Only a few miles from the glamor of France’s famed Riviera lies a little-known French national laboratory in large part used to conduct material analysis for next generation semiconductors. But a team at the Valbonne lab, the CNRS-CRHEA (Research Center on Hetero-Epitaxy and its Applications) is now analyzing 100 milligrams of tiny grains from NASA’s OSIRIS-REx sample return mission to the asteroid Bennu.
In fact, the Valbonne sample contains some surprises which will be announced by NASA as early as next week, Guy Libourel, a cosmochemist at the Observatoire de la Cote D’Azur in Nice and a OSIRIS-REx co-principal investigator, told me here. This object is very pristine because since it formed, it didn’t evolve, didn’t transform, he says.
The sample, safely encased in nitrogen since its retrieval by OSIRIS-REx dates back to the earliest beginnings of our solar system’s protosolar nebula, some 4.567 billion years ago.
The French team has used a technique known as hetero-epitaxy to analyze various crystalline substrates to identify its mineralogy. Among other things, thus far they’ve identified iron oxide, lot of sulfides; the elements of manganese and magnesium, as well as silicate serpentines that point to the fact that Bennu was once rife with water.
Some of the mineral fragments inside Bennu could be older than the solar system itself, says NASA.
These microscopic grains of dust could be the same ones that spewed from dying stars and eventually coalesced to make the sun and its planets nearly 4.6 billion years ago, notes NASA.
What makes the French lab in Valbonne unique is that it is using a newly improvised method of cathodoluminescence. That’s a process by which beams of electrons inside a scanning electron microscope strike luminescent materials and generate either an image or a spectrum, Marc Portail, a French CNRS research engineer, told me at the lab.
Much of the Bennu sample material consists of silicate crystals capable of emitting light when bombarded with a high incidence of electron beams. By analyzing the luminescence from both the images and the spectra as the beams strike the sample, researchers learn details about the crystalline distribution of the sample’s minerals.
In short, the scanning electron microscope allows us to have a very detailed map of these tiny grains to detail the mineralogy, says Libourel.
What’s So Special About These Bennu Samples?
Meteorites that survive the violent, fiery decent to our planet’s surface, get contaminated when they land in the dirt, sand, or snow, says nasa. Some even get hammered by the elements, like rain and snow, for hundreds or thousands of years. Such events change the chemistry of meteorites, obscuring their ancient records, NASA notes.
But the samples inside the spacecraft that landed in the Utah desert this past September were wholly protected from the ravages of crossing Earth’s atmosphere from the get-go. Unlike meteorites, NASA’s samples were carefully encased in chemically inert nitrogen to avoid the destructive influence of oxygen in our own atmosphere.
NASA picked Bennu as its target because it’s rich in carbon and could contain the chemical building blocks of life as we know it. The asteroid also has a minute chance of impacting Earth early in the next century. If so, Nasa says that studying Bennu could also help us learn how to be prepare to defend ourselves against such a potential impact.
It’s pretty obvious that Bennu was part of a larger body at one point, so what we are observing now is a chunk of big boulders, says Libourel.
But the Bennu samples may arguably be most useful as long term chemical mile markers for future planetary scientists.
The composition and the mineralogy of asteroids observed from Earth (using telescopes) is only assessed based on their optical spectrum measuring the sunlight they reflect, says Libourel.
To be able to analyze the composition and mineralogy of Bennu in detail is a unique opportunity to learn the chemical ground truth about such a celestial object. As such, Bennu will forever remain a reference, says Libourel.
And here in Valbonne, we will have the sample until the end of next year, says Libourel.
What Excites Libourel Most About The Samples?
During my career as a cosmochemist, I have often analyzed meteorites, says Libourel. But these samples, he says, are preserved in nitrogen which gives us the ability to analyze their primitive character as if we were some 300 million kms away on Bennu.
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Dr. Thomas Hughes is a UK-based scientist and science communicator who makes complex topics accessible to readers. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
