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Eight-year Climatology of Dust Optical Depth on Mars
Abstract and Figures
We have produced a multiannual climatology of airborne dust from Martian year
24 to 31 using multiple datasets of retrieved or estimated column optical
depths. The datasets are based on observations of the Martian atmosphere from
April 1999 to July 2013 made by different orbiting instruments: the Thermal
Emission Spectrometer (TES) aboard Mars Global Surveyor, the Thermal Emission
Imaging System (THEMIS) aboard Mars Odyssey, and the Mars Climate Sounder (MCS)
aboard Mars Reconnaissance Orbiter (MRO). The procedure we have adopted
consists of gridding the available retrievals of column dust optical depth
(CDOD) from TES and THEMIS nadir observations, as well as the estimates of this
quantity from MCS limb observations. Our gridding method calculates averages
and uncertainties on a regularly spaced, but possibly incomplete,
spatio-temporal grid, using an iterative procedure weighted in space, time, and
retrieval uncertainty. In order to evaluate strengths and weaknesses of the
resulting gridded maps, we validate them with independent observations of CDOD.
We have statistically analyzed the irregularly gridded maps to provide an
overview of the dust climatology on Mars over eight years, specifically in
relation to its interseasonal and interannual variability. Finally, we have
produced multiannual, regular daily maps of CDOD by spatially interpolating the
irregularly gridded maps using a kriging method. These synoptic maps are used
as dust scenarios in the Mars Climate Database version 5, and are useful in
many modelling applications in addition to forming a basis for instrument
intercomparisons. The derived dust maps for the eight available Martian years
are publicly available and distributed with open access.
Figures - uploaded by Mark T. Lemmon
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... The 1D model uses the method described in Spiga and Forget (2008) to compute the radiative budget on slopes, taking into account scattering by aerosols and the thermal emission from adjacent flat surfaces. We ran the model for several slope angles and azimuths on several locations on Mars, using a nominal dust opacity profile derived by averaging the available observations of dust from Martian Year (MY) 24,25,26,28,29,30, and 31 outside the global dust storm period (Montabone et al., 2015). Figure 2a illustrates satisfying linear correlations (R 2 > 0.95 in all cases) found between the parameter µ and the annual mean solar flux defined as the sum of the solar flux at infrared and visible wavelength calculated by the model. ...
... Dust opacity is set based on the maps from Montabone et al. (2015) and we used in the following the nominal dust scenario as described in section 2. ...
... Vincendon et al. (2010a) showed that the beginning of condensation is sensitive to the amount of dust in the atmosphere, the presence of ice in the subsurface, and the thermal inertia of the surface. Dust is set to the observations of Montabone et al. (2015) and can not be tuned to match the observations. The subsurface ice is predicted to be stable at depth of ∼ 1 m in the 35°-45°S band (see section 3.1.3). ...
A large number of surface phenomena (e.g., frost and ice deposits, gullies, slope streaks, recurring slope lineae) are observed on Martian slopes. Their formation is associated with specific microclimates on these slopes that have been mostly studied with one-dimensional radiative balance models to date. We demonstrate here that any Martian slope can be thermally represented by a poleward or equatorward slope, i.e., the daily average, minimum, and maximum surface temperatures depend on the North-South component of the slope. Based on this observation, we propose here a subgrid-scale parameterization to represent slope microclimates in coarse-resolution global climate models. We implement this parameterization in the Mars Planetary Climate Model and validate it through comparisons with surface temperature measurements and frost detections on sloped terrains. With this new model, we show that these slope microclimates do not have a significant impact on the seasonal CO2 and H2O cycle. Our model also simulates for the first time the heating of the atmosphere by warm plains surrounding slopes. Active gullies are mostly found where our model predicts CO$_2$ frost, suggesting that the formation of gullies is mostly related to processes involving CO2 ice. However, the low thicknesses predicted there rule out mechanisms involving large amounts of ice. This model opens the way to new studies on surface-atmosphere interactions in present and past climates.
... Surface properties (albedo, emissivity, thermal inertia) are set to the observations from the Thermal Emission Spectrom-eter (TES, Christensen et al., 2001;Putzig et al., 2005). A nominal dust opacity profile is used (Montabone et al., 2015). ...
... The Mellon and Sizemore (2022)'s model is a priori less sensitive to this last effect since the infrared flux is computed with the atmospheric model of Pollack et al. (1990). Differences may occur since our model has improved the radiative treatment of dust and clouds (Madeleine et al., , 2012, and directly takes into account the dust observations by Montabone et al. (2015). Finally, in Mellon and Sizemore (2022); Aharonson and Schorghofer (2006)'s models, p vap,surf in Eq. 1 is computed with surface humidity from column-integrated measurements by TES obtained during daytime (Smith, 2002) if the surface is not at saturation. ...
Two arguments have suggested the presence of subsurface water ice at latitudes lower than 30\textdegree~on Mars. First, the absence of CO2 frost on pole-facing slopes was explained by the presence of subsurface ice. Second, models suggested that subsurface ice could be stable underneath these slopes. We revisit these arguments with a new slope microclimate model. Our model shows that below 30{\deg} latitude, slopes are warmer than previously estimated as the air above is heated by warm surrounding plains. This additional heat prevents the formation of CO2 and subsurface water ice for most slopes. Higher than 30{\deg}S, our model suggests the presence of subsurface water ice. In sparse cases (steep dusty slopes), subsurface ice may exist down to 25{\deg}S. While hypothetical unstable ice deposits cannot be excluded by our model, our results suggest that water ice is rarer than previously thought in the +- 30{\deg} latitude range considered for human exploration.
... As a main driver of the Martian climate is the amount of airborne dust in the atmosphere, we present and discuss results obtained with PCM6.0 with dust scenarios from MY29 to MY35, a period which includes the planet encircling global dust storm of MY34 (Montabone et al., 2015. ...
In this paper, the non-orographic Gravity Waves (GW) parameterization of the Mars PCM (Planetary Climate Model) previously implemented by Gilli et al. (2020) is revisited and extended to the exobase ( ∼250 km). The simulations performed with the new scheme correct some known biases in the modelled thermal tide amplitudes and polar warming, improving the agreement with MCS (Mars Climate Sounder) observed thermal structures and tides below ∼ 100 km. Additionally, we find that the simulated densities above 150 km are compatible with NGIMS (Neutral Gas and Ion Mass Spectrometer) measured abundances. Large drag depositions ranging up to > ∼ 950 m.s−1.sol−1 are induced at altitude of 90-170 km due to the wave saturation (breaking) and depletion, leading to winds damped to magnitudes of ∼ 150-225 m.s−1 and ∼ 80 m.s−1 in the zonal and meridional directions, respectively. Resulting temperature variations are ∼± 10-30 K or 5-10 % at most latitudes except in the polar regions (where they can reach ∼± 30-60 K). The results indicate that non-orographic gravity waves play a significant role in the dynamics of the middle-upper atmosphere of Mars via the induced transfer of momentum and energy from the lower atmosphere.
... This demonstrates a relatively stable atmospheric condition without dust storms. In general, these values and trends are consistent with the historical visible column optical depths 4 of 8 (MY24-MY35) of Zhurong landing site estimated from the orbital observations (Montabone et al., 2015). The low atmospheric optical depths also align with the values of other landing sites during the low dust opacity season (Martínez et al., 2017), indicating clear weather with relatively low dust content at the Zhurong landing site over the initial 300 sols. ...
Dust deposition is one of the most predominant processes occurring on Mars. Until now, just a few in situ observations have been conducted to investigate the Martian dust. The Multispectral Camera (MSCam) onboard the Zhurong rover with its calibration target can be used to monitor dust deposition, providing a new ground observation. In this work, we focused on the observations of the MSCam calibration target to retrieve atmospheric optical depth and dust deposition rate over the first 300 sols. The derived atmospheric optical depths are around 0.44, suggesting relatively low airborne dust. The estimated dust deposition rate reveals a distinctive deposition process compared with that of other rovers or landers. Notably, no evident dust is presented during the initial 110 sols, after which dust starts to accumulate. Combining in situ meteorological measurements and numerical modeling, wind speed could be a critical factor to control the dust deposition rate.
... The presence of this plateau between L s = 170° and L s = 190° in the model which is not observed in the EMIRS retrievals leads to the smaller extent of the SNPC predicted by the PCM compared to our retrievals during the second half of the expansion phase. One may also consider that the PCM has been run here for a "nominal dust scenario" (Forget et al., 1999Millour et al., 2022;Montabone et al., 2015), that is, not including the specificities of MY 36. Previous studies (e.g., Calvin et al., 2015;Piqueux et al., 2015) have shown the presence of interannual variations of a few degrees in latitude (typically up to 3-4°) in the extent of the seasonal polar cap deposits for the same values of L s . ...
Plain Language Summary
The H2O and CO2 ices that form at the surface on Mars play an important role in the exchange between the atmosphere and the surface of the planet. While most of the ice is located within the two polar caps that grew and shrink seasonally, ice is also known to condensate as surface frost during the night and sublimate during the day. This nighttime surface frost deposition can be observed even at equatorial latitudes. In this paper we use data from the Emirates Mars Infrared Spectrometer onboard the Emirates Mars Mission to detect the H2O and CO2 ices at the surface of the planet at all local times over almost one Martian Year, which allows us to monitor both the seasonal and diurnal evolution of the distribution of ices at the surface of Mars. We observe that nighttime CO2 frost forms at equatorial latitudes in the second half of the night to disappear at sunrise around the Martian equinoxes.
... This results in approximately 2 weeks of possible solar fuel and oxygen production followed by 2 weeks of darkness at the equator, increasing the requirement for reliable energy storage methods or the strategic positioning of solar-driven devices at the poles. A Martian year consists of 668.60 Martian days (sols), which each approximately equal to 1.03 Earth days 44 . These sols are much more characteristic to Earth's day and night (diurnal) cycle as they have similar day-night time ratios. ...
Human deep space exploration is presented with multiple challenges, such as the reliable, efficient and sustainable operation of life support systems. The production and recycling of oxygen, carbon dioxide (CO2) and fuels are hereby key, as a resource resupply will not be possible. Photoelectrochemical (PEC) devices are investigated for the light-assisted production of hydrogen and carbon-based fuels from CO2 within the green energy transition on Earth. Their monolithic design and the sole reliance on solar energy makes them attractive for applications in space. Here, we establish the framework to evaluate PEC device performances on Moon and Mars. We present a refined Martian solar irradiance spectrum and establish the thermodynamic and realistic efficiency limits of solar-driven lunar water-splitting and Martian carbon dioxide reduction (CO2R) devices. Finally, we discuss the technological viability of PEC devices in space by assessing the performance combined with solar concentrator devices and explore their fabrication via in-situ resource utilization.
Dust storms have been frequently observed on Mars. While others dust storms are global some are regional and local. Many observations have been carried out between MY10 and MY34 (Martin, Icarus 66:2–21, 1986, 1995; Heavens et al., J. Geophys. Res. Planets 119:1748–1774, 2014; Montmessin et al., Icarus 297:195–216, 2017; Willame et al., Planet Space Sci. 142:9–25, 2017; Smith, J. Geophys. Res. Planets 124:2929–2944, 2019; Guzewich et al., Geophys. Res. Lett. 46:71–79, 2019; Guzewich et al., J Geophys. Res. Planets 126:e2021JE006825, 2021). TES onboard MGS have observed a GDS in MY 25 at latitude 25° S, where the IR optical depths were increased up to ~ 1.7 at Ls = 210° (Smith, Icarus 167:148–165, 2004; Sheel and Haider, J. Geophys. Res. Space Phys. 121:8038–8054, 2016) (see Fig. 26.1). Later THEMIS onboard Mars Odyssey observed two major dust storms in MY28 and MY 34 at latitude 25°S, where the IR optical depths were increased up to ~ 1.2 and 1.3 at Ls =280° and Ls = 195° respectively (Smith, Icarus 202:444–452, 2009; Smith, J. Geophys. Res. Planets 124:2929–2944, 2019; Montabone et al., Icarus 251:65–95, 2015; Sheel and Haider, J. Geophys. Res. Space Phys. 121:8038–8054, 2016; Smith, J. Geophys. Res. Planets 124:2929–2944, 2019) (see Fig. 26.2a, b).KeywordsDust layersOptical depthDust density
The infrared spectroscopy is an important remote sensing technique to study the planetary atmospheres and surfaces. Over several decades this technique has been used on Mars to study the composition of the surface, minerals, dust, water ice clouds, temperature and atmospheric gases (Hanel et al., Icarus 17:423–442, 1972; Kieffer et al., J. Geophys. Res. 82:4249–4291, 1977; Christensen et al., J. Geophys. Res. Planets 106:23,873–23,885, 2001). The Martian atmosphere consist CO2 bands, water vapour lines, water ice clouds, and signatures of dust periodically stirred up by strong surface winds. The surface of Mars has been observed in certain spectral windows: 780–1000 cm−1, 1080–1240 cm−1 and 2500–2800 cm−1.The presence of water and dust on Martian surface have been observed by Mariner 9, Viking, MGS, Mars Odyssey and MEX from infrared thermal emission spectrometer. (Hanel et al., Icarus 17:423–442, 1972; Kieffer et al., J. Geophys. Res. 82:4249–4291, 1977; Christensen et al., J. Geophys. Res. Planets 106:23,873–23,885, 2001). These missions have also observed surface minerals, rocks and temperatures on Mars.KeywordsPFS observationsThermal emissionsBrightness
The martian solsticial pause, presented in a companion paper (. Lewis et al., 2016), was investigated further through a series of model runs using the UK version of the LMD/UK Mars Global Climate Model. It was found that the pause could not be adequately reproduced if radiatively active water ice clouds were omitted from the model. When clouds were used, along with a realistic time-dependent dust opacity distribution, a substantial minimum in near-surface transient eddy activity formed around solstice in both hemispheres. The net effect of the clouds in the model is, by altering the thermal structure of the atmosphere, to decrease the vertical shear of the westerly jet near the surface around solstice, and thus reduce baroclinic growth rates. A similar effect was seen under conditions of large dust loading, implying that northern midlatitude eddy activity will tend to become suppressed after a period of intense flushing storm formation around the northern cap edge. Suppression of baroclinic eddy generation by the barotropic component of the flow and via diabatic eddy dissipation were also investigated as possible mechanisms leading to the formation of the solsticial pause but were found not to make major contributions. Zonal variations in topography were found to be important, as their presence results in weakened transient eddies around winter solstice in both hemispheres, through modification of the near-surface flow. The zonal topographic asymmetry appears to be the primary reason for the weakness of eddy activity in the southern hemisphere relative to the northern hemisphere, and the ultimate cause of the solsticial pause in both hemispheres. The meridional topographic gradient was found to exert a much weaker influence on near-surface transient eddies.
Mars Daily Global Maps (MDGM) derived from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) and Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) are used to study the distribution and evolution of large dust storms over the period from Mars years 24–30 (1999–2001). Large storms are defined here as discrete dust events visible in image sequences extending over at least 5 sols (Mars days) and where the dust covers areas beyond the origination region. A total of 65 large dust storms meeting these criteria are identified during the observational period and all are observed during the Ls = 135–30° seasonal window. Dust storms originating in the northern and southern hemispheres appear to form two distinct families. All but two of the storms originating in the northern hemisphere are observed in two seasonal windows at Ls = 180–240° and Ls = 305–350°; while all but two of those originating in the southern hemisphere are observed during Ls = 135–245°.
None of the large dust storms originating in the northern hemisphere are observed to develop to global scale, but some of them develop into large regional storms with peak area >1 × 10⁷ km² and duration on the order of several weeks. In comparison, large dust storms originating in the southern hemisphere are typically much smaller, except notably in the two cases that expanded to global scale (the 2001 and 2007 global storms).
Distinct locations of preferred storm origination emerge from the dust storm image sequences, including Acidalia, Utopia, Arcadia and Hellas. A route (trajectory) ‘graph’ for the observed sequences is provided. The routes are highly asymmetric between the two hemispheres. In the south, for non-global dust storms, the main routes are primarily oriented eastwest, whereas in the north, the routes are primarily north–south and zonally-concentrated into meridional channels. In a few impressive cases, storms originating in the northern hemisphere are observed to “flush” through Acidalia and Utopia, across the equator, and then branch in the low- and mid-southern latitudes. The origin of the 2007 global dust storm is ambiguous from the imaging data. Immediately prior to the global storm, a dust storm sequence from Chryse is identified. This storm’s connection to the explosive expansion observed to start from Noachis/West Hellas is unclear due to image coverage. This paper further identifies and describes three different styles of dust storm development, which we refer to as “consecutive dust storms”, “sequential activation” and “merging.” The evolution of a given dust storm sequence can exhibit different combinations of these growth styles at different stages of development. Dust storm sequences can overlap in time, which makes them good candidate to grow into larger scale.
We present eight Mars Years of nearly continuous tracking of the CO2 seasonal cap edges from Mars Year (MY) 24 to 31 using Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) and Mars Reconnaissance Orbiter (MRO) Mars Climate Sounder (MCS) thermal infrared data. Spatial and temporal resolutions are 1 pixel per degree and 10°Ls (aerocentric longitude of the Sun). The seasonal caps are defined as the regions where the diurnal radiometric temperature variations at ∼32 μm wavelength do not exceed 5 K. With this definition, terrains with small areal fraction of defrosted regolith able to experience measurable diurnal temperature cycles are not mapped as part of the cap. This technique is adequate to distinguish CO2 from H2O ices, and effective during the polar night or under low illumination conditions. The present analysis answers outstanding questions stemming from fragmented observations at visible wavelengths: (1) the previously sparsely documented growth of the North seasonal caps (160° < Ls < 270°) is shown to be repeatable within 1–2° equivalent latitude, and monotonic over the MY 24–31 time period; high repeatability is observed during the retreat of the caps in non-dusty years (∼1° or less equivalent latitude); (2) the MY 25 storm does not seem to have impacted the growth rate, maximal extents, or recession rate of the North seasonal caps, whereas the MY 28 dust storm clearly sped up the recession of the cap (∼2° smaller on average after the storm, during the recession, compared to other years); (3) during non-dusty years, the growth of the South seasonal cap (350° < Ls < 100°) presents noticeable variability (up to ∼4° equivalent latitude near Ls = 20°) with a maximum extent reached near Ls = 90°; (4) the retreat of the Southern seasonal cap (100° < Ls < 310°) exhibits large inter-annual variability, especially near 190° < Ls < 220°; (5) the recession of the MY 25 South seasonal cap is significantly accelerated during the equinox global dust storm, with surface temperatures suggesting increased patchiness or enhanced dust mantling on the CO2 ice. These results suggest that atmospheric temperatures and dust loading are the primary source of variability in an otherwise remarkably repeatable cycle of seasonal cap growth and recession.
A clarification for the enumeration of Mars years prior to 1955 is presented, along with a table providing the Julian Dates associated with Ls = 0° for Mars years −183 (beginning of the telescopic study of Mars) to 100. A practical algorithm for computing Ls as a function of the Julian Date is provided. No new science results are presented.
Airborne dust modifies the thermal structure of the Martian atmosphere. The Mars Climate Sounder (MCS) first revealed local maxima of dust mass mixing ratio detached from the surface, not reproduced by Global Climate Models (GCM). In this paper, the thermal signature of such detached layers is detected using data assimilation, an optimal combination of a GCM and observations. As dust influences the atmospheric temperatures, MCS temperature profiles are used to estimate the amount of dust in the atmosphere. Data assimilation of only MCS temperature information reproduces detached dust layers, independently confirming MCS's direct observations of dust. The resulting analyzed state has a smaller bias than an assimilation that does not estimate dust. This makes it a promising technique for Martian data assimilation, which is intended to support weather forecasting and weather research on Mars.
The Mars Orbiter Camera on board the Mars Global Surveyor from March 9, 1999 (Ls = 107°, where Ls is the areocentric longitude of the Sun measured in degrees from Mars' northern spring equinox), to December 31, 1999 (Ls = 274°), has obtained 7.5 km pixel−1 daily global maps of the Martian surface in two wavelength bands: blue (400–450 nm) and red (575–625 nm). Visual inspection of these maps during the 1999 dust storm season has resulted in the detection of 783 dust storms, ranging in size from “local” (>102 km2) to “regional” (>1.6×106 km2). No global storms were observed. The difference in the numbers of dust storms occurring in the two hemispheres (north: 343; south: 440) was not statistically significant. Fifty percent of the regional size dust storms formed as a result of the “merger” of two or more smaller local storms. The regional storms from Ls = 207° to Ls = 223° were observed to move from the northern hemisphere into the southern hemisphere between 30°W and 50°W longitude. This cross-equatorial transport of dust suggests the location of the low-lying southward flowing branch of the Hadley circulation. Observations show that dust storms occur in several regions on Mars: at the two polar cap edges, at the base of high elevation regions in the northern hemisphere, near the polar hood during northern fall, and at mid-latitudes in both hemispheres. Specific regions such as Solis Planum and Hesperia, which were regions of significant dust activity in the past, showed almost no dust storm activity in 1999, suggesting that regional dust sources are variable over a 20-year time frame. One region of exceptional activity not noted previously was the Arcadia-Amazonis border. However, other regions, such as near Elysium Mons, Acidalia, Chryse, Hellas, Noachis, Argyre, Cimmeria, and Sirenum, again were active dust storm regions. Relative dust opacities were modeled for 117 red wavelength events and ranged from 0.54 “diffuse haze” to 2.13 “concentrated local events.” From the dust opacities we estimated the north polar sedimentation rate to be 6.0–10×10−4 g cm−2 yr−1, a factor of 40 smaller than previous estimates from the two 1977 global dust storms [Pollack et al., 1979], along with the global dust mass loading (2.6–4.0×10−4 g cm−2) and cross-equatorial dust mass loading (3.6×10−4 g cm−2). The 1999 cross-equatorial mass dust loading suggests that the southern hemisphere subtropical latitudes require at least 2–3 Martian years to replenish their dust sources before global storms can form.