In October 2020, a van-sized robotic spacecraft briefly touched down on the floor of Bennu, a 525-metre-wide asteroid 320 million kilometres from Earth.
As a part of NASA’s OSIRIS-REx mission, the spacecraft not solely spent two years orbiting and imaging the asteroid, it additionally collected a valuable pattern of mud and small rocks from Bennu’s rubbly floor.
In September 2023, a capsule containing the pristine asteroid pattern returned to Earth, touchdown within the Utah desert in the USA.
Since then, a global group of scientists – of which we’re members – have been busy finding out the roughly 120 grams of fabric collected from Bennu.
Our findings are revealed in two new papers printed in Nature and Nature Astronomy right this moment. They point out that water could have as soon as been current on Bennu’s mum or dad physique, and supply new insights into the chemistry of the early Photo voltaic System.
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Pristine remnants of rocks from deep time
Asteroids are fragmentary remnants of pre-existing mum or dad our bodies from early in our Photo voltaic System’s historical past which have since been destroyed by collisions with different objects. They orbit the Solar and are available many alternative shapes, sizes and chemical compositions.
Asteroid Bennu was focused for the OSIRIS-REx mission as a result of distant sensing observations from Earth indicated it as a B-type asteroid.
These asteroids are wealthy in carbon and hydrated clay minerals, presumably sharing similarities to essentially the most primitive group of meteorites on Earth, often called carbonaceous chondrites.
Not like meteorite samples, samples collected from asteroids haven’t been bodily or chemically modified by Earth’s environment and biosphere. This permits us to sort out key questions concerning the evolution of the early Photo voltaic System, planet formation, and the substances for all times.
One other purpose of the OSIRIS-REx mission is to hyperlink findings from samples within the laboratory to these from distant sensing strategies. This helps us corroborate astronomical observations of asteroids to enhance our surveys of the Photo voltaic System.
Tiny crystals of salt minerals
To stop contamination, the sealed capsule containing the pattern was saved and dealt with in an enormous glass field when it was returned to Earth.
This tank had rubber gloves feeding into it from the aspect so scientists might deal with the samples with out instantly touching them. It had additionally been purged with nitrogen to maintain out moisture and oxygen from Earth’s environment.
Once we analysed the inside of Bennu’s mud particles, we had been shocked to search out tiny crystals of the salt minerals often called halite and sylvite.
This was a breakthrough discovery.
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Halite is extraordinarily uncommon in meteorites. It has solely been present in three out of a whole lot of 1000’s of identified meteorites on Earth. We additionally know that halite is extremely soluble. It may well degrade shortly when uncovered to air or water on Earth.
Different members of the OSIRIS-REx pattern evaluation group recognized quite a lot of different salt minerals within the Bennu pattern. These included sodium carbonates, phosphates, sulphates and fluorides.
These minerals can type by the evaporation of brines – just like deposits that type in Earth’s salt lakes.
By evaluating these outcomes with the chemical make-up of salt lakes on Earth, an image started to emerge of brines evaporating on the mum or dad physique of asteroid Bennu, abandoning salts as proof.
A wide range of natural compounds
This discovery supplies a brand new perception into water exercise throughout the earliest occasions in our Photo voltaic System. However the presence of salt minerals is critical for an additional motive.
On Earth, these minerals are a catalyst for the formation of natural compounds corresponding to nucleobases and nucleosides – the prebiotic constructing blocks of terrestrial biology.
And certainly, in a separate evaluation of the Bennu pattern, different colleagues on the OSIRIS-REx mission recognized all kinds of natural compounds current on the carbon- and nitrogen-rich asteroid.
These compounds embrace 14 of the 20 amino acids we additionally discover in Earth’s organic processes. Additionally they embrace a number of amino acids which can be absent in identified biology, ammonia, and all 5 nucleobases present in RNA and DNA.
Though no life was detected on Bennu, the 2 new research present {that a} briny, carbon-rich atmosphere on Bennu’s mum or dad physique was appropriate for assembling the constructing blocks of life.
Ongoing investigations
The findings from returned samples of asteroid Bennu could present researchers perception into what occurs on distant icy our bodies in our Photo voltaic System.
A few of these our bodies embrace Saturn‘s moon Enceladus and the dwarf planet Ceres within the asteroid belt between Mars and Jupiter.
Each Enceladus and Ceres have subsurface brine oceans. Might they presumably harbour life?
We’re persevering with to analyze Bennu utilizing the pristine samples collected again in 2020. We’re at present researching the timing of the Bennu mum or dad physique breakup occasion and searching for proof of impacts recorded by numerous minerals within the samples.
The authors of this text acknowledge the contribution of the next folks to the analysis at Curtin College: Fred Jourdan, Steven Reddy, David Saxey, Celia Mayers, and Xiao Solar, in addition to your entire OSIRIS-REx group.
Nick Timms, Affiliate Professor, College of Earth and Planetary Sciences, Curtin College; Phil Bland, Director, Binar House Program, Curtin College, and William Rickard, Affiliate Professor, College of Science and Engineering, Curtin College
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