A mobile Lander-Borne radar to investigate the subsurface of the planet Mars

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Revived interest in exploration of the planet Mars had led to a Soviet suggestion that a radar on the surface of the planet could be used for both sub-surface and atmospheric studies. This paper reviews the present understanding of the electromagnetic properties of the martian sub-surface and the possibility of the presence of water. This is used in the development of the requirements for a radar sensor and an investigation into techniques such as aperture synthesis, needed to meet these requirements. Some techniques rely on motion of the radar, hence on the use of a Mars rover. A possible radar design is presented.

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The planet Mars has been visited in the past by orbital probes and landers to study the atmosphere and the ground. But despite these numerous missions, more than 20 years ago, many parameters and phenomena are not known at this time. The large possibilities given by new technologies, in terms of weight and power consumption, allow the realization of new experiments at the surface of Mars. The aim is to propose the installation of a bottomside ionospheric sounder. This instrument will contribute to our scientific understanding of Mars. It will answer one of the main scientific objectives of the IMEWG (International Mars Exploration Working Group) mission scenario: the characterization of the Martian upper atmosphere and its interaction with the solar wind. Ionospheric sounding is a well-known technique at the surface of the Earth which has proven to be very useful for the study of the lower ionosphere. The principle is to transmit a radio pulse vertically and to measure the time which elapses before the echo is received. By varying the frequency of the pulse carrier wave, a plot can be obtained of echo delay versus frequency. It gives information about the propagation medium. The scientific objectives are described which can be achieved with such an experiment and the parameters which can be measured underlining the specificity of the Martian atmosphere are given. The theoretical scientific background of this sounder is briefly described and, finally, its feasibility is discussed.
The history of the use of sinusoidal functions and the suitability of these functions for the transmission of information are discussed, taking into account also possibilities for a use of nonsinusoidal functions. It is shown that the available technology is capable of radiating and selectively receiving nonsinusoidal waves. As a basis for an evaluation of the application possibilities for nonsinusoidal electromagnetic waves, attention is given to a concept which makes it possible to distinguish quantitatively between theoretical sinusoidal waves, practical (almost) sinusoidal waves, and nonsinusoidal waves. A suitable measure is provided by the concept of the relative bandwidth. It is pointed out that semiconductor technology has made it possible to use radio signals with large relative bandwidth or nonsinusoidal signals, instead of conventional signals with small relative bandwidth or (almost) sinusoidal signals. The practical level of this new development was reached with the ground-probing radar. Many more applications are possible.
Volcanic flows with very large areas characterize the Martian volcano Alba Patera. Photogeologic analysis indicates a change of eruptive style with time, from early flood lavas to relatively short, narrow, leveed summit flows during the dying phase of activity. Estimates of mass effusion rate and rheological properties derived from dimensional parameters confirm the view that the magmas involved were mafic, and indicate extremely high effusion rates (5 - 1610×103m3sec-1) for the earlier flows. The data substantiates the view that during the active life of Alba volcano mass eruption rates in the Tharsis region of Mars were significantly higher than in most analogous terrestrial provinces, but probably not as high as those for lunar mare basalts.
RF losses at 100 Mc/s in artificial samples of salty ice and frozen, fresh-water-saturated earths were measured in the laboratory, and pronounced attenuation of radio waves within distances of a few meters are predicted as a general rule. Salty ice dielectric constants averaged 3.5, and resistivities ‘across the grain’ varied from about 55 ohm-meters at −10°C to about 1200 ohm meters at −40°C for ice containing about 5% of salts. These results may or may not apply to natural sea ice and permafrost.
Apollo 11 lunar samples dielectric constants, losses and electrical conductivities as function of temperature and frequency, comparing with terrestrial and simulated lunar rocks
Knowledge regarding the geology of the terrestrial planets has increased considerably during the last four years. The present investigation provides a brief summary of work during these years on the geology of Mercury, Venus, moon, and Mars. Following the Mariner 10 encounter with Mercury in 1974, the geologic history of the planet was broadly outlined by Strom (1979). McCauley et al. (1981) recognized several facies of ejecta around Caloris. Hostetler and Drake (1980) showed that unless Mercury received more than 60-70 percent of its thermal energy from tidal interactions, it must have undergone early, almost global melting. Knowledge of the Venusian surface has increased substantially over the last few years both through improvement of earth-based observations and in connection with the Pioneer Venus mission. A topographic map of Venus is presented. Attention is also given to the composition and character of lunar highlands, the evolution of different maria, photographs obtained of almost the entire planet Mars, and Martian craters and volcanism.
The Martian volcanic complex Alba Patera exhibits a suite of well-defined, long and relatively narrow lava flows qualitatively resembling those found in Hawaii. Even without any information on the duration of the Martian flows, eruption rates (total volume discharge/duration of the extrusion) estimates are implied by the physical dimensions of the flows and the likely conjecture that Stephan-Boltzmann radiation is the dominating thermal loss mechanism. The ten flows in this analysis emanate radially from the central vent and were recently measured in length, plan areas, and average thicknesses by shadow measurement techniques. The dimensions of interest are shown. Although perhaps morphologically congruent to certain Hawaiian flows, the dramatically expanded physical dimensions of the Martian flows argues for some markedly distinct differences in lava flow composition for eruption characteristics.
Theoretical arguments are presented in support of the idea that Mars possessed a dense CO2 atmosphere and a wet, warm climate early in its history. Calculations with a one-dimensional radiative-convective climate model indicate that CO2 pressures between 1 and 5 bars would have been required to keep the surface temperature above the freezing point of water early in the planet's history. The higher value corresponds to globally and orbitally averaged conditions and a 30% reduction in solar luminosity; the lower value corresponds to conditions at the equator during perihelion at times of high orbital eccentricity and the same reduced solar luminosity. The plausibility of such a CO2 greenhouse is tested by formulating a simple model of the CO2 geochemical cycle on early Mars. By appropriately scaling the rate of silicate weathering on present Earth, we estimate a weathering time constant of the order of several times 10(7) years for early Mars. Thus, a dense atmosphere could have persisted for a geologically significant time period (approximately 10(9) years) only if atmospheric CO2 was being continuously resupplied. The most likely mechanism by which this might have been accomplished is the thermal decomposition of carbonate rocks induced directly and indirectly (through burial) by intense, global-scale volcanism. For plausible values of the early heat flux, the recycling time constant is also of the order of several times 10(7) years. The amount of CO2 dissolved in standing bodies of water was probably small; thus, the total surficial CO2 inventory required to maintain these conditions was approximately 2 to 10 bars. The amount of CO2 in Mars' atmosphere would eventually have dwindled, and the climate cooled, as the planet's internal heat engine ran down. A test for this theory will be provided by spectroscopic searches for carbonates in Mars' crust.
Polygenetic eruptions on Alba Patera Mars: evidence of channel erosion on pyroclastic flows
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