NASA’s NEOWISE Spacecraft Helped Crack The Secret Of What Lies On The Surface Of Asteroids

The asteroid-hunting spacecraft took thermal data on more than 100 near-Earth space rocks and revealed what goes on with their surface regolith.

Asteroids in the Asteroid Belt.
Paul Fleet / Shutterstock

The asteroid-hunting spacecraft took thermal data on more than 100 near-Earth space rocks and revealed what goes on with their surface regolith.

In December 2009, NASA launched the Wide-field Infrared Survey Explorer (WISE) mission with the purpose of imaging the entire sky in infrared light so that we could learn more about the stars, other galaxies, and the celestial bodies in our own solar system.

After completing its main objective in two years’ time, the WISE spacecraft remained dormant for another two years, when it was awoken from its slumber in 2013 and given a new name and a new purpose.

Now called the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), the spacecraft orbits our planet in order to detect, identify, and characterize near-Earth objects (the clue is in the name).

Armed with thermal sensors that enable it to make infrared observations, the NEOWISE spacecraft is actively hunting for asteroids to gather data on their orbit, size, surface characteristics, and chemical composition. Its mission has helped discover the surface properties of more than 100 space rocks in the Asteroid Belt, NASA has recently announced.

A new study published in the journal Icarus and available online on the arXiv server examined the NEOWISE archive and found a bounty of data that helped reveal what happens on the surface of many main belt asteroids.

The research, led by Josef Hanuš of the Astronomical Institute of Charles University in Prague, Czech Republic, used thermal observations from the NEOWISE spacecraft to perform detailed “thermophysical” modeling of these asteroids and uncover the properties of their surface regolith — fine grains of dust and broken rocks produced by thermal cracking and deposited on the surface of asteroids.

“Thermophysical modeling is a gold mine for asteroid researchers because it allows a more comprehensive analysis of the nature of asteroids,” stated NASA officials, who noted that the NEOWISE thermal data helped build thermophysical models for three times as many asteroids as ever before.

While combing through the NEOWISE archive, the researchers came across infrared data for 122 asteroids that they had previously modeled to see their shape and understand how they rotate. This helped add thermal data to the space rocks’ 3D shape and rotation models.

“Using archived data from the NEOWISE mission and our previously derived shape models, we were able to create highly detailed thermophysical models of 122 main belt asteroids,” said Hanuš.

According to the study lead author, the NEOWISE thermal observations were instrumental in finding out that asteroids have very little dust on their surface.

“We now have a better idea of the properties of the surface regolith and show that small asteroids, as well as fast-rotating asteroids, have little, if any, dust covering their surfaces.”

As NASA explains, fine regolith grains have a hard time clinging to the surface of fast-spinning space rocks, because the asteroids’ low gravity and high rotation rates prevent small particles from remaining attached to the surface.

Another reason for the lack of regolith on this type of asteroids could be tied to their small chances of thermal cracking. Since solar rays are more rapidly distributed across their fast-rotating surface, these asteroids don’t go through large temperature changes and, therefore, are less prone to crack and create fine grains of regolith.

One other thing that the new study unraveled was that the NEOWISE spacecraft did a fantastic job at gathering data on the size of the asteroids.

The researchers redid the calculations with more elaborate models and found that their results matched those of the NEOWISE team.

“The uncertainties were within 10 percent between the two sets of results,” Hanuš pointed out.