The Bennu sample return mission was a boon for many branches of science.

Collection of the OSIRIS-REx sample return capsule. Credit: NASA/Keegan Barber, CC BY.

The Earth is constantly bombarded by fragments of rock and ice, also known as meteoroids, from outer space. Most meteoroids are as small as grains of sand and small pebbles, and burn up completely high in the atmosphere. You can see meteoroids larger than a golf ball when they light up like meteors or shooting stars on a dark and clear night.

While very small meteorites are common, larger ones (bigger than a dishwasher) are not.

Meteoroids are difficult objects to find. aerospace and geophysics researchers We like to study them, because we usually can't predict when and where they will reach the atmosphere. But on very rare occasions we can study artificial objects that enter the atmosphere in much the same way as a meteoroid would.

These objects come from space missions designed to transport extraterrestrial physical samples from outer space to Earth. Because of this similarity to meteorite input, we often refer to these sample return capsules, or SRCs, as “artificial meteorites.”

More than 80 researchers from more than a dozen institutions recently worked together to study such an “artificial meteorite.” NASA OSIRIS-REx Sample Return Capsule – when it re-entered Earth's atmosphere.

These institutions included Sandia National LaboratoriesThe NASA Jet propulsion laboratory, Los Alamos National Laboratoryhe Defense Threat Reduction Agency, TDA Research Inc.he University of Hawaiihe Air Force Research Laboratoryhe Blacknest Atomic Weapons Establishment, Boise State University, Idaho National Laboratory, Johns Hopkins University, Kochi Technological University, Nevada National Security Site, Southern Methodist Universityhe University of Memphis and Oklahoma State University.

This sample return provided our teams with a unique opportunity to measure sound waves and other phenomena produced by space objects as they pass through Earth's atmosphere.

To capture signals, we installed many sensitive microphones and other instruments at key locations near the SRC's flight path.

While space agencies and private companies launch objects into space all the time, the OSIRIS-REx SRC is one of the few objects to have returned to Earth from interplanetary space since the end of the Apollo missions. Only these objects can reach the speed of natural meteoroids, which makes Your re-entry is valuable. to study the properties of natural objects.

Asteroid sampling

NASA launched Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer or OSIRIS-RExmission on September 8, 2016. He traveled to Bennu, an asteroid near Earthand collected a sample of its surface in October 2020.

Related: NASA Asteroid Bennu Samples Have Rocks Unlike Any Meteorite Ever Found

The sample returned to earth in the early hours of September 24, 2023, in a sample return capsule. The SRC re-entered Earth's atmosphere over the Pacific Ocean at a speed of more than 43,500 kph (27,000 mph) and landed in Utah just a few minutes later.

SRCs produce a shock wave as they dive deep into the atmosphere, similar to the sonic boom generated by a supersonic aircraft breaking the sound barrier. The shock wave then loses strength until all that remains is a low-frequency sound, called infrasound.

While humans cannot hear infrasound, sensitive scientific instruments can detect it, even at great distances. Some of these instruments are on the ground, while others are suspended in the air from balloons.

Observing the Bennu SRC

Our teams of scientists used the SRC re-entry as an opportunity to learn more about meteors. One of the teams, led by Siddharth Krishnamoorthy at NASA's Jet Propulsion Laboratory, used SRC reentry to test infrasound-detecting balloons that could later be used in the planet venus.

Another team, led by one of us… Elizabeth Silber – and Danny Bowman at Sandia National Labs used the SRC to better understand how we can use sound to (gather information about meteoroids).

Researchers from many institutions throughout the country participated in these observation campaigns.

Our teams strategically placed instruments in locations across a distance of 300 miles (482 km) stretching from Eureka, Nevada, to near the landing site in Utah. Instruments ranged from high-tech custom sensors to smartphones on the ground around the SRC's flight path and landing site. They monitored the low-frequency sound waves of SRC re-entry.

In addition to ground-based sensors, our researchers attached instruments to balloons floating at twice the altitude of commercial airliners during SRC re-entry. Sensors attached to these balloons recorded the sound waves produced by the SRC shock wave. These sound waves carried information about the SRC, its movement, and the environment it passed through.

The balloon teams had to time the balloons carefully to ensure they were in the correct position when the SRC passed. NASA team members. Jet propulsion laboratory, Oklahoma State University and Sandia National Laboratories launched a few different types of balloons before dawn from Eureka, Nevada.

Researchers from OSU, Sandia and the University of Hawaii It also deployed ground infrasound sensors closer to the SRC landing site, along the Utah-Nevada border and at Wendover Airport. While the SRC was already slowing down and Wendover Airport was approximately three times farther out of the flight path than the Eureka deployment, we also detected a clear infrasound signal at this site.

Researchers on these teams are now analyzing the data to identify points along the trajectory where instruments recorded SRC re-entry signals. Because the SRC's flight path spanned approximately 300 miles (482 km), researchers needed to determine the points of origin of the signals as they were detected by different sensors.

This was the most instrumented. hypersonic reentry in history.

This research will help our teams discover what patterns low-frequency sound waves propagated through the atmosphere and where the shock wave reached its maximum intensity.

While our teams are still analyzing the data, preliminary results show that our instruments captured many signals that will help future research use low-frequency sound waves to study meteors.

And gaining insight into the complexities of how low-frequency sound waves travel through the atmosphere can help researchers use infrasound to detect dangers on Earth. like tornadoes and avalanches.

This article first appeared in The conversation. It is republished here under a Creative Commons license.