What’s next for OSIRIS-REx after historic landing on Bennu?

21 Oct 2020

Illustration of NASA’s OSIRIS-REx mission about to touch the surface of asteroid Bennu. Image: NASA/Goddard/University of Arizona

NASA’s OSIRIS-REx spacecraft briefly touched down on the surface of asteroid Bennu, with the goal of collecting samples for scientists to study.

NASA is celebrating the successful – albeit brief – landing of one of its spacecrafts on the surface of an asteroid yesterday (20 October). The Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) unfurled its robotic arm 321 million km from Earth on the surface of Bennu to collect dust and pebbles in what was called a ‘touch-and-go’ (TAG) event.

If all goes according to plan, the samples collected by the craft will be returned to Earth in 2023 for scientists to examine. This could potentially offer a window into the early solar system as it was first taking shape billions of years ago and offer more clues to what could have helped seed life on Earth.

By 30 October, NASA’s scientists will determine whether the spacecraft has collected enough of a sample. If successful, OSIRIS-REx will be commanded to begin stowing its precious cargo to begin its journey back to Earth in March 2021. If not, OSIRIS-REx will prepare for another attempt on 12 January.

NASA’s administrator, Jim Bridenstine, said that if the collection event was successful, it means it will be “possible to hold a piece of the most ancient solar system in our hands”.

Brush with ‘Mount Doom’

The landing began at 6.50pm Irish time and included a treacherous 11-minute coast past a boulder the size of a two-storey building, nicknamed ‘Mount Doom’, to touch down in a clear spot in a crater on Bennu’s northern hemisphere. All of the TAG manoeuvre was done autonomously, NASA said.

Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, said this was “an incredible feat”.

“A piece of primordial rock that has witnessed our solar system’s entire history may now be ready to come home for generations of scientific discovery, and we can’t wait to see what comes next,” he said.

The OSIRIS-REx team hopes to collect at least 60g of dust and pebbles from Bennu to send back to Earth. To help determine this, it will take pictures of the collector using what it referred to as a ‘SamCam’. Engineers will also attempt to snap photos that could, given the right lighting conditions, show the inside of the collector head so engineers can look for evidence of sample inside of it.

Another method of finding out how much sample was collected will involve extending the collector out to the side of the spacecraft and slowly spinning the spacecraft about an axis perpendicular to the arm.

This is similar to a person spinning with one arm extended while holding a string with a ball attached to the end. Just like how a person can sense the mass of the ball from the tension in the string, the researchers can tell how much space debris is in the collector.

The spacecraft was launched on 8 September 2016 and finally arrived in Bennu’s orbit on 3 December 2018. Soon after, the spacecraft helped confirm the discovery of water beneath the asteroid’s surface.

Colm Gorey was a senior journalist with Silicon Republic