Proceedings of the MEVTV Workshop on The Evolution of Magma Bodies on Mars

The workshop focused on many of the diverse approaches related to the evolution of magma bodies on Mars that have been pursued during the course of the Mars Evolution of Volcanism, Tectonism, and Volatiles (MEVTV) Program. Approximately 35 scientists from the Mars volcanology, petrology, geochemistry, and modeling communities attended. Segments of the meeting concentrated of laboratory analyses and investigations of SNC meteorites, the interpretation of Viking Orbiter and Lander datasets, and the interpretation of computer codes that model volcanic and tectonic processes on Mars. Abstracts of these reports are presented

Possible origin of some channels on Alba Patera, Mars

Several alternative models were proposed for the origin and mode of formation of channels and valley networks on Martian volcanoes, notably Hecates Tholus, Ceraunius Tholus, and Alba Patera. Early interpretations of Mariner 9 and Viking images suggested that these features on Alba were lava channels, while those on Ceraunius Tholus were interpreted as fluvial or volcanic debris channels. Subsequent mapping of Tyrrehna Patera and Hecate Tholus has suggested that pyroclastic activity may have characterized eruptions on these volcanoes, and that at least for Hecates the channels were probably formed by fluvial erosion of unconsolidated ash deposits on the flanks of the volcano. As part of a continuing program to better understand the eruptive history of the young volcanic centers on Mars, numerous channels were identified on the flanks of Alba Patera that resemble the channels on Hecates. As a result, the possibility is being explored that some of the small channels on the flanks of Alba Patera may be fluvial in origin and potentail water sources and modes of formation are being explored

Depth/diameter relationships of fresh craters within Hesperia Planum, Mars

Meteorite impact craters represent important geological features for revealing the near-surface layers of a planetary surface. In the case of Mars, this characteristic was proposed as a useful method to study spatial variations of such attributes as the distribution of sub-surface volatiles, and heat flow. Using the Planetary Image Cartography System (PICS) software, a quantitative analysis was completed of the geometry of fresh impact craters in the Hesperia Planum region of Mars, where an uniform target material and optimum viewing geometry make possible an analysis of target effects over a large geographic region. Because of the morphologic similarity to the lunar maria, it is likely that Hesperia Planum comprises a series of flood lavas that partially infilled topographic depressions within the Martian highlands. Measurements of partially buried crater rims suggest that the lava flows within Hesperia Planum are between 200-400 m thick

Significant achievements in the planetary geology program, 1981

Recent developments in planetology research are summarized. Important developments are summarized in topics ranging from solar system evolution, comparative planetology, and geologic processes, to techniques and instrument development for future exploration

The Interaction of Impact Melt, Impact-Derived Sediment, and Volatiles at Crater Tooting, Mars

We are producing a 1:200K geologic map of Tooting crater, Mars. This work has shown that an incredible amount of information can be gleaned from mapping at even larger scales (1:10K 1:25K) using CTX and HiRISE data. We have produced two new science papers (Morris et al., 2010; Mouginis-Mark and Boyce, 2010) from this mapping, and additional science questions continue to arise from our on-going analysis of Tooting crater: 1) What was the interplay of impact melt and volatile-rich sediments that, presumably, were created during the impact? Kieffer and Simonds [1980] predicted that melt would have been destroyed during impacts on Mars because of the volatiles present within the target we seek to understand if this is indeed the case at Tooting crater. We have identified pitted and fractured terrain that formed during crater modification, but the timing of the formation of these materials in different parts of the crater remains to be resolved. Stratigraphic relationships between these units and the central peak may reveal deformation features as well as overlapping relationships. 2) Morris et al. [2010] identified several lobate flows on the inner and outer walls of Tooting crater. It is not yet clear what the physical characteristics of the source areas of these flows really are; e.g., what are the sizes of the source areas, what elevations are they located at relative to the floor of the crater, are they interconnected, and are they on horizontal or tilted surfaces? 3) What were the details of dewatering of the inner wall of Tooting crater (Fig. 1)? We find evidence within Tooting crater of channels carved by water release, and the remobilization of sediment (which is inferred to have formed during the impact event). Sapping can be identified along the crest of unit 8 near the floor of the crater (Fig. 2a, 2b). This unit displays amphitheater-headed canyons that elsewhere on Mars are typically attributed to water leaking from the substrate [Laity and Malin, 1985; Malin and Edgett, 2000]

Altimetric system: Earth observing system. Volume 2h: Panel report

A rationale and recommendations for planning, implementing, and operating an altimetric system aboard the Earth observing system (Eos) spacecraft is provided. In keeping with the recommendations of the Eos Science and Mission Requirements Working Group, a complete altimetric system is defined that is capable of perpetuating the data set to be derived from TOPEX/Poseidon, enabling key scientific questions to be addressed. Since the scientific utility and technical maturity of spaceborne radar altimeters is well documented, the discussion is limited to highlighting those Eos-specific considerations that materially impact upon radar altimetric measurements

The geological history of Nili Patera, Mars

Nili Patera is a 50 km diameter caldera at the center of the Syrtis Major Planum volcanic province. The caldera is unique among Martian volcanic terrains in hosting: (i) evidence of both effusive and explosive volcanism, (ii) hydrothermal silica, and (iii) compositional diversity from olivine-rich basalts to silica-enriched units. We have produced a new geological map using three mosaicked 18 m/pixel Context Camera digital elevation models, supplemented by Compact Remote Imaging Spectrometer for Mars Hyperspectral data. The map contextualizes these discoveries, formulating a stratigraphy in which Nili Patera formed by trapdoor collapse into a volcanotectonic depression. The distinctive bright floor of Nili Patera formed either as part of a felsic pluton, exposed during caldera formation, or as remnants of welded ignimbrite(s) associated with caldera formation—both scenarios deriving from melting in the Noachian highland basement. After caldera collapse, there were five magmatic episodes: (1) a basaltic unit in the caldera's north, (2) a silica-enriched unit and the associated Nili Tholus cone, (3) an intrusive event, forming a ~300 m high elliptical dome; (4) an extrusive basaltic unit, emplaced from small cones in the east; and (5) an extreme olivine-bearing unit, formed on the western caldera ring fault. The mapping, together with evidence for hydrated materials, implies magmatic interaction with subsurface volatiles. This, in an area of elevated geothermal gradient, presents a possible habitable environment (sampled by the hydrothermal deposits). Additionally, similarities to other highland volcanoes imply similar mechanisms and thus astrobiological potential within those edifices

Morphometry of subaerial shield volcanoes and glaciovolcanoes from Reykjanes Peninsula, Iceland: Effects of eruption environment

We present a morphometric study of 33 basaltic volcanic edifices from the Reykjanes Peninsula, Iceland, using a 20 m resolution digital elevation model (DEM). Slope values distinguish subaerial from intraglacial eruption environments, with glaciovolcanic edifices having average slope values that are > 5° higher than subaerial shields. The 26 analyzed glaciovolcanic edifices are separated into 3 groups based on size, and are also categorized following the new classification scheme of tuyas by Russell et al. (2014), into 15 tindars, 1 conical tuya, 3 flat-topped tuyas and 7 complex tuyas. The glaciovolcanic edifices show a continuum of landforms ranging from small elongated tindars to large equidimensional flat-topped tuyas. The smaller edifices ( 0.1 km3) are flat-topped tuyas. The mid-sized edifices (0.01–0.1 km3) show a wide variety of shapes and classify either as tindars or as complex tuyas, with only one edifice classifying as a conical tuya. Edifice elongation tends to decrease with volume, suggesting that small edifices are primarily fissure controlled, whereas larger edifices are mainly controlled by a central vent. The mid-sized complex tuyas are transitional edifices, suggesting that some intraglacial eruptions start as fissure eruptions that subsequently concentrate into one or more central vents, whereas the mid-sized tindars suggest a sustained fissure eruption. There is a tectonic control on the orientation of the edifices evidenced by a strong correlation between edifice elongation azimuth and mapped faults and fractures. Most edifice elongations cluster between 020° and 080°, coinciding with the strike of normal faults within and at the boundary of regional volcanic systems, but some edifices have elongations that correlate with N–S striking book-shelf faults. This implies that intraglacial eruptions are controlled by pre-existing pathways in the crust, as has been previously observed for subaerial fissure eruptions. In terms of classification, quantification of the limits between the four tuya types proposed by Russell et al. (2014) is difficult because of the transitional nature shown by several edifices. A threshold of 1.8 in ellipticity index (E.I.) values can be used to distinguish tindars from the other three types. Flat-topped tuyas are distinguished by their greater overall size, their large and relatively flat summit regions, reflected in bimodal slope distributions, and their low E.I. and low to intermediate irregularity index (I.I.) values. The only analyzed conical tuya has very low E.I. and I.I. values, very small summit regions and very steep flank slopes. The complex tuyas have variable morphometries, but are in general characterized by high I.I. values and very irregular slope distributions. No correlation is observed between edifice-scale morphology and lithology (e.g. pillow dominated or hyaloclastite dominated).Fil: Pedersen, G. B. M.. University of Iceland. Institute of Earth Sciences. Nordic Volcanological Center; IslandiaFil: Grosse, Pablo. Fundación Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán; Argentin