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Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer, or OSIRIS-REx is the first NASA mission to collect the largest sample of material from asteroids. It has already collected a sample from asteroid Bennu. Now it is moving on to study asteroid Apophis in 2029.
Asteroids are debris leftover from when our Solar System first formed. Scientists hope that they can teach us about the history of our Solar System and answer some fundamental human questions. Where have we come from and what will be our destiny? As well as helping us understand asteroids which could impact the Earth.
Bennu is a carbonaceous asteroid, dating from around 4.5 billion years old, when the Solar System and our own planet were forming. The regolith (the layer of unconsolidated solid material covering the bedrock of a planet) is hoped to contain records of the early history of our Solar System. Bennu may harbour evidence of the molecular precursors to the origin of life and the Earth’s oceans. As well as this interesting history, Bennu is also considered to be one of the most potentially hazardous asteroids. Its probability of impacting the Earth during the 2100’s is relatively high. This mission is determining Bennu’s physical and chemical properties, vital for potential future impact mitigation missions.
Additionally, asteroids such as Bennu contain natural resources such as water, organics, and precious metals. Scientists hope the Bennu sample OSIRIS-REx dropped into the Utah desert will offer insight into whether asteroids colliding with Earth millions of years ago brought these and other key ingredients for life to Earth originally.
The main mission goal of OSIRIS was to return and analyze the largest sample of rock from the surface of an asteroid. The sample return has already been a success! The mission’s other goals included mapping the asteroid, and documenting the sample site. Additionally, it aimed to measure the orbit deviation caused by non-gravitational forces (the Yarkovsky effect) and compare observations at the asteroid to ground-based observations.
OSIRIS-REx launched on 8th September 2016. Then, on 3rd December 2018 the spacecraft arrived at the near-Earth asteroid Bennu where it spent a few years flying over the asteroid. OSIRIS-REx mapped the asteroid in detail. During this time the mission team searched for a safe sample-collection site. This was challenging since Bennu has an extremely rocky surface with hazardous boulders. A year later the sample site was selected, called “Nightingale”, situated in a northern crater 140m wide. This is thought to be a relatively young crater and the regolith freshly exposed giving a more pristine sample, and thus a clearer insight into Bennu’s history.
On 20th October 2020 OSIRIS-REx unfurled its robotic arm. It collected rocks and dust from the surface, through a maneuver known as “Touch-And-Go” or TAG.
After the sample collection phase, OSIRIS-REx carried out further flyover of Bennu, during which it imaged the asteroid for 5.9 hours, more than a full rotation of the asteroid. The mission flew very close to the surface of Bennu, only 2.1 miles. Images during this time show the aftermath of the mission encounter with Bennu. This last flyover was completed on the 7th April 2021. After which OSIRIS-REx started to drift away from the asteroid.
On the 10th May 2021 the spacecraft began its journey back to Earth where it delivered the sample capsule to Earth on 24th September 2023. The capsule was released into the Earth’s atmosphere and parachuted down to earth the Department of Defense’s Utah Test and Training Range, where the OSIRIS-REx team was waiting.
The mission is continuing now onto another asteroid Apophis. This mission has now been renamed OSIRIS-APEX (OSIRIS-Apophis Explorer). This asteroid is approximately 370 meters in diameter and will come within 20,000 miles of the Earth in 2029.
The initial results from the sample returned form Bennu are very exciting as they contain high levels of water and carbon, the building blocks of life as we know it.
The science cannister containing the sample, was covered in an abundance of extra asteroid dust. This was a lucky addition of 70.3 grams, but needed to be removed and cleaned to prevent contamination of the main sample. The main sample within the cannister was 51.2 grams. So the probe collected more than double its mission goal. This is a huge sample, especially when compared to the Japanese Aerospace Agencies Hayabusa2 mission, which only returned 5 grams of material from the asteroid Ryugu in December 2020.
Scientists and engineers have been working for years to develop specialized glove boxes and tools which enable the asteroid material to be kept and studied in pristine condition. The scientist carried out the analysis of the sample wearing clean suits to avoid any contamination of the sample.
During the quick look at the initial analysis of the sample, as well as discovering water and carbon they have also created a 3D model of one of the grains, demonstrating its diverse interior. This is just the tip of the iceberg of the exciting results which will follow over the next few years from over 200 scientists around the world working on these studies.
The NASA mission OSIRIS-REx collected the largest sample of material from an asteroid, Bennu, and returned it to Earth. The quick look studies of this sample are already exciting as they show that the asteroid contains high levels of water and carbon, the building blocks of life as we know it. Giving us tantalizing evidence that maybe an asteroid impact could be how water and carbon were delivered to Earth in the early Solar System allowing life to develop here.
This post was written by Dr Heather Campbell for Mission Astro.
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