The traditional model of the natural history museum developed during an age of exploration. In the twenty-first century, natural history museums can demonstrate the excitement of science and enhance geoscience education by using the space-age exploration of our solar system and incorporating the geoscience subdiscipline of planetary geology. Natural history museums reach a self-selected, self-directed, and multigenerational audience. This audience can choose to pursue a range of exhibits and programs in various sciences offered by a museum. The public may be interested in geoscience but often has limited knowledge or understanding of the science. Planetary geology offers an effective way to add content and technology to the traditional natural history museum and a new way to interest museum visitors in basic geoscience. Over the past decade, the New Mexico Museum of Natural History and Science (NMMNHS) has successfully used planetary geology to enhance geoscience education by incorporating the following techniques: (1) geoscience related to a specific planet or planetary mission; (2) geoscience related to a planetary problem; and (3) planetary geology related to art. Use of these techniques has allowed the NMMNHS to reach multiple and underrepresented audiences, to encourage interest in basic geoscience, and to better serve the science education needs of the state of New Mexico. The addition of planetary geology to the traditional range of science topics enables natural history museums to continue their evolution as relevant sources of geoscience and provides them with an additional and effective way to teach geoscience in the twenty-first century.

Introduction: In late 2003, the New Mexico Museum of Natural History and Science (NMMNHS) began an integrated program of museum exhibits and education using Mars and the Mars Exploration Rover (MER) mission. The goals of the program were to: (1) teach about Mars and the rover mission; (2) increase planetary science awareness and literacy for students, teachers, and the general public; (3) increase support for and understanding of planetary missions; (4) use the exploration of Mars to teach science. The NMMNHS is a statewide institution and serves a statewide population that includes a total of 52% Hispanic and Native American populations, as well as a high percentage of rural communities, and therefore reaches an audience traditionally underrepresented in science. Informal science education (free-choice learning) continues throughout a person’s lifetime [1]. It is the science information acquired from museums, zoos, parks, visitors’ centers, books, internet, and TV. Museums with physical, earth, or space science expertise are good partners for NASA mission EPO efforts. In a time of decreased national funding, they are local partners adept in interacting with the public. The average person spends only 5% of their life [1] in a classroom (including four years of college). The best way to increase the public’s science literacy is to reach them during the other 95% of their lives.

APPLICATION TO IDENTIFYING INFLATED LAVA FLOWS ON PLANETARY SURFACES. J. R. Zimbelman 1 , W. B. Garry 2 , J. E. Bleacher 2 , L. S. Crumpler 3 , S. Self 4 , J. C. Aubele 3 , S. M. Baloga 5 , L. S. Glaze 2 , R. A. Schultz 6 , 1 CEPS/NASM MRC 315, Smithsonian Institution, Washington, DC 20013-7012; zimbelmanj@si.edu, 2 Planetary Geodynamics Laboratory, Code 698, NASA Goddard Space Flight Center, Greenbelt, MD 20771, 3 New Mexico Museum of Natural History and Science, 1801 Mountain Rd NW, Albuquerque, NM 87104, 4 Department of Earth and Environmental Science, The Open University, Walton Hall, UK, and Nuclear Regulatory Commission, Rockville, MD 20852, 5 Proxemy Research Inc., 20528 Farcroft Lane, Gaithersburg, MD 20882, 6 ConocoPhillips, 600 North Dairy Ashford, PR-2010, Houston, TX 77079.

Basaltic lavas typically form channels or tubes, which are recognized on the Earth and Mars. Although largely unrecognized in the planetary community, terrestrial inflated sheet flows also display morphologies that share many commonalities with lava plains on Mars. The McCartys lava flow field is among the youngest (approx.3000 yrs) basaltic flows in the continental United States. The southwest sections of the flow displays smooth, flat-topped plateaus with irregularly shaped pits and hummocky inter-plateau units that form a polygonal surface. Plateaus are typically elongate in map view, up to 20 m high and display lineations within the glassy crust. Lineated surfaces occasionally display small < 1m diameter lava coils. Lineations are generally straight and parallel each other, sometimes for over 100 meters. The boundaries between plateaus and depressions are also lineated and tilted to angles sometimes approaching vertical. Plateau-parallel cracks, sometimes containing squeeze-ups, mark the boundary between tilted crust and plateau. Some plateau depressions display level floors with hummocky surfaces, while some are bowl shaped with floors covered in broken lava slabs. The lower walls of pits sometimes display lateral, sagged lava wedges. Infrequently, pit floors display the upper portion of a tumulus from an older flow. In some places the surface crust has been disrupted forming a slabby texture. Slabs are typically on the scale of a meter or less across and no less than 7-10 cm thick. The slabs preserve the lineated textures of the undisturbed plateau crust. It appears that this style of terrain represents the emplacement of an extensive sheet that experiences inflation episodes within preferred regions where lateral spreading of the sheet is inhibited, thereby forming plateaus. Rough surfaces represent inflation-related disruption of pahoehoe lava and not a a lava. Depressions are often the result of non-inflation and can be clearly identified by lateral squeeze-outs along the pit walls that form when the rising crust exposes the still liquid core of the sheet. The plains of Tharsis and Elysium, Mars, display many analogous features

Based on mapping of the McCartys lava flow, comparison with flow-fields in Hawaii, and observations of actively inflating flows, we are beginning to untangle the sequence of emplacement mechanisms on large flow-fields, particularly those with characteristics attributed to inflation.These results are providing insights that we believe will enable us to map the sequence of events during the emplacement of the McCartys lava flow.

This map uses Viking Orbiter image data and Viking 1 Lander image data to evaluate the geologic history of a part of Chryse Planitia, Mars. The map area lies at the termini of the Maja and Kasei Valles outwash channels and includes the site of the Viking 1 Lander. The photomosaic base for these quadrangles was assembled from 98 Viking Orbiter frames comprising 1204 pixels per line and 1056 lines and ranging in resolution from 20 to 200 m/pixel. These orbital image data were supplemented with images of the surface as seen from the Viking 1 Lander, one of only three sites on the martian surface where planetary geologic mapping is assisted by ground truth.

The Marsokhod rover returned data from six stations that were used to decipher the geomorphology and geology of a region not previously visited by members of the geomorphology field team. Satellite images and simulated descent images provided information about the regional setting. The landing zone was on an alluvial apron flanking a mountain block to the west and a playa surface to the east. Rover color images, infrared spectra analysis of the mountains, and the apron surface provided insight into the rock composition of the nearby mountains. From the return data the geomorphology team interpreted the region to consist of compressionally deformed, ancient marine sediments and igneous rocks exposed by more recent extensional tectonics. Unconsolidated alluvial materials blanket the lower flanks of the mountains. An ancient shoreline cut into alluvial material marks a high stand of water during a past, wetter climate period. Playa sediments floor a present‐day, seasonally, dry lake. Observations made by the rover using panoramic and close‐up (hand specimens—scale) image data and color scene data confirmed the presence of boulders, cobbles, and fines of various provinces. Rover traverses to sites identified as geologically distinct, such as fan, channel, shoreline, and playa, provided useful clues to the geologic interpretations. Analysis of local rocks was given context only through comparison with distant geologic features. These results demonstrated the importance of a multifaceted approach to site interpretation through comparison of interpretations derived by differing geologic techniques.

The Raton-Clayton (RCVF) and Ocate Volcanic Fields (OVF) constitute the most significant late Cenozoic volcanic activity east of the Rocky Mountains. A salient characteristic of volcanic fields is the relatively low volumetric rates of eruption compared with major volcanic centers. The RCVF consists of about 125 vents and, including outlying portions, covers nearly 20,000 km2• Rocks range from about 9 Ma to less than 60,000 yrs, yielding a recurrence rate of approximately 1.3 X I O.S volcanic events per year. The RCVF can be divided into three main phases of volcanic activity: (1) Raton, which includes basalt flows and rhyodacite domes; (2) Clayton, which includes voluminous basalt flows and the Sierra Grande shield volcano; and (3) Capulin, which includes cinder cones and flows centered on Capulin Volcano National Monument. Although widely cited, the previous age estimate of less than 10,000 yrs for Capulin Volcano was based on an interpreted correlation, not an absolute date. TWo dating techniques, the cosmogenic helium technique and the Ar-Ar technique indicate a date for Capulin of about 58,000 yrs. Three major series of Java flow units were erupted from Capulin, with the second and third series erupted from the base of the cone at the "boca". It is likely that the eruption of the boca flow altered the profile of Capulin, subsequently its symmetry was restored by continued building of the cone. The Ocate Volcanic Field consists of at least 16 flows and about 50 associated vents ranging in age from 8.34±0.50 Ma to 0.81±0.14 Ma. Like the RCVF, three major topographic levels of lava flows relate to three age groups: {I) older than 5 Ma, which includes flows capping mesas with surfaces around 3000m in elevation and an apparent E-W fissure line of vents near Wagon Mound; (2) 5-4 Ma, which includes most of the flows around Agua Fria; and (3) younger than 4 Ma, which includes the most abundant flows in the OVF and such vents as Cerrito Pelon, Cerro Negro, Cerro del Oro and Maxon Crater. Flows from Maxon flowed 90 km eastward along the canyon cut by the Mora River where they occur lOOm below the rim of the canyon and 125m above the present level ofthe river. The youngest flows in the field were erupted from Cerro del Oro, in the central part of Charette Mesa, northwest of Wagon Mound.

nantly of monogenetic cinder cones and their associated flows. The field within Arizona encompasses about 3,000 km2 and has a volume of about 300 km3; it contains approximately 400 cones (Condit and others, 1989b). An estimated 100 km2 of the field extends eastward into New Mexico. The geology of the field’s 2,166 km2 of volcanic outcrop in Arizona was mapped at 1:24,000 scale, compiled at 1:50,000 scale, and reduced to a scale of 1:100,000. The south-central part of the field (fig. 5, sheet 1) was not mapped because of access problems, and detailed mapping in the central part of the field extends as far north as about lat 34°27' N. Reconnaissance suggests that an additional 50 km2 to the north is also covered by flows, a large part of which are diktytaxitic; sampling by Cooper and others (1990) shows that the northern end of this area (Volcanic Mountain, fig. 5, sheet 1) is composed of tholeiitic lavas; a sample from Volcanic Mountain has an age of 5.31 Ma (Cooper and others, 1990). The mapped units of the Springerville field range in age from 2.1 to 0.3 Ma, with the exception of six older flows around the periphery of the field. The oldest two of these six flows, found on the southwest edge of the field and dated at 8.66 and 8.97 Ma (table 3), have a source on Mount Baldy (fig. 1; Condit, 1984). Two northern units have ages of 7.6 and about 6.6 Ma (two aliquots have ages of 6.52±0.12 and 6.66±0.12 Ma); the last two of the older flows, on the southeast margin of the field, are dated at 2.94 Ma and 3.1 Ma. Sources for these last four units are unidentified. The lithologic types and chemical classes of the map area, as defined in this report, are summarized in table 1A. The areal data were obtained directly from digital map images. The most common rock is olivine phyric basalt (lithologic types b, c, and d); these lithologies make up about 46 percent of the volcanic outcrop area. Olivine phyric lithologies most commonly belong either to chemical class alkali olivine basalt (AOB, table 1A), or to a transitional (TRANS) chemical class between AOB and tholeiite (THOL). The next most abundant lithology is diktytaxitic basalt (types f and g, which together cover about 32 percent of the volcanic area); most flows of this lithology are tholeiitic. The only other lithologic type to cover more than 3 percent of the outINTRODUCTION

1:500,000‐scale geologic mapping in the central Chryse Planitia region of Mars was correlated with “ground‐truth” data gathered by the Viking 1 lander. Materials within the Chryse basin can be subdivided into plains and channel units that are typically separated from one another by gradational contacts. Hesperian Ridged plains materials, unit 1 (Hr1) are the oldest materials mapped. Typically, these materials contain numerous fresh impact craters and have sharply defined, mare‐like wrinkle ridges similar to those appearing on the lunar maria. These materials grade into Hesperian Ridged plains materials, unit 2 (Hr2), which are characterized by buried and eroded impact craters and subdued wrinkle ridges. From analyses of crater age dates and their associated geologic contacts, channel materials appear to have formed at the same time as Hr2 materials, and it is likely both units represent fluvial sediments. Measurements of buried craters contained in Hr2 materials suggest that in places this unit may be ∼50 m thick, but crater size‐frequency distribution curves suggest that the areal average may be closer to ∼170 m. Based on these observations, our interpretation is that Hr2 materials were deposited into a standing body of water during channel formation. This interpretation implies that many of the rocks visible in the Viking 1 lander images were emplaced by fluvial processes. Possibly, finer‐grained sediments remained in suspension and were subsequently transported out of Chryse Planitia and into the northern plains during draining of the ponded water. East‐west trending surface undulations, visible in lander views toward the south, may represent aeolian dunes, lava flow fronts, or sediment waves formed at the bottom of the standing body of water. Broad physiographic units seen at the surface are not clearly visible in Viking orbiter images; however, they can be projected at the resolution of the orbiter images. These units show that concentrations of drift materials are oriented in a northwesterly direction, contrary to the strongest prevailing wind direction which is toward the northeast. These materials were probably deposited on Ridged plains materials, unit 2, during a period of time when aeolian processes were more active in the region. Both Earth‐based radar and Viking thermal data suggest that the Mars Pathfinder landing site will be similar geologically to the Viking 1 site. If this is true, then the Mars Pathfinder mission provides the opportunity for building directly on results of the Viking program. Some of the outstanding questions that Mars Pathfinder may be able to address include determining the aeolian modification history of the Chryse Planitia region, the degree and possibly the relative rate of sediment induration, the fraction of rocks and boulders emplaced by impact processes, the possibility that some materials are the result of in situ weathering, and whether materials were emplaced by fluvial processes and the associated depositional environment.

INTRODUCTION. The stratigraphic position and age of volcanic features on Venus is important to the determination of absolute and relative ages of the surface, the assessment of the global magmatic history, and tests of models of global stratigraphy and resurfacing events. Large shield volcanoes are an obvious choice for attempts to determine crater ages because they are large enough that the total area of large shield volcanoes may not be trivial in terms of crater age estimates, and they are large enough that some reliable stratigraphic relations may be determined with surrounding craters, plains, ridges, fractures and related deformation. An additional supposition is that they appear frequently to be stratigraphically young and should provide an estimate of the time elapsed since the proposed period of enhanced global resurfacing [I]. A separate issue is the timing of large volcano emplacement with respect to tectonic characteristics, particularly rifts, fracture belts, and plains type ridge deformation that may have taken place subsequent to resurfacing events. Several estimates of the collective crater age of large shield volcanoes and related volcanic features have been made [2]. Ideally, these characteristics together with an estimate of the total area of the population of large volcanoes should provide a collective age for the population as a whole either with respect to resurfacing or global and local tectonic characteristics. A number of issues remain unresolved. Because a detailed individual assessment of the geologic characteristics of large volcanoes in our data base [4] has as yet to be completed, including documentation of the diversity of their stratigraphic behavior, efforts to determine crater ages, while extremely valuable, are preliminary and should be used with consideration given to some of the obvious, as well as less obvious, complications. In the following we discuss briefly the results of preliminary global geologic mapping of large shield volcanoes, and review some characteristics that illustrate the variety of ways in which large shield volcanoes are subject to interaction with differing types of geologic and structural features. STRATIGRAPHIC RELATIONSHIPS. Four fundamental tectonic and geologic features are identified with which large volcanoes stratigraphically interact in an identifiable manner: (1) extensional fractures, (2) ridges, (3) impact craters, including ejecta, and (4) surrounding plains, including external lava flows. Of the nine classes of large edifices previously identified [3] many are associated with complex structural patterns that further complicate the issue of stratigraphy owing to the inability to define in detail when tectonic processes have operated as opposed to local magmatic processes. About 19% of the total population are associated with coronae (Type IX), which are frequently situated on regional fracture networks or are the site of radiating fracture patterns. Approximately 30% are identified as simple volcanoes (Type I) free of regional tectonic characteristics (Fig. 1) and may be reliably located with respect to regional plains and impact craters. An additional 12% are rift-related (Type VII). Only a few percent of the population are included in each of the remaining classes. Extensional fractures: In a few cases volcanoes appear to either pre-date a set of through-going (rift) fractures (Fig. 2) or post-date most of the fractures (Fig. 3). More frequently the stratigraphic relationship is complicated where large volcanoes have formed simultaneously with regional and local fractures. Regional fractures include the network of fractures associated with coronae, arachnoids, stellate f~acture centers, sets of plains fractures, fracture belts, and rift zones. Local fractures include those associated with local magma reservoir evolution and surface deformation. Fractures that trend through the center of an edifice are themselves misleading as to whether the regional fractures have cut the edifice or whether the fissure patterns that normally develop in an edifice have occupied existing stress directions because dike propagation at individual centers follow existing patterns of stress. Only in rare cases where no lava flows have been emplaced over existing structural trends or where regional fractures are totally inundated by local edifice flows can the stratigraphic relationship with regional fractures be estimated with reasonable confidence. Ridge type features: Wrinkle ridges appear to be attenuated near the centers of many edifices, and it is unclear whether the ridges are diverted as a result of the mechanical characteristics of the local volcanic pile, or whether the central parts of these edifices are younger than ridging events. A few large shield volcanoes appear to clearly pre-date ridged plains. The relationship with fracture patterns and ridge patterns are complicated by diversion of lava flows along areas between graben and ridges, although relationships may be locally apparent (Fig. 4). The apparent source of Baltis Vallis (Fig. 5) is another example of a large volcano that pre-dates regional plains ridges. Impact craters: The relationship to impact craters is subject to many potential confusions. Reliable indicators appear to be where there is overlap of dark haloes, diversion of ejecta flow patterns away from edifice flanks (Fig. 6), and interruption of individual lava flow lobes. In the absence of these indicators, the relationship is more often than not equivocal and require exmemely detailed inspection to resolve. Surrounding plains: Stratigraphic relations with large volcanoes, and corresponding difficulty in the treatment of impact crater populations may result from inability to identify the extent of lava flows associated with large volcanoes. An example is MVC351277LV (Fig. 7) where a broad apron of lava flows from this edifice would go undetected it not for the presence of surrounding tessera. Many intermediate volcanoes may be large volcanoes that are partially inundated (Fig. 8). Detection of these types of stratigraphic relation may be difficult locally.

Abstract Calderas and flank structures of martian volcanoes yield insight into general questions of volcano structural evolution and the underlying magma chambers in an environment where erosion is minimal. We have documented, through detailed geological mapping, the structures, associated volcanological features, and the stratigraphical relationships between the flank structures and caldera events during the building of each martian edifice. Two fundamentally different types of calderas are identified on Mars (the Olympus type and the Arsia type) that may represent end member variations in the size and depth of magma chambers. Many of the flank structures adjacent to caldera rims are consistent with the predicted effects of magma chamber inflation as well as deflation that exert significant influences in the structural development of many volcanoes. Large-scale terracing and steepening of the upper flanks of the larger martian volcanoes may originate from magma chamber inflation and radial thrusting. Thus the endogenous component of volcano growth resulting from accumulated magma chamber growth may be significant. Many of the deepest calderas are associated with evidence for voluminous eruptions elsewhere on the flanks and along through-going fissures and appear to result largely from evacuation and deflation of magma chambers without extensive precursor inflation. Draining of the magma chamber in these cases may be aided by the lateral propagation of magma in the form of shallow dykes up to several hundred kilometres in length and the associated formation of linear fissures. Nested caldera sequences, related flank pits, large-scale slumping, terracing, and sector structure are frequently arranged in linear patterns and are part of through-going eruptive lines or fissures several hundred kilometres in length that characterize several martian shield volcanoes. Fissures this long are interpreted to be dykes propagated outward from shallow magma chambers that have followed a minimum regional stress orientation. Comparison of the observed shape and orientation of caldera structures with orientation and style of flank deformation, and with the predictions from theory, indicate that regional stresses have probably been an important influence on the caldera and flank structures of martian volcanoes. The minimum regional stress orientation may be controlled largely by regional slopes associated with the Tharsis region and Elysium regions, and, in the case of Tyrrhena Patera, pre-existing radial fractures associated with the Hellas basin.