A Miniaturized Variable Pressure Scanning Electron Microscope for In-Situ Use on Mars

Variable Pressure Scanning Electron Microscopy (VP SEM) combined with Energy Dispersive x-ray Spectroscopy (EDS) is one of the most powerful methods for characterizing the sub-micron topography and chemical composition of uncoated samples in their natural state. Terrestrially, VP SEM is extensively used to non-destructively study geologic materials with high spatial resolution (sub-micron), large depth-of-field and minimal to no sample preparation. The results of these studies provide invaluable insight into the formation and evolution of the parent body. Adaption of this instrument for in-situ Mars surface studies would provide a new capability that is at least 2 orders of magnitude higher resolution than the Mars Hand Lens Imager (MAHLI) on the Mars Science Laboratory (MSL), and an order of magnitude higher resolution than the Atomic Force Microscope (AFM) on the PHOENIX Mars lander, and with the added capability of simultaneous chemical analysis. This proposal is for the development of a Miniaturized Variable Pressure - Scanning Electron Microscope (MVP-SEM) capable of in-situ topographical imaging with sub-micron resolution and compositional x-ray fluorescence mapping of uncoated conductive and non-conductive samples on the surface of Mars. A unique feature of the MVP-SEM is a variable pressure system which will utilize the Martian ambient atmosphere as an imaging medium. This atmospheric-mode imaging will eliminate negative charging of non-conductive, uncoated samples, resulting in very fine resolution at high magnification, and permit the use of unique imaging techniques. This effort is in collaboration with NASA Marshall Space Flight Center (MSFC), NASA Jet Propulsion Laboratory (JPL), Creare, Applied Physics Technologies, Jacobs, and Case Western Reserve University. This development will leverage several previous projects including: a MSFC mini-SEM development for the Moon (funded by the NASA Planetary Instrument Definition and Development Program), a NASA SBIR effort to design a mini-SEM for the International Space Station (ISS), and flight heritage design features from the JPL- developed Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) sample wheel and translation stage used to deliver samples to the optical microscope and AFM on Phoenix. During this multi-year effort, the necessary refinements and modifications to the existing lunar and ISS designs, to allow for operation on the martian surface will be addressed. By the end of the effort, a prototype of the primary proof-of-concept components (i.e., the electron gun, focusing optics and scanning system) will be assembled and preliminary testing in a Mars analog chamber at JPL will be completed to bring the instrument to a TRL of 4-5. A follow-on proposal will then be submitted to the Maturation of Instruments for Solar System Exploration (MatISSE) Program for development to a TRL of 6. The goal of this effort is to prove feasibility by obtaining an image with a resolution of ~10 nm, or around 10x better than that of the AFM on Phoenix, and to determine the best configuration for performing EDS chemical analysis on relevant samples in a relevant environment.