Planetary and Lunar Exploration Space Science in the Twenty-First Century -- Imperatives for the Decades 1995 to 2015 (1988) / Chapter Skim
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4. Future Programs
4. Future Programs
Pages 88-112
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From page 88... ...
This phase is carried out by longlived orbiters equipped with a variety of cameras and other remote sensing instruments and may include entry probes to measure the chemical composition of the planet's atmosphere or surface. Such missions can image the surface of the planet; provide a global map of the distribution of elements and minerals on the planet's surface; 88
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From page 89... ...
The measurement of heat flow is fundamental for understanding the interior characteristics of planets and satellites, yet obtaining valid data remains a major technological problem. All present means for emplacing instruments in the subsurface (e.g., penetrators, drilled holes)
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From page 90... ...
The detailed chemical character of a rock can thus be the key to identifying global planetary processes core formation, crustal separation, or episodes of widespread volcanism. The measurement of radioactive parent and daughter elements in a rock provides independent information about the timing of major planetary events origin, major meteorite impacts, and volcanism.
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From page 91... ...
Such data from surface materials will provide powerful tools for understanding the evolution of the planet's surface and interior. From our experience with lunar samples, meteorites, and terrestrial rocks, Xe isotopes are expected to be the most versatile, as the isotopic patterns may reflect several processes—extinct short-lived isotopes, fission of long-lived and extinct isotopes of U and Pu, and the mixing effects of various reservoirs of gas.
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From page 92... ...
The major mission recommended for the initial decade of the study period is a Mars rover and sample return program consisting of linked missions launched in 1996 to 1998. This is envisioned as a very comprehensive mission one with a capable rover to collect selected samples for return to Earth and carry out extensive observations over the surface of the planet.
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From page 93... ...
Although the rover's prime objective is to support sample collection, it is important to note that its capabilities, and the data it collects to characterize possible samples, would also be scientifically unportant during an extended traverse to analyze and characterize martian surface materials up to a significant
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From page 94... ...
Such a post-sampling traverse would provide an important regional context for the sample suite and would also help understand better the complex processes that have taken place on the martian surface. Eventually, manned missions will offer the most complete and comprehensive execution of the intensive phase of planetary exploration.
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From page 95... ...
This would allow direct measurement of particle physical and chemical properties, and direct observations of inter-particle collisions. Planned Missions As described in the recent publication, A Strategy for Exploration of the Outer Planets: 1986-1996 (National Academy Press, 1986)
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From page 96... ...
. Future Missions and Progeny for Primitive Bodies and the Origin of the Solar System We can expect that, by 1995, reconnaissance missions to comet nuclei and asteroids will have transformed our view of these bodies from unresolvable points of light into planetary bodies of distinct shape and surface morphology.
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From page 97... ...
A sample return mission of this kind could be of much importance in itself, as well as a valuable forerunner of collection and return to Earth of Pristine samples of a cometary nucleus. The earth-approach~ng Apollo and Amor objects are a special class of primitive bodies.
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From page 98... ...
The variety and number of rendezvous and sample return opportunities to primitive bodies are now limited by existing ballistic propulsion systems. Full exploitation of the potential offered by such studies will require development of low-thrust propulsion systems that permit selection of targets primarily because of their scientific interest rather than on the basis of their accessibility.
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From page 99... ...
For reasons of its ease of exploration, comparability to the Earth and Moon, geologically active history, record of climate change, and possible environment for origin of life, Mars is unquestionably the best planet on which to focus this campaign. Already we have enough detailed information on Mars to identify sites where intensive study of the surface would provide critical information on the crustal evolution, geologic history, present and past water and atmosphere inventory, and history of climate variation.
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From page 100... ...
Because of the interest that they hold within the broader context of solar system studies, the terrestrial planets should be a special concern of solar system exploration within an overall balanced program. This general conclusion leads to a recommendation for a detailed exploration of the most available terrestrial planet, Mars.
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From page 101... ...
The early presence of liquid water and a substantial atmosphere is shown by the weathering of old craters and the dendritic stream channels on ancient surfaces. Further, a record of at least recent climate change may be preserved in the sedimentary layered rocks near the martian poles.
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From page 102... ...
Scientific Objectives for a Mare Focus The scientific utility of studying a second terrestrial planet in sufficient depth that the past and present processes can be identified and compared with similar ones on the Earth leads naturally to the recommendation of a major focus on intensive exploration of Mars. Current understanding of the origin, early history, and present state of Mars motivates a set of scientific goals whose accomplishment defines the scope of the recommended campaign to understand Mars: 1.
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From page 103... ...
The next major scientific objectives beyond those addressed by current missions could be met with a capable rover to collect selected samples for return to Earth and to carry out extensive observations over the surface of the planet. The return and study of pristine martian materials could provide data on the absolute chronology of martian rock units, on detailed detection and characterization of possible contemporary or fossilized life, on surface-atmospheric interaction processes and rates, and on the composition and evolution of Mars' crust and mantle.
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From page 104... ...
The collection of these samples involves increased complexity with far-traveling, highly capable rover laboratory/observers and drill stations capable of drilling deep holes. Instruments to measure seismic waves, composition and physical properties of the surface, heat flow, and meteorological parameters should be emplaced in a network of at least 3 to 4 stations; 6 to 12 stations would be preferable.
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From page 105... ...
Second, it is difficult for autonomous devices, even remotely linked to Earth by cameras, to achieve the scientific goals set forward above. Ultimately, to resolve the important questions and to compare Mars in detail with the Earth will require exploration capabilities on the surface of Mars possessed now only by humans.
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From page 106... ...
A viable planetary program must contain all five elements spacecraft missions, telescope observations, field investigations, laboratories, and modelsand the task group's recommendations speak to each. Melioration of the Solar System Figures 2.2, 2.3, and 2.4 in Chapter 2 show the status of planetary exploration expected by 1995, and the missions recommended for the period 1995 to 2015.
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From page 107... ...
The other proposed inner planet mission concepts involve the intensive study phase. For the Moon, the near-term geophysical studies from orbit wall undoubtedly raise questions requiring additional sample return for their resolution.
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From page 108... ...
The hostile environment of the planet requires much more technological development for future missions than is the case for the other terrestrial planets. Nevertheless, the kind of geophysical and geochemical information desired from Venus is similar to that desired from the other terrestrial planets, and the means needed to acquire this will include probes, the establishment of a global network, and sample returns.
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From page 109... ...
The material constituting comets is likely to be the most primitive form of matter preserved from the environment of the early solar system that will ever be available to us. Thus sample return is vitally important for further studies of comets.
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From page 110... ...
The task group recommends that development efforts in these areas of technology be initiated as soon as possible. Telescopes on Earth and in earth orbit complement space probes by providing observational data that, while usually of lower spatial resolution, can be synoptic in scope and quickly responsive to phenomena.
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From page 111... ...
That investigation must continue. But a major Mars campaign could be carried out concurrently, in the same way that the first decade of planetary exploration was carried out by Mariner spacecraft in parallel with the Apollo Moon program.
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