After the Mars Polar Lander: Where to Next? D. A. Paige1 , W. V. Boynton2, D

Concepts and Approaches for Mars Exploration 6122.pdf

After the Mars Polar Lander: Where to next? D. A. Paige1 , W. V. Boynton2, D. Crisp3, E. DeJong3, C. J. Han- sen3, A. M. Harri4, H. U. Keller5, L. A. Leshin6, R. D. May7, P. H. Smith2, R. W. Zurek3, 1Dept. of Earth and Space Sciences, UCLA, Los Angeles, Ca 90095 [email protected], 2University of Arizona,. 3Jet Propulsion Laboratory, 4Finnish Meteorological Institute, 5Max Planck Institute for Aeronomy, 6Arizona State University, 7Spectrasensors Inc.

Introduction: The recent loss of the Mars Polar cant new datasets which are revolutionizing our un- Lander (MPL) mission represents a serious setback to derstanding of the planet. The MGS results in the Mars science and exploration. Targeted to land on the north and south polar regions that have been pub- Martian south polar layered deposits at 76° S latitude lished to date have been particularly exciting. MOLA and 195° W longitude, it would have been the first topographic maps show that both polar caps have ap- mission to study the geology, atmospheric environ- proximately 3 km of total relief; and have shapes that ment and volatiles at a high-latitude landing site. are consistent with those expected for large ice sheets. Since the conception of the MPL mission, a Mars ex- The MOLA data also suggest that both caps may have ploration strategy has emerged which focuses on Cli- been significantly larger at some point in their past mate, Resources and Life, with the behavior and his- history [1]. The north polar cap lies in a regional tory of water as the unifying theme. A successful MPL topographic depression which may have once held an mission would have made significant contributions ancient ocean. The south polar deposits lie on a re- towards these goals, particularly in understanding the gional topographic high[ 2] , and show distinct evi- distribution and behavior of near-surface water, and dence for glacial flow [1]. Both polar regions show the nature and climate history of the south polar lay- evidence for the outflow of liquid water into sur- ered deposits. Unfortunately, due to concerns re- rounding depressions [2]. In the south, the flow of garding the design of the MPL spacecraft, the rarity of water can be traced into the Argyre basin, and then direct trajectories that enable high-latitude landings, across the equator into the northern lowlands [3]. The and funding, an exact reflight of MPL is not feasible high-resolution MOC images of the north and south within the present planning horizon. However, there polar caps show a diverse array of fresh surface tex- remains significant interest in recapturing the scien- tures on the residual caps and associated layered de- tific goals of the MPL mission. The following is a posits which suggest that the polar regions are not discussion of scientific and strategic issues relevant to presently being “mantled” by dust and ice as thought planning the next polar lander mission, and beyond. previously, but instead are being actively modified by Volatiles and Atmospheric Measurements: MPL processes that have as yet, been not defined [4,5]. In included the most sophisticated package of meteorol- total, the MGS data suggest that the Martian polar ogy and volatile-sensing instruments ever flown. Its regions we see today are the product of a complex deployment at a high-latitude landing site during the climatological and hydrological history which may be late spring season would have provided the first op- intimately connected to the climatological and hydro- portunity to characterize global-scale weather patterns logical history of the planet as a whole. in the southern hemisphere, as well as measurements Polar Landing Sites: MPL was the first Mars of the abundance of water ice and adsorbed water and mission whose scientific strategy was driven by the carbon-dioxide in the soil, and water vapor in the desire to obtain detailed measurements at a pre-chosen overlying atmosphere. These would have been com- landing site. Because of their extensive geographic bined with orbital atmospheric sounding and general extent, and the expected uniformity in their morpho- circulation models to provide a much better picture of logical characteristics, the south polar layered deposits the behavior and distribution of water on Mars. In- represented an excellent target for the first polar situ measurements like those intended by MPL are the lander mission. The north residual cap is another only means of obtaining this type of information, and good example of a large, relatively homogeneous tar- should definitely be repeated in future polar lander get. However, as we study the Martian polar regions in missions. greater detail, it is becoming clear that to sample the MGS Results: In 1995, when the concept for the true diversity of polar terrains, and to reconstruct the MPL mission was originated, our understanding of geologic and climatologic history they may contain, Mars was based almost exclusively on then Viking many more landings will eventually be required. In and Mariner 9 datasets. Since that time, the Mars many cases, a precision landing with an error ellipse Global Surveyor (MGS) orbiter has provided signifi- of less than 5 km would be required to enable detailed Concepts and Approaches for Mars Exploration 6122.pdf

AFTER THE MARS POLAR LANDER: D. A. Paige et al.

examination of specific features of great scientific and in evolved gases from heated soil and ice samples interest, i.e. an exposure of layers or a suspected an- is a powerful and robust approach. Improvements in cient outflow channel or esker deposit. TDL technology in future mission should enable de- The Desirability of Landing Robustness and tailed in-situ characterizations of the isotopic compo- Mobility: One of the key new pieces of information sition of Martian water and carbon-dioxide. The use that the MGS MOC images have provided, is that of a focusable camera mounted on the robotic arm that polar terrains that appear to be smooth and homoge- can obtain close-up images of the surface and samples neous at 1000m scales, are definitely not smooth and is also a very powerful technique that can be extended homogeneous on 10 m scales. Figure 1 shows exam- to true microscopic resolution on future payloads. ples of high-resolution textures in the north and south Future polar lander payloads should also include polar regions revealed by MOC. newly-developed instruments which could take ad- vantage of the sample acquisition and analysis capabilities of the MVACS payload in a complimentary manner. For example, the addition of an organics detection experiment could significantly extend the search for near-surface organics begun by the Viking landers during the 1970’s to environments that could have a greater potential for the preservation of organics. Conclusions: While the near-term prospects for recovering the scientific objectives of the MPL mission are uncertain, it is clear that an integrated scientific strategy to study Mars’ climate, resources and life must include detailed study of the polar regions at multiple landing sites. The MGS results indicate that both the north and south polar regions contain a number of sites of high-scientific interest, and that with foreseeable improvements in our capabilities for robust, precisely-targeted landers, these sites should be accessible to the next generation of Mars landers. The scientific strategy advocated here is basically an extension of that originally employed for MPL. It Figure 1. MGS MOC images of surface textures at the Martian north residual water ice cap (top), and starts with the selection of a specific landing site of south polar layered deposits (bottom). [6] high-scientific interest, followed by the design of a The implications of this new information are two- flexible integrated payload package that is capable of fold. First, a robust landing system will be required to characterizing its environmental conditions, the abun- ensure safe landings on most polar terrains. Second, a dance and behavior of its volatiles, and the fine-scale mobile traverse of on the order of 200m should be composition and geology of its deposits at and below sufficient to sample the fine-scale diversity of most the surface. While the return of samples from polar polar terrains. sites may result in significant additional science return, we are presently very far from a situation where Instrumentation: The MPL MVACS payload de- sample return is required to make further scientific veloped a number of new experimental approaches progress. Instead, we would argue that Mars science and technologies that were successfully demonstrated would be best served by a series of reliable in-situ mis- in testing. The use of a dexterous, multi-jointed ro- sions which explore the diversity of the Martian sur- botic arm to obtain surface and subsurface soil and ice face environments, including those found at the north samples within a wide workspace appears to be a very and south polar regions. flexible approach that can be adapted to a wide range of future mission scenarios. Tests of the TEGA in- References: [1] Head, J. W. (2000) LPS XXXI. strument demonstrated excellent sensitivity the pres- [2] Smith, D. et al. (2000) LPS XXXI. [3] Parker, T. ence of water ice and hydrated minerals in soil sam- J., Clifford S. M. and Banerdt, W. B. (2000) LPS ples. The use of Tunable Diode Laser Spectrometers XXXI [4] Malin, M. C. and Edgett, K. S. (2000) LPS (TDL) to measure the concentration of water vapor XXXI. [5] Thomas etal. (2000) LPS XXXI. [6] MSSS and carbon dioxide gas in the Martian atmosphere, Website (http://www.msss.com)