MarsNews.com

Did Mars Once Have Three Moons?

Rather than the two Moons we see today, a collision followed by a circumplanetary disk may have given rise to three moons of Mars, where only two survive today. Image credit: Labex UnivEarths / Université Paris Diderot.

Rather than the two Moons we see today, a collision followed by a circumplanetary disk may have given rise to three moons of Mars, where only two survive today. Image credit: Labex UnivEarths / Université Paris Diderot.

Mars’ two moons, Phobos and Deimos, are small, irregular, but orbit in the same equatorial plane as the red planet. Although they’ve long been thought to be captured asteroids, those orbits would be supremely unlikely. Another possibility would have been if a massive impact created a debris disk, similar to how Earth’s Moon was formed. That alternative creates equatorial orbits, but normally produces at least one very large moon. However, a new simulation was performed, showing how an impact could create three moons around Mars, where the largest, inner one decays, creating Martian system we see today.