One week after OSIRIS-REx caught up with the famous space rock that it had been chasing for 27 months, NASA has made a big announcement about its first asteroid-sampling mission.
Water On Asteroid Bennu
According to data picked up by two instruments on board NASA’s pioneering spacecraft, OSIRIS-REx has detected traces of water on the asteroid’ surface. More specifically, the probe uncovered that the 1,650-foot-wide space rock contains water-bearing clay minerals, which foster oxygen and hydrogen atoms that are bonded together in pairs called hydroxyls.
As NASA pointed out, the mission team suspects that these hydroxyl groups are widespread on the asteroid’s surface, which suggests that Bennu interacted with water sometime in its past.
As the Inquisitr previously reported, the near-Earth asteroid — located some 76 million miles away, between the orbits of Earth and Mars — is believed to have originated further out in the solar system. Scientists hypothesize that the carbon-rich asteroid broke off of a much bigger space rock nestled within the Asteroid Belt stretching between Mars and Jupiter and drifted closer to Earth.
Since Bennu has been deemed too small for liquid water to have ever existed on its surface, this new discovery suggests that the hydroxyls likely came from the asteroid’s parent body, which probably hosted liquid water at some point in its distant past.
While Bennu is too small to have free-flowing water or chunks of ice, our data suggest the asteroid’s larger parent body hosted liquid water in the distant past. It also means that mining water from asteroids like Bennu may be possible on future missions. #WelcomeToBennu #AGU18 pic.twitter.com/xMORSb7Woo— NASA's OSIRIS-REx (@OSIRISREx) December 10, 2018
Similar To Carbon-Rich, Water-Rich Meteorites
This revelation comes from data gathered by the probe’s two spectrometers, the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the OSIRIS-REx Thermal Emission Spectrometer (OTES). The two instruments took a good look at Bennu during the spacecraft’s asteroid approach phase — or the last stretch of 1.4 million miles covered by OSIRIS-REx before it finally parked within 12 miles of the space rock’s surface on December 3.
The OVIRS and OTES observations also revealed that Bennu gives off the same kind of light wavelength spectrum as carbonaceous chondrite meteorites — ancient meteorites that formed in the early days of the solar system and mashed together to create primitive asteroids. The great news is that this type of meteorites, which have often fallen on Earth, are known to contain both water and organic compounds — a boon for the OSIRIS-REx mission.
The OVIRS and OTES spectra of asteroid Bennu also mirror those of carbonaceous chondrite meteorites that contain both water and organic compounds – exactly the type of material we hope to return in 2023! #WelcomeToBennu #AGU18 pic.twitter.com/3Tf56Ua9I1— NASA's OSIRIS-REx (@OSIRISREx) December 10, 2018
“The presence of hydrated minerals across the asteroid confirms that Bennu, a remnant from early in the formation of the solar system, is an excellent specimen for the OSIRIS-REx mission to study the composition of primitive volatiles and organics,” said Amy Simon, OVIRS deputy instrument scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “When samples of this material are returned by the mission to Earth in 2023, scientists will receive a treasure trove of new information about the history and evolution of our solar system.”
Clearest Image Of Bennu
While OVIRS and OTES were busy scanning the asteroid to uncover more clues about its composition, another instrument on board the OSIRIS-REx spacecraft was preoccupied with Bennu’s look.
The OSIRIS-REx PolyCam took advantage of the close proximity to this mysterious space rock and snapped 12 close-up photos from a distance of about 15 miles away. The snapshots, taken on December 2 — one day before the probe’s highly anticipated rendezvous with Bennu — were used to create a mosaic image which provides the clearest view yet of the diamond-shaped asteroid.
According to the mission’s team, this is “the highest resolution imagery of asteroid Bennu so far.”
“Each pixel represents about 13 inches (33 cm) on Bennu’s surface,” the OSIRIS-REx team explained via Twitter.
Looking For A Landing Spot
This close-up view of asteroid Bennu enabled the scientists to take a better look at some of the space rock’s surface features. The new photos unveiled that the asteroid’s surface is strewn with a lot more boulders than previously estimated.
On Dec. 2 at a range of 15 miles (24 km), PolyCam snapped this image showing three different boulder features on Bennu, each circled in white and then magnified. ???? ????Their widths are about 52 feet (16 m), 115 feet (35 m), and 102 feet (31 m), respectively. #WelcomeToBennu #AGU18 pic.twitter.com/80XgulZiT1— NASA's OSIRIS-REx (@OSIRISREx) December 10, 2018
In fact, according to NASA, “Bennu’s surface material is a mix of very rocky, boulder-filled regions and a few relatively smooth regions that lack boulders.”
The OSIRIS-REx mission controllers will continue to monitor the asteroid’s rugged terrain in order to find the perfect spot for a touch-and-go landing, so that the spacecraft can eventually swoop down and gather samples from the carbon-rich, water-rich space rock.
My team is keeping an eye out for areas on Bennu with loose rock and dirt that are potential places to collect a sample. ???? On Dec. 2, PolyCam imaged this crater, which is about 66 feet (20 m) across and appears to have loose material in the bottom. #WelcomeToBennu #AGU18 pic.twitter.com/LtgmnC4sSz— NASA's OSIRIS-REx (@OSIRISREx) December 10, 2018
3D Shape Model Of Asteroid Bennu
The entire OSIRIS-REx mission was planned based on a shape model of the unfamiliar space rock, developed in 2013 with the help of ground-based telescopes. This close proximity to Bennu has finally created the opportunity for the spacecraft to image the asteroid with the PolyCam and the OSIRIS-REx Camera Suite (OCAMS) to verify those initial projections.
The fresh, on-site observations have yielded a 3D shape model of asteroid Bennu, which confirms the scientists’ original predictions about the space rock’s diameter, rotation rate, inclination, and overall shape.
The only notable difference between the old model and the new one has to do with the estimated size of a large boulder spotted near Bennu’s south pole. The initial model indicated that the boulder was at least 33 feet tall. However, these latest measurements found it to be 164 feet high and 180 feet wide.
☄️Beautiful new shape model of Bennu? ✅— NASA's OSIRIS-REx (@OSIRISREx) December 10, 2018
???? Water bound up in the clay minerals on the asteroid's surface? ✅
???? Awesome new imagery showing its rugged terrain? ✅
Read more about the discoveries my team has made about Bennu so far: https://t.co/In5Pow2lgt #WelcomeToBennu #AGU18 pic.twitter.com/s9s1uTbzo6
“Our initial data show that the team picked the right asteroid as the target of the OSIRIS-REx mission. We have not discovered any insurmountable issues at Bennu so far,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. “The spacecraft is healthy and the science instruments are working better than required. It is time now for our adventure to begin.”
Going Into Orbit
The OSIRIS-REx spacecraft will continue its planned flyby’s of Bennu’s poles and equator until December 31, when the probe makes its first dive into the asteroid’s orbit. By that time, mission controllers will have gained enough data on the asteroid’s mass and gravitational pull to plan the spacecraft’s insertion into orbit.
Once this first orbital phase kicks in, OSIRIS-REx will circle the asteroid at a range between 0.9 miles and 1.24 miles (2.0 km) from its center, thereby “setting new records for the smallest body ever orbited by a spacecraft and the closest orbit of a planetary body by any spacecraft.”
OSIRIS-REx will orbit Bennu until mid-February 2019, then move on to another series of scheduled flybys marking the next survey phase of the asteroid. The spacecraft is slated to grab the asteroid samples in July 2020 and head back home on March 2021.
Early data from Bennu show that I’m exactly where I need to be to achieve our science goals. The biggest surprise so far is the number and size of boulders on Bennu’s surface, but my team is more than ready to tackle that challenge. Let the adventure begin! #WelcomeToBennu #AGU18 pic.twitter.com/z6TCHaBpM2— NASA's OSIRIS-REx (@OSIRISREx) December 10, 2018