OSIRIS-REx

NASA’s asteroid explorer has been at Bennu for over a year now, but the best part is yet to come

Mission type

Sample return

Operator

NASA

Launch date

8 September 2016

Target

101955 Bennu Arrival at target

3 December 2018

Primary objective

Survey and collect a sample from a carbon-rich near-Earth asteroid

Status

Operational

OSIRIS-REx is the third part of NASA’s New Frontiers Program, succeeding the likes of New Horizons and Juno. All three are completely reshaping our understanding of the Solar System, and OSIRIS-REx is doing so at the asteroid 101955 Bennu.

The Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRISREx) spacecraft was launched with a game plan to break records and do something that hasn’t been done since the Apollo era. “It’s a mission to reach out to a near-Earth asteroid named Bennu and survey that object in great detail, ultimately selecting a single location on the asteroid surface to send the spacecraft down for a brief contact to collect material that we will return to Earth for analysis in our laboratories,” explains Lauretta.

When the spacecraft sends its return capsule to Earth from Bennu in September 2023, carrying at the very least 60 grams (2.1 ounces) of asteroid regolith, it will deliver a sample from space in a quantity that hasn’t been seen since the Apollo astronauts returned lunar samples in the 1960s and 1970s. But what makes Bennu so special?

First is that Bennu is a near-Earth asteroid, and being in close proximity to Earth means the spacecraft doesn’t have to journey to the outskirts of the Solar System to sample it. Secondly, the asteroid is small enough – with a diameter of roughly 500 metres (1,600 feet) – and rotates slowly enough that it enables OSIRIS-REx to enter its orbit and conduct close-up observations without orbital complications. Thirdly, Bennu is a rare B-type carbon-rich asteroid that astronomers believe could hold clues about the Solar System’s inception. Bennu can be thought of as a frozen time capsule, left over from the formation of the planets.

“We chose Bennu specifically because we knew a lot about it and intriguing hints about its composition,” says Laurette. “We think Bennu may have water in the form of clay minerals and organic molecules that we think may have represented the seeds for the origin of life on Earth.”

4.5 billion years ago, asteroids, comets and other pieces of space rock began to accumulate until they formed the planets and dwarf planets that are seen today. In the process, some of these planets acquired liquid water on the surface, such as Earth and Mars, and Earth was even blessed with organic compounds that provided the building blocks for human life. Scientists believe that asteroids such as Bennu are the key to understanding how chemistry created biology. “OSIRIS-REx really seeks to answer some of the most fundamental questions that we ask ourselves,” says Laurette. “It’s a great example of what humanity can accomplish when a talented group of dedicated people put their minds on a single objective.”

This sample-return mission has another goal in understanding the current nature of near-Earth asteroids. When it comes to around-the-clock asteroid observations, modern techniques have brought to light just how hazardous these objects can be. By scrutinising Bennu, the mission could provide vigilant astronomers with important information about a future Earth-bound asteroid. Not only that, but asteroids could soon become utilised in space mining. Companies could soon be sending mining missions to asteroids to extract their rare resources, and OSIRIS-REx can provide a more complete understanding of what resources might be hidden within.

OSIRIS-REx arrived at Bennu on 3 December 2018, beginning an in-depth survey of the entire surface, mapping from pole to pole. While doing so it has been slowly decreasing the altitude of its orbit, and it will continue until it hovers just 240 metres (800 feet) over the asteroid’s surface. In July 2020 OSIRIS-REx will perform NASA’s first-ever robotic sample collection of a celestial object using the Touch-And-Go (TAG) sampling manoeuvre. After collecting an adequate sample the spacecraft will depart from Bennu in March 2021, where it will cruise back to Earth and drop off an uncontaminated sample – fresh from the vacuum of space – in the Utah Desert in September 2023.

©NASA/UniversityofArizona MapCam MapCam maps the surface in colour and will provide the images that then create topographic maps. It will observe the area around the asteroid for satellites and outgassing plumes. OSIRIS-REx Thermal Emission Spectrometer (OTES) The spectrometer will acquire infrared data between 5.71 and 100 micrometres, which will provide important information about temperatures and the mineralogy of several regions. OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) As the name suggests, this particular spectrometer will acquire data in the visible and infrared light spectrum to find the spectral signatures of a range of materials. Touch-And-Go Sample Acquisition Mechanism (TAGSAM) The sampler head and arm will retrieve the surface sample that astronomers are eagerly awaiting. TAGSAM has three separate bottles of gas which will allow up to three attempts of collecting a sample. Regolith X-ray Imaging Spectrometer (REXIS) This is a student experiment that will scrutinise which elements are present on the surface and their abundances. Solar X-rays and the solar wind interact with the surface regolith to reveal the elements that are present. SamCam One of three, this camera will continuously image and document the entire TAG sampling manoeuvre performed by OSIRIS-REx using its close-range capabilities. PolyCam This long-range telescope was the first to see the asteroid from afar. It identifies any hazardous areas and creates high-resolution images of the surface. OSIRIS-REx Laser Altimeter (OLA) OLA is a light detection and ranging (LIDAR) instrument that uses light, in the form of laser pulses, to measure distances. This provides high-resolution topographic data of the surface of Bennu.