We call it “The Red Planet.” But how did it get that way? SkyGuy looks at some possible explanations.

Mars! People have always been curious about this next-door neighbor of ours. First, Mars looks really cool. It is a beautiful shade of rusty red and it is often very bright in the night sky. Also, it is similar to Earth in some ways. So people can’t help but wonder whether there’s life there.

If we find evidence, no matter how small, that life once existed on Mars, that greatly increases the odds that there is life elsewhere in the universe. Maybe even intelligent life.

There have been several missions to Mars using robotic landers and satellites. Five years ago, NASA sent two rovers to Mars: Spirit and Opportunity. Those little rovers were designed to last just a few months, but five years later they are STILL GOING! They’ve gathered more information about our brother planet than we could have hoped for.

One of the most important things scientists want to know about Mars is this: is there now, or was there ever, liquid water there? Water is so important because if it is there, that could mean two things:

First, it increases the chances that there was or is some basic life on Mars.

Second, it would make it a lot easier for humans to visit Mars. We wouldn’t have to bring so much water with us from Earth.

The less stuff you have to bring with you, the easier it is to travel!

Scientists know that there is water on Mars, but right now it exists only as ice.

Mars is too cold and the atmosphere is too thin for liquid water to exist on the surface of the planet. But in the past, things might have been very different there. Many canyons and other features on mars sure look like they might have been created by erosion from running water. It’s possible there still is liquid water under the surface somewhere.

A lot of people want to know: Why is Mars red?

The answer to that question ties back to our search for water there — but in a strange way. Mars looks red because the Martian soil is rich in a substance called iron oxide. Iron oxide is just another name for “rust.”

Rust gets made when oxygen (a key part of both air and water) comes in long-term contact with iron. Over time, oxygen combines with the iron at an atomic level. And that turns into iron oxide.

On earth, iron usually gets rusty when it’s exposed to water.

This is why you don’t want to leave iron exposed to the elements and let rain fall on it. Rust is a bad thing for buildings and cars. It causes the metal to become weak and brittle. And if you landed your spaceship on Mars, you certainly wouldn’t want it to rust!

But here’s a puzzle: If there’s no liquid water on Mars, then how did the whole planet get so rusty?

For a long time, scientists thought it was possible that there had been liquid water on Mars billions of years ago. In fact, evidence that Mars was once a very wet planet has been growing steadily. So it seems logical that, if at one time water flowed freely on the Martian landscape, it might have combined with rocks that contain lots of iron — creating the rust that we see today.

But in 1997, NASA’s Pathfinder found that Martian soil contains more iron than Martian rocks. So where did the extra iron come from? Maybe meteorites? Well, that makes sense. We see craters all over Mars. Clearly, lots of meteorites have hit that planet.

I feel kinda sorry for Mars — Getting rocks thrown at it all the time …. that must hurt!

There is another possible answer, though.

Recently, scientists in Denmark suggested that the red dust on Mars might have been formed by a stranger process: the ongoing grinding of quartz and magnetite.

By simply tumbling these two kinds of rocks in a flask for several months, scientists were able to create the same kind of red dust that appears on Mars. No water was needed at all! The only thing you would need is wind, and there’s plenty of that on Mars.

OK, I’m not saying that the rust on Mars definitely comes from wind grinding up certain kinds of rocks. The truth is, we just don’t know for certain why Mars is red.

Yet.

But scientists are still working hard to answer this question.

Hmmm… Who knows, maybe you will be the scientist (or astronaut) who finally figures that out! And how cool would that be?

Personally, I like to think that at one time there was a lot of water on Mars, and that the rust is what’s leftover.

I like thinking of all that water on the surface of Mars.

It is a terribly dry, inhospitable place today and I like to think it looks that way partially because of all that water that used to flow on Mars billions of years ago.

But science doesn’t work like that.

You can imagine all kinds of answers, but the real job is to explore, test, and figure it out for real. That’s fun too.

Mars is a great planet to study. Sure, it doesn’t have oceans and so far it looks very unlikely there is any life there. But by sending these rovers and orbiters, we are learning so much about the planet’s history, its climate, and a lot about the potential for life on Mars in the past.

So remember … the sky is not the limit. You can go a lot farther than that. Just … Maybe pick a cozier place than Mars.