Observations of the martian atmosphere with the mars climate sounder

The Mars Climate Sounder (MCS) has obtained measurements of the Martian atmosphere for one Mars year. Onboard the Mars Reconnaissance Orbiter (MRO), MCS continues to acquire high vertical resolution profiles of temperature, dust, condensates of CO2 and H2O, and water vapor by observing the limb of the atmosphere from the surface to 80 km in the spectral intervals 0.3 – 3 ?m and 11.5 – 45 ?m [1]. This paper describes the investigation and introduces some of the observations being studied by the MCS science team. Other presentations by the team at this workshop will describe in greater detail results of ongoing research using MCS data

A single-scattering approximation for infrared radiative transfer in limb geometry in the Martian atmosphere

We present a single-scattering approximation for infrared radiative transfer in limb geometry in the Martian atmosphere. It is based on the assumption that the upwelling internal radiation field is dominated by a surface with a uniform brightness temperature. It allows the calculation of the scattering source function for individual aerosol types, mixtures of aerosol types, and mixtures of gas and aerosol. The approximation can be applied in a Curtis-Godson radiative transfer code and is used for operational retrievals from Mars Climate Sounder measurements. Radiance comparisons with a multiple scattering model show good agreement in the mid- and far-infrared although the approximate model tends to underestimate the radiances in realistic conditions of the Martian atmosphere. Relative radiance differences are found to be about 2% in the lowermost atmosphere, increasing to ~10% in the middle atmosphere of Mars. The increasing differences with altitude are mostly due to the increasing contribution to limb radiance of scattering relative to emission at the colder, higher atmospheric levels. This effect becomes smaller toward longer wavelengths at typical Martian temperatures. The relative radiance differences are expected to produce systematic errors of similar magnitude in retrieved opacity profiles. © 2011 Elsevier Ltd

Mars Climate Sounder limb profile retrieval of atmospheric temperature, pressure, and dust and water ice opacity

The Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter is the latest of a series of investigations devoted to improving the understanding of current Martian climate. MCS is a nine-channel passive midinfrared and far-infrared filter radiometer designed to measure thermal emission in limb and on-planet geometries from which vertical profiles of atmospheric temperature, water vapor, dust, and condensates can be retrieved. Here we describe the algorithm that is used to retrieve atmospheric profiles from MCS limb measurements for delivery to the Planetary Data System. The algorithm is based on a modified Chahine method and uses a fast radiative transfer scheme based on the Curtis-Godson approximation. It retrieves pressure and vertical profiles of atmospheric temperature, dust opacity, and water ice opacity. Water vapor retrievals involve a different approach and will be reported separately. Pressure can be retrieved to a precision of 1–2% and is used to establish the vertical coordinate. Temperature profiles are retrieved over a range from 5–10 to 80–90 km altitude with a typical altitude resolution of 4–6 km and a precision between 0.5 and 2 K over most of this altitude range. Dust and water ice opacity profiles also achieve vertical resolutions of about 5 km and typically have precisions of 10^(−4)–10^(−5) km^(−1) at 463 cm^(−1) and 843 cm^(−1), respectively. Examples of temperature profiles as well as dust and water ice opacity profiles from the first year of the MCS mission are presented, and atmospheric features observed during periods employing different MCS operational modes are described. An intercomparison with historical temperature measurements from the Mars Global Surveyor mission shows good agreement

The Distinct and Surprisingly Diverse Populations and Properties of Mars Mesospheric Aerosols

International audienceAnalysis of a 2009-2016 set of MRO CRISM limb observations and contemporaneous MCS and MARCI observations yields a new and uniquely comprehensive characterization of dust and ice aerosol distributions and physical characteristics in the Mars mesosphere (50-100 km). Key conclusions are: [1] very distinct aphelion (Ls=0-160º) and perihelion (Ls=160-360º) aerosol populations, in which low latitude CO2 clouds at 60-70 km altitudes dominate the aphelion mesosphere and H2O ice clouds at 50-75 km altitudes dominate the perihelion mesosphere; [2] mesospheric H2O clouds composed of small particle sizes (Reff=0.2 μm) and CO2 cloud particles exhibiting a very broad range of particle sizes (Reff=0.3-2.5 μm) with small particle sizes prominent at the latitude/altitude boundaries of mesospheric CO2 cloud formation; [3] infrequent mesospheric dust aerosols in these non-planet encircling dust storm years with small particle sizes (Reff=0.3-0.6 μm); [4] MCS temperature measurements indicating saturation conditions in the vicinity of mesospheric ice aerosols and enhanced solar heating in the presence of dust aerosols; [5] very narrow CO2 particle size distributions (Veff=0.01-0.03) indicative of iridescence and rapid, uniform cloud nucleation; [6] MCS-CRISM comparisons indicating comparable daytime (3pm) CO2 cloud particle sizes but also MCS nighttime (3am) measurements indicating pervasive low latitude mesospheric CO2 clouds at lower altitudes (55-65 km) and with larger particle sizes (Reff=4-6 μm); [7] MARCI imaging of mesospheric ice clouds displaying wave forms indicative of gravity-wave forcing; and [8] strong indications that cloud nucleation centers, whatever they may be, are not lacking in Mars' mesosphere

Trajectory Studies of Large HNO3-Containing PSC Particles in the Arctic: Evidence for the Role of NAT

Large (5 to >20 micron diameter) nitric-acid-containing polar stratospheric cloud (PSC) particles were observed in the Arctic stratosphere during the winter of 1999-2000. We use a particle growth and sedimentation model to investigate the environment in which these particles grew and the likely phase of the largest particles. Particle trajectory calculations show that, while simulated nitric acid dihydrate (NAD) particle sizes are significantly smaller than the observed maximum particle sizes, nitric acid trihydrate (NAT) particle trajectories are consistent with the largest observed particle sizes

Measurements on a prototype segmented Clover detector

International audienc