365NEWSX
365NEWSX
Subscribe

Welcome

NASA OSIRIS-REx Mission Helps Solve a Mystery: Why Are Some Asteroid Surfaces Rocky? - SciTechDaily

NASA OSIRIS-REx Mission Helps Solve a Mystery: Why Are Some Asteroid Surfaces Rocky? - SciTechDaily

NASA OSIRIS-REx Mission Helps Solve a Mystery: Why Are Some Asteroid Surfaces Rocky? - SciTechDaily
Oct 25, 2021 3 mins, 32 secs

Scientists thought Bennu’s surface was like a sandy beach, abundant in fine sand and pebbles, which would have been perfect for collecting samples.

The mysterious lack of fine regolith became even more surprising when mission scientists observed evidence of processes potentially capable of grinding boulders into fine regolith.

He and his colleagues ultimately found that Bennu’s highly porous rocks are responsible for the surface’s surprising lack of fine regolith.

It was taken by the PolyCam camera on NASA’s OSIRIS-REx spacecraft on March 28, 2019, from a distance of 2.1 miles (3.4 km).

“The ‘REx’ in OSIRIS-REx stands for Regolith Explorer, so mapping and characterizing the surface of the asteroid was a main goal,” said study co-author and OSIRIS-REx Principal Investigator Dante Lauretta, a Regents Professor of Planetary Sciences at the University of Arizona.

“The spacecraft collected very high-resolution data for Bennu’s entire surface, which was down to 3 millimeters per pixel at some locations.

Beyond scientific interest, the lack of fine regolith became a challenge for the mission itself, because the spacecraft was designed to collect such material.”.

“When the first images of Bennu came in, we noted some areas where the resolution was not high enough to see whether there were small rocks or fine regolith.

We started using our machine learning approach to distinguish fine regolith from rocks using thermal emission (infrared) data,” Cambioni said.

The thermal emission from fine regolith is different from that of larger rocks, because the size of its particles controls the former, while the latter is controlled by rock porosity.

The team first built a library of thermal emissions associated with fine regolith mixed in different proportions with rocks of various porosity.

This mosaic of Bennu was created using observations made by NASA’s OSIRIS-REx spacecraft that was in close proximity to the asteroid for over two years.

The team concluded that very little fine regolith is produced from Bennu’s highly porous rocks because these are compressed rather than fragmented by meteoroid impacts.

“Basically, a big part of the energy of the impact goes into crushing the pores restricting the fragmentation of the rocks and the production of new fine regolith,” said study co-author Chrysa Avdellidou, a postdoctoral researcher at the French National Centre for Scientific Research (CNRS) – Lagrange Laboratory of the Côte d’Azur Observatory and University in France.

Additionally, Cambioni and colleagues showed that cracking caused by the heating and cooling of Bennu’s rocks as the asteroid rotates through day and night proceeds more slowly in porous rocks than in denser rocks, further frustrating the production of fine regolith.

This image shows a view of asteroid Bennu’s surface in a region near the equator.

It was taken by the PolyCam camera on NASA’s OSIRIS-REx spacecraft on March 21, 2019, from a distance of 2.2 miles (3.5 km).

The Japan Aerospace and Exploration Agency (JAXA) Hayabusa2 mission to Ryugu, a carbonaceous asteroid like Bennu, found that Ryugu also lacks fine regolith and has high-porosity rocks.

Conversely, JAXA’s Hayabusa mission in 2005 revealed abundant fine regolith on the surface of asteroid Itokawa, an S-type asteroid with rocks of a different composition than Bennu and Ryugu.

A previous study also from Cambioni and colleagues provided evidence that its rocks are less porous than Bennu’s and Ryugu’s using observations from Earth.

“The most indisputable evidence that these small asteroids could have substantial fine regolith emerged when spacecraft visited S-type asteroids Eros and Itokawa in the 2000s and found fine regolith on their surfaces.”.

The team predicts that large swaths of fine regolith should be uncommon on carbonaceous asteroids, the most common of all asteroid types observed, and which the team expects to have high-porosity rocks like BennuJ

By contrast, they predict terrains rich in fine regolith to be common on S-type asteroids, the second-most populous type of asteroids observed in the solar system, which they expect to have denser, less porous rocks than carbonaceous asteroids.

For more on this discovery, read Asteroid Bennu’s Surface Surprised Scientists – Here’s the Reason for the Mysterious Lack of Fine RegolithP

Summarized by 365NEWSX ROBOTS

RECENT NEWS

SUBSCRIBE

Get monthly updates and free resources.

CONNECT WITH US

© Copyright 2024 365NEWSX - All RIGHTS RESERVED