Argon on Uranus and Neptune may reveal more about their origins than their interiors

• New research led by Southwest Research Institute (SwRI) measured the atmospheric argon-40 in Uranus and Neptune to estimate the amount of rock in their interiors. The study found that the argon-40 likely has two origins: primordial argon from the protosolar nebula and argon produced by radioactive decay in rocky materials. The team concluded that primordial argon overwhelms any contributions from radioactive decay, suggesting that atmospheric argon-40 measurements may reveal more about the planets' formation environments than their icy or rocky interiors.
• The research may help scientists determine whether Uranus and Neptune are dominated by ice or rock, or if argon-40 measurements can provide vital clues about where and how the planets formed in our solar system. The study used a numerical model of the protosolar nebula to track the condensation and transport of primordial argon inside ice particles, which accumulated to form the planets.
• The findings may guide future study of Uranus and Neptune's atmospheres, as future probe missions could directly sample noble gases and isotopic ratios that cannot be reliably determined through remote observations. The research is part of an ongoing exploration of these planets, with a 2026 study suggesting their chemical origins may differ despite similar characteristics.

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