Happy 32! Happy New Mars Year!

They're too far apart to have a party, but today Curiosity and Opportunity could have rung in the New Mars Year. Today Mars reached a solar longitude of zero degrees and the Sun crossed Mars' equator, heralding the arrival of spring in the northern hemisphere and autumn in the southern hemisphere. This is the date that Martian climatologists have identified as the zero-point for Mars' calendar. Mars Year 31 was a good one, with Opportunity active at the rim of Endeavour crater and Curiosity arriving at Gale. Mars Year 32 should be even better, as Opportunity rolls up Solander point and maybe even Cape Tribulation, and Curiosity should explore the rocks in the mountain that drew her to Gale in the first place. And there'll be two orbiters arriving (we hope). MAVEN and the Mars Orbiter Mission's capabilities should warm the hearts of the climatologists who care about how one Mars year differs from the next enough to need to make up a calendar to mark their passage!

Since both rovers are (barely) in the southern hemisphere, the coming of the new year actually signals the time when they need to be looking ahead to winter cold. (Southern hemisphere winters are longer and colder than northern hemisphere winters because they coincide with aphelion on Mars' elliptical orbit.) Curiosity will be less affected by this than Opportunity, but still, cooler temperatures mean more power needed to heat rather than operate mechanical devices, so we're going into a less productive time. Winter solstice will be on February 15, 2014; so the first half of 2014 will be a very low time for Opportunity's activity in particular. The next equinox comes more than an Earth year from now, on August 17, 2014. Summer solstice is on January 11, 2015, and Mars Year 33 will begin with the next equinox on June 18, 2015.

You can read more about this particular calendar for Mars here. Like map coordinate systems, calendar systems are arbitrary, designed by people who need to reckon time for some reason, to suit their own particular needs. Someday there may be people on Mars, and they may well devise a totally different calendar. This one suits climatologists and robotic explorers just fine!