By 2023, priceless property will land somewhere in the Utah desert. When it happens, a team of engineers and scientists will be waiting on the ground. Thousands of people will stare at the smartphone and TV to watch the landing. Headlines around the world will tell about this journey.

Property? 2 to 70 ounces of asteroid dirt.

This 4.5-billion-year-old sample, officially called the weathered layer, looks like a small pile of dusty rubble, which was collected in five seconds by NASA’s OSIRIS-REx spacecraft. The near-earth asteroid is called Bennu.

The sample encapsulated and landed at the Utah Test and Training Ground about 80 miles west of Salt Lake City, and will begin a new phase of its existence: analysis. After being transported to the Johnson Space Center in Houston, the dirt will be removed from the space capsule and distributed to scientists for research.

OSIRIS-REx is the first US mission to send asteroid samples back to Earth, but for scientists like Tom Zega, the return is just the beginning. Zega is a sample scientist at the University of Arizona. As a collaborator of the OSIRIS-REx mission led by UA, he will be one of the first scientists to analyze Bennu's weathering layer.

Zega said that one of the main goals of the OSIRIS-REx mission is to understand the earliest history of our solar system and the origin of life. The original weathered layer from the asteroid may be our best shot, unaffected by the influence and pollution of the atmosphere.

Zega said: "Sample returns are great, otherwise you will be at the mercy of things falling from the sky." "Sample returns are a treasure trove of information. The samples you get are older than the earth. I can literally hold our solar system. Part of the origin, it is earlier than the earth, earlier than human beings, and earlier than everything we know.

"These atoms were assembled four or five billion years ago and became the cornerstone of our planet."

So, the question is how to deal with such a pile of dirt with scientific value.

Establish a laboratory suitable for analysis

Analysis means two things-both require the use of large equipment in a stable environment. First: high-resolution imaging. The second one: measuring chemistry. Answer the question "What does it look like?" And "What is it made of?"

"We are a bit like forensic scientists," Zega said. "Nature has cultivated these materials, and we are fundamentally analyzing it to determine under what conditions."

Zega works in the 5,000-square-foot basement of the Kuiper Space Science Building, which was built at UA in 1964 with NASA funding. The basement was once the mirror laboratory and publication library of the telescope. The telescope has become bigger, the laboratory has also become bigger, and it now lives under the Arizona Stadium. The publication is online. Now, the high-tech electron microscope collected by UA-used to study the returned asteroid dirt-lives here.

Electron microscopes are sensitive to stimuli and need a place with minimal vibration, minimal electromagnetic interference, and good acoustics. It turns out that the basement is a good place to put these microscopes. According to Zega, as of today, when samples from OSIRIS-REx appeared, the laboratory was "ready."

In fact, the laboratory is studying samples from Hayabusa 1, which is the asteroid sample return mission of the Japan Aerospace Exploration Agency (JAXA), which is equivalent to Japan's NASA. Like OSIRIS-REx, Hayabusa 2 is now cruising towards its target, the asteroid Ryugu.

Zega opened the two frosted doors of the laboratory, revealing a long, clean, brightly lit corridor.

At the end of the corridor in the left room is where the asteroid sample actually begins in the laboratory. After installing it on a glass slide and polishing it smoothly, Zega puts the sample into the electron microprobe.

"Microprobes provide us with the richest background information," Zega said.

It allowed him to photograph the entire sample at high resolution and map its chemical composition element by element. These elements, such as iron, nickel, and magnesium, appear as colors on the computer screen.

"You want to sit down and actually process this data," Zega said. "Before deciding what the next step is, you may want to use maps and overlay them on the high-resolution images you create. This may take some time.

"Before a more detailed analysis, you really want to spend some time here."

Then, all the way to the other end of the corridor, near the doorway, there are two scanning electron microscopes. Like microprobes, they also image and chemically map samples, but at a more detailed level. Here, Zega can view dirt at the micrometer and nanometer scale-one-billionth of a meter. A piece of paper is about 100,000 nanometers thick.

In the next room, a focused ion beam scanning electron microscope can observe the sample in more detail. It can also drill a hole in the dust of the asteroid by launching gallium ions at the asteroid like a small bullet.

Atom with a story

"Every atom has something to tell us," Zega said, walking towards the final destination of the asteroid sample: transmission electron microscope or TEM. This is a towering off-white and blue box, about 12 feet high. Its size has an innate sense of humor, because TEM is the only machine in the world that can see things as tiny as a single atom.

TEM was purchased from Hitachi High Technologies in 2016 and shipped from Japan a few months ago. Since November last year, a team of engineers from the company’s headquarters outside Tokyo have been installing and calibrating microscopes here. They are expected to return home in June.

"Observing the microstructure is useful for finding the origin," Zega explained.

When you want to determine how something is formed, which atoms of the element are adjacent to or stacked on which other atoms are important.

In the best case, analyzing asteroid fouling means "we have rewritten the textbook on our understanding of the origin of the solar system," Zega said. "I think this is the most ingenious thing about a task like this. It can be full of surprises.

"Whether we are scientists or not, we all look up at the starry sky and ask'how?' and "why?" "We want to know how this happened," he said. "The work we do at the University of Arizona helps answer these questions."

TEM and FIB analysis was performed at the Kuiper core imaging and characterization facility at the University of Arizona, supported in part by NSF Grant 1531243 and NASA Grants NNX15AJ22G and NNX12AL47G.

UA Lunar and Planetary Laboratory

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