After an almost two-year chase, the OSIRIS-REx probe from NASA finally has its asteroid target in sight.
OSIRIS-REx, which was launched in September 2016, captured its first images of the 1,650-meter-wide (500-meter) space stone Bennu, as NASA officials announced today (24 August).
The spacecraft snapped the photos on August 17 – the same day it officially started its last approach to Bennu – from a distance of 1.4 million miles (2.2 million kilometers). [OSIRIS-REx: NASA’s Asteroid Sample-Return Mission in Pictures]
"I can not explain enough how much it meant to the team," OSIRIS-REx principal investigator Dante Lauretta, of the University of Arizona, told reporters today. "I know that Bennu is just a bright spot here, but many of us have been working for years and years to bring down this first image and it really is the beginning of the great scientific expedition that OSIRIS-REx is."
– Dante Lauretta (@DSLauretta) August 24, 2018
Bennu will look further and further into the crosshairs of OSIRIS-REx in the coming months. If everything goes according to plan, the probe will arrive at the space rock on December 3rd. He will perform a series of close flybys, take measurements that determine the mass of the asteroid and then circle Bennu on December 31st.
That will not be a sinecure.
"It is the size and small mass of Bennu that makes the navigation challenges on this mission unprecedented, really," said Michael Moreau, OSIRIS-REx system manager for flight dynamics at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "On December 31, when we orbit the earth, it will become the smallest planetary object ever to be pumped around by a spacecraft."
By way of comparison, the asteroid Ryugu, which the Japanese spaceship Hayabusa2 has been in orbit since the end of June, is about twice as wide as Bennu and about six times the volume, Lauretta said. (Intriguingly, Bennu seems to share Ryugu's strange "spin-top" shape, he added.)
OSIRIS-REx will examine Bennu for a while and then rinse down to get a significant sample of the rock surface in the middle of 2020. The spacecraft will leave Bennu in March 2021 and the sample, packed in a special return capsule, Parachute to earth in September 2023.
Bennu is a carbon-rich asteroid, the type that, according to many scientists, the chemical building blocks of life, along with a lot of water, delivered to our planet through shocks a long time ago. So, analyzes of the returned sample in laboratories around the world can reveal important insights about the early solar system and the origins of life on Earth, members of the Mission Team have said.
But the mission of $ 800 million will also investigate a number of other questions, as the full name suggests. (OSIRIS-REx stands for "Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer.")
For example, Bennu is a potentially dangerous asteroid; there is a small chance that the rock can hit the earth by the end of the 22nd century. The observations of OSIRIS-REx should help scientists better understand the forces that form asteroids paths through space, and therefore better predict where, exactly, dangerous stones are going, Lauretta said.
And then there is the aspect "resource". Bennu probably contains a lot of water, where space companies like Planetary Resources are very interested. The idea is to split asteroid water into its constituent hydrogen and oxygen – the main components of rocket fuel – and then use this material to set up propellant deposits from the earth. Voyaging spaceships can supplement their tanks at such service stations, making exploring the space cheaper and more efficient.
OSIRIS-REx's work will reveal how resource-rich Bennu really is. And the precision maneuvers of the probe around the rock will show vital navigational skills, said Lauretta, who serves on the Planetary Resources Scientific Advisory Board.
"Every asteroid mining must come to understand how that's done," he said.
OSIRIS-REx is not the only asteroid sampling mission currently under way. Hayabusa2 will take samples of Ryugu relatively quickly, perhaps already in October; this material is planned to come to earth by the end of 2020.
The OSIRIS-REx and Hayabusa2 teams have worked together and will continue to do so, Lauretta said.
"All information about the interaction between the spacecraft and the asteroid surface of the Hayabusa2 will also be important for OSIRIS-REx as we are finalizing the time [sampling] maneuvers for our mission, "he said.