Just as summer is giving way to autumn in the Earth's northern hemisphere, the seasons are changing on Mars, too. Near the Martian north pole, the Mars Phoenix Lander is watching its environment grow darker and colder, bringing Phoenix a little closer the end of its mission each day. Meanwhile, in Mars' southern hemisphere, the rovers Spirit and Opportunity have been reinvigorated with increased sunlight to power their solar panels, and are on the move once more. Phoenix, which has conducted fascinating experiments on the planet's soil and water ice, saw the sun dip below the horizon yesterday for the first time since it landed on May 25. NASA officials originally planned a 90-day mission for Phoenix, which would have ended operations this week, but since the lander is in excellent condition NASA extended its mission.
"It's doing fabulously," said Barry Goldstein, NASA's Phoenix project manager at the Jet Propulsion Laboratory in Pasadena, Calif. "But I've made it clear to the science team that the warranty's over.... The vehicle is not going to tip over and die," Goldstein said. "But we're getting to the point where we're going to start seeing the creaks and groans" [SPACE.com].
Researchers expect Phoenix to continue working through the end of September, and say it may be able to persevere for a month or two beyond that date. But temperatures are getting steadily colder, researchers say, and the amount of power generated by Phoenix's two solar arrays is also on the decline, with the probe currently generating about 2,500 watt-hours each day - or about 1,000 watt-hours less than when it landed - because of waning sunlight. The absolute minimum needed for Phoenix to perform the most basic operations is about 1,000 watt-hours, mission managers said
. When Phoenix reaches that cut-off point it will cease functioning, and the harsh winter freeze is expected to damage the lander's equipment and end the mission for good.
But on the outside chance that spring sunlight recharges the craft next year ... it has been programmed with a “Lazarus mode” to signal that it has risen from the dead [The New York Times].
Below the Martian equator, however, the Mars rovers Spirit and Opportunity easily made it through the southern hemisphere's winter, and have picked up their work once more. Spirit, which is still recharging its batteries, is
busying itself taking a panoramic picture of the surrounding area. Once the sun comes up some more, Spirit will drive off Home Plate to an area that could contain silica-rich soil, which could be evidence of hot water [Nature News].
Opportunity, meanwhile, is preparing to climb out of the Victoria crater, which is has been exploring for nearly a year. But after over four and a half years on the planet, both rovers are worse for wear. NASA decided to steer Opportunity out of the crater
after one of the rover's six wheels seemed to show an early sign of failure – a scenario that could have trapped the rover inside the crater forever [New Scientist].
Image: NASA/JPL-Caltech/University of Arizona/Texas A&M University