Does Mars Have Rings?

QUICK ANSWER

Mars currently has no rings, but it may have them in the relatively near future (cosmically speaking). Phobos, Mars's larger moon, is slowly spiraling toward the planet. In about 50 million years, it will either crash into Mars or break apart from tidal forces, possibly forming a ring around Mars.

Mars has no rings today, which fits the pattern: only the four giant outer planets have ring systems. But Mars is unusual in that it might actually develop rings in the future, due to a doomed moon that's slowly falling inward.

Does Mars have rings now?

No. According to NASA, Mars has no rings. Only the four giant outer planets (Jupiter, Saturn, Uranus, and Neptune) have known ring systems. Mars's two moons, Phobos and Deimos, are tiny and don't have enough material between them to form anything visible. Mars also doesn't have the same gravitational and orbital conditions that the gas giants use to maintain stable rings. For now, the planet looks just as ringless as Mercury, Venus, and Earth.

Will Mars ever have rings?

Possibly, and within a geologically short timeframe. Phobos, Mars's larger moon, is spiraling inward toward Mars at about 6 feet every century. In about 50 million years, it will reach the Roche limit, the distance at which tidal forces will rip it apart. Some models suggest Phobos's debris could form a temporary ring around Mars before either falling to the surface or being lost to space. Other models suggest Phobos may simply crash into Mars whole, creating a massive impact instead of a ring.

Has Mars had rings before?

Possibly multiple times. Some scientists have proposed that Mars has cycled between having moons and having rings over its long history. According to this idea, when a large object gets close enough to Mars, it gets torn apart into a ring; the ring debris then gradually clumps back together into a new moon, which eventually spirals inward to be torn apart again. The cycle would have repeated several times over billions of years. There's no direct evidence for past Mars rings, but the math is plausible.

Why do only the outer planets have rings?

Because they have the right conditions. Ring systems need a steady supply of material (usually from broken-up moons or comets), strong enough planetary gravity to hold material in orbit, and an environment where the Sun's gravity doesn't quickly destabilize orbits. The four giant planets have strong gravity, many moons feeding rings, and are far enough from the Sun that particles stay stable. Inner rocky planets have none of these advantages.

Mars has no rings today, but it's the rare inner planet that's likely to get them. When Phobos eventually breaks apart in around 50 million years, Mars may briefly join the ranks of the ringed planets. It would be the only rocky planet in our solar system with rings, even if temporarily.

Does Mars Have Rings?