China’s Tianwen-2 asteroid sample return mission is set to launch this month, May 2025, en route to the asteroid Kamoʻoalewa (2016 HO3). The country could join the United States and Japan, whose space agencies have both successfully .
Released from the OSIRIS-REx craft, the sample return capsule hurtled down to Earth in a heavy box about the size of a microwave. Aside from the fact that it had been released from a spacecraft about 63,000 miles (102,000 kilometers) away, the return looked strikingly similar to that of a meteorite hitting Earth.
Scientists don’t often have the advance notice needed to study how real meteoroids – the term given to meteorites before they hit the ground – behave when they enter the atmosphere, so they jumped on the opportunity to study the capsule as it returned to Earth.
As physicists Brian Elbing from Oklahoma State University and Elizabeth A. Silber from Sandia National Laboratories discussed in their article, OSIRIS-REx’s reentry was the perfect opportunity to study what happens in the atmosphere when meteoroid-size objects fly through.
The teams set up networks of sensitive microphones and other instruments – both on the ground and attached to balloons – to log the sound wave frequencies that the capsule generated in the atmosphere. Understanding how waves travel through the atmosphere can help scientists figure out how to detect hazards such as natural disasters.
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3. Building blocks of life on Bennu
Once the OSIRIS-REx return capsule was safely back on Earth, researchers across the world – including geologist Timothy J. McCoy from the Smithsonian Institution and planetary scientist Sara Russell from the Natural History Museum in the U.K. – got to work running tests on its contents, while handling the sample carefully to avoid contaminating it.
As they described in their article, McCoy and Russell found the sample was mostly water-rich clay, which they expected from a carbon-rich asteroid. But they also found a surprising amount of salty and brine-related minerals. These minerals form when water evaporates off a rock’s surface.
NASA’s OSIRIS-REx mission, depicted in this illustration, traveled to the carbon-rich asteroid Bennu to take a sample and send it back to Earth in a return capsule.
NASA/Goddard Space Flight Center via AP
Because these minerals – aptly called evaporites – dissolve when they come into contact with moisture, scientists had never seen them in the meteorites that fly through Earth’s atmosphere, even ones with similar compositions to Bennu. The spacecraft’s sample container kept the Bennu sample airtight, so these evaporites stayed intact.
These results suggest that the asteroid used to be wet and muddy. And a salty, water-rich environment…
