 ANALYSIS OF POLYGONAL TERRAINS ON MARS BASED ON SVALBARD ANALOGUES.  P. Pina1, G. Vieira2, H.H. Christiansen3, M.T. Barata4, J. Saraiva1, L. Bandeira1, C. Lira1, N. Benavente1, C. Mora2, M. Neves2, M. Jorge2 and A. Ferreira2, 1CERENA/IST, Lisboa, Portugal (ppina@ist.utl.pt), 2CEG/IGOT, Lisboa, Portugal, 3UNIS, Svalbard, Norway, 4CGUC, Coimbra, Portugal.   Introduction: Polygonal networks are a much more common surface feature on Mars than on Earth. Detailed images have shown large areas covered by widely diverse polygonal terrain [1-4], a fact that highlights the ubiquity of the presence of ice in the Martian ground. There is still much to be learned about the conditions that give rise to such a variety of morphologies and dimensions. Thus, a full understanding of their origin, age and evolution requires that their thorough characterization is attained. The number of polygons in a given network can be very large [5-7], depending on their average dimensions and the area occupied by the network. Collecting quantitative data on these networks is a daunting task that can be avoided through the use of an automated procedure [8]. This takes advantage of the characteristics presented by the networks on digital images to map the edges of the polygons. The application of this methodology to the vast northern plains of Mars around the Phoenix landing site [9-10] raised the possibility of using it to map and characterize the same type of feature on Earth. The advantages can be clearly seen: the automated results can be compared with a real groundtruth (and thus provide clues for refinement of the methodology when strictly applied to remotely sensed data, such as in the case of Mars), and some measure of comparison can be established between Martian polygons and terrestrial analogues, illuminating some issues and probably raising many interesting new questions. Three Portuguese research groups (CERENA/IST, CEG/IGOT and CGUC) together with one Norweagian research group (UNIS), organized around a research project, named ANAPOLIS, funded by the Portuguese Science Foundation (FCT), will try in the period 20102012 to give a major contribution to the understanding of polygonal networks on Mars through the combination of remote sensing analysis and in situ detailed characterization of terrestrial analogues. Field sites: Terrestrial polygonal networks will be studied in detail at test sites in Svalbard (Norway) (Figure 1), since field survey is crucial for gathering accurate data on the geometry of the polygons. The common and diversified occurrence of this type of patterned ground, previous basic process studies [1112] and the easy access to that archipelago make it a good choice for terrestrial analogue studies, as other teams testing probes for future planetary missions or working on similar studies on these and other geomorphological features are currently demonstrating [1314].     Figure 1 - Location of Svalbard archipelago (latitude 76-81º North).  Plan and methods: Combining GPS measurements, high resolution aerial photography and high resolution satellite imagery will enable a better understanding of the relation between in situ measurements and the appearance of the networks on images at various scales, allowing the improvement of the algorithm for the automatic extraction of polygonal networks. Knowledge on the specific environmental conditions related to the genesis of the terrestrial networks contributes to inferences about the past and present environmental conditions related to the Martian polygonal networks. Ground truthing also allows for a better discrimination between the strictly periglacial polygonal networks and the features with other origin (i.e. tectonic). In this way, a more sustained interpretation on the past and present environmental significance of the polygonal networks of Mars can be made. Furthermore, the significance of the geometric and topological properties of terrestrial polygonal networks has not been properly acknowledged yet, so that the use of an algorithm for the automatic extraction of the networks from remote sensing products can also be of great use for studies in the harsh access areas of Earth´s periglacial domain. Thus, the activities to develop will be organized into the following main tasks:  1. Data acquisition - Compilation of existing data on terrestrial and Martian polygonal terrains, and its organization into a database. 2. Field surveying and mapping - Selection and detailed mapping of areas of occurrence of polygonal networks in Svalbard (Norway). This will lead to the acquisition of ground truth data for validation of the automated identification and classification algorithms. 3. Data integration - Integration of the detailed local data obtained in the field campaigns in Svalbard with the remotely sensed data relative to the same area in order to validate the automated methodology for mapping of polygonal networks. 4. Analysis of networks of Earth and Mars - Accurate identification and characterization of polygons on remote sensing images, by an automated procedure that can process large extensions of terrain in a small period of time and produce an accurate and precise definition of the networks. Expected results:  It is expected that the full development of the ANAPOLIS project will lead to:   1. The completion of a robust methodology for the identification and characterization of polygonal networks on Mars, the Earth and any other planetary surfaces where similar features occur.  2. Significant advances in our understanding of this type of features on Mars, their relation with current and past environmental conditions, including the development of an objective classification scheme.  3. The construction of a very useful tool (filling a perceived gap in the methods employed) for the study of terrestrial periglacial polygons and what they can tell us about the changing climatic conditions on our planet. Acknowledgements: This research will be carried out in the period 2010-2012 in the frame of project ANAPOLIS funded by FCT, the Portuguese Science Foundation, under the contract PTDC/CTESPA/99041/2008.  References: [1] Kuzmin R. and Zabalueva R. (2003) LPS XXXIV, Abs. #1912. [2] Mangold N. et al. (2004) JGR-Planets, 109: E08001. [3] Mangold N. (2005) Icarus, 174: 336-359. [4] Levy J.S. et al. (2010) Icarus (in press). [5] Levy J.S. et al. (2008) Geophys. Res. Lett. 35(4): L04202. [6] Mellon M.T. et al. (2008) JGR-Planets, 113:E00A23. [7] Saraiva et al. (2009), Phil. Mag. Lett., 89(3):185-193. [8] Pina P. et al. (2008) Planet. Space Sci., 56(15):1919-1924. [9] Saraiva J. et al. (2009) LPS XL, Abs. #1323. [10] Pina P. et al. (2009) LPS XL, Abs. #2035. [11] Sorbel L and Tolgensbakk J. (2002) Norwegian J. of Geography, 56: 62-66. [12] Christiansen H.H. (2005) Permafrost and Periglac. Process., 16: 87-98. [13] Hauber E. et al. (2009) LPS XL, Abs. #1658. [14] Reiss D. et al. 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