NASA spacecraft to examine ‘the mess it made’ on asteroid Bennu

6 Apr 2021

Artist’s concept shows the planned flight path of NASA’s OSIRIS-REx during its final flyby of asteroid Bennu, which is scheduled for 7 April. Image: NASA/Goddard/University of Arizona

The OSIRIS-REx mission will get one last close encounter with Bennu as it performs a final flyover this week.

NASA has said that its OSIRIS-REx mission is on the brink of discovering “the mess it made” on a distant asteroid.

The spacecraft briefly landed on the surface of Bennu last October to collect dust and rocks in a ‘touch-and-go’ event. But NASA has said that the surface of the asteroid was “significantly disturbed” by this landing.

Now, OSIRIS-REx will get one last close look at Bennu as it performs a final flyover to capture images of the asteroid’s surface. Tomorrow (7 April), the spacecraft is scheduled to observe Bennu from a distance of around 3.7km, which is the closest it has been since the October sampling event.

The OSIRIS-REx team added this last flyover to learn how the spacecraft’s contact with the surface may have altered the sample site and the region surrounding it.

NASA said that during touchdown, the spacecraft’s sampling head sunk 48.8cm into the asteroid’s surface and its thrusters mobilised a substantial amount of surface material during the back-away burn. Because Bennu’s gravity is so weak, NASA added, these various forces had a “dramatic effect” on the sample site.

OSIRIS-REx will image the asteroid for a period of nearly six hours, getting high-resolution images that can be sent back to Earth and compared with previous imagery from 2019.

The spacecraft will remain in Bennu’s vicinity until 10 May, when it will begin its two-year journey back to Earth. As it approaches, it will jettison a capsule that contains the rocks and dust collected from Bennu.

These samples, which are expected to land in Utah in September 2023, will enable scientists to study the formation of our solar system.

OSIRIS-REx was launched in September 2016 and finally arrived in Bennu’s orbit on 3 December 2018. Soon after its arrival, the spacecraft helped confirm the discovery of water beneath the asteroid’s surface.

Sarah Harford was sub-editor of Silicon Republic