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Mars gets its close-up

This month, Mars has been more than ready for its close-up - and fortunately, the Hubble Space Telescope was ready as well, snapping pictures of the Red Planet during its orbital approach. If the skies are clear, you can have your own close encounter with Mars tonight - the closest encounter possible until the year 2016.

Tonight marks the very night when Mars stops coming closer and starts moving away from us in its roughly 26-month orbital cycle - at 6:47 p.m. ET, according to this handy list of the planet's oppositions and close approaches.

This year, Mars comes as close as 54.8 million miles - not as close as the historic pass-by of 2003 (34.6 million miles), but still a night-brightener. It shouldn't be hard to pick out the butterscotch-colored, steadily glowing jewel in the sky, but if you need help, just consult Space.com's sky chart.

NASA / ESA / STScI / Cornell / SSI
CLICK FOR VIDEO: The Hubble Space Telescope
took this picture on Dec. 17. In the southern
hemisphere, the dark triangular shape to the right is
Syrtis Major. The dark horizontal lane to the left is
Sinus Meridiani. NASA's Opportunity rover landed at
the western end of this region in 2004. Click on the
picture to watch a video clip narrated by Alan Boyle.

The Hubble telescope has been capturing Mars up close for more than a decade, since before NASA's first Mars rover ever bounced down to the surface. Today, two rovers are surveying the planet from ground level, three orbiters are mapping the globe from above, and another lander is on the way. So is it really worth Hubble's precious time to be taking pictures from afar?

"It's often surprising to people that, despite the fact that we have this armada of orbiters, landers and rovers on Mars, we can still do useful and unique scientific observations of Mars from Earth," said Cornell astronomer Jim Bell, who is a member of the Hubble observation team as well as the lead scientist for the panoramic color cameras on NASA's Mars Exploration Rovers.

Because of its far-seeing perspective, Hubble still provides the best all-at-once global views of the planet. Although the orbiters can produce much higher-resolution mosaics, they're just too close to see the whole planet at once.

"They're only seeing a bit at a time - strips of data taken at the same time of day," Bell told me today. "You don't get an overall perspective."

The Hubble views show how all the parts of a planet work together: dust storms and icy clouds, the permanent ice caps and the ebb and flow of seasonal frost. The latest pictures document thin, bluish clouds of water ice that are appearing just as springtime is coming to northern latitudes. That's a view that Hubble really hasn't seen up close before, Bell said.

"This data set really fills in what had been a missing gap in coverage during Mars' year," he said.

Scientists are particularly interested in how water moves around between Mars' surface ice and the atmosphere due to the planet's seasonal changes. "There's an enormous amount of water-ice cloudiness in the wintertime," Bell said. "How that super-cloudy season changes from the wintertime through the spring and the summer is still a subject of scientific debate."

NASA's Phoenix Mars lander, currently zooming toward a May landing in Mars' northern polar region, could help answer questions about the planet's water cycle - which naturally lead to the even bigger questions about past or present life.

Thanks to his double role, Bell gets to work with the big picture as part of the Hubble team, plus the up-close-and-personal views taken by the panoramic cameras, or Pancams, aboard the Spirit and Opportunity rovers. The Pancams are the instruments that have been capturing the stunning color views cataloged on NASA's Web site for the rover missions, as well as in Bell's coffee-table book, "Postcards From Mars." For the latest Pancam views, you can also check out the imaging team's Web site at Cornell University.

The rovers' primary mission was slated to last just 90 days - but almost four years later, they're still going strong, and so are the cameras.

"We haven't detected any degradation," Bell said. "Nothing seems to be wearing out."

Even though the rovers have been surprisingly resilient, Bell and his colleagues on the rover science team are handling them with exceeding care. Right now their top priority is to check out a safe haven for Spirit.

Just as spring is coming to Mars' northern hemisphere, winter is coming to the southern hemisphere, where Spirit is located. The solar-powered rovers almost didn't make it through a huge dust storm earlier this year, so the team wants to make sure that Spirit is in a good sun-facing position for the coming winter.

"We've been focusing on taking pictures of the region where we will have to park the rover very soon," Bell said. "The rover could spend most of 2008 at this one location."

Meanwhile, Opportunity is carefully making its way down the slopes of Victoria Crater, taking lots of pictures as it goes. "We're being very methodical at each location," Bell said. "We've been using the photography to try to relate the specific areas where the rover is to the layers that we see elsewhere in the crater."

Will the rovers still be taking pictures when Mars has its next close approach to Earth, in early 2010? Four years ago, no one would have predicted that, but Bell has given up trying to guess how long the rovers and their cameras will last. "There's nothing that we can use as a predictor to say, 'Oh, man, the end is coming,'" he said.

To keep tabs on Mars exploration until the bitter end, check in with our special report, "Return to the Red Planet." And for great views of Mars as well as Hubble's glories, take a tour of our space gallery.