An artist’s impression of OSIRIS-REx approaching Bennu. Image: NASA/Goddard/University of Arizona
On 8 September, NASA will launch its OSIRIS-REx spacecraft, whose mission is to travel to a near-Earth asteroid called Bennu and not only map it, but return a sample, too.
Following the massive interest and success in the European Space Agency’s (ESA) Rosetta mission to land a craft on Comet 67p, NASA will now attempt to do one better by sending a spacecraft to map, and land on, the asteroid Bennu.
Named after a mythological Egyptian bird, Bennu is one of many large near-Earth asteroids that are categorised as being a potential Earth impactor, ranking highly on the Palermo Technical Impact Hazard Scale.
Searching for water
While Bennu is not expected to be a threat to Earth for a number of years, NASA will now be using one of the asteroid’s closest approaches to our planet to perform measurements on the potential planet-killer.
On 8 September, the OSIRIS-REx spacecraft will begin its journey to map Bennu and its mean diameter of over 1,500ft, using the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS).
By using OVIRS, OSIRIS-REx will be able to measure visible and near-infrared light from the asteroid, and then split that light into its component wavelengths, similar to a prism creating a rainbow from sunlight.
Additionally, the OSIRIS-REx Thermal Emission Spectrometer (OTES) will use infrared spectrometry to help NASA determine if water-laden areas exist on the asteroid’s surface.
Returning in 2023
By looking at Bennu through these light spectra, the mineral composition of the asteroid will come into focus, allowing scientists back on Earth to identify various organic materials – as well as carbonates, silicates and absorbed water – on the surface of the asteroid.
More importantly, by analysing areas of high-interest to scientists, NASA can determine where the best possible landing site for OSIRIS-REx is. After landing on Bennu, it will then return to Earth for scientists to scrutinise.
While water will be of considerable interest to NASA and the research team, considerable efforts have been taken to ensure that the liquid will not jeopardise the mission, as any water inside the OVIRS instrument could nullify the scientific readings.
To counteract this, heaters will be turned on immediately after OSIRIS-REx takes off from Earth to evaporate any water that may have accumulated on OVIRS.
“OVIRS is key to our search for organics on Bennu,” said Dante Lauretta, principal investigator for the OSIRIS-REx mission. “In particular, we will rely on it to find the areas of Bennu rich in organic molecules to identify possible sample sites of high science value, as well as the asteroid’s general composition.”
Going by current mission objectives, OSIRIS-Rex will return the obtained samples to Earth in 2023, seven years after launch.
