Discovery offers new support for the theory that life may have been seeded from outer space
Agence France-Presse in Tokyo
Specks of dust that a Japanese space probe retrieved from an asteroid about 186 million miles (300m kilometres) from Earth have revealed a surprising component: a drop of water.
The discovery offers new support for the theory that life on Earth may have been seeded from outer space.
The findings are in the latest research to be published from analysis of 5.4 grammes of stones and dust that the Hayabusa-2 probe gathered from the asteroid Ryugu.
“This drop of water has great meaning,” the lead scientist, Tomoki Nakamura of Tohoku University, told reporters before publication of the research in the journal Science on Friday.
Hayabusa2 comes home: remarkable space probe could open another window into how life originated
“Many researchers believe that water was brought [from outer space], but we actually discovered water in Ryugu, an asteroid near Earth, for the first time.”
Hayabusa-2 was launched in 2014 on its mission to Ryugu, and returned to Earth’s orbit two years ago to drop off a capsule containing the sample.
The precious cargo has already yielded several insights, including organic material that showed some of the building blocks of life on Earth, amino acids, may have been formed in space.
The team’s latest discovery was a drop of fluid in the Ryugu sample “which was carbonated water containing salt and organic matter”, Nakamura said.
That bolsters the theory that asteroids such as Ryugu, or its larger parent asteroid, could have “provided water, which contains salt and organic matter” in collisions with Earth, he said.
“We have discovered evidence that this may have been directly linked to, for example, the origin of the oceans or organic matter on Earth.”
Nakamura’s team, which is made up of about 150 researchers – including 30 from the US, Britain, France, Italy and China – is one of the largest teams analysing the sample from Ryugu.
Kensei Kobayashi, an astrobiology expert and professor emeritus at Yokohama National University who is not part of the research group, hailed the discovery.
“The fact that water was discovered in the sample itself is surprising”, given its fragility and the chances of it being destroyed in outer space, he said.
“It does suggest that the asteroid contained water, in the form of fluid and not just ice, and organic matter may have been generated in that water.”
Researchers have used beams of muons to analyze the elemental composition of Asteroid Ryugu samples
IMAGE: FIGURE 1: (LEFT) A MUONIC X-RAY CREATED AFTER A MUON IS CAPTURED BY AN IRRADIATED MATERIAL, AND (RIGHT) A SAMPLE OF THE ASTEROID RYUGU. view more
CREDIT: (LEFT IMAGE) MUON ANALYSIS TEAM, (RIGHT IMAGE) JAXA
Stone samples brought back to Earth from asteroid Ryugu have had their elemental composition analyzed using an artificially generated muon beam from the particle accelerator in J-PARC. Researchers found a number of important elements needed to sustain life, including carbon, nitrogen, and oxygen, but also found the oxygen abundance relative to silicon in asteroid Ryugu was different from all m
eteorites that have been found on Earth, reports a new study in Science.
In 2014, the unmanned asteroid explorer Hayabusa 2 was launched into space by the Japan Aerospace Exploration Agency (JAXA) with a mission to bring back samples from asteroid Ryugu, a type C asteroid that researchers believed was rich in carbon. After successfully landing on Ryugu and collecting samples, Hayabusa 2 returned to Earth in December 2020 with samples intact.
Since 2021, researchers have been running the first analyses of the samples, led by University of Tokyo Professor Shogo Tachibana. Split into several teams, researchers have been studying the samples in different ways, including stone shapes, elemental distribution, and mineral composition.
In this study, led by Tohoku University Professor Tomoki Nakamura, Professor Tadayuki Takahashi and graduate student Shunsaku Nagasawa of the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), University of Tokyo, in collaboration with the High Energy Accelerator Research Organization (KEK) Institute for Materials Structure Science, Osaka University, Japan Atomic Energy Agency (JAEA), Kyoto University, International Christian University, Institute of Space and Astronautical Science (ISAS), and Tohoku University, have applied elemental analysis methods using negative muons, elementary particles produced by the accelerator at J-PARC. They applied the elemental analysis method using negative muons to stones from the asteroid Ryugu, succeeding in nondestructively determining their elemental compositions.
This was important, because if asteroids in the Solar System were built at the beginning of the formation of the Solar System itself, then they would still be withholding information about the average elemental composition at that time, and therefore of the entire Solar System.
Analysis of meteorites that have fallen to Earth have been carried out in the past, but it is possible these samples have been contaminated by the Earth's atmosphere. So, until Hayabusa 2, no one knew what the chemical composition of an asteroid was for sure.
But the researchers faced a challenge. Because of the limited amount of samples and the large number of other researchers wanting to study them, they needed to find a way to run their analyses without damaging them so that the samples could be passed on to other groups.
The team had developed a new method, which involved shooting a quantum beam, or specifically a beam of negative muons, produced by one of the world's largest high-energy particle accelerators J-PARC in Ibaraki prefecture, Japan, to identify the chemical elements of sensitive samples without breaking them.
Takahashi and Nagasawa then applied statistical analysis techniques in X-ray astronomy and particle physics experiments to analyze muon characteristic X-ray.
Muons are one of the elementary particles in the universe. Their ability to penetrate deeper into materials than X-rays makes them ideal in material analysis. When a negative muon is captured by the irradiated sample, a muonic atom is formed (figure 1). The muonic X-rays emitted from the new muonic atoms have high energy, and so can be detected with high sensitivity. This method was used to analyze the Ryugu samples.
But there was another challenge. In order to keep the samples from being contaminated by the Earth's atmosphere, the researchers needed to keep the samples out of contact with oxygen and water in the air. Therefore, they had to develop an experimental setup, casing the sample in a chamber of helium gas (figure 2). The inner walls of the chamber were lined with pure copper to minimize the background noise when analyzing the samples.
In June 2021, 0.1 grams of Ryugu asteroid were brought into J-PARC, and the researchers ran their muon X-ray analysis, which produced an energy spectrum (figure 3). In it, they found the elements needed to produce life, carbon, nitrogen and oxygen, but they also found the sample had a composition similar to that of carbonaceous chondrite (CI chondrite) asteroids, which are often referred to as the standard for solid substances in the Solar System. This showed the Ryugu stones were some of the earliest stones to have formed in our Solar System.
However, while similar in composition to CI chondrites, the Ryugu sample’s oxygen abundance relative to silicon was about 25 per cent less than that of the CI chondrite (figure 4). The researchers say this could indicate that the excess oxygen abundance relative to silicon in CI chondrites could have come from contamination after they entered Earth's atmosphere. Ryugu stones could set a new standard for matter in the Solar System.
The team’s results show the success of the muonic x-ray method, and that it can be used to analyze samples from future space missions.
Details of this study were published in Science on September 22.
Figure 2: The custom-made experiment setup developed to avoid the samples from being contaminated by the Earth’s atmosphere. The interior is filled with helium gas, and the chamber is lined with pure copper to minimize background noise.
CREDIT
Muon analysis team
Figure 3: Muonic x-ray spectral comparison of asteroid Ryugu sample and CI chondrite Orgueil.
CREDIT
Muon analysis team
Figure 4: Comparison of the elemental composition of asteroid Ryugu sample and CI chondrite Orgueil (K. Lodders, The Astrophysical Journal, 591, 1220-1247, 2003). The oxygen x-ray shows the Ryugu sample’s oxygen abundance relative to silicon was less compared to CI chondrite.
CREDIT
Muon analysis team
Figure 5: Group photo of the researchers.
CREDIT
Muon analysis team
JOURNAL
Science
ARTICLE TITLE
Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples
ARTICLE PUBLICATION DATE
22-Sep-2022
Analysis of particles of the asteroid Ryugu delivers surprising results
Team from Goethe University Frankfurt contributes to article in Science
Peer-Reviewed PublicationFRANKFURT. Frank Brenker and his team are world leaders in a method that makes it possible to analyse the chemical composition of material in a three-dimensional and entirely non-destructive way and without complicated sample preparation – yet with a resolution of under 100 nanometres. Resolution expresses the smallest perceptible difference between two measured values. The method’s long name is “Synchrotron Radiation induced X-Ray Fluorescence Computed Tomography”, in short SR-XRF-CT.
Japan had chosen Ryugu (English: Dragon’s Palace) as the probe’s destination because it is an asteroid which, due to its high carbon content, promised to deliver particularly extensive information about the origin of life in our solar system. The analyses conducted on 16 particles by the researchers together with the scientists in Frankfurt have now shown that Ryugu is composed of CI-type material. These are very similar to the Sun in terms of their chemical composition. So far, CI-material has only rarely been found on Earth – material of which it was unclear how much it had been altered or contaminated when entering Earth’s atmosphere or upon impact with our planet. Furthermore, the analysis confirms the assumption that Ryugu originated from a parent asteroid which formed in the outer solar nebula.
Until now, scientists had assumed that there was hardly any transport of material within the asteroid due to the low temperatures during the formation of the CI material in the early days of the solar system and therefore scarcely any possibility for a massive accumulation of elements. By means of SR-XRF-CT, however, the researchers in Frankfurt found a fine vein of magnetite – an iron oxide mineral – and hydroxyapatite, a phosphate mineral, in one of the grains of the asteroid. Other groups of scientists established that the structure and other magnetite-hydroxyapatite regions in the Ryugu samples must have formed at a surprisingly low temperature of under 40 °C. This finding is fundamental for interpreting almost all the results that the analysis of the Ryugu samples has generated and will generate in future.
In areas of the samples containing hydroxyapatite, Frank Brenker’s team additionally detected rare earth metals – a group of chemical elements indispensable today for alloys and glassware for high-tech applications, among others. “The rare earths occur in the hydroxyapatite of the asteroid in concentrations 100 times higher than elsewhere in the solar system,” says Brenker. What’s more, he says, all the elements of the rare earth metals have accumulated in the phosphate mineral to the same degree – which is also unusual. Brenker is convinced: “This equal distribution of rare earths is a further indication that Ryugu is a very pristine asteroid that represents the beginnings of our solar system.”
It is by no means a matter of course that researchers from Goethe University Frankfurt were allowed to examine samples from the Hayabusa 2 mission: after all, Japan undertook this space mission alone and, according to information from 2010, raised €123 million for it. It therefore also wants to reap a large part of the scientific harvest. But ultimately Japan did not want to forego the expertise of the German SR-XRF-CT specialists.
The research results by the Hayabusa2 Initial Analysis of Stones Team (led by Prof. Tomoki Nakamura, Tohoku University), including this research result, were published in Science on Thursday, September 22, 14pm. JAXA press release: https://global.jaxa.jp/press/2022/09/20220923-1_e.html
JOURNAL
Science
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Formation and evolution of Cb-type asteroid Ryugu: Direct evidence from returned samples
ARTICLE PUBLICATION DATE
22-Sep-2022
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