In its first major scientific breakthrough, NASA's OSIRIS-REx probe found water in the Bennu asteroid. The discovery was made through observations during the OSIRIS-REx approach of the Near Earth asteroid between mid-August and early December 2018 and confirms the earlier thoughts that Bennu may be a place that harbors water in the inner solar system.
The discovery also has significant potential in terms of Bennu's material. OSIRIS-REx hopes to return to Earth at the beginning of the next decade. The return of this water-containing material may help solidify or distance scientists from a theory that asteroids sowed Earth billions of years ago with water that now dominates the surface of our planet.
An incredible start to the main scientific mission of OSIRIS-REX:
Last week, when all eyes were on OSIRIS-REX for the arrival of the spacecraft to the asteroid Bennu, the mission scientists were completing a comparison of several months between the OSIRIS-REx instruments (Spectral Interpretation, Resource Identification, Security-Regolith Explorer) to confirm data showing the presence of water in the Near Earth Asteroid.
During the 3.5-month OSIRIS-REx approach phase to Bennu, mission scientists pointed three of the spacecraft's instruments toward the asteroid and began making the first scientific observations of the mission.
OSIRIS-REx Spectrometers, the OSIRIS-REx Infrared Spectrometer (OVIRS) and the OSIRIS-REx Thermal Emission Spectrometer (OTES), revealed the presence of molecules containing bound oxygen and hydrogen atoms known as hydroxyls – revealing a global distribution of clay minerals with water in Bennu.
Although the discovery of water is not a discovery of liquid water on the surface of Bennu, it is a discovery of water containing clay minerals. And since Bennu is too small to have harbored liquid water on its own, the discovery indicates that the body of origin from which Bennu originated – a larger asteroid – contained liquid water itself.
Speaking at the American Geophysical Union meeting in the fall of 2018, members of the OSIRIS-REx team said that a major goal of the mission was accomplished so quickly but reiterated that much work remains to be done for the mission – which is also important. in charge of recovering a sample of the surface of Bennu and returning the sample back to Earth.
"The presence of hydrated minerals through the asteroid confirms that Bennu, a remnant since the beginning of the formation of the solar system, is an excellent specimen for the OSIRIS-REx mission to study the composition of volatile and organic primitive," said Amy Simon, Vice OVIRS an instrument scientist at NASA's Goddard Space Flight Center.
"When samples of this material are returned by the mission to Earth in 2023, scientists will receive a treasure trove of new information about the history and evolution of our solar system."
Putting these materials back on Earth will be complicated, but it is something for which the team and the spacecraft are well prepared.
From the outset, OSIRIS-REX was designed not only to arrive and fly in training with Bennu – something that the spacecraft achieved on December 3 – but also to enter the orbit of the asteroid (scheduled for December 31, 2018) surface in some time in 2020.
That touchdown – more of a "fit" than a landing, as described by the OSIRIS-REx team – will allow the ship to retrieve a sample from the Bennu surface, store it in a sample return vessel and take the sample back the land. for further investigation.
But touching any surface requires a good understanding of the local terrain as well as the ability to see dangers that need to be avoided.
Bennu – before the launch of OSIRIS-REx – was thought to be less daring than is now understood thanks to the high resolution image of the asteroid, images that will only improve the closer the OSIRIS-REx reaches the asteroid.
Based on the first observations of OSIRIS-REx, we now know that the Bennu surface is a mixture of very rocky areas, full of pebbles, with few relatively smooth regions that do not have pebbles and that the number of stones on the surface is greater than expected.
This means that a very detailed survey of the Bennu surface will be required to determine a safe landing site for OSIRIS-REx and that the spacecraft will have to approach much closer to Bennu before scientific teams can accurately assess where a sample can be withdrawn. surface.
"Our initial data show that the team chose the correct asteroid as the target of the OSIRIS-REx mission. We have not yet discovered any insurmountable problems at Bennu, "said Dante Lauretta, principal investigator at OSIRIS-REx at the University of Arizona in Tucson.
To ensure that no problems occur during part of the 2020 sample and landing mission, scientists will pass 2019 collecting detailed surface observations before selecting a landing site in the same year.
Once the site is chosen, teams will perform various landing sequence simulations – leveraging NASA's experience on docking spacecrafts put together. Bennu's low mass and low gravitational field make OSIRIS-REx landing much more like docking than landing a craft on the moon's surface.
The OSIRIS-REx landing at Bennu is scheduled to occur sometime in 2020, as well as the actual collection of the sample to be returned to Earth.
If all goes according to plan, the sample return will return to Earth in September 2023.