Parts of the asteroid Ryugu are among the “most primitive” materials ever examined

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Small particles of rock collected from the asteroid Ryugu are some of the most abundant bits of raw material ever examined on Earth and can give us a glimpse into the origins of the Solar System.

Asteroid 162173 Ryugu is about 2,953 feet (900 meters) in diameter and orbits the sun between Earth and Mars, occasionally crossing Earth’s orbit, according to Live Science’s sister site Space.com. The Carboniferous, or C-type asteroid, spins like a crest as it smashes through space, and like other C-type asteroids, Ryugu likely contains material from the nebula (a giant cloud of dust and gas) that gave birth to the Sun. Scientists believe the planets were billions of years ago. the years.

In 2019, the Japanese spacecraft Hayabusa2 collected samples from the surface of Ryugu, and on December 6, 2020, these samples were successfully flown back to Earth in an airtight container inside the re-entry capsule. Now, in two new papers published Monday (December 20) in Nature Astronomy, scientists present the results of a preliminary analysis of these remarkable pieces of space rock.

Related Topics: The 7 Strangest Asteroids: Strange Space Rocks in Our Solar System

“We are still at the beginning of our investigations, but our results indicate that these samples are among the most primitive materials available in our laboratories,” said Cedric Bellorget, associate professor at the Institute of Astrophysics at the University of Paris-Saclay. France and first author of one study. The exact age of the substance is still unknown but it needs to be revealed in future studies.

In total, the asteroid samples include about 0.2 ounces (5.4 grams) of material. The largest rock particles are about 0.31 inch (8 mm) in diameter; The smallest ones have diameters of less than 0.04 inch (1 mm), so they resemble fine dust. To the naked eye, the samples look like pieces of incredibly dark black pepper, Toru Yada, a senior research associate at the Japan Aerospace Exploration Agency and first author of the second study, told Live Science.

While dealing with the space rock, Yada and his colleagues kept the materials in a vacuum chamber or in a sealed environment filled with pure nitrogen. “So, the Ryugu samples were processed without exposing them [them] to Earth’s atmosphere.” The team evaluated the samples using an optical microscope and various instruments that measure how the rocks absorb, emit, and reflect different wavelengths of light in the visible and infrared spectra.

Asteroid 162173 Ryugu (Image source: ISAS/JAXA, CC BY 4.0, via Commons Wikimedia)

The team found that the pitch-dark parts of the asteroid reflect only 2% to 3% of the light that hits them. The researchers were surprised to discover that the samples’ bulk density — the mass of the particles divided by the total volume they occupy — was lower than the density of known carbonaceous meteorites, Yada said. This discovery indicates that the rocks are highly porous, which means that between the individual grains of material in the rocks there are many empty pockets that allow water and gas to seep through.

The discovery is consistent with preliminary data collected by the Hayabusa2 spacecraft, which also hinted that the rocks on Ryugu’s surface are highly porous, according to Space.com.

After Yada’s analyzes, Bellorgit and his team used a technique known as hyperspectral microscopy to take a closer look at the composition of the asteroid samples. Their hyperspectral microscope works by illuminating samples with different wavelengths of light in the visible and infrared spectra and capturing high-resolution images while doing so. Each shot measures approximately 0.2 x 0.2 inches (5 mm x 5 mm), and each pixel provides data at the microscopic scale. In this way, the team revealed minute details about the rocks’ colour, structure and chemical composition.

Footage from the Ryugu samples revealed that the rock particles consisted of an “aqueous matrix,” which includes materials such as clay, with carbon-based compounds embedded all around. “Some of the material properties were close to those of carbonaceous chondrites, the ‘class of carbonaceous meteorites’ that we have in our collections, while some were clearly distinct,” Bellorgate said.

For example, the Ryugu samples are among the darkest ever examined, and “we have to understand why and what this means in terms of the composition and evolution of this material,” he said. In addition, the team discovered traces of ammonia-rich compounds in the rock, which “could have some ramifications regarding the origin of Ryugu and our understanding of the raw materials.”

These preliminary analyzes represent the first step in figuring out what Ryugu can tell us about the early solar system, but it will take time to reveal all the secrets of space rocks. “A lot will come from combining additional technologies – in particular, those that will be able to get to very precise metrics,” Bellorgate said.

These additional techniques will include various chemical analyzes, Yada said, which can reveal the chronological history of when the asteroid first formed and at what ages it came into contact with water. Additional assessments of the organic compounds and minerals in the samples will also provide key information about how the asteroid and its original body first formed. Researchers can also examine volatile compounds, or those that can be easily vaporized, within samples; Yada said these types of tests could reveal how the solar wind has shaped the asteroid’s surface over time.

“Again, we are only at the beginning of our investigations,” Bellorgi said.

Originally published on Live Science.

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