The probe was launched on 8 September 2016 on top of a United Launch Alliance Atlas V 411 from Cape Canaveral in Florida and immediately headed toward the near-Earth asteroid formally known as 1999 RQ36, now simply known as 101955 Bennu, or Bennu. Upon arrival at Bennu in December 2018, OSIRIS-REx began a 2-year mission to orbit the asteroid and undertake detailed surface mapping to identify the perfect spot to touch down and collect a surface sample, a feat it achieved successfully on 20 October 2020.
Following the successful collection of surface deposits, the spacecraft fired its engines in May 2021 and began the journey back to Earth. The craft successfully delivered its precious cargo of samples on 24 September 2023.
Watch the moment of surface collection, and the joy from the scientists and engineers, via this video from NASA.
Why did NASA choose Bennu?
Bennu is classified as a B-type asteroid and is one of the less common carbonaceous asteroids created at the dawn of the solar system. The LINER Project discovered the asteroid on 11 September 1999, and in common with other asteroids of this type, it was determined to be relatively primitive and rocky, without any evidence of any geological change since it was formed. This gave scientists the ideal target to collect a surface sample containing material formed at the birth of our solar system. Bennu was also identified as having high quantities of pristine carbon, which mirrors the creation of our own planet and an essential building block for carbon-based life.
There is also a more sinister reason to gain more information about the structural makeup of asteroid Bennu, as it is one of the asteroids that are considered potentially hazardous to us due to their near-Earth orbits. Bennu currently has the highest cumulative risk rating on the Palermo Technical Impact Hazard Scale, with a cumulative 1-in-1,750 chance of impacting Earth between 2178 and 2290, with the most significant risk being on 24 September 2182. Therefore, knowing more about how this object is constructed may give scientists and engineers of the future important information on how to disrupt or destroy the asteroid if necessary.
What have we learned from the samples so far?
First, the device used to collect the sample from Bennu was much more successful than planned, making the process of accessing all the stored samples much slower than anticipated. Just opening the cover of the science container, which is not where the samples are stored, showed an abundance of Bennu surface material on the outside of the container. This was an unexpected bonus; OSIRIS-REx, as a mission, was due to collect 60 grams of surface material to be considered a success; estimates already suggest it has collected over three times that amount.
Material from outside the bulk collection storage underwent a “quick look analysis” using a range of high-end scientific devices, including a scanning electron microscope, infrared analysis, and x-ray diffraction to help understand the molecular make up of the material. Early results have shown an abundance of carbon and water, which gives a tantalizing insight into where the water on our planet may have initially come from – possibly the Earth was made with its water from the start, and not necessarily having it added afterward by subsequent impact events.
NASA is encouraged by the early results and is already looking forward to what the samples may tell us about the history of our planet and our place upon it. Speaking at the media unveiling of the initial results, NASA Administrator Bill Nelson said,
“The OSIRIS-REx sample is the biggest carbon-rich asteroid sample ever delivered to Earth and will help scientists investigate the origins of life on our own planet for generations to come.”
“Almost everything we do at NASA seeks to answer questions about who we are and where we come from. NASA missions like OSIRIS-REx will improve our understanding of asteroids that could threaten Earth while giving us a glimpse into what lies beyond. The sample has made it back to Earth, but there is still so much science to come – science like we’ve never seen before.”
“Almost everything we do at NASA seeks to answer questions about who we are and where we come from. NASA missions like OSIRIS-REx will improve our understanding of asteroids that could threaten Earth while giving us a glimpse into what lies beyond. The sample has made it back to Earth, but there is still so much science to come – science like we’ve never seen before.”
After returning to Earth and releasing its precious cargo of Bennu surface material, the mission for the OSIRIS-REx spacecraft was extended to include a close encounter and long-duration rendezvous with one of the most infamous asteroids of them all, 99942 Apophis.
On 13 April 2029, asteroid Apophis will make a very close approach to Earth, passing approximately 31,600km (19,600 miles) above the surface. This is incredibly close, ten times closer than the orbit of The Moon and within the orbits of geostationary satellites.
It was this close encounter, combined with the asteroid's size, which initially had this approach categorized as a level 4 on the Torino Scale, a scale used by scientists to measure the impact hazards of near-Earth objects. Whilst detailed orbital mapping has now shown there is zero possibility of an impact in 2029, the initial probability rose to a staggering 2.7% chance, which in astronomical terms, was very significant indeed.
OSIRIS REx will rendezvous with Apophis a few days after the close approach, study the asteroid for 18 months, perform a manoeuvre like the one it did at Bennu, and use its thrusters to clear an area on the surface to allow sub-surface analysis.
In recognition of its new mission, OSIRIS REx has been renamed OSIRIS-APEX, short for OSIRIS Apophis Explorer.
What did you think about this article? What do you think scientists might learn from studying the surface of objects like asteroids?
WRITTEN BY WoorLord
EDITED BY WoorLord
IMAGES SOURCED FROM NASA - NASA
