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Both the size-frequency distribution and morphometry of rock populations emplaced by a variety of geologic processes in Hawaii indicate that such information may be useful in planning future landing sites on Mars and interpreting the surface geology.
Topographic mapping in at least three distinct regions of Ganymede reveals that smooth terrains are flat and are topographically depressed. This and embayment relationships are consistent with volcanic resurfacing. Additional information is contained in the original extended abstract.
MOLA data allow us to distinguish the nature of a viscosity change in the presence of degassing. For a 35 km flow in Elysium we conclude that the viscosity increased exponentially at least 50 times, compared to only 10 times if no degassing occurs. Additional information is contained in the original extended abstract.
The eyes of Galileo: See Pele's glory at many wavelengths. Additional information is contained in the original extended abstract.
Using high resolution MOLA (Mars Orbiter Laser Altimeter) topographic data to accurately model flow rates, we find that Alba Patera tube-fed flows within the mid to lower flanks could accommodate flow rates between 10 Pa s to 1.308 x 10(exp 6) Pa s. Additional information is contained in the original extended abstract.
Clementine spectral reflectance and compositional data, Lunar Prospector gamma ray and neutron spectrometer data, and sample analysis of lunar soils are used to examine the origin of high-Th in Eratosthenian basalts of the Procellarum KREEP. Additional information is contained in the original extended abstract.
We experienced much success in reaching our stated goals in our original MDAP proposal. Our work made substantial contributions towards an integrated understanding of the counting and calibration of crater data on Mars, and changing nature of the Martian surface influenced by craters, water, and wind, and their general relationship to Martian geothermal history. We accomplished this while being to responsive to the rapid changes in the field brought about by several key NASA missions that returned data during the life of the grant. Our integrated effort included three stages: The first major area of research (Crater Count Research) was conducted by Jennifer Grier (P.I.), Lazslo Keszthelyi (Collaborator), William Hartmann (Collaborator), with assistance from Dan Berman (Graduate student) and concerned the mapping and the collection of crater count data on various Martian terrains. The second major area of study (Absolute Age Calibration) was conducted by William Bottke (Co-I) at SWRI, and concerned constraining the nature of the Moon and Mars impactor populations to create better absolute age calibrations for counted areas. The third major area of study was the integration and leverage of this effort with ongoing related Mars crater work at PSI (Integrated and Continuing Studies - Older Volcanoes), headed by David Crown (PSI Scientist), assisted by Les Bleamaster (PSI Scientist) and Dan Berman (Graduate Student).
Mount Etna in Sicily is the most active volcano in Europe, erupting.
Popocatepetl volcano is 5452 m in altitude and capped by glaciers with a long Late Pleistocene-Holocene history. Volcanic activity has been intense during the last 10 000 years. Therefore, the valleys at the NE foothills of the volcano, covered by air-fall ejecta and drained by the runoff of the glaciers, became very attractive to ancient inhabitants of the Xalizintla Valley (XV) west of Puebla City, because of fertility of soils. The XV was occupied by humans about 2000 years ago who witnessed five events related to volcanic activity related to Popo. These events, described in this paper, are being taken into account for volcanic risk evaluation since several towns with a population of more than 23 000 people reoccupied again the Xalizintla Valley.
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The Moessbauer spectrometers on the Mars Exploration Rovers Spirit (Gusev crater) and Opportunity (Meridiani Planum) have returned information on the oxidation state of iron, the mineralogical composition of Fe-bearing phases, and the distribution of Fe among oxidation states and phases [1,2,3]. To date, ~100 and ~85 surface targets have been analyzed by the Spirit and Opportunity spectrometers, respectively. Twelve component subspectra (8 doublets and 4 sextets) have been identified and most have been assigned to mineralogical compositions [4]. Two sextet subspectra result from the opaque and strongly magnetic mineral magnetite (Fe3O4 for the stoichiometric composition), one each for the crystallographic sites occupied by tetrahedrally-coordinated Fe3+ and by octahedrally-coordinated Fe3+ and Fe2+. At Gusev crater, the percentage of total Fe associated with magnetite for rocks ranges from 0 to ~ 35% (Fig. 1) [3]. The range for soils (~5 to ~12% of total Fe from Mt, with one exception) is narrower. The ubiquitous presence of Mt in soil firmly establishes the phase as the strongly magnetic component in martian soil
The Moessbauer spectrometers on the Mars Exploration Rovers Spirit (Gusev crater) and Opportunity (Meridiani Planum) have returned information on the oxidation state of iron, the mineralogical composition of Fe-bearing phases, and the distribution of Fe among oxidation states and phases [1,2,3]. To date, approx.100 and approx.85 surface targets have been analyzed by the Spirit and Opportunity spectrometers, respectively. Twelve component subspectra (8 doublets and 4 sextets) have been identified and most have been assigned to mineralogical compositions [4]. Two sextet subspectra result from the opaque and strongly magnetic mineral magnetite (Fe3O4 for the stoichiometric composition), one each for the crystallographic sites occupied by tetrahedrally-coordinated Fe3+ and by octahedrally-coordinated Fe3+ and Fe2+. At Gusev crater, the percentage of total Fe associated with magnetite for rocks ranges from 0 to approx. 35% (Fig. 1) [3]. The range for soils (approx.5 to approx.12% of total Fe from Mt, with one exception) is narrower. The ubiquitous presence of Mt in soil firmly establishes the phase as the strongly magnetic component in martian soil [4,5].
There is ample evidence that Europa is currently geologically active. Crater counts suggest that the surface is no more than 90 Myr old, and cryovolcanism may have played a role in resurfacing the satellite in recent geological times. Europa's surface exhibits many putative cryovolcanic features, and previous investigations have suggested that a number of domes imaged by the Galileo spacecraft may be volcanic in origin. Consequently, several Europa domes have been modeled as viscous effusions of cryolava. However, previous models for the formation of silicic domes on the terrestrial planets contain fundamental shortcomings. Many of these shortcomings have been alleviated in our new modeling approach, which warrants a re-assessment of the possibility of cryovolcanic domes on Europa.
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Irregular mare patches (IMPs) were previously proposed as sites of young lunar volcanism and/or endogenic activity [1-3], raising the possibility that volcanism on the Moon may not have ended approximately 1 Ga as determined from surface ages [4]. The wide-spread occurrence of more than 70 IMPs on the lunar nearside suggests a correlation with Th-rich PKT regions and a basaltic composition [1,2]. IMPs exhibit at least two types of deposit morphologies: (a) dome-like, steep-sided and smooth mounds and (b) low-relief ropy (LRR) to hummocky (LRH) materials (Fig. 1). Morphologic indicators such as steep (>40 deg) margin slopes across distances <10 m and crisp boundaries imply ages less than a few 100 Ma [e.g.,1-3]. The IMPs also have relatively few superposed craters >10 m in diameter, and young absolute model ages, which when combined with their superposition on young crater deposits like the continuous ejecta of Aristarchus crater, imply ages approximately 10 Ma to 100 Ma [1,2]. However, the mounds do not exhibit blocky crater morphologies, nor fracturing typical of young volcanic deposits, and the mound texture resembles that of mature regolith [e.g., 2,5], implying a much older age (approximately 3.5 Ga). These contrasting indicators have led to the proposal of widely varying formation mechanisms that range from ancient volcanism modified by recent tectonism [6] or outgassing [3,7], ancient volcanism of atypical materials [8], to Copernican-era volcanism [1,2].
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