkovsky effect and compare them with ground based observations. When an asteroid makes a close pass the gravitational pull from a planet changes the asteroid's orbit but there are also other small forces continuously acting on the asteroid to change its orbit. The most significant of these smaller forces is the Yarkovsky effect caused when the asteroid is warmed up by the sun and then re-radiates the heat in a different direction causing a minute push on the asteroid.

1999 RQ36 completes an orbit of the Sun every 436.604 days (1.2 years). This orbit takes it close to the Earth every six years. Recent calculations produced a 1 in 1800 chance of impact with Earth in the year 2182.

The OSIRIS-REx team is led by Dr. Michael Drake, Director of the University of Arizona's Lunar and Planetary Laboratory.

"OSIRIS-REx will explore our past and help determine our destiny," said Drake. "It will return samples of pristine organic material that scientists think might have seeded the sterile early Earth with the building blocks that led to life. Such samples do not currently exist on Earth. OSIRIS-REx will also provide the knowledge that will guide humanity in deflecting any future asteroid that could collide with Earth, allowing humanity to avoid the fate of the dinosaurs."

NASA's Goddard Space Flight Center is project managing the mission. The spacecraft is being built by Lockheed Martin Space Systems.


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