While NASA's Spirit rover provides spectacular close-up views of Mars, Earthlings can still spot the planet from afar on any clear night. Though nowhere near as close as it was during the historic approach last August, Mars is still plainly visible each evening as it continues to fade in brightness.
Now in the dim zodiacal constellation of Pisces the Fishes, Mars is about 112 million miles (180 million kilometers) from Earth and shining at a magnitude 0.4. That’s just a trifle fainter than Procyon, the eighth-brightest star in the sky.
Still, it is a tremendous comedown from last August, when Mars ranked as the third-brightest object in the night sky, just after the moon and Venus. In fact, this topaz-tinted world now only appears one-twentieth as bright as it did 4½ months ago.
Time is running out on your last chance to get a decent view.
Mars is farther from the sun than Earth is, so it takes longer to make a complete orbit. Earth has passed Mars on an inner track and is racing away from the Red Planet.
By the end of February, Mars will have receded to 154 million miles (247 million kilometers) from Earth and will have dimmed further to magnitude 1.1 (about as bright as the star Pollux in Gemini).
Mars is now rather disappointing in telescopes, as its apparent diameter also shrinks. It’s apparent size as seen through telescopes is only about 30 percent of what it was back in late August — just 7.7 arcseconds in width, in astronomers' parlance.
Put another way: You would need an eyepiece that magnifies approximately 230 power to make Mars appear as large as the moon does with your unaided eye. Most novice observers have small telescopes where such a magnification is not recommended because it would only serve to make the image appear rather dim and fuzzy.
Mars doesn’t even appear as a full disk at the present time; the angle of illumination between Mars, Earth and the sun makes Mars appear more like a gibbous moon, about 88 percent illuminated.
During the next several weeks, the Red Planet will be setting roughly between 11:30 p.m. and midnight. Although getting progressively dimmer, Mars will still do a pretty good job of staying well ahead of the sun through about midspring. But toward the end of May it will begin sliding more rapidly toward the sun’s vicinity, eventually setting before the end of evening twilight by the middle of June.
Along the way it will meet up with a couple of naked-eye planets.
In the last week of April Mars will appear to hover near dazzling Venus. By the third week of May it flirts with Saturn, and on the evening of May 22 it will form a loose triangle with Saturn and a lovely crescent moon.
Mars will continue to fade as it gets farther away from Earth through the balance of spring and into early summer. Finally, sometime during mid- or late July, it will become so deeply immersed in the bright evening twilight as to be rendered completely invisible. By then it will also be at its absolute faintest magnitude of +1.8, putting it in the rank of second-magnitude stars.
On Aug. 7 Mars will reach the aphelion part of its orbit, placing it at its greatest distance from the sun: nearly 155 million miles (249 million kilometers).
Finally, just over a month later, on Sept. 15, it will be at conjunction with the sun and 248 million miles (398 million kilometers) from Earth. An inglorious end to the best apparition of Mars that any of us will ever see in our lifetimes.