Studies of the surface and atmosphere of Mars from NASA's Phoenix Lander

This work will be part of NASA's Phoenix Lander Mission, which will send a spacecraft to lands Mars in May 2008 and take a close-up look of the Martian northern polar region. Large amounts ice lie just below the surface there. A robotic arm will dig into the ground, looking for clues about where the ice came from and whether microbes might have lived in Mars' early history. Our contribution to the mission will help understand Mars in three ways. Firstly, we will ensure that microscopes take the best possible pictures of the soil and ice in the Martian arctic. We will examine those pictures to determine whether the soil was once deposited from sediments in a lake or sea, or carried there by the wind, or came directly from the erosion and break down of volcanic lava. Secondly, when the Phoenix spacecraft falls to the surface of Mars from space it gets slowed down by friction with the air and decelerates. The amount that the lander decelerates depends on the air pressure and temperature. We will use the measured deceleration of the Phoenix lander to calculate how the air pressure and temperature changes with height. This can tell us information about the climate, for example, whether there were clouds present during landing or whether the air was dry with a lot of dust. Thirdly, the Phoenix lander has an experiment where soil is scooped up by the robotic arm and mixed with water. Salts in the soil will dissolve in the water and probes in the solution will measure the type of salts, for example whether sodium chloride is present, the salt people use for food. We hope to find out whether the salts on Mars were left behind when a big sea dried up or whether they come from the chemical reaction of volcanic gases with the soil. The microscopy station on Phoenix, that forms a large chunk of our research, consists of a conventional optical microscope and a very-high-resolution microscope called an atomic-force microscope, or AFM. This microscopy station was originally built by Dr Tom Pike while working at NASA's Jet Propulsion Laboratory in California. Although the microscopy station was completed, the lander that would have carried the microscopy station to the equator of Mars in 2001 was cancelled. However, it will now fly to the Martian arctic in 2007. The different conditions of the Martian artic mean the microscopy station will have to be operated in different ways to its original design. This work will put a copy of the microscopy station into a simulation chamber. Various ice and soil samples will be dropped from a copy of the robot-arm scoop into the station, and microscope images taken with the optical microscope and AFM. At first there will need to be some human intervention to ensure that good images are taken, but as experience with the station is built up more and more of the operations will be performed automatically through computer control. Eventually the microscopy station will be able to take good images by itself, as it will have to on Mars. These methods for automatic operation, or algorithms, will be built into the computer code used on the Phoenix mission to control the microscopy station. The samples will be carried to the microscopes on specially selected holders. Using techniques similar to those used to make silicon chips, it will be possible to cut some silicon so as to best make holders for the small ice and soil particles for microscope imaging. Our research is a unique opportunity for a UK contribution to an important international Mars exploration programme at a modest cost. This research will therefore help build up the UK's limited experience of landing on Mars and bring the excitement of Mars exploration to the British public.