Analysis of Phoenix Optical Microscopy Images to Understand Soil Processes on Mars

Grant #: NNX11AI91G
Senior Scientist: John Marshall

Objectives: Images from the Phoenix MECA Optical Microscope (POM) of soil grains at the Phoenix landing site, with higher resolution than any images previously obtained on Mars, have revealed enigmatic grain shapes. Interpretations of the grain shapes vary from chemical weathering, to vesicular grains, or simply aeolian basaltic particles embedded in dust. We plan a systematic study of the Phoenix OM images with the objective of better understanding the geology producing these grain morphologies in the northern plains of Mars. 

Approach: We will perform a more extensive analysis of the POM images. Using image data from the PDS, carefully processed to best preserve color and focus, each individual identifiable grain in the suite of POM images will be categorized according to size, shape, texture, optical properties and color. The database generated by this method will then be interrogated to evaluate correlations between these properties to answer a range of questions related to grain provenance. For example, are there correlations between shape and grain size? May some of the grains be microtectites or the result of aqueous weathering? Does color relate to grain size or other properties? Can some grains be characterized by distinctive physical properties or is there simply a gradation of parameters between the grains? Identifying such correlations can lead to clues about the provenance and history of the soil particles. Some of the puzzles from the Phoenix microscopy result from the limits of resolution and lighting conditions from the instrument. To better understand the POM results and how the characteristics of the imaging system effect interpretations, we will compare the OM images from Phoenix with carefully-produced control/calibration images acquired with an engineering model of the Phoenix OM. 

Relevance: The results of this work will help to better understand the geology of the Phoenix landing site, and physical processes on Mars, in particular, the potential role of aqueous weathering in the northern hemisphere.