Mark S. Anderson

Atomic Force Microscope Studies of Fullerene Films: Highly Stable C60 fcc (311) Free Surfaces

Atomic force microscopy and x-ray diffractometry were used to study 1500 �-thick films of pure C60 grown by sublimation in ultrahigh vacuum onto a CaF2 (111) substrate. Topographs of the films did not reveal the expected close-packed structures, but they showed instead large regions that correspond to a face-centered cubic (311) surface and distortions of this surface. The open (311) structure may have a relatively low free energy because the low packing density contributes to a high entropy of the exposed surface.

O atom etching of graphite in low earth orbit

Abstract Samples of highly ordered pyrolytic graphite were placed aboard the space shuttle Atlantis (mission STS46) and exposed to the atmosphere present in low earth orbit to observe the effects of chemical etching by atomic oxygen on carbon-based materials. During the 43 h exposure, approximately 2.25 μm of graphite were removed from the sample, which corresponds to an etch yield of one C atom for every eight incident O atoms. The topography of the etched samples was analyzed quantitatively within the framework of scaling theory, and the experimental data agree with the static scaling behavior predicted for a model in which surface diffusion and reaction at step edges dominates the etching mechanism.

Fourier transform infrared spectroscopy for Mars science

Presented here is a Fourier transform infrared spectrometer (FTIR) for field studies that serves as a prototype for future Mars science applications. Infrared spectroscopy provides chemical information that is relevant to a number of Mars science questions. This includes mineralogical analysis, nitrogen compound recognition, truth testing of remote sensing measurements, and the ability to detect organic compounds. The challenges and scientific opportunities are given for the in situ FTIR analysis of Mars soil and rock samples. Various FTIR sampling techniques are assessed and compared to other analytical instrumentation. The prototype instrument presented is capable of providing field analysis in a Mars analog Antarctic environment. FTIR analysis of endolithic microbial communities in Antarctic rocks and a Mars meteor are given as analytical examples.

Analysis of semi-volatile residues using diffuse reflectance infrared Fourier transform spectroscopy

Semi-volatile residues on aerospace hardware can be analyzed using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). This method can be correlated with quantitative Mil-STD 1246 NVR measurements while simultaneously providing qualitative identification of a large variety of compounds. Its high sensitivity supports the direct sampling of small areas of critical surfaces. This method involves transferring the contaminant film to a small solvent-saturated wipe, followed by extraction of the wipe, then concentration of the solvent extract and subsequent spectroscopic analysis using an FT-IR with a diffuse reflectance accessory. A library of standard curves for different classes of typical aerospace contaminants has been established. Quantitative analysis has been proven successful over orders of magnitude and detection limits exceeding 0.1 ug/cm2 are routinely achieved. Several practical applications have been performed using this analytical method and detailed discussion of analysis techniques is presented. The discussion will include: instrumentation setup, selection and preparation of sample collection materials, sample extract preparation, preparation of standard calibration curves and spectral interpretation.

Utilizing active mid-infrared microspectrometry for in situ analysis of cryptoendolithic microbial communities of Battleship Promontory, Dry Valleys, Antarctica

We have constructed an active mid-infrared Fourier transform micro-spectrometer capable of analyzing mineralogy and organic chemistry of specimens in the field. While of great utility for terrestrial studies, the instrument has also been designed for potential use on future robotic missions to Mars. The device operates in the spectral range of 650 cm-1 (15 µm) to 3800 cm-1 (2.6 µm) and has a 4 cm-1 spectral resolution. The spectrometer is coupled to a microscope yielding a spatial resolution on the sample of approximately one millimeter. Mounted to the spectrometer are two motors that allow for spatial scanning of the sample. Maximum scanning range in both X and Y directions is approximately 2.5 centimeters. During a recent field campaign (Jan-Feb. 2005), our instrument successfully detected cryptoendolithic microbial communities in the Dry Valleys of Antarctica. Colonized rocks of Beacon sandstone in the Battleship Promontory formation were examined non-invasively both from the surface and in cross-section. Samples characteristic of the various communities (lichen, cyanobacterial) were analyzed. Detection of C-H bands on the surface, indicative of possible biology below, was successful. Several organic functional groups, characteristic of microorganisms, were detected in both lichen and cyanobacterial-dominated communities. In addition, the vertical distribution of inorganic compounds suggests that the organisms may play an active role in rock weathering.

Calibration target for far-infrared spaceborne applications

We describe progress in the development of a calibration target for use in the EOS-MLS 2.5 THz radiometer on NASAs CHEM-1 spacecraft. Although the intended use is as a stable, isothermal black body load at a frequency of 2.5 THz, the design is suitable for use throughout the far-infrared. A wedge design is used for the target body to enhance the emissivity to desired levels at 2.5 THz. The body is machined from aluminum, giving the best trade between issues such as cost, thermal conductivity, mass, and strength. The target utilizes a white coating to reduce the destabilizing effects of periodic solar illumination. The coating can be made relatively thin to allow accurate temperature measurements of the FIR-absorbing medium. Emissivity of greater than 0.99 is achieved at 2.5 THz, while the solar absorptance is estimated at <0.5.

Atomic force microscope mediated chromatography

An atomic force microscope (AFM) is presented as an instrument for rapid, miniaturized chromatography. The AFM is used to inject a sample, provide shear driven liquid flow over a functionalized substrate, and detect separated components. The components are then analyzed with surface enhanced Raman spectroscopy using AFM deposition of gold nanoparticles on the separated bands. This AFM mediated chromatography (AFM-MC) is demonstrated using lipophilic dyes and normal phase chemistry. A significant reduction in both size and separation time scales is achieved with 25 μm length scale and 1 s separation times. AFM-MC has general applications to trace chemical analysis and microfluidics.

Development and Optical Testing of the Camera, Hand Lens, and Microscope Probe with Scannable Laser Spectroscopy (CHAMP-SLS)

Conducting high resolution field microscopy with coupled laser spectroscopy that can be used to selectively analyze the surface chemistry of individual pixels in a scene is an enabling capability for next generation robotic and manned spaceflight missions, civil, and military applications. In the laboratory, we use a range of imaging and surface preparation tools that provide us with in-focus images, context imaging for identifying features that we want to investigate at high magnification, and surface-optical coupling that allows us to apply optical spectroscopic analysis techniques for analyzing surface chemistry particularly at high magnifications. The camera, handlens, and microscope probe with scannable laser spectroscopy (CHAMP-SLS) is an imaging/spectroscopy instrument capable of imaging continuously from infinity down to high resolution microscopy (resolution of ~1 micron/pixel in a final camera format), the closer CHAMP-SLS is placed to a feature, the higher the resultant magnification. At hand lens to microscopic magnifications, the imaged scene can be selectively interrogated with point spectroscopic techniques such as Raman spectroscopy, microscopic Laser Induced Breakdown Spectroscopy (micro-LIBS), laser ablation mass-spectrometry, Fluorescence spectroscopy, and/or Reflectance spectroscopy. This paper summarizes the optical design, development, and testing of the CHAMP-SLS optics.

Mars 2020 sample cleanliness molecular transport model

“NASA’s Mars 2020 mission … rover is being designed to seek signs of past life on Mars, collect and store a set of soil and rock samples that could be returned to Earth in the future.”1 The Mars 2020 Project has a top-level requirement that soil and rock samples contain less than 10 ppb Total Organic Carbon (TOC) of terrestrial origin 2. The approach taken to meet this requirement is to identify and model for each Mars 2020 mission phase the TOC sources, model TOC transport from sources to sample contacting surfaces, and combine them into an end-to-end model that calculates the TOC in each sample during the mission. The calculations show that Mars 2020 can achieve the TOC sample cleanliness requirement because the project has adopted specific TOC mitigations strategies.

An In-Depth Assessment of Internal Contamination in the Wide Field/Planetary Camera: Republished from the Journal of the IES May-June 1990 issue, pages 29-35

Following thermal vacuum/thermal balance testing, a gray haze was discovered on the corners of the Wide Field/Planetary Camera (WF/PC) aperture window. The phenomenon was suggested to be a result of molecular transport from a low outgassing structural adhesive. Detailed analyses, both chemical and analytical, were conducted to assess the formation of the haze. Each material was considered individually, as it was not known if the actual contamination was a result of one, many, or possibly none of the materials considered. Results of the analytical assessment and the comparison with the aforementioned chemical analyses provided incontrovertible evidence as to the cause of the window haze. The resultant cleanup and subsequent elimination of the problem are also addressed.Following thermal vacuum/thermal balance testing, a gray haze was discovered on the corners of the Wide Field/Planetary Camera (WF/PC) aperture window. The phenomenon was suggested to be a result of molecular transport from a low outgassing structural adhesive. Detailed analyses, both chemical and analytical, were conducted to assess the formation of the haze. Each material was considered individually, as it was not known if the actual contamination was a result of one, many, or possibly none of the materials considered. Results of the analytical assessment and the comparison with the aforementioned chemical analyses provided incontrovertible evidence as to the cause of the window haze. The resultant cleanup and subsequent elimination of the problem are also addressed. [Editors Note: This 1990 paper is republished as part of the Journal of the IEST 50th anniversary celebration. It is accompanied by remarks from Patti Hansen, author of Overview of the HST Contamination Engineering Program at 15 Years: A ...