ALBERT

Description: Thermal infrared spectra of the martian atmosphere taken by the Miniature Thermal Emission Spectrometer (Mini-TES) were used to determine the atmospheric temperatures in the planetary boundary layer and the column-integrated optical depth of aerosols. Mini-TES observations show the diurnal variation of the martian boundary layer thermal structure, including a near-surface superadiabatic layer during the afternoon and an inversion layer at night. Upward-looking Mini-TES observations show warm and cool parcels of air moving through the Mini-TES field of view on a time scale of 30 seconds. The retrieved dust optical depth shows a downward trend at both sites.

Description: The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard the Mars Reconnaissance Orbiter (MRO) spacecraft began taking observations in September 2006 and has now collected more than a full Martian year of data. Retrievals performed using the near-infrared spectra obtained by CRISM are used to characterize the seasonal and spatial variation of the column abundance of water vapor and the column-averaged mixing ratio of carbon monoxide. CRISM retrievals show nominal behavior in water vapor during northern hemisphere spring and summer with maximum abundance reaching 50 precipitable micrometers. Water vapor abundance during the southern hemisphere spring and summer appears significantly reduced compared to observations by other instruments taken during previous years. The CRISM retrievals show the seasonally and globally averaged carbon monoxide mixing ratio to be 700 ppm, but with strong seasonal variations at high latitudes. The summertime near-polar carbon monoxide mixing ratio falls to 200 ppm in the south and 400 ppm in the north as carbon dioxide sublimates from the seasonal polar ice caps and dilutes noncondensable species including carbon monoxide. At low latitudes, the carbon monoxide mixing ratio varies in response to the mean seasonal cycle of surface pressure.

Description: Near-infrared spectra returned by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM, [1]) on-board the Mars Reconnaissance Orbiter (MRO) contain the clear spectral signature of several atmospheric gases including carbon dioxide (CO2), water vapor (H2O), and carbon monoxide (CO). Here we describe the seasonal and spatial mapping of water vapor and carbon dioxide for one full Martian year using CRISM spectra.

Description: Near-infrared spectra taken in a limb-viewing geometry by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on-board the Mars Reconnaissance Orbiter (MRO) provide a useful tool for probing atmospheric structure. Specifically, the observed radiance as a function of wavelength and height above the limb allows the vertical distribution of both dust and ice aerosols to be retrieved. These data serve as an important supplement to the aerosol profiling provided by the MRO/MCS instrument allowing independent validation and giving additional information on particle physical and scattering properties through multi-wavelength studies. A total of at least ten CRISM limb observations have been taken so far covering a full Martian year. Each set of limb observations nominally contains about four dozen scans across the limb giving pole-to-pole coverage for two orbits at roughly 100 and 290 W longitude over the Tharsis and Syrtis/Hellas regions, respectively. At each longitude, limb scans are spaced roughly 10 degrees apart in latitude, with a vertical spatial resolution on the limb of roughly 800 m. Radiative transfer modeling is used to model the observations. We compute synthetic CRISM limb spectra using a discrete-ordinates radiative transfer code that accounts for multiple scattering from aerosols and accounts for spherical geometry of the limb observations by integrating the source functions along curved paths in that coordinate system. Retrieved are 14-point vertical profiles for dust and water ice aerosols with resolution of 0.4 scale heights between one and six scale heights above the surface. After the aerosol retrieval is completed, the abundances of C02 (or surface pressure) and H20 gas are retrieved by matching the depth of absorption bands at 2000 nm for carbon dioxide and at 2600 run for water vapor. In addition to the column abundance of water vapor, limited information on its vertical structure can also be retrieved depending on the signal available from aerosol scattering.

Description: During the period October 1997 to September 1999 we obtained and analyzed over 100 millimeter-wave observations of Mars atmospheric CO line absorption for atmospheric temperature profiles. These measurements extend through one full Mars year (solar longitudes L(sub S) of 190 deg in 1997 to 180 deg in 1999) and coincide with atmospheric temperature profile and dust column measurements front the Thermal Emission Spectrometer (TES) experiment on board the Mars Global Surveyor (MGS) spacecraft. A comparison of Mars atmospheric temperatures retrieved by these distinct methods provides the first opportunity to place the long-term (1982-1999) millimeter retrievals of Mars atmospheric temperatures within the context of contemporaneous, spatially mapped spacecraft, observations. Profile comparisons of 0-30 km altitude atmospheric temperatures retrieved with the two techniques agree typically to within the 5 K calibration accuracy of the millimeter observations. At the 0.5 mbar pressure level (approximately 25 km altitude) the 30N/30S average for TES infrared temperatures and the disk-averaged millimeter temperatures are also well correlated in their seasonal and dust-storm-related variations over the 1997-1999 period. This period includes the Noachis Terra regional dust storm, which led to very abrupt heating (approximately 15 K at 0.5 mbar) of the global Mars atmosphere at L(sub S)=224 deg in 1997 [Christensen et al., 1998; Conrath et al., this issue; Smith et al., this issue]. Much colder (10-20 K) global atmospheric temperatures were observed during the 1997 versus 1977 perihelion periods (L(sub S)=200 deg-330 deg), consistent with the much (2 to 8 times) lower global dust loading of the atmosphere during the 1997 perihelion dust storm season versus the Viking period of the 1977a,b storms. The 1998-1999 Mars atmosphere revealed by both the millimeter and TES observations is also 10-15 K colder than presented by the Viking climatology during the aphelion season (L(sub S)=0 deg-180 deg, northern spring/summer) of Mars. We reassess the observational basis of the Viking dusty-warm climatology for this season to conclude that the global aphelion atmosphere of Mars is colder, less dusty, and cloudier than indicated by the established Viking climatology even for the Viking period. We also conclude that Mars atmospheric temperatures exhibit their most significant interannual variations during the perihelion dust storm season (10-20 K for L(sub S)=200 deg-340 deg) and during the post-aphelion northern summer season (5-10 K for L(sub S)=100 deg-200 deg).

Description: The Cloud Ozone Dust Imager (CODI) is proposed to investigate the current climatic balance of the Mars atmosphere, with particular emphasis on the important but poorly understood roles which dust and water ice aerosols play in this balance. The large atmospheric heating (20-50 K) resulting from global dust storms around Mars perihelion is well recognized. However, groundbased observations of Mars atmospheric temperatures, water vapor, and clouds since the Viking missions have identified a much colder, cloudier atmosphere around Mars aphelion that may prove as important as global dust storms in determining the interannual and long-term behavior of the Mars climate. The key climate issues CODI is designed to investigate are: 1) the degree to which non-linear interactions between atmospheric dust heating, water vapor saturation, and cloud nucleation influence the seasonal and interannual variability of the Mars atmosphere, and 2) whether the strong orbital forcing of atmospheric dust loading, temperatures and water vapor saturation determines the long-term balance of Mars water, as reflected in the north-south hemispheric asymmetries of atmospheric water vapor and polar water ice abundances. The CODI experiment will measure the daily, seasonal and (potentially) interannual variability of atmospheric dust and cloud opacities, and the key physical properties of these aerosols which determine their role in the climate cycles of Mars. CODI is a small (1.2 kg), fixed pointing camera, in which four wide-angle (+/- 70 deg) lenses illuminate fixed filters and CCD arrays. Simultaneous sky/surface imaging of Mars is obtained at an angular resolution of 0.28 deg/pixel for wavelengths of 255, 336, 502, and 673 nm (similar to Hubble Space Telescope filters). These wavelengths serve to measure atmospheric ozone (255 and 336 nm), discriminate ice and dust aerosols (336 and 673 nm), and construct color images (336, 502, and 673 nm). The CODI images are detected on four 512 x 512 pixel arrays, as partitioned on two 1024 x 1024 CCD's operated in frame transfer mode. The center of the CODI field-of-view is canted 40 deg from the zenith direction to obtain sky brightness measurements and a 20 deg surface field-of-view. Daily image observations will be conducted when the Sun is greater than or equal to 5 deg outside the edge of the CODI field-of-view, and twilight and nighttime imaging will obtained on a weekly basis. The 673 nm channel includes a polarizer wheel to obtain sky/surface polarimetry. A dust cover protects the entire lens assemblies of all four CODI channels. This opaque dust cover, which is normally opened for CODI imaging, includes a small fixed mirror and transparent window positioned above the 673 nm lens, to redirect the 673 nm field-of-view to the surface for descent imaging. Fixed pointing, internal data buffering, low operating power (2-4 W for less than or equal to 30 seconds), selective data transmission, and simple operational characteristics of the CODI experiment place minimum resource and operational demands on the Mars Surveyor 1998 lander. The CODI science goals are optimized for, but not restricted to, a low-latitude landing site (20 deg S-30 deg N). The primary CODI measurement objectives are the opacities, wave forms, particle properties (size, shape, and alignment), and heights of clouds; the opacities, particle properties, and vertical distribution of dust; and the opacity and vertical distribution of ozone. The variability of cloud, ozone, and dust opacities will be determined on diurnal, daily, and seasonal timescales. Wind velocities will be determined from cloud motions and wave characteristics; and the temporal variability of atmospheric water vapor, with limited altitude information, will be inferred from the CODI ozone observations. Secondary measurement objectives include limited descent imaging capability, surface uv-visible photometry and polarimetry, photochemistry, and meteorite infall rates.

Description: The Martian polar night distribution of 1.27 micron (0-0) band emission from O2 singlet delta [O2(1Delta(sub g))] is determined from an extensive set of Mars Reconnaissance Orbiter (MRO) Compact Reconnaissance Imaging Spectral Mapping (CRISM) limb scans observed over a wide range of Mars seasons, high latitudes, local times, and longitudes between 2009 and 2011. This polar nightglow reflects meridional transport and winter polar descent of atomic oxygen produced from CO2 photodissociation. A distinct peak in 1.27 micron nightglow appears prominently over 70-90NS latitudes at 40-60 km altitudes, as retrieved for over 100 vertical profiles of O2(1Delta(sub g)) 1.27 micron volume emission rates (VER). We also present the first detection of much (x80+/-20) weaker 1.58 micron (0-1) band emission from Mars O2(1Delta(sub g)). Co-located polar night CRISM O2(1Delta(sub g)) and Mars Climate Sounder (MCS) (McCleese et al., 2008) temperature profiles are compared to the same profiles as simulated by the Laboratoire de Mtorologie Dynamique (LMD) general circulation/photochemical model (e.g., Lefvre et al., 2004). Both standard and interactive aerosol LMD simulations (Madeleine et al., 2011a) underproduce CRISM O2(1Delta(sub g)) total emission rates by 40%, due to inadequate transport of atomic oxygen to the winter polar emission regions. Incorporation of interactive cloud radiative forcing on the global circulation leads to distinct but insufficient improvements in modeled polar O2(1Delta(sub g)) and temperatures. The observed and modeled anti-correlations between temperatures and 1.27 mm band VER reflect the temperature dependence of the rate coefficient for O2(1Delta(sub g)) formation, as provided in Roble (1995).

Description: The reported detection of methane in the atmosphere of Mars as well as its potentially large seasonal spatial variations challenge our understanding of both the sources and sinks of atmospheric trace gases. The presence of methane suggests ongoing exchange between the subsurface and the atmosphere of potentially biogenic trace gases, while the spatial and temporal variations cannot be accounted for with current knowledge of martian photochemistry. A Joint Instrument Definition Team (JIDT) was asked to assess concepts for a mission that might follow up on these discoveries within the framework of a series of joint missions being considered by ESA and NASA for possible future exploration of Mars. The following is based on the report of the JIDT to the space agencies (Zurek et al., 2009); a synopsis of the report was presented at the Workshop on Mars Methane held in Frascati, Italy, in November 2009. To summarize, the JIDT believed that a scientifically exciting and credible mission could be conducted within the evolving capabilities of the science/telecommunications orbiter being considered by ESA and NASA for possible launch in the 2016 opportunity for Mars.

Description: Since November of 2006, The Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter (MRO) has obtained multiple-filter daily global images of Mars centered upon a local time (LT) of 3 pm. Ultraviolet imaging bands placed within (260 nm) and longward (320 nm) of Hartley band (240-300 nm) ozone (O3) absorption support retrievals of atmospheric ozone columns, with detection limits (approximately 1 micrometer-atm) appropriate to mapping elevated O3 abundances at low latitudes around Mars aphelion, and over mid-to-high latitudes during fall/winter/spring seasons. MARCI O3 maps for these regions reveal the detailed spatial (approximately 1 deg lat/long, for 8 x 8 pixel binned resolution) and temporal (daily, with substantial LT coverage at pole) behaviors of water vapor saturation conditions that force large variations in water vapor photolysis products (HOx-OH, HO2, and H) responsible for the catalytic destruction of O3 in the Mars atmosphere. A detailed description of the MARCI O3 data set, including measurement and retrieval characteristics, is provided in conjunction with comparisons to Mars Express SPICAM ozone measurements (Perrier, S. et al. [2006]. J. Geophys. Res. (Planets) 111) and LMD GCM simulated O3 abundances (Lefevre, F. [2004]. J. Geophys. Res. (Planets) 109). Presented aspects of the MARCI ozone mapping data set include aphelion increases in low latitude O3, dynamically evolving high latitude O3 maxima associated with planetary waves and weather fronts during northern early spring, and distinctive winter/spring O3 and CO increases within the Hellas Basin associated with transport of condensation enhanced south polar air mass. Comparisons of coincident MARCI measurements and LMD simulations for ice cloud and O3 columns are considered in the context of potential heterogeneous photochemical processes (Lefevre, F. [2008]. Nature 454, 971-975), which are not strongly evidenced in the MARCI observations. Modest interannual variations are exhibited, most notably a 20% reduction in aphelion low latitude O3 columns following the 2007 perihelic global dust storm.

Description: Since July of 2009, The Compact Reconnaissance Imaging Spectral Mapper (CRISM) onboard the Mars Re- connaissance Orbiter (MRO) has periodically obtained pole-to-pole observations (i.e., full MRO orbits) of limb scanned visible/near IR spectra (lambda= 0.4 - 4.0 micrometers, delta lambda approx. 10 nm- Murchie et al., 2007). These CRISM limb observations support the first seasonally and spatially extensive set of Mars 1.27 micometers O2 (1 delta(sub g)) day-glow profile retrievals (approx. 1100) over greater than or equal to 8-80 km altitudes. Their comparison to Laboratoire de Meteorologie Dynamique (LMD) global climate model (GCM) simulated O2 (1 delta(sub g)) volume emission rate (VER) profiles, as a function of altitude, latitude, and season (solar longitude, L(sub s), supports several key conclusions regarding Mars atmospheric water vapor (which is derived from O2 (1 delta(sub g)) emission rates), Mars O3, and the collisional de-excitation of O2 (1 delta(sub g)) in the Mars CO2 atmosphere. Current (Navarro et al., 2014) LMDGCM simulations of Mars atmospheric water vapor fall 2-3 times below CRISM derived water vapor abundances at 20-40 km altitudes over low-to-mid latitudes in northern spring (L(sub s) = 30-60 deg), and northern mid-to-high latitudes over northern summer (L(sub s) = 60-140 deg). In contrast, LMDGCM simulated water vapor is 2-5 times greater than CRISM derived values at all latitudes and seasons above 40 km, within the aphelion cloud belt (ACB), and over high-southern to mid-southern latitudes in southern summer (L(sub s) = 190-340 deg) at 15-35 km altitudes. Overall, the solstitial summer-to-winter hemisphere gradients in water vapor are reversed between the LMDGCM modeled versus the CRISM derived water vapor abundances above 10-30 km altitudes. LMDGCM-CRISM differences in water vapor profiles correlate with LMDGCM-CRISM differences in cloud mixing profiles; and likely reflect limitations in simulating cloud microphysics and radiative forcing, both of which restrict meridional transport of water from summer- to-winter hemispheres on Mars (Clancy et al., 1996; Montmessin et al., 2004; Steele et al., 2014; Navarro et al., 2014) and depend on uncertain cloud microphysical properties (Navarro et al., 2014). The derived low-to-mid latitude changes in Mars water vapor vertical distributions should reduce current model- data disagreements in column O3 and H2O2 abundances over low-to-mid latitudes (e.g., within the ACB; Lefevre et al., 2008; Encrenaz et al., 2015; Clancy et al., 2016). Lastly, the global/seasonal average com- parison of CRISM and LMDGCM O2 (1 delta(sub g)) VER below 20 km altitudes indicates a factor of approx. 3 times lower value (0.25 x 10(exp -20) cu cm sec(exp -1)) for the CO2 collisional de-excitation rate coefficient of O2 (1 delta(sub g)) than derived recently by Guslyakova et al. (2016).