The Phoenix lander will try to stockpile soil samples as quickly as possible to make the most of diminishing solar power as the Martian winter approaches. But making full use of the lander鈥檚 instruments may require an additional extension of the mission.
Less sunlight and new technical problems have prompted Phoenix team members to revise their strategy for the lander鈥檚 TEGA (Thermal and Evolved Gas Analyzer) instrument, which cooks soil samples and looks for evidence of organic compounds as well as minerals that have been formed by liquid water.
The new plan is to place samples in the remaining four TEGA ovens, or cells, and conduct preliminary analysis by the end of September.
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鈥淭he strategy is to get all the cells filled as quickly as possible,鈥� says project manager Barry Goldstein of NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California.
Each sample will be heated at the lowest setting to vaporise any water 鈥� a key target of study 鈥� and dry out the sample for more analysis.
But experiments at higher temperatures, which can reveal the presence of chemicals such as perchlorate, will wait until October.
Since Phoenix鈥檚 mission, which was already extended once, is set to end at the end of September, NASA is currently working on an agreement to extend the mission further to accommodate those tests, Goldstein says.
Floating freely
The next sample to be delivered will be icy soil from one of the first trenches Phoenix ever dug, dubbed 鈥楽now White鈥�.
But a glitch means TEGA will not be able to help push vapour produced when the soil is heated into TEGA鈥檚 mass spectrometer, which measures its chemical composition.
That鈥檚 because the team can no longer control the flow of 鈥榗arrier gas鈥� used to push the vapour produced in the ovens into the spectrometer for analysis.
On Thursday, the team sent new instructions to the lander to circumvent this problem. Gas from the instrument鈥檚 four remaining ovens will now waft passively into the mass spectrometer instead of being pushed by the carrier gas.
Although the team is not sure how this unaided wafting will affect the analysis, Goldstein says they expect that the pressure of vaporised water and carbon dioxide will carry enough of the less common chemicals of interest through to be detected.
鈥淎dmittedly it鈥檚 limping along, but at least we鈥檙e not dead,鈥� Goldstein told New 杏吧原创.
Digging at dawn
Phoenix鈥檚 first attempt to deliver ice to TEGA was foiled in July, when the Sun seemed to partially melt the ice-bearing soil, causing it to stick to the walls of the scoop at the end of the lander鈥檚 robotic arm.
To circumvent the problem, the digging in Snow White is planned for early in the Martian morning, says robotic arm lead scientist Ray Arvidson.
The grinding rasp at the end of the robotic arm will be used to shave off bits of the ice, which the scoop will then collect. To deliver the sample to TEGA, the arm will be manoeuvred so it will keep the sample out direct contact with the Sun as much as possible.
The Phoenix team tested this collection strategy earlier this week, and the approach seemed to be successful. 鈥淲hen we did that it all fell out of the scoop,鈥� Arvidson told New 杏吧原创.
Mars Rovers 鈥� Mars is full of surprises; learn more in our continually updated .
