Can rocky planets gain rings?
Jupiter, Saturn, Uranus and Neptune all have rings, while the inner, rocky planets do not. Scientists don’t have any strong reasons to think rocky planets can never have rings, but their rings might be very different from those that we’re used to in our Solar System. For example, Saturn’s rings have an icy composition, but most rocky planets are much closer to their parent star. Similarly, ice material would not be able to exist here, so we would expect the rings to be composed of much rockier material.
In the future we will hopefully be able to search for these rings around other rocky planets elsewhere in the Milky Way galaxy. Amazingly, we now know of more than 4,000 planets, so there will be a lot of chances to search for these rings. Such rings would produce unique signatures as the planets pass in front of their parent stars and block the star’s light. Unfortunately, none of these other rocky planets have conclusive evidence of rings, but this is mostly because the signal of rings is still very small. Astronomers will be able to better search for them in the future as our telescopes and instrumentation get more powerful.
Coming back to our Solar System, none of the inner, rocky planets have rings now, but did they have rings at any time in the past or future?
Interestingly enough, Mars has two moons, and right now its inner moon, Phobos, is being pushed towards Mars from the gravitational interaction with the outer moon, Deimos. Astronomers can roughly estimate that if this continues, in about 50 to 100 million years Phobos will be so close to Mars that Mars’ gravity will rip Phobos apart,
producing rocky rings.