Red Planet | Universe Today

Written by Fraser Cain

Mars is the 4th planet from the Sun, and it has the nickname, "Red Planet". Of course, it got this name because Mars looks red in the sky. When Mars and Earth get to their closest point, Mars can get quite bright and red, so it's easy to see how it got this name.

Mars is named after the Roman god of war, as its red color reminded ancient astronomers of blood on the battlefield. The Babylonians called it Nergal, after their god of fire, war and destruction. In almost every culture, astronomers referred to the red color of Mars.

So why is Mars red? The outer crust of Mars has rocks rich in iron oxide. This is essentially rust, so Mars is red because its surface is rusty. Of course, with its thin atmosphere and lack of rain, it's not like new metal on the surface of Mars would rust. This happened because oxygen was locked up with the iron in the rocks billions of years ago.

Thanks to the Mars Exploration rovers, astronomers know that there was once large quantities of liquid water on the surface of Mars. Over time this water evaporated away, or was locked into ice beneath the surface of Mars. The surface of Mars is actually mostly basalt, and should look black like lava rocks, but the rocks have been steadily worn away by erosion over billions of years. It's possible that this process of reddening happened without water at all. Instead, Mars rocks reduced to a fine powder mixed with iron to create the reddish iron-oxide that we see today.

We've written many articles about the Red Planet for Universe Today. Here's an article about how scientists are finding out about Mars' watery past, and here's an article about why Mars is red.

If you'd like more info on Mars, check out NASA's Mars Exploration page. This has all the latest news and photos from Mars. Were you looking for information on the Red Planet movie? Here's a link to the IMDB page.

We've also recorded several episodes of Astronomy Cast about Mars. Start here, Episode 52: Mars.

Filed under: Astronomy