Asteroid Sand Brought Down to Earth

In 2018 and 2019, JAXA’s Hayabusa2 spacecraft visited a near-Earth asteroid called Ryugu. Hayabusa2 spent more than a year flying alongside the asteroid to study it. The spacecraft also touched down to collect surface samples. And it blasted a small crater into the asteroid to expose subsurface material, which it also collected during a second landing.

Hayabusa2 sent a re-entry capsule containing about 5 grams (0.17 ounces) of matte black sand and pebble samples back to Earth in 2020. Although this amounts to only one teaspoon of material, it was a larger quantity than researchers had anticipated.

And because the samples arrived in a sealed capsule, they are different from any meteorite that has been found on Earth. When a fragment of an asteroid crashes through the atmosphere and lands on Earth, it is immediately contaminated. Japanese researchers say the Ryugu samples are the most pristine extraterrestrial material ever studied.

Scientists worked under carefully controlled conditions to keep the materials uncontaminated. The samples were opened in a vacuum within a clean chamber, and a portion of the samples was examined in a high-purity nitrogen environment. Other sample material was saved in a vacuum environment for future research. This approach allows researchers to protect the material, keeping it just as it was in space. 

The initial analyses of the samples relied on microscopes, spectrometers, and an electronic balance. To weigh the asteroid sand, JAXA researchers used a METTLER TOLEDO XPR404S precision balance, which allows for a minimum weight of 12 milligrams and offers readability to 0.1 milligrams. For this unique application, where purity of the asteroid sample was crucial, the scale was modified. The weighing unit and display were separated, and the weighing unit was placed inside a clean chamber.

Research teams published their first findings in two scientific papers. One study showed that the surface and subsurface materials are the same; the collected samples are representative of the entire asteroid. The second study found that the asteroid material contains carbon-rich organic compounds.