Moon and Mars cozy up to each other
The first half of January is the coldest time of the year, and as you bustle homeward after dark on a clear night, the glittering stars seem especially frosty and far. So now is a good time to consider a couple of much bleaker, wilder worlds currently in view high in the evening sky. Compared to these, the coldest January night in the wilderness is as warm and cozy as pillows by the fireplace with blankets and intimate friends.
One of these worlds is the bright white moon, shining high this week. The other is orange-tinted Mars. For the next few nights they appear rather close together, as shown here. Early this evening, Mars shines to the moon's left. Later tonight, as the sky wheels around, look for Mars above the moon.
Tomorrow they'll appear much closer together, a sight to catch the eye.
Although the moon and Mars seem like neighbors in the sky, looks are deceiving. The moon is just an astronomical stone's throw away, at 240,000 miles (less than I've driven my last two cars combined), while Mars is 330 times farther in the background. Moreover, despite Mars's pinpoint appearance, it's twice as big.
Following the Apollo moon landings from 1969 to 1972, the word ''moonscape" entered the language to mean any bleak, blasted terrain, such as after a carpet-bombing or a volcanic eruption. The real moon is much more barren than that. Not a breath of air, not a trace of moisture, never a sound crosses the dusty, changeless lunar hills and plains from one century to the next. The moon is a small world compared with Earth (if Earth were a basketball, the moon would be a tennis ball), but it still has 59 million lonely square miles of rubbly flats, boulder-strewn hills, and crumbled mountain cliffs -- every scene as wild and forlorn as the next.
Mars has about four times as much land, in fact a little more than Earth if you don't count our oceans. And compared with the Moon, Mars is almost homey. It has thin breezes and winds that kick up dust on the sunny, rusty plains. The daytime sky is full of light, sometimes with cirrus clouds and eerie blue sunsets, instead of the moon's empty black view of outer space. Valleys sometimes fill with morning fogs, and winter frosts can brighten the bare ground.
But the air is less than 1 percent as thick as Earth's, making it a pretty good vacuum by most people's standards. The sky is usually brownish orange with fine dust, and the dust is corrosive and probably carcinogenic. And the landscapes!
The gorgeous desert panoramas that are still being sent back by NASA's two Mars Exploration Rovers, Spirit and Opportunity, give a whole new meaning to the word ''bleak" (just go online to marsrovers.jpl.nasa.gov). And Mars is all like that, beyond every horizon around the globe.
And it's cold -- as frigid as minus-100 degrees Fahrenheit at sunrise even at the equator. The polar regions are so much colder that some of the atmosphere freezes right onto the ground as layers of dry ice.
Settlers on Mars, insulated from their deadly environment by spacesuits, will surely long for the gentle, rich lands of Earth -- where even in January, you can breathe the air and watch the stars with a bare face open to a remarkably friendly night.
Alan M. MacRobert is a senior editor of Sky & Telescope and Night Sky magazines in Cambridge (SkyandTelescope.com, NightSkyMag.com). His Star Watch column appears the first Saturday of every month. 
