Introduction

In an extraordinary mission that began in 2016, NASA's OSIRIS-REx spacecraft made its ambitious journey to asteroid Bennu, located approximately 320 million kilometers (200 million miles) from Earth. By 2020, the spacecraft achieved a historic feat, successfully touching the asteroid's surface and collecting samples of loose debris instead of a solid ground.

Samples' Arrival and Research Opportunity

Fast forward to late September 2023, when the highly anticipated samples from OSIRIS-REx arrived on Earth in a protective capsule. As NASA handled the tracking and retrieval of the vessel for analysis, a separate research team seized a unique scientific opportunity. They aimed to use the capsule's reentry as a case study to better understand the effects of meteor impacts on our planet.

Challenges in Predicting Meteor Impacts

The researchers emphasized the challenge of predicting shock waves and impacts from objects the size of a meter, mainly due to uncertainties in their trajectories. Consequently, previous recordings of atmospheric entries using ground-based geophysical instruments, such as seismometers and infrasound sensors, were often coincidental and limited in detail. However, with the precise trajectory and timing of the OSIRIS-REx capsule's return, this team was equipped to strategically position their instruments to gather crucial geophysical data.

Innovative Use of Distributed Acoustic Sensing (DAS)

Employing Distributed Acoustic Sensing (DAS), a cutting-edge laser-based technology that detects vibrations through optical fibers, the team set up measurements alongside traditional seismometers and infrasound sensors across two locations near Eureka, Nevada. This innovative approach involved the deployment of 12 kilometers (7.46 miles) of fiber optic cables to effectively capture the descent of the sample return capsule.

Results of the Descent and Data Collection

When the capsule entered the Earth's atmosphere at hypersonic speeds, the results were astonishing. The data obtained marked a pioneering achievement in the use of DAS for this type of observation. The research team recorded initial impulsive signals that persisted strongly for about a second, something that conventional monitoring might have overlooked due to spatial limitations. This allowed them to analyze the sonic boom and track how the shock wave evolved as it approached the ground.

Future Implications of the Research

The potential of this method extends far beyond the OSIRIS-REx mission. The team envisions applying their techniques to gain deeper insights into future impacts, as they strive to enhance understanding of the interactions between acoustic and seismic phenomena recorded via surface-draped DAS fibers.

NASA's Next Steps with OSIRIS-APEX

Meanwhile, NASA has rebranded OSIRIS-REx as OSIRIS-APEX, as it sets its sights on asteroid 99942 Apophis. This asteroid will have a close encounter with Earth in 2029, leading NASA to anticipate significant gravitational shifts that may alter Apophis’s orbit, spin, and surface stability. The upcoming mission aims to provide vital observations of these anticipated changes.

Conclusion and Significance of Future Research

The OSIRIS-APEX spacecraft is not only tasked with monitoring Apophis but will also execute a maneuver to skim the asteroid's surface. This operation involves firing its engines to disturb loose rocks and dust, allowing scientists to analyze the materials just beneath the asteroid's surface—potentially revealing the cosmic building blocks of our solar system. As researchers continue to explore these groundbreaking methods and future missions, our understanding of both asteroids and the impact phenomena they create on Earth is progressing at a rapid pace, offering exciting implications for science and planetary defense.