Mars and Moon Put on Sky Show Tonight

March 25, 2010 — -- If you live in a place with clear weather tonight, go out and take a look at the waxing crescent moon in the evening sky. The bright star near it -- you may be able to make out a subtle salmon hue -- is the planet Mars, and this is about as pretty as the view of it gets.

Mars is just a couple of months past opposition -- when it is directly opposite the sun, and therefore about as close to us as orbital mechanics allow. The earth, 93 million miles from the sun, takes 365 days to make one orbit; Mars, 141 miles out on average, takes 687. We overtake it on our inside track once every 22 months or so.

If you have a telescope (fewer people do these days), this will be a good night to use it. You may see subtle striations in color -- the same ones that had the 19th-century astronomer Giovanni Schiaparelli convinced he was looking at channels carved by water on the Martian surface.

Schiaparelli's Italian "canali" was inevitably translated as "canals" -- and soon enough there were perfectly intelligent earthlings wondering if intelligent Martians were irrigating their planet while planning invasions of ours.

Tales of a Rusty-Red World

Today we know better, or at least we think we do. The twin Mars rovers, Spirit and Opportunity, found evidence that Mars probably did have standing water on its surface millions of years ago, though it would have been in brackish ponds instead of artificially-made canals.

The rovers, which were expected to last 90 days after they landed in January 2004, still are transmitting six years later -- though Spirit, the first one, broke through some crusty soil last year and is probably trapped in its final resting place.

As a bonus, a probe called Phoenix landed in the Martian arctic in 2008 and found ice just beneath the surface. So Mars keeps getting more and more interesting in close-ups.

Moon and Mars Put on Sky Show

Tonight, if you see it, it won't be in closeup at all; it is almost 90 million miles away now. At opposition, because its orbit is lopsided, it sometimes comes within 40 million miles.

Spirit and Opportunity were launched during the last such close pass in 2003, and Steve Squyres, the principal investigator, told me they would have been too heavy to send at any other time.

Mars will slowly fade in brightness during the spring as we move away in our faster orbit. There will be another opposition in March 2012.

For now, though, it's just a night to enjoy the view -- if the weather holds.