Scientists suggest Venus once had a moon, later destroyed by tides

Scientists say Venus may have once hosted a small moon that was destroyed in a collision, offering a simple answer to why the planet has no natural satellite today. The hypothesis, presented by a team from the University of Arizona and published in Nature Astronomy on Tuesday, argues that a moon formed after a giant impact was later pulled into Venus by tidal forces and vaporized in a final plunge.

Venus is the only terrestrial planet in the inner solar system without a moon, a fact that has puzzled astronomers for decades. Earth’s large Moon and Mars’s two tiny moons are thought to be remnants of early collisions that shaped the planets. Without a moon, Venus lacks the stabilizing torque that moderates Earth’s axial tilt, a factor that may have contributed to its extreme climate. Understanding whether Venus ever had a moon helps scientists test models of planetary formation and the role of satellites in climate evolution.

The researchers used high‑resolution N‑body simulations to trace the fate of debris from a hypothesized impact that could have created a moon about 2,000 km across. Their models show that, within a few million years, tidal interactions would have caused the moon’s orbit to decay, spiraling it inward until it reached Venus’s Roche limit and broke apart. The resulting debris would have heated the atmosphere, leaving a brief spike in volcanic activity that matches geological evidence of a resurfacing event 500 million years ago. Co‑author Dr. Lina Patel said the scenario “fits the timing, the lack of a current satellite, and the anomalous heat flow we see on Venus.”

The team plans to test the theory with data from upcoming missions such as NASA’s VERITAS and ESA’s EnVision, which will map Venus’s surface and gravity field in unprecedented detail. If subtle mass anomalies or impact scars consistent with a moon’s disintegration are found, the hypothesis could reshape our view of Venus’s early history. Even without direct proof, the study highlights how planetary moons can be transient, reminding scientists that the solar system’s architecture is still evolving.