Does Mars Have Rings?

Recently, while discussing what she had learned in class, my daughter asked me: ”does Mars have rings?”. She is ten and it is fun to see her interested in anything educational. Unfortunately, I had to tell her that no, Mars does not have rings. While saying no was disappointing, it left a good opportunity to teach her how planetary rings are formed..

Planetary ring systems are formed in two ways. The first is by ice and dust like those around the ice giants and similar to the rings around Saturn. Scientist believe that the particle have been captured by a planet’s gravity and are prevented from combining into a moon by that gravity. The rings are visible because of the light that the particles reflect. In the case of Saturn, some of the moons within the rings system have ice geysers that some scientist think are constantly replenishing the rings.

A second way that a planetary ring may form is through impact. If a large enough asteroid were to impact a planet, dust and rock debris would be thrown into space. That debris would then be captured by the planet’s gravity. Scientists believe that the debris will fall back to the planet, but do not know how long it would take.

Mars may develop a ring system in the future. Scientists know that Mar’s moon, Phobos, is in a decaying orbit around the planet. In anywhere from 10 million to 100 million years it will crash into the planet forming a ring system as the debris is ejected back into space. After a million or so years, that ring system will collapse back onto the planet’s surface, causing an extensive crater field.

That begs the question of how did Phobos find itself in such a predicament. Well, it is most likely a captured asteroid. Its orbit took it too close to Mars and it did not have enough velocity to escape the planet’s gravity. Many moons in our Solar System have come to orbit their primaries in this fashion. Usually, small moons are captured and large moons form in situ, so to speak.

Now you know the answer to ”does Mars have rings?” and a little about a rings in the planet’s future. Don’t forget to read up on Mar’s other moon Deimos and maybe look a little deeper into Phobos. If planetary rings interest you, NASA has plenty of information on their website.

Here’s an article the describes how Phobos will eventually crash into Mars. And here’s some more information about what Saturn’s rings are made of.

The Planetary Rings Node has many resources for Saturn’s rings. And here’s an article about potential rings around Pluto.

We’ve covered Mars in the past at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars. We also talk about Saturn’s rings in Episode 59: Saturn.

Sources:
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/981027a.html
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos
http://apod.nasa.gov/apod/ap080414.html