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 treasured 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 US.
Since then, a world group of scientists – of which we’re members – have been busy learning the roughly 120 grams of fabric collected from Bennu.
Our findings are revealed in two new papers printed in Nature and Nature Astronomy at this time. They point out that water could have as soon as been current on Bennu’s dad or mum 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 dad or mum 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 various 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 known as carbonaceous chondrites.
In contrast to 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 components 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 methods. This helps us corroborate astronomical observations of asteroids to enhance our surveys of the Photo voltaic System.
Tiny crystals of salt minerals
To forestall 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 facet 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.
After we analysed the inside of Bennu’s mud particles, we had been shocked to seek out tiny crystals of the salt minerals often known as 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 bunch of hundreds of recognized meteorites on Earth. We additionally know that halite is very soluble. It may well degrade rapidly when uncovered to air or water on Earth.
Different members of the OSIRIS-REx pattern evaluation group recognized a wide range of different salt minerals within the Bennu pattern. These included sodium carbonates, phosphates, sulphates and fluorides.
These minerals can kind by the evaporation of brines – just like deposits that kind 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 dad or mum physique of asteroid Bennu, forsaking salts as proof.
A wide range of natural compounds
This discovery offers a brand new perception into water exercise in the course of the earliest occasions in our Photo voltaic System. However the presence of salt minerals is critical for an additional purpose.
On Earth, these minerals are a catalyst for the formation of natural compounds reminiscent of 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. In addition they embrace a number of amino acids which might be absent in recognized biology, ammonia, and all 5 nucleobases present in RNA and DNA.
Despite the fact that no life was detected on Bennu, the 2 new research present {that a} briny, carbon-rich atmosphere on Bennu’s dad or mum 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. May they presumably harbour life?
We’re persevering with to analyze Bennu utilizing the pristine samples collected again in 2020. We’re at the moment researching the timing of the Bennu dad or mum physique breakup occasion and on the lookout 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, School of Science and Engineering, Curtin College
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