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

这项工作将是美国宇航局凤凰号着陆器使命的一部分，凤凰号将于2008年5月发射一艘宇宙飞船登陆火星，并近距离观察火星北方极地地区。大量的冰就躺在那里的表面之下。一个机械臂将挖掘地面，寻找冰来自哪里的线索，以及微生物是否可能在火星早期历史中生活过。我们对使命的贡献将有助于从三个方面了解火星。首先，我们将确保显微镜拍摄火星北极土壤和冰的最佳照片。我们将检查这些照片，以确定土壤是否曾经从湖泊或海洋的沉积物中沉积下来，或者被风带到那里，或者直接来自火山熔岩的侵蚀和分解。其次，当凤凰号飞船从太空福尔斯到火星表面时，它会因与空气的摩擦而减速。着陆器减速的量取决于气压和温度。我们将使用测量到的凤凰号着陆器的减速来计算气压和温度如何随高度变化。这可以告诉我们有关气候的信息，例如，着陆时是否有云，或者空气是否干燥，有很多灰尘。第三，凤凰号着陆器有一个实验，土壤被机械臂铲起并与水混合。土壤中的盐会溶解在水中，溶液中的探针会测量盐的类型，例如是否存在氯化钠，人们用于食物的盐。我们希望弄清楚火星上的盐是大海干涸后留下的，还是火山气体与土壤发生化学反应的产物。凤凰城的显微镜站构成了我们研究的一大部分，由一个传统的光学显微镜和一个称为原子力显微镜（AFM）的超高分辨率显微镜组成。这个显微镜工作站最初是由汤姆·派克博士在加州的美国宇航局喷气推进实验室工作时建造的。虽然显微镜站已经完成，但2001年将显微镜站带到火星赤道的着陆器被取消了。然而，它将于2007年飞往火星北极。火星的不同条件意味着显微镜站将不得不以不同的方式操作它的原始设计。这项工作将把一个副本的显微镜站到一个模拟室。各种冰和土壤样本将从机器人臂勺的副本中放入空间站，并用光学显微镜和AFM拍摄显微镜图像。起初，需要人为干预，以确保拍摄到良好的图像，但随着空间站经验的积累，越来越多的操作将通过计算机控制自动进行。最终，显微镜站将能够自己拍摄良好的图像，就像在火星上一样。这些自动操作的方法或算法将被纳入凤凰号使命上使用的计算机代码中，以控制显微镜站。样品将通过特殊选择的支架运送至显微镜。使用类似于制造硅芯片的技术，将有可能切割一些硅，以便最好地制造用于显微镜成像的小冰和土壤颗粒的支架。我们的研究是一个独特的机会，英国的贡献，以一个重要的国际火星探测计划，在一个适度的成本。因此，这项研究将有助于建立英国有限的登陆火星的经验，并将火星探索的兴奋带给英国公众。

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.