OSIRIS-REx, NASA’s first asteroid sample delivery mission, is set to return pristine material from asteroid Bennu on September 24, 2023. Bennu was earlier known as 1999 RQ36. OSIRIS-REx stands for Origins, Spectral Interpretation, Resource Identification and Security — Regolith Explorer. After OSIRIS-REx enters the Earth’s atmosphere, it will release the sample return capsule which will make a landing in the Utah desert.
OSIRIS-REx was launched on September 8, 2016, and reached Bennu in December 2018.
OSIRIS-REx collected rocks and dust from Bennu, a near-Earth asteroid, in 2020, after mapping the asteroid for two years.
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On May 10, 2021, OSIRIS-REx departed Bennu’s vicinity. Bennu has spent seven years in space.
It is important to study these materials because they might provide insights into what the universe was like when the Sun and planets of the solar system were forming 4.5 billion years ago.
OSIRIS-REX’s sample return will be a major milestone for the US because this will mark the country’s first-ever mission to return an asteroid sample to Earth.
How will OSIRIS-REx’s asteroid sample be recovered?
Delivering the asteroid sample to Earth is a challenging mission, because OSIRIS-REx will have to protect the sample from heat, vibrations and earthly contaminations.
OSIRIS-REx is expected to bring asteroid material of mass 250 grams ± 101 grams to the Earth. This is the largest asteroid sample ever received on the Earth.
The sample return capsule is scheduled to land in the Utah western desert on September 24, at 10:55 am EDT (8:25 pm IST). According to NASA, the sample return capsule will land within a 58 kilometre × 14 kilometre ellipse located inside the US Department of Defense property.
Since the capsule has no global positioning system (GPS) or beacon that will allow it to be tracked, NASA and the US Air Force will use tracking cameras on the ground and in the air to locate the sample capsule.
After touchdown, the sample return capsule will be secured and taken to a portable clean room. Next, the heat shield, back shell and other components will be removed, to prepare the sample canister for transport to Houston.
Recovery helicopters will fly the capsule to the temporary clean room at the Dugway Proving Ground, a US Army Facility in the Utah Test and Training Range.
The asteroid return sample will be transported to NASA’s Johnson Space Center on September 25.
What will happen after the OSIRIS-REx asteroid sample is retrieved?
A new laboratory for the material has been built at NASA’s Johnson Space Center in Houston. Over the next six months, the OSIRIS-REx team will practise and refine the procedures needed to recover the asteroid sample in the Utah desert and transport it to the new laboratory.
At the new laboratory, scientists will unpack the sample, distribute up to a quarter of it to the OSIRIS-REx science team around the world for analysis, and curate the rest for other scientists to study.
NASA will release a sample catalogue about six months after the sample return takes place. Scientists will also be allowed to access samples from Bennu to conduct their research.
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A sample analysis team of over 200 members from more than 35 globally distributed institutions will receive portions of samples from Bennu provided by NASA’s Johnson Space Center.
NASA teams will have access to about 25 per cent of the returned sample from Bennu. The Canadian Space Agency (CSA) will receive four per cent of the total returned sample. The CSA contributed the OSIRIS-REx Laser Altimeter (OLA) onboard the spacecraft.
The Japan Aerospace Exploration Agency (JAXA) will receive 0.5 per cent of the total returned sample.
Which other missions have brought back asteroid samples to the Earth?
Previous missions that brought asteroid samples back to Earth were the JAXA Hayabusa and Hayabusa2 missions. Hayabusa returned samples from the asteroid Itokawa, and Hayabusa2 returned five grams of asteroid samples from Ryugu in November 2021. About 10 per cent of these samples were shared with NASA.
What will happen to OSIRIS-REx after it has returned samples from Bennu to Earth?
OSIRIS-REx, which is a robotic mission, will not end its journey after returning samples from Bennu. The spacecraft will fire its engines about 20 minutes after returning the sample on September 24, and set off on a new mission to explore asteroid Apophis. After this, the name of OSIRIS-REx will be changed to OSIRIS-Apophis Explorer, or OSIRIS-APEX.
The spacecraft will take six years to reach Apophis. In 2029, the asteroid will also make its closest approach to Earth.
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Why NASA chose Bennu as the target asteroid for OSIRIS-REx
Scientists wish to understand if asteroids played a role in delivering molecular precursors to life to Earth’s surface over four billion years. For this, a pristine sample from space, free from terrestrial contaminants, is required.
There are about 10 reasons why NASA chose Bennu as the target asteroid for OSIRIS-REx. These reasons include Bennu’s close proximity to the Earth, the asteroid’s size, its age, it being a well-preserved asteroid, it containing clues to the origin of life on the Earth, it containing valuable materials, it helping scientists understand other asteroids, it helping astronomers understand a solar phenomenon, it keeping other asteroids at bay, and it being a gift that will keep on giving.
Bennu makes its closest approach to the Earth every six years, and has a diameter of 492 metres, which makes it approachable and rich in regolith.
Since Bennu is a leftover fragment from the formation of the solar system, its mineral fragments could be older than the solar system, and can provide information about dying stars that formed the Sun and the solar system’s planets 4.6 billion years ago.
Bennu has been preserved in the vacuum of space, and hence, is a time capsule from the early solar system.
The asteroid is rich in carbon, which is the building block of organic materials. Since organic materials are present in all life forms, analysing Bennu’s samples may provide insights into the origin of life on the Earth.
Also, Bennu is believed to be rich in iron, aluminium, and platinum, and may contain water. Scientists can experiment ways to extract hydrogen and oxygen from the water locked up in the minerals, and learn how to make rocket fuel. In this way, in the future, asteroids may serve as fuel stations for space exploration missions to Mars and beyond.
Since Bennu was discovered in 1999, the asteroid’s orbit has drifted about 280 metres per year towards the Sun due to a phenomenon called the Yarkovsky effect. This is a phenomenon in which sunlight warms one side of a small, dark asteroid, and then radiates heat off the asteroid as it rotates. Due to the heat energy, the asteroid is thrust away from the Sun, or towards the Sun, depending on whether the asteroid has a prograde or a retrograde spin.
Bennu has a retrograde spin, which means that it rotates in the direction opposite to the direction of its orbit around Earth. As a result, Bennu is being thrust towards the Sun.
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Understanding the Yarkovsky effect is important because it will allow scientists to estimate when a particular asteroid will come close to the Earth. For instance, Bennu is expected to come closer to the Earth than the Moon in 2135.
Such calculations will allow scientists to devise technologies to deflect asteroids, if need be.
Finally, analysing the samples returned from Bennu will be like opening a treasure trove of cosmic mysteries.
When and how to watch the landing of the sample return capsule
One can watch the landing of OSIRIS-REx’s sample return capsule in the Utah desert on the official YouTube channel of NASA, on NASA Television, or on the space agency’s official website.
The livestream will begin at 7:30 pm IST on September 24.