Dust in ultraviolet: The best way to study solar wear and tear?

Category: Cover Story

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PSI scientists and collaborators developed a new way of assessing how radiation from the Sun wears down and alters planetary surfaces, a phenomenon known as space weathering.

Researchers crushed olivine – a major mineral component of some asteroids, the Moon and the Earth – in an inert environment and bombarded it with a mixture of particles that mimicked the Sun’s rays for 40 hours. They then observed the olivine in a wide range of light, both before and after the bombardment, to gauge how each wavelength might tell a different story of the changes made by the effects of solar particles.

They found that ultraviolet light, rather than just visible or infrared, revealed the most about how much a surface has been fundamentally changed by space weathering.

“These results provide a rationale for why people should look at surfaces in a broad range of wavelengths, including the ultraviolet, if they really want to understand how interactions with the Sun affect planetary surfaces,” said paper co-author Deborah Domingue, a Senior Scientist at the Planetary Science Institute.

Their findings were published in The Planetary Science Journal. The paper was led by Camilo Jaramillo-Correa of Princeton University. Other authors include PSI Senior Scientists Roger Clark, Faith Vilas, Amanda Hendrix and PSI laboratory technician Neil Pearson, as well as Daniel Savin of Columbia University.

“The concept of space weathering arose when we got back lunar samples from the Apollo missions,” Domingue said. “When we took a look at them in the lab, their spectra (patterns of light that reveal composition) didn’t match the lunar spectra as seen through a telescope. Scientists have been working for decades to understand why.”

Past research into space weathering focused observations on narrow bands of light. This study spanned a much wider range – from the infrared, which are wavelengths longer and less energetic than visible light, to the ultraviolet, which are shorter and more energetic than visible. Olivine was an ideal test subject because it has been studied before, it’s also easy to procure, crush and handle. Comparisons with past studies also confirm the growing knowledge base regarding space weathering.

“Space weathering leads to changes in spectra that mask the identification of materials,” Domingue said. “If we’re to mine for resources on asteroids for example, we need to know the composition. This is a way to do that. Understanding the effects of weathering also guides our understanding of the evolution of a planet or other body.”

Understanding composition is also important for planetary defense.

“If we want to deflect an asteroid headed for Earth, we need to know the material properties of that asteroid,” Pearson said. “We need to know how space weathering has affected the surface so that we can best interpret our ground-based telescopic observations.”

This work was supported by NASA’s SERVII Toolbox for Research and Exploration, or TREX, grant. PSI’s contribution was also supported by NASA’s Solar System Workings grant numbers 80NSCC18K0521 and 80NSCC22K0099.