Samples returned from the asteroid Ryugu are older than the planets and contain building blocks of life

Ryugu soil samples
Backscattered electron (BSE) image of Ryugu sample A0058-C1001 (12). The black space in the figure is a pore. Yokoyama et al Science 2022
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Hayabusa2 a Japan Aerospace Exploration Agency (JAXA) mission, returned soil samples from asteroid Ryugu, which have now been analysed to reveal that they are some of the most primitive ever studied here on Earth. No other material from space that we have had the luck to observe and analyse has ever been so primitive. Because those materials had been lying around on our planet for so long, they are no longer pristine – the sample from Ryugu is. Furthermore, these samples also contain amino acids, which are the building blocks of life.

According to the analysis published in the June 9 issue of the journal Science, Ryugu (a diamond-shaped asteroid 200 million miles from Earth), contains some of the most primitive material ever analysed in our laboratories on Earth, dating from just around five million years after the solar system started to form. Basically, Ryugu is made up of the same stuff as the planets and because these samples are so old, they will help scientists understand the beginning of our solar system.

Analysis of Ryugu soil samples Yokoyama et al, Science 2022

(A) Backscattered electron (BSE) image of Ryugu sample A0058-C1001 (12). The black space in the figure is a pore. (B) Combined elemental map of the same sample, with characteristic X-rays of Ca Kα, Fe Kα, and S Kα lines assigned to RGB color channels as indicated in the legend. Carbonate (dolomite), sulfide (pyrrhotite) and iron-oxide (magnetite) minerals are embedded in a matrix of phyllosilicates, and in some cases precipitated in small veins. The sulfide texture is similar to that in the ungrouped chondrite Flensburg (52). (C) Ternary diagram between Fe, Mg, and Si+Al showing bulk chemical compositions of phyllosilicates in A0058-C1001. Black lines are compositions of solid solution for serpentine and saponite. Each open red circle shows bulk chemical composition of phyllosilicates measured in various locations of panels A and B, each location being 5–10 μm square. We chose each size to exclude minerals other than phyllosilicates in the area. The bulk compositions differ from place to place, with a distribution indicating that the phyllosilicates consist of serpentine and saponite with variable Fe/Mg ratios. Uncertainties on each measurement are smaller than the symbol size. (D) BSE image of Ryugu sample C0002-C1001, showing brecciated matrix. The texture is similar to CI chondrites. Source: Yokoyama et al Science 2022

 

These particular samples were analysed by a team led by Tetsuya Yokoyama, professor at the Tokyo Institute of Technology. Their study inidcates that the sample ingredients are a very close match to the nebula that condensed to form the solar system 4.5 billion years ago.

“The samples have a chemical composition that more closely resembles the Sun’s photosphere than other natural samples do”, according to the paper.

The team used various techniques such as electron microscopy, X-ray fluorescence, plasma mass spectrometry and thermal ionization to reveal that the samples had formed within liquid water, at temperatures of approximately 81 to 117 degrees Fahrenheit or 27 to 47 degrees Celsius, around five million years after the solar system had started its life.

The paper highlights that Ryugu is made up of carbonaceous chondrite – a carbon-rich stony material, and some of the oldest rocks ever found. The asteroid is a C-type object (the most common class in our solar system), with a diamter of about 900 meters or 3,000 feet. This means that it is too small to generate enough heat to melt water-ice. Because the soil formed in liquid water, it indicates that Ryugu must have formed from another larger object (which had water) that formed just two million to four million years after the birth of the solar system. After around five million years that parent object was impacted by another asteroid, breaking it apart. The fragments from this impact later coalesced to form Ryugu.

 

Asteroid Ryugu

Asteroid Ryugu/ ESA

 

In another study, researchers said that they have found more than ten types of amino acids, the building blocks of proteins, in samples collected from Ryugu. These amino acids are extremely important for living beings and could old clues to the origin of life on Earth and maybe elewhere. These findings were presented at the Lunar and Planetary Conference in March 2022.

How did the samples reach Earth?

Hayabusa2 had the objective to rendezvous with Ryugu (1999 JU3), land a probe and rovers on its surface, and then return to Earth with soil samples. Launched in December 2014 and Hayabusa2 arrived at Ryugu in June 2018; two rovers (Minerva II) and a lander (MASCOT) were deployed on Ryugu’s surface in September and October 2018.

Hayabusa2 follows on from the earlier Hayabusa mission, which ALSO returned asteroid samples in 2010 and those samples were also analysed. But with new technology that we have now the analysis of the new samples has revealed so much more.

Hayabusa Spacecraft

Hayabusa Spacecraft/ JAXA

 

An exciting thing happened in February 2019, when Hayabusa 2 fired an impactor into Ryugu, created an artificial crater and collected sub surface soil samples. These along with two other soil samples (altogether 5.4 grams) left Ryugu in November 2019 on board Hayabusa2 and were returned to Earth in December 2020. The science instruments on the orbiter and rovers investigated the surface of the asteroid, providing environmental and geological data about the samples collected, which were distributed amongst various scientific groups and analysed.

When Hayabusa2 flew past Earth in late 2020, it released the capsule containing the soil samples, which re-entered the Earth’s atmosphere, deployed a radar-reflective parachute at an altitude of about 10 km, and ejected its heat-shield, while transmitting a position beacon signal. The sample capsule landed at the Woomera Test Range in Australia.

Samples being extracted from capsule

 

What will happen to Hayabusa2? It will retain 30 kg of its propellant, with the hope that this will able to extend its mission and fly to new targets.

The Ryugu soil samples will continue to be studied to understand the elemental composition of the early solar system. Excitingly, Osiris-Rex, which visited the asteroid Bennu in 2020 is also expected to return samples to Earth in September 2023 and will help further increase our understanding of the Sun and the planets around it.

 

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I am a Chartered Environmentalist from the Royal Society for the Environment, UK and co-owner of DoLocal Digital Marketing Agency Ltd, with a Master of Environmental Management from Yale University, an MBA in Finance, and a Bachelor of Science in Physics and Mathematics. I am passionate about science, history and environment and love to create content on these topics.