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Study Says Venus Likely Swallowed a Moon

Computer models show Venus’s very slow spin would pull a satellite inward, creating a testable explanation for the planet’s lack of a moon.

Overview

  • Researchers at the University of California, Riverside and the University of Bordeaux used physics-based simulations to show a hypothetical Venusian moon would most often spiral inward and impact the planet.
  • The work, reported Monday, finds modeled moon lifetimes typically range from about 30 million to roughly 1.7 billion years before inward migration ends in a collision.
  • The inward pull happens because Venus’s extremely slow rotation transfers angular momentum in a way that drives satellites closer rather than pushing them away as Earth’s faster spin does.
  • Sources differ over the paper’s status—some accounts call it an arXiv preprint not yet peer reviewed while others say it appears in The Astrophysical Journal—so independent review is still needed.
  • NASA missions planned for the late 2020s, including DAVINCI+ and VERITAS, could collect geological and atmospheric data that help test whether Venus once had and then lost a moon.