On April 8th, Earth will soar between the Sun and Mars. When it does, the Red Planet will reach what astronomers call "opposition" in the night sky. Just a few days later, Earth will be closer to Mars than it's been in more than six years – and during a total lunar eclipse! Here's how to watch.
April is the best month in 2014 to watch for the Red Planet. In fact, the last time conditions were this perfect for Mars-viewing was all the way back in December 2007. The explanation for this is pretty straightforward: Earth and Mars circle our parent star along different orbits. While our home planet takes just 365 days to complete a trip around the Sun, Mars takes 687*. This discrepancy means the planets spend all of their time at varying distances from one another, and most of their time in different positions relative to the Sun.
But every two years or so those positions align, bringing Earth and Mars into relatively close proximity. It is during this time, when the planets are on their closest approach, that those of us here on Earth are afforded the best possible views of the Red Planet. What's especially beautiful about the dance between Earth and Mars is that it's constantly changing. Because the planets are only in alignment about once every two years and two months, the date of opposition is always changing, as is the distance between the planets when that date arrives. The diagram featured here, via the Sydney Observatory, illustrates the 15- to 17-year cycle of extra-distant and extra-close Martian oppositions. Earthsky.org gives a good summary of this cycle:
The inner dark circle represents Earth's orbit around the sun; the outer dark circle represents Mars' orbit. When Mars is near the sun, as it was in 2003, we have an extra-close opposition. On the other hand, 2012 was a particularly distant opposition of Mars because Mars was far from the sun in its orbit. At the 2014 opposition, Mars is getting closer to the sun again and therefore it'll be closer to us than it was in 2012. But it's not as close at this opposition as it will be in 2018.
When should you look for Mars? Anytime in April, really, but there are two dates, in particular, that you'll want to mark on your calendar. The first is Tuesday, April 8th, when Earth will pass between Mars and the Sun. In this unique celestial configuration, Mars is said to be in opposition; positioned opposite the Sun in our sky, Mars rises in the East just as the Sun dips below the Western horizon, its red face fully illumined by the light of our parent star.
The second date you'll want to remember is the night of Monday April 14th/ early morning of April 15th, when Mars and Earth will be at their closest. If you can dedicate one night to watching the sky this month, make it the night of April 14th. Not only will the Red Planet be at its biggest in more than six years, it will coincide with a total lunar eclipse. What's more, the Moon and Mars will actually appear beside each other, the two of them blazing red in the night sky. It'll be the first total lunar eclipse visible from North America since December 2011. That it happens to coincide with our close pass of Mars is just incredible. You owe it to yourself to get outside and watch it for yourself.
Skygazers will be able to spot Mars coming up over the Eastern horizon right around sunset for most of April. As for the rest of the night, Mars should be pretty hard to miss – just look for the orange-red spot shining (but not twinkling) brighter than just about anything else. Around the middle of the month, NASA says, "the full moon will be gliding by the Red Planet in the constellation Virgo" throughout the night, "providing a can't-miss landmark in the midnight sky":
The lunar eclipse kicks off the night of April 14th at 4:37 Universal Time (that's 12:37 AM Eastern), when the Moon enters the western edge of Earth's shadow, but the best views will come shortly after 7:00 UT (3:00 AM Eastern), at the start of totality. This deepest, darkest period of the eclipse will last until almost 4:30 AM Eastern, and should make for a stunning view with Mars accompanying it through the night sky.
Bring a reclining lawn chair, a blanket, some pillows, a coat in case it gets chilly — whatever you need to get comfortable and still keep your eyes on the sky. You shouldn't really need a telescope or binoculars, although even a moderately powerful telescope should be able to bring surface features of the Red Planet (like its white polar ice caps) into view. Of course, the most important thing you can bring is some good company. Enjoy the view, everybody!
*That's Earth-days. Martian days are measured in "sols." A Martian day is about 40 minutes longer than an Earth days, so 1 Mars Year = 687 Earth days = 669 sols.