Infrared spectroscopy of Mars

When measured with sufficient spectral range, resolution, and signal-to-noise ratio, nearly every mineral has a unique infrared spectral signature. However, determining which minerals are present on Mars using infrared spectroscopy has proven to be very difficult. The goal of this work is to examine complicating factors inherent to spacecraft-based infrared spectral measurements of Mars, and to determine methods to extract mineralogical information from spectra that cover the wavelength range 0.77 to 50 mum. On Earth, infrared spectra of an unknown mineral or gas can be measured under controlled conditions. However, a spacecraft spectrometer measures Mars through both atmospheric gases and aerosols, and at varying viewing geometries. Spectra of the surface of Mars have very subtle variations, so examining them requires well-calibrated spectra of excellent quality, and extended spectral range. These combined effects greatly complicate interpretations. The work presented here details a straightforward method to remove effects of varying viewing geometry on near-infrared spectra of Mars, using 1989 Phobos 2 ISM spectra. Next, it details the recovery and calibration of the 1969 Mariner Mars IRS data set, and presents IRS spectral evidence for goethite on Mars. Finally, a method is developed to utilize night spectra to examine the aerosol mineralogy, followed by a discussion of the importance of accounting for the aerosol re-emission when utilizing day measurements to examine surface mineralogy. This work utilizes spectra from all five infrared spectrometers flown to Mars. It addresses a range of issues, but the unifying theme is how to extract mineralogic information from the spectra. The results show that the most important spectral criteria for determining mineralogy from spacecraft infrared spectra are an extended spectral range, high spectral resolution, and high signal-to-noise ratio. Here, an extended spectral range is defined as coverage of at least two of the three infrared spectral regions: reflected (∼0.8--3 mum), overtone (∼3--7 mum), and fundamental (∼7--50 mum). Spectra with low spectral resolution, low spectral range, or low signal-to-noise ratio allow different spectral type units to be mapped, but such data sets do not provide enough information to determine uniquely the mineral phases present

Technique For Achieving High Throughput With A Pushbroom Imaging Spectrometer

Static Fourier transform spectrometers have the ability to combine the principle advantages of the two traditional techniques used for imaging spectrometry: The throughput advantage offered by Fourier transform spectrometers, and the advantage of no moving parts offered by dispersive spectrometers. The imaging versions of these spectrometers obtain both spectral information, and spatial information in one dimension, in a single exposure. The second spatial dimension may be obtained by sweeping a narrow field mask across the object while acquiring successive exposures. When employed as a pushbroom sensor from an aircraft or spacecraft, no moving parts are required, since the platform itself provides this motion. But the use of this narrow field mask to obtain the second spatial dimension prevents the throughput advantage from being realized. We present a technique that allows the use of a field stop that is wide in the along-track direction, while preserving the spatial resolution, and thus enables such an instrument to actually exploit the throughput advantage when used as a pushbroom sensor. The basis of this advance is a deconvolution technique we have developed to recover the spatial resolution in data acquired with a field stop that is wide in the along-track direction. The effectiveness is demonstrated by application of this deconvolution technique to simulated data

Comparison Of Signal Collection Abilities Of Different Classes Of Imaging Spectrometers

Although the throughput and multiplex advantages of Fourier transform spectrometry were established in the early 1950\u27s (by Jacquinot11,2,3 and Fellgettz4,5 respectively) confusion and debate6 arise when these advantages are cited in reference to imaging spectrometry. In non-imaging spectrometry the terms throughput and spectra! bandwidth clearly refer to the throughput of the entire field-of-view (FOV), and the spectral bandwidth of the entire FOV, but in imaging spectrometry these terms may refer to either the entire FOV or to a single element in the FOV. The continued development of new and fundamentally different types of imaging spectrometers also adds to the complexity of predictions of signal and comparisons of signal collection abilities. Imaging spectrometers used for remote sensing may be divided into classes according to how they relate the object space coordinates of cross-track position, along-track position, and wavelength (or wavenumber) to the image space coordinates of column number, row number, and exposure number for the detector array. This transformation must be taken into account when predicting the signal or comparing the signal collection abilities of different classes of imaging spectrometer. The invariance of radiance in an imaging system allows the calculation of signal to be performed at any space in the system, from the object space to the final image space. Our calculations of signal - performed at several different spaces in several different classes of imaging spectrometer - show an interesting result; regardless of the plane in which the calculation is performed, interferometric (Fourier transform) spectrometers have a dramatic advantage in signal, but the term in the signal equation from which the advantage results depends upon the space in which the calculation is performed. In image space, the advantage results from the spectral term in the signal equation, suggesting that this could be referred to as the multiplex (Fellgett) advantage. In an intermediate image plane the advantage results from a difference in a spatial term, while for the exit pupil plane it results from the angular term, both of which suggest the throughput (Jacquinot) advantage. When the calculation is performed in object coordinates the advantage results from differences in the temporal term

Mars Infrared Spectroscopy: From Theory and the Laboratory To Field Observations

The continuity and timely implementation of the Mars exploration strategy relies heavily on the ability of the planetary community to interpret infrared spectral data. However, the increasing mission rate, data volume, and data variety, combined with the small number of spectroscopists within the planetary community, will require a coordinated community effort for effective and timely interpretation of the newly acquired and planned data sets. Relevant spectroscopic instruments include the 1996 TES, 2001 THEMIS, 2003 Pancam, 2003 Mini-TES, 2003 Mars Express OMEGA, 2003 Mars Express PFS, and 2005 CFUSM. In light of that, leaders of the Mars spectral community met June 4-6 to address the question: What terrestrial theoretical, laboratory, and field studies are most needed to best support timely interpretations of current and planned visible infrared spectrometer data sets, in light of the Mars Program goals? A primary goal of the spectral community is to provide a reservoir of information to enhance and expand the exploration of Mars. Spectroscopy has a long history of providing the fundamental compositional discoveries in the solar system, from atmospheric constituents to surface mineralogy, from earth-based to spacecraft-based observations. However, such spectroscopic compositional discoveries, especially surface mineralogies, have usually come after long periods of detailed integration of remote observations, laboratory analyses, and field measurements. Spectroscopic information of surfaces is particularly complex and often is confounded by interference of broad, overlapping absorption features as well as confusing issues of mixtures, coatings, and grain size effects. Thus some spectroscopic compositional discoveries have come only after many years of research. However, we are entering an era of Mars exploration with missions carrying sophisticated spectrometers launching about every 2 years. It is critical that each mission provide answers to relevant questions to optimize the success of the next mission. That will not occur effectively unless the spectroscopic remote sensing data can be processed and understood on an approximate 2-year rate. Our current knowledge of spectral properties of materials and confounding effects of the natural environment are note well enough understood for the accurate interpretations needed for such ambitious and time critical exploration objectives. This workshop focused on identify ing critical gaps in moving the field towards the goal of rapid and accurate analysis and interpretation

The ChemCam Instrument Suite on the Mars Science Laboratory (MSL) Rover: Body Unit and Combined System Tests

The ChemCam instrument suite on the Mars Science Laboratory (MSL) rover Curiosity provides remote compositional information using the first laser-induced breakdown spectrometer (LIBS) on a planetary mission, and provides sample texture and morphology data using a remote micro-imager (RMI). Overall, ChemCam supports MSL with five capabilities: remote classification of rock and soil characteristics; quantitative elemental compositions including light elements like hydrogen and some elements to which LIBS is uniquely sensitive (e.g., Li, Be, Rb, Sr, Ba); remote removal of surface dust and depth profiling through surface coatings; context imaging; and passive spectroscopy over the 240-905 nm range. ChemCam is built in two sections: The mast unit, consisting of a laser, telescope, RMI, and associated electronics, resides on the rover's mast, and is described in a companion paper. ChemCam's body unit, which is mounted in the body of the rover, comprises an optical demultiplexer, three spectrometers, detectors, their coolers, and associated electronics and data handling logic. Additional instrument components include a 6 m optical fiber which transfers the LIBS light from the telescope to the body unit, and a set of onboard calibration targets. ChemCam was integrated and tested at Los Alamos National Laboratory where it also underwent LIBS calibration with 69 geological standards prior to integration with the rover. Post-integration testing used coordinated mast and instrument commands, including LIBS line scans on rock targets during system-level thermal-vacuum tests. In this paper we describe the body unit, optical fiber, and calibration targets, and the assembly, testing, and verification of the instrument prior to launch

Isotope ratios of H, C, and O in CO2 and H2O of the Martian atmosphere

Stable isotope ratios of H, C, and O are powerful indicators of a wide variety of planetary geophysical processes, and for Mars they reveal the record of loss of its atmosphere and subsequent interactions with its surface such as carbonate formation. We report in situ measurements of the isotopic ratios of D/H and O-18/O-16 in water and C-13/C-12, O-18/O-16, O-17/O-16, and (CO)-C-13-O-18/(CO)-C-12-O-16 in carbon dioxide, made in the martian atmosphere at Gale Crater from the Curiosity rover using the Sample Analysis at Mars (SAM)'s tunable laser spectrometer (TLS). Comparison between our measurements in the modern atmosphere and those of martian meteorites such as ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established similar to 4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing