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Frozen Death Looms for Phoenix Mars Lander
2008-10-08
After more than four months on the arctic plains of the red planet, NASA's Phoenix Mars Lander's days are finally numbered.As the sun begins to set for the frigid Martian winter, the spacecraft will lose its energy supply, freeze and eventually fall into a mechanical coma from which it will likely never wake up. Muzi.com News 10080764-0 (muzi.com) Muzi.com News 10080764-1 (muzi.com) Phoenix's mission has been to dig up samples of Martian dirt and the subsurface layer of rock-hard water ice at its landing site in Mars' Vastitas Borealis plains. The lander has been scanning the samples for signs of the region's past potential for habitability. Muzi.com News 10080764-2 (muzi.com) Muzi.com News 10080764-3 (muzi.com) Phoenix landed on Mars on May 25, late spring in the Martian northern hemisphere. The mission was originally slated to last three months, to the end of August, but was extended twice; first to the end of September and recently through the end of December. Muzi.com News 10080764-4 (muzi.com) Muzi.com News 10080764-5 (muzi.com) But whether or not Phoenix will survive that long is uncertain and depends on how the spacecraft's systems handle its ever-dwindling energy supply and the harsh conditions of the Martian winter. Muzi.com News 10080764-6 (muzi.com) Muzi.com News 10080764-7 (muzi.com) "We're at the mercy of Mars," said Phoenix project manger Barry Goldstein, of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Muzi.com News 10080764-8 (muzi.com) Muzi.com News 10080764-9 (muzi.com) Winter sets in Muzi.com News 10080764-10 (muzi.com) Muzi.com News 10080764-11 (muzi.com) As winter descends on the Martian arctic, two important things will happen: The sun will sink below the horizon, and "it's going to get cold," said Phoenix meteorological team member Peter Taylor of York University in Toronto, Canada. Muzi.com News 10080764-12 (muzi.com) Muzi.com News 10080764-13 (muzi.com) Of course, Mars is never warm by Earth standards (it is further from the sun and lacks our planet's thick, heat-trapping atmosphere), but summer above the Martian arctic circle is downright balmy compared to the winter. Muzi.com News 10080764-14 (muzi.com) Muzi.com News 10080764-15 (muzi.com) Midday temperatures at Phoenix's landing site hit about -4 degrees Fahrenheit (-20 degrees Celsius) in the summer (as measured by the lander's meteorological mast thermometer). Nighttime temperatures then still dropped to -112 F (-80 C). Currently, those daytime temperatures have started dipping down to -22 F (-30 C), with nighttime temperatures hitting about -130 F (-90 C). Muzi.com News 10080764-16 (muzi.com) Muzi.com News 10080764-17 (muzi.com) By mid-November, those night temperatures are expected to plummet to -184 F (-120 C). Muzi.com News 10080764-18 (muzi.com) Muzi.com News 10080764-19 (muzi.com) The reason of course, is that setting sun. Muzi.com News 10080764-20 (muzi.com) Muzi.com News 10080764-21 (muzi.com) The sun is constantly above the horizon during the arctic summer, just as it is on Earth. Come fall, it starts to dip below the horizon more and more each day until winter, when it sets for good and doesn't rise again until the spring. Muzi.com News 10080764-22 (muzi.com) Muzi.com News 10080764-23 (muzi.com) The sun has already begun to sink below the horizon for part of the day at Phoenix's location, Goldstein said. Phoenix's landing site is at a latitude similar to northern Alaska on Earth. Muzi.com News 10080764-24 (muzi.com) Muzi.com News 10080764-25 (muzi.com) Dwindling energy Muzi.com News 10080764-26 (muzi.com) Muzi.com News 10080764-27 (muzi.com) The colder temperatures and setting sun combined will diminish the energy available to Phoenix for its science operations. Muzi.com News 10080764-28 (muzi.com) Muzi.com News 10080764-29 (muzi.com) During the summer, there is plenty of sunlight hitting Phoenix's wing-like solar arrays, its sole source of power on the planet. But once the sun is gone, so is its energy supply. Muzi.com News 10080764-30 (muzi.com) Muzi.com News 10080764-31 (muzi.com) "The sun is going down, so there's less and less energy being fed into the batteries through the solar panels, and that really is the biggest problem" facing the mission, Taylor said. Muzi.com News 10080764-32 (muzi.com) Muzi.com News 10080764-33 (muzi.com) Specifically, the orientation of Phoenix's solar arrays limits how much sunlight it can take in as the sun changes its position in the sky. Muzi.com News 10080764-34 (muzi.com) Muzi.com News 10080764-35 (muzi.com) "The problem is that the solar panels are horizontal, and we can't tilt them, so as the sun gets lower and lower on the horizon, there's less and less power being generated," Taylor explained. Muzi.com News 10080764-36 (muzi.com) Muzi.com News 10080764-37 (muzi.com) At the beginning of the mission, Goldstein said, Phoenix's solar arrays were generating about 3300 Watt-hours per sol, or Martian day (about 24 hours, 39 minutes) — that's enough energy to light a 60-Watt light bulb for 55 hours. Muzi.com News 10080764-38 (muzi.com) Muzi.com News 10080764-39 (muzi.com)
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