Uranus Moon Study Finds 5-Fold Deuterium Gap, Undercutting Giant-Impact Formation Theory
Updated
Updated · Astrobites · Aug 10
Uranus Moon Study Finds 5-Fold Deuterium Gap, Undercutting Giant-Impact Formation Theory
1 articles · Updated · Astrobites · Aug 10
Summary
PNAS researchers report Uranus’s five major moons carry deuterium-to-hydrogen ratios about five times higher than Uranus itself, indicating the moons likely did not form from the planet’s own material.
James Webb’s NIRSpec data revealed a 4.14-micron semiheavy-water absorption feature, which the team calibrated with lab ice spectra to estimate each moon’s D/H ratio.
Those ratios more closely match icy comets in the outer solar system than Uranus, weakening the long-standing idea that one giant impact both tilted the planet by 98 degrees and created its major moons.
The paper instead points to two alternatives: Uranus may have tidally disrupted an icy passing body into a moon-forming disk, or impact debris may have realigned pre-existing moons after the tilt event.