August 29, 2008
90 Days on Mars: Phoenix Lander Sends Martian Postcard
As the sun dips lower in the Martian sky with each passing day, NASA's solar-powered Phoenix Mars Lander took time this week to send a postcard of sorts to scientists on Earth after more than three months studying the red planet.
Phoenix beamed home a view of its trench-filled worksite after surpassing the 90-day mark of its initial mission to hunt for water ice buried beneath the barren arctic plains of Mars. While the Martian days, or sols, are getting colder and the sun expected to dip completely below the horizon tonight for the first time since Phoenix landed in late May, the probe itself is in fine health, mission managers said."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."
Goldstein told SPACE.com Thursday that Phoenix scientists are using the spacecraft to collect as much data as possible through the end of September, when its mission extension concludes, and have submitted a proposal for a second extension through mid-November should the probe survive that long. Researchers at the University of Arizona in Tucson are overseeing the mission.
"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."
Phoenix landed in the northern Vastitas Borealis region of Mars on May 25 and began a planned three-month mission to search for water ice using a shovel-tipped robotic arm and a science tool kit that included eight small ovens and a wet chemistry lab with four beakers, each the size of a teacup. Researchers hoped that those tools and a Canadian-built weather station would find definitive proof of local water ice and help determine if the Martian arctic could have once served as a welcome oasis for primitive life.
Since that time, Phoenix has successfully scooped, touched and tasted bits of actual Martian ice even as mission scientists race to collect more information from the probe's arctic landing site before winter closes in on Mars.
The days, Goldstein said, are steadily growing colder.
During Phoenix's first 50 days on Mars, the lander experienced temperatures that dipped down to minus 80 degrees Celsius (minus 112 degrees Fahrenheit) at their coldest. Now, the probe is experiencing temperatures as low as minus 85 degrees C (minus 121 degrees F) and its going to keep getting colder, Goldstein added.
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.
"We're predicting that's the end of mission," Goldstein said, adding that current projections put that power benchmark in November.
But for now, the $420 million Phoenix is forging ahead to study the Martian arctic, and is expected to use one of its two remaining wet chemistry lab beakers to study a sample of Mars this Saturday, Goldstein added. There are also four remaining ovens that stand ready to bake Martian samples and determine their composition, but it may be a challenge to fill all of them before the current mission extension ends next month, he said.
"We're in that mode now where we're collecting a lot of data," Goldstein said. "Everybody is so busy trying to make hay as the sun shines, literally and figuratively, that we haven't had a chance to take a breath to see what the biggest science find has been."
Goldstein also worked on NASA's long-lived Mars Exploration Rovers (MER) Spirit and Opportunity, which have been exploring different parts of the red planet since January 2004, and said it's a somewhat sad and weird feeling to know that those older spacecraft will outlive Phoenix.
But while Spirit and Opportunity, the latter of which began climbing out of the vast Victoria Crater this week, have returned thousands of images of Martian days and evenings from the planet's equatorial regions, Phoenix's views from the planet's arctic circle stand apart.
"We have those shots from MER of Martian sunsets and sunrises, but its something about the arctic," Goldstein said. "There's just something about that."