// SPACE.COM — SPAZIO & SCIENZA
Did Venus eat its own moon?
"An interesting aspect is that a heavier moon is destroyed faster, since a massive moon would drain Venus's spin so efficiently that it hastens its destruction."
When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works.
Scientists may finally know why Venus, Earth's twin, lacks a moon, finding that the hottest planet in the solar system may have consumed its own natural satellite.
Venus is often referred to as Earth's twin due to its size, mass, rocky composition, and distance from the sun, but there are some glaring differences between the two planets. Aside from Venus' blisteringly hot temperature, which could melt lead, incredible surface pressure, violent high-speed winds, and clouds of sulfuric acid, one of the key differences between Earth and Venus can be seen from afar. While our planet has a constant companion in the form of the moon, Venus lacks a moon of its own. In fact, the only solar system planets lacking moons are Venus, the second planet from the sun, and Mercury, the closest planet to the sun.
One question that scientists have puzzled over for years is whether Venus always lacked a moon, or if the hottest planet in the solar system once had a natural satellite and somehow lost it. Now, a team of researchers may have arrived at an answer, determining the fate that would have befallen a hypothetical moon orbiting Venus.
"I have always had a fascination with moon formation and evolution in the solar system, and particularly with Venus since my research is centered around its evolution and potential for past habitability," team leader Stephen R. Kane of the University of California, Riverside told Space.com. "Venus is Earth's twin, and both are nearly identical in size, mass, and composition. However, Earth has a large moon, and Venus has no moon at all, not even a small captured satellite."Venus undoubtedly experienced large impacts, just as Earth has, and so has had as much, if not more, opportunity to form a moon similar to what we see in our own skies."
Kane and colleagues constructed a simulation to test their ideas of what could have become of the Venusian moon.
"The work involved going back to fundamental physics and creating the simulation from the ground up, which I validated by ensuring I could reproduce the evolution of the Earth-moon system," Kane said. "The moment I realized that our model provided a complete explanation for Venus not having a moon was an exciting one!"
The team modelled a gravitational tug-of-war between Venus, a hypothetical moon, and the sun, following this forward over billions of years.
"This is the same physics that governs our own moon, which is slowly drifting away from Earth. We ran the calculations across a wide range of possibilities for how fast Venus was spinning and how massive its moon might have been, using two independent mathematical descriptions of how tides work," Kane explained.The researcher said that this was done so the conclusions reached wouldn't hinge on one set of assumptions. They found in most cases a Venusian moon would not drift safely outward the way ours does. Instead, the modelling showed that a moon orbiting Venus would eventually reverse its course and spiral inward, causing it to be torn apart by the planet's gravity.