Artist concept of the Phoenix lander,
sleeping under the darkening polar skies of Martian autumn.It seems like only last month that we witnessed the drama of NASA’s Phoenix landing on Mars. We were on the edge of our seats in Chabot’s planetarium during those “seven minutes of terror” as Phoenix burned a meteoric path through Mars’ atmosphere.
But that was last May, and Phoenix has operated near Mars’ northern polar ice cap going on six months now! The mission has continued a couple months longer than originally planned, giving Phoenix more time to dig in the icy soil, bake scooped up samples to detect what chemicals sublimate, track the polar weather day and night, and look to the skies with its various instruments.
Phoenix sent back some very interesting news. Indeed, it had landed on what turned out to be dust-coated water ice; ice that contains chemicals like calcite and perchlorate— the former of which may indicate past liquid water on Mars, the latter of which, however, is generally toxic, and may complicate arguments for life, past or present, on Mars.
One of the more “fanciful” detections by Phoenix was falling snow: two or three miles above, Phoenix detected ice crystals falling from clouds– albeit flakes that never made it to the ground, instead evaporating like Earthly virga back into the atmosphere.
But Phoenix’s mission has a built-in conclusion (unlike the seemingly perpetual Energizer Bunnies exploring the Martian tropics, aka the Mars Exploration Rovers). Phoenix landed at 68 degrees north latitude– that’s equivalent on Earth to the north coast of Alaska, Norway, or south central Greenland– prior to Martian northern summer solstice (which was June 25). As with Earthly summertime, the polar days were unending, the Sun above the horizon 24 hours a day (yes, Mars’ day is about 24 hours long, just as on Earth). This provided Phoenix with its electrical power, generated by photovoltaic panels.
But now the Sun is dipping below the horizon several hours a day as the Martian northern hemisphere slides in the direction of autumnal equinox (December 26, 2008), at which time the Sun will spend half the time below the horizon, the other half never rising very high. Already, Phoenix’s solar panels are generating considerably less power than in the heyday of its mission. A dust storm, filling the air and blocking some of the already weak sunlight, has also cut available power to the lander for a time in October.
The diminishing conditions also caused Phoenix to put itself into an automatic “sleep” mode in late October, waking up for only a short time each day, when solar energy was at a peak. To give a flavor of the temperatures Phoenix is enduring, on Sol 151 (the 151st Martian day since landing-October 27th, Earth time), the daily high reached a balmy 50.8 degrees F-negative 50.8 that is! The night time low hit -128 degrees F… .
With every day possibly being the last we hear from Phoenix, scientists are collecting as much data as possible, mostly focusing on meteorological conditions. Reporting from the Martian polar ice cap, as the icy darkness of winter begins to settle in, this is Phoenix Lander, signing off….