Martian volcanism: A review

Martian volcanism is reviewed. It is emphasized that lava plains constitute the major type of effusive flow, and can be differentiated by morphologic characteristics. Shield volcanoes, domes, and patera constitute the major constructional landforms, and recent work has suggested that explosive activity and resulting pyroclastic deposits may have been involved with formation of some of the small shields. Analysis of morphology, presumed composition, and spectroscopic data all indicate that Martian volcanism was dominantly basaltic in composition

Mars: A water-rich planet

Good geomorphic evidence is presented for a planet that was once water rich, and that a lower limit on the amount of water available for a given Martian watershed may be estimated by assuming that the volume of material eroded was equal to the volume of water available. This estimate, coupled with high latitude water estimates of 50 to 100 m gives a global inventory of about 500 m total water in the subsurface. It was emphasized that this is a lower limit as considerable water may be bound in weathered debris and in primary minerals

Water on Mars: Clue to accretional history

Geological evidence for large amounts of water at the Martian surface appears to be in conflict with geochemical evidence from SNC meteorites that suggests that the Mars mantle is dry and should have lost almost all of its initially large inventory of water during accretion. Here, several possibilities are suggested as to how the apparently conflicting data from two sources may be reconciled. The considerations examined indicate that several plausible explanations for the apparent conflict between geochemical evidence of little water on Mars and geologic evidence of abundant water. One possible conclusion is that Mars has a primitive volatile-rich crust that has been partly overplated with young, dry, mantle-derived volcanoes of which we have samples in the SNC meteorites

Rationale for Mars Rover/Sampler Return mission

A Mars Rover/Sample Return (MRSR) mission is currently being studied for the late 1990's. The objectives of the mission are to better understand the origin and evolution of Mars, to search for evidence of former life, and to improve the knowledge of the Martian environment in preparation for subsequent human exploration. Having formed in a different part of the Solar System from Earth, Mars will provide clues that will better enable the discrimination between conflicting theories of Solar System formations. Mars is also a natural laboratory on which a wide range of geologic and meteorological processes have operated under conditions very different from those on Earth. Samples are needed so that the full range of analytical techniques available here on Earth can be applied to the study of these issues. The rover provides the mobility needed to access different materials, and can be equipped with an analytical capability so that the planet can be sampled intelligently. The rover will also provide the means of exploring the planet on a human scale and performing a wide range of in situ measurements at different locations. Different mission scenarios are currently being studied with the goal of achieveing sample return before the end of the century

Overview of Mars: Viking results

As a result of the Viking orbiter observations, the entire surface of Mars has been imaged at a resolution of 200 meters, and fractions of the surface down to resolutions of 10 meters, the thermal inertia of the entire surface is known to a resolution of 30 km, and the water content of the atmosphere has been monitored over two Martian years. In addition, at two sites, the Viking landers analyzed the atmosphere, imaged the surface, performed organic and inorganic analyses on the soil, and monitored meteorological conditions for almost three Martian years. The results show that Mars is a highly variegated planet with a long and complex history of volcanic and tectonic activity, a surface that has been modified by wind, water and ice, and an atmosphere that has experienced substantial changes, both periodic and secular. The variety of processes that have operated on the surface, and the long history of their action, result in a much broader range of sampling problems and opportunities than was experienced in the case of the Moon

MRSR: Rationale for a Mars Rover/Sample Return mission

The Solar System Exploration Committee of the NASA Advisory Council has recommended that a Mars Rover/Sample Return mission be launched before the year 2000. The recommendation is consistent with the science objectives as outlined by the National Academy of Sciences committees on Planetary and Lunar Exploration, and Planetary Biology and Chemical Evolution. Interest has also focused on Mars Rover/Sample Return (MRSR) missions, because of their crucial role as precursors for human exploration. As a result of this consensus among the advisory groups, a study of an MRSR mission began early in 1987. The study has the following goals: (1) to assess the technical feasibility of the mission; (2) to converge on two or three options for the general architecture of the mission; (3) to determine what new technologies need to be developed in order to implement the mission; (4) to define the different options sufficiently well that preliminary cost estimates can be made; and (5) to better define the science requirements. This chapter briefly describes Mars Rover/Sample Return missions that were examined in the late 1980s. These missions generally include a large (1000 kg) rover and return of over 5 kg of sample