An Introduction to the Mars Atmospheric Trace Molecule Occultation Spectrometer (MATMOS)
No abstract available
low resolution mapping↗
Engineering topics
Clancy, R. T.
Publications and source records attributed to Clancy, R. T..
Scientific Goals and Objectives for the Human Exploration of Mars: 1. Biology and Atmosphere/Climate
To prepare for the exploration of Mars by humans, as outlined in the new national vision for Space Exploration (VSE), the Mars Exploration Program Analysis Group (MEPAG), chartered by NASA's Mars Exploration Program (MEP), formed a Human Exploration of Mars Science Analysis Group (HEM-SAG), in March 2007. HEM-SAG was chartered to develop the scientific goals and objectives for the human exploration of Mars based on the Mars Scientific Goals, Objectives, Investigations, and Priorities.1 The HEM-SAG is one of several humans to Mars scientific, engineering and mission architecture studies chartered in 2007 to support NASA s plans for the human exploration of Mars. The HEM-SAG is composed of about 30 Mars scientists representing the disciplines of Mars biology, climate/atmosphere, geology and geophysics from the U.S., Canada, England, France, Italy and Spain. MEPAG selected Drs. James B. Garvin (NASA Goddard Space Flight Center) and Joel S. Levine (NASA Langley Research Center) to serve as HEMSAG co-chairs. The HEM-SAG team conducted 20 telecons and convened three face-to-face meetings from March through October 2007. The management of MEP and MEPAG were briefed on the HEM-SAG interim findings in May. The HEM-SAG final report was presented on-line to the full MEPAG membership and was presented at the MEPAG meeting on February 20-21, 2008. This presentation will outline the HEM-SAG biology and climate/atmosphere goals and objectives. A companion paper will outline the HEM-SAG geology and geophysics goals and objectives.
Levine, Joel S.↗
CRISM: Compact Reconnaissance Imaging Spectrometer for Mars on the Mars Reconnaissance Orbiter
The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on the Mars Reconnaissance Orbiter (MRO) will conduct a global survey to find high priority sites, full-resolution measurement of thousands of sites, and tracking of variations in atmospheric and surface properties. Additional information is contained in the original extended abstract.
Murchie, S.↗
CRISM: Compact Reconnaissance Imaging Spectrometer for Mars on the Mars Reconnaissance Orbiter
The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on the Mars Reconnaissance Orbiter (MRO) will conduct a comprehensive series of investigations of the Martian surface and atmosphere. The investigations will be accomplished using an instrument design that provides high spatial and spectral resolutions, extended wave- length range, and ability to gimbal through a range of orientations. Baseline investigations include a near-global survey to find high science priority sites, full- resolution measurement of thousands of such sites, and tracking of seasonal variations in atmospheric and surface properties.
Murchie, S.↗
Some Characteristics of the Martian Aphelion Global Cloud Belt
The presence of discrete condensate clouds on Mars is certainly not a new discovery, having been observed through most of the documented history of telescopic monitoring. Furthermore, spacecraft data have been used to study discrete cloud features in the Martian atmosphere in greater detail, e.g., morphology, seasonal occurrence. Condensate clouds, specifically discrete water ice clouds, appeared to be regarded as fairly common but, with the possible exception of the polar regions, generally uninteresting from a climatological point of view. However, recent observations indicate that in addition to their large spatial scale, the water ice clouds may in fact play a more prominent role in the Martian climate. In this paper, we wish to examine the spatial and temporal variations of the cloud belt optical depth, as well as the microphysical characteristics of the water ice particles themselves.
Wolff, M. J.↗
Results from the Mars Global Surveyor Thermal Emission Spectrometer
The Thermal Emission Spectrometer spectra of low albedo surface materials suggests that a four to one mixture of pyroxene to plagioclase, together with about a 35 percent dust component provides the best fit to the spectrum. Qualitative upper limits can be placed on the concentration of carbonates (<10 percent), olivine (<10 percent), clay minerals (<20 percent), and quartz (<5 percent) in the limited regions observed. Limb observations in the northern hemisphere reveal low-lying dust hazes and detached water-ice clouds at altitudes up to 55 kilometers. At an aerocentric longitude of 224 degrees a major dust storm developed in the Noachis Terra region. The south polar cap retreat was similar to that observed by Viking.
unmanned↗
Microwave Observations andf Modeling of O(sub 2) ((sup 1)delta-(sub g)) and O(sub 3) Diurnal Variation in the Mesosphere
The first microwave measurements of an electronically excited molecular species in the Earth's atmosphere are presented. Local thermodynamic equilibrium (LTE) rotational line emission from mesopheric O(sub 2) ((sup 1)delta-(sub g)) was observed at a frequency of 255.01794 GHz (Lambda approx. 1.2mm), employing the National Radio Astronomy Observatory (NRAO) millimeter facility at Kitt Peak, Arizona (32(deg)N, 111(deg)W).
photolysis ozone↗
A new model for Mars atmospheric dust based upon analysis of ultraviolet through infrared observations from Mariner 9, Viking, and Phobos
We propose key modifications to the Toon et al. (1977) model of the particle size distribution and composition of Mars atmospheric dust, based on a variety of spacecraft and wavelength observations of the dust. A much broader (r(sub eff) variance approximately 0.8 micrometers), smaller particle size (r(sub mode) approximately 0.02 micrometers) distribution coupled with a 'palagonite-like' composition is argued to fit the complete ultraviolet-to-30-micrometer absorption properties of the dust better than the montmorillonite-basalt, r(sub eff) variance = 0.4 micrometers, r(sub mode) = 0.40 dust model of Toon et al. Mariner 9 (infrared interferometer spectrometer) IRIS spectra of high atmospheric dust opacities during the 1971-1972 Mars global dust storm are analyzed in terms of the Toon et al. dust model, and a Hawaiian palagonite sample (Rousch et al., 1991) with two different size distribution models incorporating smaller dust particle sizes. Viking Infrared Thermal Mapper (IRTM) emmission-phase-function (EPF) observations at 9 micrometers are analyzed to retrieve 9-micrometer dust opacities coincident with solar band dust opacities obtained from the same EPF sequences (Clancy and Lee, 1991). These EPF dust opacities provide an independent measurement of the visible/9-micrometer extinction opacity ratio (greater than or = 2) for Mars atmospheric dust, which is consistent with a previous measurement by Martin (1986). Model values for the visible/9-micrometer opacity ratio and the ultraviolet and visible single-scattering albedos are calculated for the palagonite model with the smaller particle size distributions compared to the same properties for the Toon et al. model of dust. The montmorillonite model of the dust is found to fit the detailed shape of the dust 9-micrometer absorption well. However, it predicts structured, deep aborptions at 20 micrometers which are not observed and requires a separate ultraviolet-visible absorbing component to match the observed behavior of the dust in this wavelength region. The modeled palagonite does not match the 8-to 9-micrometer absorption presented by the dust in the IRIS spectra, probably due to its low SiO2 content (31%). However, it does provide consistent levels of ultraviolet/visible absorption, 9-to 12-micrometer absorption, and a lack of structured absorption at 20 micrometers. The ratios of dust extinction opacities at visible, 9 micrometers, and 30 micrometers are strongly affected by the dust particle size distribution. The Toon et al. dust size distribution (r(sub mode) = 0.40,r(sub eff) variance = 0.4 micrometers, r(sub cwmu) = 2.7 micrometers) predicts the correct ratio of the 9- to 30-micrometer opacity, but underpredicts the visible/9-micrometer opacity ratio considerably (1 versus greater than or = 2). A similar particle distribution width with smaller particle sizes (r(sub mode) = 0.17, r(sub eff) variance = 0.4 micrometers, r(sub cwmu) = 1.2 micrometers) will fit the observed visible/9-micrometer opacity ratio, but overpredicts the observed 9-micrometer/30-micrometer opacity ratio. A smaller and much broader particle size distribution (r(sub mode) = 0.002, r(sub eff) variance = 0.8 micrometers, r(sub cwmu) = 1.8 micrometers) can fit both dust opacity ratios. Overall, the nanocrystalline structure of palagonite coupled with a smaller, broader distribution of dust particle sizes provides a more consistent fit than the Toon et al. model of the dust to the IRIS spectra, the observed visible/9-micrometer dust opacity ratio, the Phobos occulation measurements of the dust particle sizes (Chassefiere et al., 1992), and the weakness of surface near IR absorptions expected for clay minerals (Clark, 1992; Bell and Crisp, 1993).
Clancy, R. T.↗
A new model for Mars atmospheric dust based upon analysis of ultraviolet through infrared observations from Mariner 9, Viking, and Phobos
We propose key modifications to the Toon et al. (1977) model of the particle size distribution and composition of Mars atmospheric dust, based on a variety of spacecraft and wavelength observations of the dust. A much broader (r(sub eff)variance-0.8 micron), smaller particle size (r(sub mode)-0.02 microns) distribution coupled with a "palagonite-like" composition is argued to fit the complete ultraviolet-to-30-micron absorption properties of the dust better than the montmorillonite-basalt r(sub eff)variance= 0.4 micron, r(sub mode)= 0.40 micron dust model of Toon et al. Mariner 9 (infrared interferometer spectrometer) IRIS spectra of high atmospheric dust opacities during the 1971 - 1972 Mars global dust storm are analyzed in terms of the Toon et al. dust model, and a Hawaiian palagonite sample with two different size distribution models incorporating smaller dust particle sizes. Viking Infrared Thermal Mapper (IRTM) emission-phase-function (EPF) observations at 9 microns are analyzed to retrieve 9-micron dust opacities coincident with solar band dust opacities obtained from the same EPF sequences. These EPF dust opacities provide an independent measurement of the visible/9-microns extinction opacity ratio (> or equal to 2) for Mars atmospheric dust, which is consistent with a previous measurement by Martin (1986). Model values for the visible/9-microns opacity ratio and the ultraviolet and visible single-scattering albedos are calculated for the palagonite model with the smaller particle size distributions and compared to the same properties for the Toon et al. model of dust. The montmorillonite model of the dust is found to fit the detailed shape of the dust 9-micron absorption well. However, it predicts structured, deep absorptions at 20 microns which are not observed and requires a separate ultraviolet-visible absorbing component to match the observed behavior of the dust in this wavelength region. The modeled palagonite does not match the 8- to 9-micron absorption presented by the dust in the IRIS spectra, probably due to its low SiO2 content (31%). However, it does provide consistent levels of ultraviolet/visible absorption, 9- to 12-micron absorption, and a lack of structured absorption at 20 microns. The ratios of dust extinction opacities at visible, 9 microns, and 30 microns are strongly affected by the dust particle size distribution. The Toon et al. dust size distribution (r(sub mode)= 0.40, r(sub eff)variance= 0.4 microns, r(sub cw mu)= 2.7 microns) predicts the correct ratio of the 9- to 30-micron opacity, but underpredicts the visible/9-micron opacity ratio considerably (1 versus > or equal to 2). A similar particle distribution width with smaller particle sizes (r(sub mode)= 0.17, r(sub eff)variance= 0.4 microns, r(sub cw mu)=1.2 microns) will fit the observed visible/9-micron opacity ratio, but overpredicts the observed 9-micron/30-micron opacity ratio. A smaller and much broader particle size distribution (r(sub mode)= 0.02, r(sub eff)variance= 0.8 microns, r(sub cw mu)= 1.8 microns) can fit both dust opacity ratios. Overall, the nanocrystalline structure of palagonite coupled with a smaller, broader distribution of dust particle sizes provides a more consistent fit than the Toon et al. model of the dust to the IRIS spectra, the observed visible/9-micron dust opacity ratio, the Phobos occultation measurements of dust particle sizes, and the weakness of surface near IR absorptions expected for clay minerals.
Clancy, R. T.↗
Comparison of satellite measurements of ozone and ozone trends
Measurements of ozone retrieved from satellite instruments over the 1979-1991 period are compared. The instruments used are the total ozone mapping spectrometer (TOMS), the solar backscattered ultraviolet experiment (SBUV), and stratospheric aerosol and gas experiments (SAGE) I and II. Although there is good agreement between the absolute densities of ozone as measured by the various instruments, the long-term changes (1979-1990) disagree sharply as a function of pressure and in the integrated ozone amount. In the upper stratosphere, SBUV trends are negative with maximum values of about -1.5%/year at high latitudes. Combined SAGE I and II trends are slightly positive in this region and peak near 0.5%/year at equatorial latitudes. In the lower stratosphere, SBUV trends reflect small decreases in ozone, generally less than -0.4%/year except at high southern latitudes where the trends rearch values of approximately -1.5%/year. SAGE ozone trends exhibit large decreases particularly in the equatorial regions where decreases of 3-6%/year are seen at pressures between 60 and 90 mbar. At higher latitudes, SAGE trends are more comparable to SBUV trends in the lower stratosphere. Total ozone trends from TOMS and SBUV agree within their uncertainties. Near-zero trends are indicated at low latitudes, and larger, negative trends (approximately -0.5%/year) are indicated near the poles. The SAGE column ozone trends depend upon the base level altitude of integration but do not exhibit a strong latitude dependence.
Rusch, D. W.↗
Solar Mesosphere Explorer satellite measurements of el Chichon stratospheric aerosols. 1: Cloud morphology
Data from the Solar Mesosphere Explorer (SME) is used to track the time, latitude, and altitude (above 18 km) development of the aerosol cloud injected into the stratosphere by the eruption of el Chichon. This unique data set, using scattering data from the near-infrared (1.27 and 1.87 microns) and visible (440 nm) spectrometers on SME, covers the period from the initial injection in April 1982 through the end of 1986. Although the bulk of the mass is contained in the latitude band from 10 deg S to 30 deg N for the entire duration of the measurements, transport of material to high latitudes is apparent in the data in the post eruption period. The times aerosol density maxima vary greatly as a function of altitude and latitude.
Rusch, D. W.↗
Solar Mesosphere Explorer satellite measurements of el Chichon stratospheric aerosols. 2: Aerosol mass and size parameters
Spatially and temporally extensive observations of the stratospheric aerosol cloud produced by the eruption of el Chichon in 1982 were made by the Solar Mesosphere Explorer satellite. Measurements of thermal emission at 6.8 microns are inverted to give aerosol extinction coefficients. At this wavelength the extinction coefficient is proportional to the cube of the particle radius, so the measured radiance is proportional to the slant column mass density of aerosols, independent of size distribution. Vertical column mass densities of aerosols and total aerosol mass are found from the 6.8-microns data. The evolution of the aerosol cloud in time and space is discussed. A peak column mass density above 22 km of 0.43 g/sq m occurred near 20 deg N latitude 8 weeks after the eruption. A maximum total global aerosol burden above 22 km of 1.3 x 10(exp 13) g occurred a week later. The aerosol mass determinations are used in conjunction with observations of scattered sunlight from the aerosols at 1.27 and 1.87 microns to derive single-mode log normal columnar size distributions for the aerosol cloud. The results are presented and the time evolution of the particle sizes is discussed.
Eparvier, F. G.↗
Particle sizes and composition of Mars atmospheric dust based upon Viking and Mariner 9 observations
Mars atmospheric dust can play an important role in the thermal structure of the Mars atmosphere during periods of high dust loading. However, the radiative properties of Mars atmospheric dust remain uncertain due to uncertain definitions of the dust composition and size distribution. The analysis by Toon et al., of Mariner 9 IRIS spectra during the 1971-1972 global dust storm indicated a reasonable match between the modeled 9-micron absorption of montmorillinite and the observed 9-micron absorption. Toon et al. also determined that an effective (cross-section weighted) mean radius of 2.5 microns (R(sub mode) = 0.4 microns) provided a consistent fit of montmorillinite to the IRIS dust spectra at 9 microns. Pollack et al. analyzed Viking lander observations of atmospheric extinction and scattering at visible-near IR wavelengths (0.5-1.0 microns), and obtained consistency with the Toon et al. dust size distribution when the effects of nonspherical particle shapes were included. An additional, minor (1 percent) component of visible-ultraviolet absorbing material was required to model the derived visible (0.86) and ultraviolet (0.4-0.6) single-scattering albedos of the dust, since montmorillinite does not absorb sufficiently in this wavelength region. A combined analysis of the Viking IRTM and Mariner 9 observations was conducted to reassess the model of Mars atmospheric ultraviolet-to-infrared measurements of dust absorption and scattering. The optical constants for palagonite are incorporated in a doubling-adding radiative transfer model of the Mars atmosphere to simulate Mariner 9 IRIS spectra as well as the Viking IRTM IR band observations. Visible and ultraviolet single-scattering albedos based on the Hansen and Travis Mie scattering code were also derived. A tentative conclusion is that smaller dust particles (R(sub mode) = 0.15 microns, cross-section weighted mean R = 1.2 microns) composed of palagonite provide a much improved fit to the Mariner 9 IRIS spectra; agreement with the observed ratio of visible-to-infrared extinction opacities; and ultraviolet and visible single-scattering albedos comparable to their observed values.
Clancy, R. T.↗
Temporal and spatial mapping of surface albedo and atmospheric dust opacity on Mars
The Mariner 9 and Viking provided abundant evidence that eolian processes are active over much of the surface of Mars. Past studies have demonstrated that variations in regional albedo and wind-streak patterns are indicative of sediment transport through a region, while thermal inertia data (derived from the Viking Infrared Thermal Mapper (IRTM) dataset) are indicative of the degree of surface mantling by dust deposits. The visual and thermal data are therefore diagnostic of whether net erosion or deposition of dust-storm fallout is taking place currently and whether such processes have been active in a region over the long term. These previous investigations, however, have not attempted to correct for the effects of atmospheric dust loading on observations of the martian surface, so quantitative studies of current sediment transport rates have included large errors due to uncertainty in the magnitude of this 'atmospheric component' of the observations. We have developed a radiative transfer model that allows the atmospheric dust opacity to be determined from IRTM thermal observations. Corrections for the effects of atmospheric dust loading on observations of surface albedo can also be modeled. This approach to determining 'dust-corrected surface albedo' incorporates the atmospheric dust opacity, the single-scattering albedo and particle phase function of atmospheric dust, and the bidirectional reflectance of the surface, and it accounts for variable lighting and viewing geometry.
Lee, S. W.↗
Mars atmospheric dust properties: A synthesis of Mariner 9, Viking, and Phobos observations
We have modified a doubling-and-adding code to reanalyze the Mariner 9 IRIS spectra of Mars atmospheric dust as well as Viking IRTM EPF sequences in the 7, 9, and 20 micron channels. The code is capable of accurate emission/ absorption/scattering radiative transfer calculations over the 5-30 micron wavelength region for variable dust composition and particle size inputs, and incorporates both the Viking IRTM channel weightings and the Mariner 9 IRIS wavelength resolution for direct comparisons to these datasets. We adopt atmospheric temperature profiles according to the algorithm of Martin (1986) in the case of the Viking IRTM comparisons, and obtained Mariner 9 IRIS temperature retrievals from the 15 micron CO2 band for the case of the IRIS comparisons. We consider palagonite as the primary alternative to the montmorillonite composition of Mars atmospheric dust, based on several considerations. Palagonite absorbs in the ultraviolet and visible wavelength region due to its Fe content. Palagonite is also, in principal, consistent with the observed lack of clays on the Mars surface. Furthermore, palagonite does not display strong, structured absorption near 20 microns as does montmorillonite (in conflict with the IRIS observations). We propose that a palagonite composition with particle sizes roughly one-half that of the Toon et al. (1977) determination provide a much improved model to Mars atmospheric dust. Since palagonite is a common weathering product of terrrestrial basalts, it would not be unreasonable for palagonite to be a major surface component for Mars. The lack of even a minor component of Al-rich clays on the surface of Mars could be consistent with a palagonite composition for Mars dust if the conditions for basalt weathering on Mars were sufficiently anhydrous. Variations in palagonite composition could also lead to the inability of the modeled palagonite to fit the details of the 9 micron absorbtion indicated by the IRIS observations.
Clancy, R. T.↗
Temporal and spatial mapping of atmospheric dust opacity and surface albedo on Mars
The Mariner 9 and Viking missions provided abundant evidence that eolian processes are active over much of the surface of Mars. Past studies have demonstrated that variations in regional albedo and wind streak patterns are indicative of sediment transport through a region, while thermal inertia data (derived from the Viking Infrared Thermal Mapper (IRTM) datasets) are indicative of the degree of surface mantling by dust deposits. We are making use of the method developed by T. Z. Martin to determine dust opacity from IRTM thermal observations. We have developed a radiative transfer model that allows corrections for the effects of atmospheric dust loading on observations of surface albedo to be made. This approach to determining 'dust-corrected surface albedo' incorporates the atmospheric dust opacity, the single-scattering albedo and particle phase function of atmospheric dust, the bidirectional reflectance of the surface, and accounts for variable lighting and viewing geometry.
Lee, S. W.↗
Mapping Mars water vapor with the Very Large Array
This paper presents the first radio measurements of Mars atmospheric water, retrieved from interferometric spectral line observations with the NRAO VLA. Large atmospheric path lengths on the limb of Mars lead to an annulus of H2O line emission which provides a measure of the diurnal and latitudinal variability of atmospheric water on Mars. The measured line shapes of the observed H2O emission yield the first direct measurements of the vertical mixing profile of H2O in the Mars atmosphere. The observations indicate a very dry Mars atmosphere in which the globally averaged water column is approximately 3 pr micron.
Clancy, R. T.↗
Mars dust and cloud opacities and scattering properties
We have recently completed an analysis of the visible emission-phase function (EPF) sequences obtained with the solar-band channel of the Infrared Thermal Mapping (IRTM) instrument onboard the two Viking Orbiters. Roughly 100 of these EPF sequences were gathered during the 1977-1980 period, in which the total broadband (.3-3.0 microns) reflectances of the atmosphere/surface above specific locations on Mars were measured versus emission angle as the spacecraft passed overhead. A multiple scattering radiative transfer program was employed to model the EPF observations in terms of the optical depths of dust/clouds, their single scattering albedos and phase functions, and the Lambert albedos and phase coefficient of the underlying surfaces. Due to the predominance of atmospheric scattering at large atmospheric pathlengths and/or large dust opacities, we were able to obtain strong constraints on the scattering properties of dust/clouds and their opacities for a wide range of latitudes, longitudes, and seasons on Mars.
Clancy, R. T.↗