J.-L. Bertaux, D. Fonteyn, O. Korablev, E. Chassefière, E. Dimarellis, J. P. Dubois, A. Hauchecorne, M. Cabane, P. Rannou, A. C. Levasseur-Regourd, G. Cernogora, E. Quemerais, C. Hermans, G. Kockarts, C. Lippens, M. D. Maziere, D. Moreau, C. Muller, B. Neefs, P. C. Simon, F. Forget, F. Hourdin, O. Talagrand, V. I. Moroz, A. Rodin, B. Sandel, and A. Stern. The study of the martian atmosphere from top to bottom with SPICAM light on mars express. Planetary and Space Science, 48:1303-1320, 2000. [ bib | DOI | ADS link ]
SPICAM Light is a small UV-IR instrument selected for Mars Express to recover most of the science that was lost with the demise of Mars 96, where the SPICAM set of sensors was dedicated to the study of the atmosphere of Mars (Spectroscopy for the investigation of the characteristics of the atmosphere of mars). The new configuration of SPICAM Light includes optical sensors and an electronics block. A UV spectrometer (118-320 nm, resolution 0.8 nm) is dedicated to Nadir viewing, limb viewing and vertical profiling by stellar occultation (3.8 kg). It addresses key issues about ozone, its coupling with H 2O, aerosols, atmospheric vertical temperature structure and ionospheric studies. An IR spectrometer (1.2- 4.8 μm, resolution 0.4-1 nm) is dedicated to vertical profiling during solar occultation of H 2O, CO 2, CO, aerosols and exploration of carbon compounds (3.5 kg). A nadir looking sensor for H 2O abundances (1.0- 1.7 μm, resolution 0.8 nm) is recently included in the package (0.8 kg). A simple data processing unit (DPU, 0.9 kg) provides the interface of these sensors with the spacecraft. In nadir orientation, SPICAM UV is essentially an ozone detector, measuring the strongest O 3 absorption band at 250 nm in the spectrum of the solar light scattered back from the ground. In the stellar occultation mode the UV Sensor will measure the vertical profiles of CO 2, temperature, O 3, clouds and aerosols. The density/temperature profiles obtained with SPICAM Light will constrain and aid in the development of the meteorological and dynamical atmospheric models, from the surface to 160 km in the atmosphere. This is essential for future missions that will rely on aerocapture and aerobraking. UV observations of the upper atmosphere will allow study of the ionosphere through the emissions of CO, CO +, and CO 2+, and its direct interaction with the solar wind. Also, it will allow a better understanding of escape mechanisms and estimates of their magnitude, crucial for insight into the long-term evolution of the atmosphere. The SPICAM Light IR sensor is inherited from the IR solar part of the SPICAM solar occultation instrument of Mars 96. Its main scientific objective is the global mapping of the vertical structure of H 2O, CO 2, CO, HDO, aerosols, atmospheric density, and temperature by the solar occultation. The wide spectral range of the IR spectrometer and its high spectral resolution allow an exploratory investigation addressing fundamental question of the possible presence of carbon compounds in the Martian atmosphere. Because of severe mass constraints this channel is still optional. An additional nadir near IR channel that employs a pioneering technology acousto-optical tuneable filter (AOTF) is dedicated to the measurement of water vapour column abundance in the IR simultaneously with ozone measured in the UV. It will be done at much lower telemetry budget compared to the other instrument of the mission, planetary fourier spectrometer (PFS).
M. J. Burgdorf, T. Encrenaz, E. Lellouch, H. Feuchtgruber, G. R. Davis, B. M. Swinyard, T. de Graauw, P. W. Morris, S. D. Sidher, M. J. Griffin, F. Forget, and T. L. Lim. ISO Observations of Mars: An Estimate of the Water Vapor Vertical Distribution and the Surface Emissivity. Icarus, 145:79-90, 2000. [ bib | DOI | ADS link ]
Infrared spectra of Mars were taken with the two complementary spectrometers onboard the European Space Agency's Infrared Space Observatory (ISO), in both moderate- and high-resolution mode. From the strengths of the observed water lines we derived information about the vertical distribution of water vapor and on the emissivity of the dust/surface system in the infrared. Assuming atmospheric and surface temperatures derived from the European Martian Climate Database with a slight adjustment to the observed 15-μm CO 2 band, the ISO data are consistent with an H 2O mixing ratio of (31)×10 -4 at the surface, a saturation level at 132 km, and a total column density of 123.5 pr-μm. The mean disk emissivity is found to be close to 1.0 at 6 μm and 0.920.02 at 40 μm. At longer wavelengths the emissivity decreases from a value of 0.970.03 at 50μm to 0.920.03 at 180 μm.
S. M. Clifford, D. Crisp, D. A. Fisher, K. E. Herkenhoff, S. E. Smrekar, P. C. Thomas, D. D. Wynn-Williams, R. W. Zurek, J. R. Barnes, B. G. Bills, E. W. Blake, W. M. Calvin, J. M. Cameron, M. H. Carr, P. R. Christensen, B. C. Clark, G. D. Clow, J. A. Cutts, D. Dahl-Jensen, W. B. Durham, F. P. Fanale, J. D. Farmer, F. Forget, K. Gotto-Azuma, R. Grard, R. M. Haberle, W. Harrison, R. Harvey, A. D. Howard, A. P. Ingersoll, P. B. James, J. S. Kargel, H. H. Kieffer, J. Larsen, K. Lepper, M. C. Malin, D. J. McCleese, B. Murray, J. F. Nye, D. A. Paige, S. R. Platt, J. J. Plaut, N. Reeh, J. W. Rice, D. E. Smith, C. R. Stoker, K. L. Tanaka, E. Mosley-Thompson, T. Thorsteinsson, S. E. Wood, A. Zent, M. T. Zuber, and H. Jay Zwally. The State and Future of Mars Polar Science and Exploration. Icarus, 144:210-242, 2000. [ bib | DOI | ADS link ]
As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of 10 6 km 2 and total as much as 3-4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to be comparatively youngpreserving a record of the seasonal and climatic cycling of atmospheric CO 2, H 2O, and dust over the past 10 5-10 8 years. For this reason, the martian polar deposits may serve as a Rosetta Stone for understanding the geologic and climatic history of the planetdocumenting variations in insolation (due to quasiperiodic oscillations in the planet's obliquity and orbital elements), volatile mass balance, atmospheric composition, dust storm activity, volcanic eruptions, large impacts, catastrophic floods, solar luminosity, supernovae, and perhaps even a record of microbial life. Beyond their scientific value, the polar regions may soon prove important for another reasonproviding a valuable and accessible reservoir of water to support the long-term human exploration of Mars. In this paper we assess the current state of Mars polar research, identify the key questions that motivate the exploration of the polar regions, discuss the extent to which current missions will address these questions, and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding.