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Arrokoth is the most distant object ever explored by a spacecraft from Earth, and it revealed clues to how the solar system has evolved, according to a team of University of Hawaiʻi at Mānoa researchers.

Located in the Kuiper Belt (a region of the Solar System beyond the orbit of Neptune), NASA‘s New Horizons spacecraft visited Arrokoth in 2019 and revealed its reddish appearance, hinting at a complex chemical composition beneath the surface. The presence of methanol-rich surface ices was also discovered, raising questions about the processes responsible for the surface coloring.

A team of scientists from UH Mānoa, Université Côte d’Azur (France) and Southwest Research Institute discovered that Arrokoth’s surface contains sugars such as ribose and glucose—biologically significant molecules essential for the building blocks of life.

“Arrokoth provides crucial insights into the processes that influenced the formation of celestial bodies like the Kuiper Belt,” said Department of Chemistry Professor Ralf I. Kaiser. “By examining the chemical makeup of Arrokoth and other distant objects, we learn more about the intricate interactions of chemistry, radiation and cosmic dynamics shaping their surfaces. Each discovery brings us closer to unraveling the origins of our solar system and the potential for life beyond Earth.”

The researchers made the discovery through a simulation of the effects of galactic cosmic rays on methanol ices, mimicking the conditions experienced by Arrokoth in the depths of space.

The exposed methanol ices replicated the distinctive colors observed on Arrokoth’s surface, providing a crucial clue to its chemical makeup. Additionally, aromatic hydrocarbons (a type of chemical compound made up of carbon and hydrogen atoms, commonly found in products like gasoline and plastics) played a pivotal role in producing the reddish appearance on Arrokoth’s surface.

The research team consisted of Kaiser, Chaojiang Zhang, Andrew M. Turner, Jia Wang, Mason Mcanally and Ashanie Herath from UH Mānoa’s Department of Chemistry; Vanessa Leyva and Cornelia Meinert from Université Côte d’Azur; and Leslie A. Young from the Southwest Research Institute in Colorado.

The research findings were published in Proceedings of the National Academy of Sciences in June 2024.

The Department of Chemistry is housed in UH Mānoa’s College of Natural Sciences.

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