Mars is the world orbiting the sun one step outward from Earth’s orbit. Earth takes one year to orbit the sun once. Mars takes about two years. The orbits of Earth and Mars are the reason Mars is one of the most fascinating planets to watch in our sky, and they are the reason Mars is sometimes bright and sometimes faint.
The brightness of Mars in our sky depends on where our two planets are in orbit around the sun. Sometimes Earth is close to Mars, and sometimes we are far away.
We are close – and Mars appears very bright in our sky – every time Earth passes between the sun and Mars. At this time, Mars appears at opposition – opposite the sun in our sky – rising in the east when the sun sets in the west. Oppositions of Mars recur about every two years and 50 days.
Image credit: Solar System Live
So Mars alternates in appearing bright and faint in our sky. It’s bright in the years we pass between Mars and the sun. It’s faint in the years in between, when Mars lies far across the solar system from Earth – at times hidden from our view by the sun itself.
In 2012, Earth passes between the sun and Mars on March 3. So Mars is relatively close to us then, and it appears as a bright reddish “star” in our night sky, rising in the east while the sun is setting in the west. Mars is excellent to view through March 2012. It’s pretty good in April and May, too! And it’ll be a charming companion to the beautiful skies of June, July and August. By September 2012, Mars will be getting very faint again – inconspicuous. It’ll be exceedingly faint and low in the southwest when 2012 ends.
Mars will also come close in April 2014, May 2016 and July 2018. And so it will be close and bright every two years for billions of years to come!
Bottom line: Mars is bright when it and Earth are on the same side of the sun. It’s faint when it and Earth are on opposite sides of the sun. 2012 is a good year to see Mars.