Close-up on a sample of an asteroid brought back to Earth

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The Hayabusa2 probe took an image of this asteroid Ryugu from a distance of 40 km when it approached the asteroid in 2018. Credit: JAXA

In December 2020, the Japanese spacecraft Hayabusa2 rocked Earth and dropped a cache of rock samples taken from a near-Earth asteroid called Ryugu. Asteroids like Ryugu are believed to represent ancient components of the solar system, and scientists have been eager to examine the returned samples.

Last week, the Japan Aerospace Exploration Agency shipped one of the samples (a millimeter-sized fragment of the surface of an asteroid) to the laboratory of planetologist Ralph Milliken at Brown University for analysis. . Milliken’s lab is one of the first labs in the United States to have examined samples from Ryugu so far.

Takahiro Hiroi, Principal Investigator at Milliken and Brown, is a member of the Hayabusa2 mission science team. They are interested in studying water mineral evidence on asteroids and have previously published research on topics based on spacecraft remote sensing equipment. Now that the samples have been returned, Milliken and Heroy are excited to compare measurements from a distance with close observations in the lab.

Milliken discussed the work in progress in an interview.

Q: Why was Brown selected as one of the labs to analyze Ryugu’s samples?

First of all, we are really delighted to be able to participate in an incredible international mission. It is a great honor to be able to analyze this sample very early in this process. I think there are several reasons why we were chosen. One was the presence of a colleague, Takahiro Hiroi, who is an expert in meteorite samples and asteroid science in general, and he also participated in the first Hayabusa mission. There are other Brown ties to the mission, such as Professor Seiji Sugita of the University of Tokyo and Dr Brown. A graduate who is the chief scientist of the spacecraft’s main camera.

Another reason is that Brown runs a NASA facility called RELAB, a reflectance lab. RELAB has a long history of working with alien samples dating back to the Apollo Moon program and the Soviet Luna program (now 30 years old). Therefore, we take high-precision measurements, work with colleagues to interpret this data, and combine these results with other observations to clearly understand the implications of these samples and the processes occurring across the world. There is a lot of expertise to be done.

Ralph Milliken looks at a small fragment of the asteroid Ryugu.Credit: Brown University

Q: Could you specify the sample itself?

It is very small, only about 1mm x 0.5mm. He’s from outside Ryugu. The Hayabusa2 spacecraft has landed in Ryugu twice. First, he landed on an undisturbed surface and grabbed some of his material. Then, for the second landing, the spacecraft expected to sample the spot where the man-made impact craters were created on the surface and release deeper material. The idea is to compare the material on this surface with the “cooler” material below, which is somewhat more protected from the effects of spatial weathering, which can alter the upper surface undisturbed. The sample we saw was from the first hit on the surface.

Q: What are you looking for in your analysis?

The Hayabusa2 mission has a large scientific team, each of whom asks different questions. Our group is very interested in minerals formed by water and organic compounds. Do they exist in these samples? If so, what are their chemistries and what do they teach us about the role of water in the first million years of our solar system? Initial data from the spacecraft’s remote sensing equipment suggests it may not be as plentiful in the water as Ryugu had predicted. One hypothesis is that the original asteroid was weathered by water to form hydrated clay and possibly other minerals, but at some point the asteroid was heated until ‘it is partially dehydrated. Now that you have the sample, you can dig deeper and see if this assumption is correct.

Close-up on a sample of an asteroid brought back to Earth

Credit: Brown University

Q: What format does the analysis take?

First, we perform a method called near infrared and mid infrared reflection spectroscopy. It analyzes the light reflected from the sample at wavelengths longer than the human eye can see, but it tells us about the minerals that are present. There is a similar device on the spacecraft that scans the surface of an asteroid on a scale of a few meters to a few centimeters. But in the lab, we’re looking at the micrometer scale. Therefore, you can examine the individual small particles, the complexity of the minerals, and their chemistries to understand if and how hydrated minerals are present in the sample. Once you have this detailed information, you can go back and look at the data from the large spacecraft and ask: Are the assumptions created on the basis of this data correct, or do the interpretations need to be changed? Having data and samples of remote sensing spacecraft for detailed laboratory analysis can really help us learn how to bridge these spatial scales.

Q: Why is it important to study asteroids like Ryugu?

We believe that asteroids like Ryugu are a fundamental part of the solar system. So, by learning more about Ryugu, we may be able to learn more about the formation of the solar system and its evolution as it is today.

Additionally, Takahiro and I are co-researchers of NASA’s OSIRIS-REx mission. This mission is now returning to Earth to bring back samples from the asteroid Bennu, which contains hydrated minerals and organic compounds, as shown by spacecraft data. .. I am also looking forward to measuring samples from this mission. Analyzing Ryugu samples in this way will also help prepare for future measurements.


Remote sensing data reveals when and how asteroid Ryugu lost water


For more information:
Kazuo Kitasato et al., Underground asteroid thermal weathering material (162173) Ryugu Nature astronomy (2021). DOI: 10.1038 / s41550-020-01271-2

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Quote: A sample of the asteroid brought back to Earth is an excerpt taken from https://phys.org/news/2021-09-asteroid-sample-brought-earth-close-up.html on September 27, 2021. Get Uplook ( September 27, 2021)

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