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NASA lands a hollow asteroid that spins itself to its death

NASA lands a hollow asteroid that spins itself to its death

NASA’S Osiris-Rex spacecraft touched down on an asteroid called Bennu. Launched on September 8, 2016, the spacecraft sets to bring a small sample back to Earth for study. Aside from the sample, the National Aeronautics and Space Administration also found something else about the asteroid they landed upon.

NASA | OSIRIS-REx Spacecraft

NASA’s Osiris-Rex lands on Bennu

The probe successfully landed on Bennu on October 20, 2020. The administration confirmed this via images taken during sampling that the probe has made contact. The spacecraft touched down within 92-centimeters or 36-inches of the target location. NASA decided to send the probe to land on Bennu for its seemingly smooth surface – a perfect landing ground.

However, when the spacecraft landed in Bennu, the images it sent back consist of a landscape covered in boulders and rock fields. Eventually, NASA found out that Bennu’s rock turned out to be incredibly soft, crumbling under the spacecraft as soon as it touched the surface. Then, the probe fired a blast of nitrogen to send rock and dust swirling – using this to collect samples.

NASA | Diagram of the orbit of Bennu in relation to Earth and other planets

Bennu – probably hollow

The act, then, caught scientists off guard. The maneuver yielded so much material that dust and rock propped the sample-collection tool open. Unfortunately, this allowed precious alien dust to leak into space. Researchers from the University of Colorado studied the sample based on the data that Osiris-Rex gathered while circling Bennu for two years.

Daniel Scheeres, a professor of Aerospace Engineering Sciences, led the research. In a press release, he confirmed that they concluded that the asteroid is probably hollow. Aside from Scheeres, Jay McMahon is also included in this study. The research also puts insight into the evolution of the solar system’s – how bodies like Bennu transform over millions of years or more.

Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu

Bennu’s gravity comes from its mass. Two sets of data allowed Scheeres and his team to calculate how material distributes through the inside of the asteroid. They used two approaches to measure the gravity field of the rubble-pile asteroid, Bennu. The first approach they used would be tracking and modeling the spacecraft in orbit about the asteroid.

The second approach they used, on the other hand, tracking and modeling pebble-sized particles naturally ejected from Bennu’s surface into sustained orbits. Comparisons with a constant-density shape model show that Bennu has a heterogeneous mass distribution. These deviations can be modeled with lower densities at Bennu’s equatorial bulge and center.

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NASA | Particles ejected from the surface of Bennu.

Bennu completes one rotation every four hours. However, it’s only getting faster. The team noted that the force of the Bennu’s spinning seems to be pushing its material outward toward the surface. Some of the thinnest parts of the asteroid are at its bulging equator. Scheeres pointed out that the ‘whole thing flying apart.’

“You could imagine maybe in a million years or less, the whole thing flying apart.”

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