NASA Launches Asteroid Collection Mission
Image Credit: NASA/GSFC

NASA Launches Asteroid Collection Mission

07/09/2016Written by Robbie Bosley

On 8 September 2016, the launch window opens for NASA's OSIRIUS-REx spacecraft, starting the clock on an extraordinary mission to an asteroid and back.

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While its name may suggest dinosaurs and Egyptian gods, NASA’s new mission, OSIRIS-REx, has a task that is equally out-of-this-world. Rather than merely sending data back to Earth, OSIRIS-REx promises to bring back actual samples from an asteroid called Bennu. These may harbour the organic building blocks needed for life.

Why choose Bennu?

Why choose Bennu?
Why choose Bennu?
Image Credit: NASA/GSFC

101955-Bennu is an asteroid just under half a kilometre wide, or about as wide as five rugby pitches arranged end-to-end. Its orbit often crosses Earth’s orbit, meaning that Bennu is one of the objects that could collide with Earth sometime in the future.

There are over half a million asteroids in the Solar System. Why, then, choose Bennu for a mission like OSIRIS-REx? There are several reasons:

– It’s close to Earth. Bennu has an orbit very similar to that of Earth’s. It’s slightly more elliptical, so that it only crosses Earth’s path occasionally. This closeness makes Bennu very accessible for sample return missions like OSIRIS-REx.

– It’s big. Small asteroids spin faster than larger ones. An asteroid less than about 200m wide spins so fast that any loose material is thrown off it. This includes any visiting spacecraft. At 492m wide, Bennu is large enough for a comfortable landing.

– It’s made of the right stuff. Studies have shown the Bennu is a fairly primitive, carbon-rich asteroid. Carbon is a vital element for life and it’s thought that we may find these kinds of organic molecules on Bennu.

What will OSIRIS-REx do?

We still don’t fully understand what asteroids are made of, but scientists think they may hold key organic ingredients necessary for life, as well as other precious minerals. In order to get a better idea of what materials are present on asteroids, OSIRIS-REx has three main objectives:

Map the surface of Bennu. OSIRIS-REx has three cameras – one for short-range mapping, one for long-range telescopic imaging, and one for capturing images of the collected samples.

Find out what Bennu is made of. Scientists want to know more about the kinds of chemicals that exist on Bennu, especially if there are any organic compounds on the surface.

Bring back bits of Bennu. OSIRIS-REx has a robotic arm and hand called TAGSAM. This will be used to collect the samples of Bennu that will be analysed back on Earth.

Timeline of OSIRIS-REx

Timeline of OSIRIS-REx
Image Credit: Lockheed Martin Corporation

OSIRIS-REx lifts off on 8 September 2016 from Cape Canaveral, Florida to begin a two-year journey to Bennu. Arrival is scheduled for August 2018.

A survey of Bennu will begin in October 2018 as OSIRIS-REx orbits the asteroid. In July 2020, OSIRIS-REx will begin the sampling process, using short blasts of nitrogen gas to eject rocks from the surface for collection in a sampler. NASA thinks that OSIRIS-REx will be able to collect between 60 grams and 2 kilograms of rock with this method. These rocks will then be stored in a Sample Return Capsule, ready for the journey home.

OSIRIS-REx will leave Bennu in March 2021, firing its main engines to push away from the asteroid. On 23 September 2023, seven years after its departure, OSIRIS-REx is scheduled to arrive back at Earth. Here, it will drop its Sample Return Capsule (SRC) for scientists to collect on Earth, and then push itself into a safe orbit around the Sun.

If you want to discover more about ORISIS-REx and its journey to Bennu and back, head to the mission webpage,, for more details.

About the Author: Robbie Bosley is a current physics student at the University of Leicester and works at the National Space Centre as a Science Interpreter.