Mars is going to disappear! Yep, for 55 minutes. On the evening of January 13, at 9:11 pm, Mars is going to disappear. About 55 minutes later, Mars will reappear. The villain in this kidnapping is the Moon. The Moon not only eclipses the Sun, but also the planets, and some stars as well.

Because the Moon is closer to us than the planets and stars, it can pass in front of them from our point of view. Rather than calling it an eclipse, astronomers say the Moon occults Mars. As the Moon orbits the Earth, the Sun shines on different faces of the Moon. When it shines on the side facing us it is a full Moon. When the Sun shines on the back side of the Moon, the Moon appears dark to us. These are referred to as phases of the Moon. It takes the Moon 29.53 days to complete each phase.

During this time, the Earth is orbiting the Sun. Because of this, each night the stars drift a little further west. Therefore, the Moon must travel fewer days to return to the same position amongst the stars. My astute granddaughter said “wait, doesn’t Mars move also.” Yes, Mars orbits the Sun every 687 Earth days and Mars drifts slowly eastward. Calculate all the math, and the Moon will occult Mars again in 26.67 days. That will be during the day on February 9 and you can’t see Mars. Also, the Moon’s orbit is inclined to the Earth’s orbit around the Sun. The Moon may occult an object one month but miss the object the next. So occultations, like eclipses, are occasional events. Gosh, how do we ever land on these moving targets?

This disappearing act is an event you don’t need to be an expert astronomer to view. The Moon is full and Mars is bright. Put on a warm coat and step outside at 9 pm. You won’t even need to escape city lights. In the east you’ll see the full Moon very close to Mars. As the minutes pass, because of Earth’s rotation, the Moon and Mars creep westward. But because the Moon orbits the Earth, the Moon is moving slowly toward Mars. At about 9:11, the Moon overtakes Mars. It typically takes 30 seconds to a minute for Mars to completely disappear.

While you wait for Mars to reappear, enjoy the beautiful and bright Sirius off to the right and the handsome Orion above it in the south. Setting in the west are the bright Venus and nearby Saturn. The full Moon washes out the dimmer stars, but not so the gems Sirius, Orion, Saturn and Venus.

At about 10:06, Mars will reappear. Let’s hope the weather permits. If so, the sight will be a beautiful promise for the year to come!