OSIRIS-REx: Transforming Our Perception of Asteroids

2023-09-22 23:30:21

How OSIRIS-REx spacecraft changed the way we think about asteroids

The OSIRIS-REx spacecraft has revolutionized our understanding of asteroids. With its comprehensive suite of instruments, OSIRIS-REx spent two years scanning the surface of asteroid Bennu and collecting a sample. This mission revealed just how little we know about these space rocks.

Prior to OSIRIS-REx, previous missions like Japan's Hayabusa 1 and NASA's NEAR-Shoemaker had studied asteroids in detail, but it was Hayabusa 1 that first confirmed the theory that many asteroids are not solid blocks of rock but conglomerations of boulders, sand, and gravel. These "rubble piles" are held together by weak gravitational forces.

Rubble piles are not alike

Scientists expected that Bennu, the target asteroid of OSIRIS-REx, would be similar to Itokawa, another asteroid. However, when the spacecraft took a close look at Bennu, it found a surprising "hellscape" of rocks rising against the asteroid's feeble gravity. The surface was not what scientists had anticipated.

These rocks on Bennu's surface were oddly porous and weak, which was unexpected. They behave in ways that defy Earthly expectations. Additionally, the density of Bennu's surface layer is much lower than the rest of the asteroid, suggesting empty spaces between rocks or the absence of fine material.

Like a swamp

During OSIRIS-REx's touchdown on Bennu, the spacecraft sank deep into the surface, as if swallowed by a swamp. This revealed the low density of Bennu's surface layer, which is less than half as dense as the entire asteroid. Scientists are still trying to understand this anomaly and how it contributes to the overall composition of Bennu.

Missing sand grains

The low density of Bennu's surface layer may be due to the absence of fine grains. Over time, these grains may have filtered through the rocks into the asteroid's interior, which would explain the higher density there. To gain more insights into the interior of rubble pile asteroids, scientists are looking forward to the upcoming HERA mission by the European Space Agency, which will study the aftermath of NASA's DART probe's impact on asteroid Dimorphos.

Surprisingly complex

OSIRIS-REx has shown that asteroids are not just lifeless rocks in space. They have a surprisingly complex geology and are the result of various physical processes. By analyzing the sample collected by OSIRIS-REx, scientists hope to uncover records of past collisions and gain a better understanding of the asteroid's history.

The OSIRIS-REx mission continues to provide valuable insights into asteroids, expanding our knowledge and challenging our preconceptions about these celestial objects.