A couple of days ago, an extraterrestrial capsule landed in the Utah desert. Yes, really! The OSIRIS-REx (“Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer”) capsule returned, bringing back NASA’s first-ever asteroid samples, including regolith (soil) and rocks. The spacecraft was launched back in 2016 and took two years to reach Bennu, a near-Earth carbon-rich asteroid approximately 500 meters (1640 feet) in diameter. After surveying the asteroid for two years, the TAGSAM (Touch-and-Go Sample Acquisition Mechanism) successfully touched down on the surface of the asteroid in 2020, collected a sample, and departed, finally making it back to Earth just a few days ago. Bennu was chosen for multiple reasons: its orbit is in close proximity to Earth’s, even crossing it. The asteroid makes its closest approach to Earth every 6 years. And it rotates once every 4.3 hours, making it ideal for collecting samples. Smaller asteroids tend to spin very fast, making it hard for spacecraft to match their velocities, let alone touch down and collect samples.
So, why go to all the trouble and expense of sampling an asteroid out in space? Bits of asteroids fall to our planet as meteorites – can’t we just study those? After surviving a fiery descent through Earth’s atmosphere, the rocks land where sometimes they don’t get discovered for hundreds or thousands of years. Meanwhile, they are getting bombarded by rain and snow, which can change the chemistry, obscuring their ancient records. With very few exceptions, it’s hard to know what kind of objects these meteorites came from. Context matters. It’s important to study pristine material – indisputably uncontaminated by our planet. Bennu is a time capsule, preserved in the vacuum of space. It’s also a leftover ancient fragment from the time of the early formation of the solar system. Analysis of the samples will reveal more about the asteroid’s composition and surface properties, as well as provide insights to the chemistry of the early solar system, dating back billions of years. These are exciting times in space science and I can’t wait to learn more about what the scientists discover!