The Phoenix Mars lander has reached the end of its mission, NASA officials said on Monday. Now, scientists will focus on analysing data collected throughout the five-month mission, searching for signs of organic chemicals that could hint at life or its precursors.
Despite stepped-up attempts to make contact with the craft using two orbiting spacecraft, Phoenix has been silent since 2 November. The team does not expect to make contact with the craft again.
鈥淎t this time, we鈥檙e pretty much convinced that the vehicle is no longer available for us to use,鈥� programme manager Barry Goldstein of NASA鈥檚 Jet Propulsion Laboratory told reporters. 鈥淲e are actually ceasing operations, declaring an end of mission operations, at this point.鈥�
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Early end
Phoenix鈥檚 end came three weeks earlier than anticipated, says Goldstein. Solar power to the craft has been dwindling as the Martian winter approaches.
But the lander鈥檚 last days were accelerated by a 28 October dust storm, which darkened the skies overhead and caused power levels to drop below a critical level. The storm sent the lander into 鈥楲azarus mode鈥�, which kept the probe off for 19 of every 21 hours to charge its batteries.
Last week, the Phoenix team had hoped to take advantage of the lander鈥檚 last days by reprogramming it to stay awake for as long as possible each day and perform a repeating sequence of science activities. But both the Mars Reconnaissance Orbiter and the Mars Odyssey spacecraft, which are used to communicate with the lander, failed to make any further contact with it.
The orbiters will continue to try to communicate with Phoenix for about three more weeks, but 鈥渢he possibility of it waking up again is very low鈥�, Goldstein says.
Health checkup
Phoenix is not expected to emerge from the Martian winter, when temperatures at the site will drop below -150 degrees C and carbon dioxide ice will encase the vehicle. The solar arrays 鈥渨ill likely crack and fall off the vehicle鈥�, says Goldstein, and coatings on the electronics are expected to become extremely brittle.
Still, the team plans to check in on Phoenix in October 2009, when the site will once again receive enough sunlight to power the lander. 鈥淭his vehicle has been so superlative in the way it鈥檚 been behaving since we landed, nothing would surprise me, so we鈥檒l look again in October,鈥� Goldstein says.
Researchers involved with the project are expecting to perform months of follow-up work to interpret results from the $475 million mission. But in Monday鈥檚 press briefing, Phoenix principal investigator Peter Smith of the University of Arizona in Tucson recapped some of Phoenix鈥檚 early findings, including:
路 The 鈥楬oly Cow鈥� feature: Phoenix snapped its first picture of ice directly underneath the belly of the lander soon after a perfect touchdown on 25 May on Mars鈥檚 northern plains. 鈥淚f you had a broom, you could make an ice-rink right where we landed,鈥� says Smith.
路 Water ice: Its presence was confirmed on 30 July, when the lander detected trace amounts in a sample of soil it had dug up.
路 Perchlorate: The team did not anticipate finding the chemical, which can act as an energy source for some terrestrial microbes.
路 Turnip-friendly soil: While previous missions, like the Mars Exploration Rovers, found mostly acidic soil, samples at Phoenix鈥檚 landing site were discovered to be alkaline. They also contained some basic mineral nutrients.
路 Calcium carbonate and clays: These minerals are thought to form through the action of liquid water. 鈥淥n the Earth, we would conclude immediately that there was liquid water in this soil. For Mars, we have to be a little more careful, and we鈥檙e going to develop this story as we can, as we interpret our data,鈥� Smith said.
The team next plans to attempt to recreate the soil conditions observed on Mars to confirm the lander鈥檚 findings. Researchers have not yet ruled out the possibility that Phoenix might have found evidence of organic chemicals on Mars, says Smith, which might signal past life or its precursors. 鈥淲e haven鈥檛 analysed the data at that level yet,鈥� he says.
