Astronomers have detected carbon monoxide in the lower atmosphere of Uranus for the first time, indicating the planet has a much icier interior than previously thought.
Thibault Cavalié at the University of Bordeaux led the study using the Atacama Large Millimeter/submillimeter Array telescope in Chile.
Observations took place three times between 2022 and 2024. The team found that only models with high ice content could explain the measured levels of carbon monoxide.
“We find that Uranus is more on the ice-giant side than on the rock-giant side,” Cavalié said. He added that the results suggest the long-standing debate over the planet’s composition may now be resolved.
Vanesa Ramirez at Leiden University noted that assumptions about chemistry and internal structure remain uncertain. She said the data alone do not fully settle whether Uranus is primarily ice-rich or rock-rich.