Martian rampart craters: Morphologic clues for the physical state of the target at time of impact

Current research attempts to describe morphologic features seen in very high resolution Viking Orbiter images of crater ejecta blankets and interiors, in order to constrain the most likely target properties at the time of crater formation. The Viking Orbiter image data set contains approximately 400 frames at a spatial resolution of better than 10 meters per pixel, and 2,200 frames at a resolution of better than 20 meters per pixel, for which the atmosphere was either clear or only slightly obscured. A search is being conducted of all these images and so far has revealed several examples of both interior and exterior features of impact craters that bear on the nature of the ejecta fluidizing medium. Preliminary observations and speculations on the physical state of the Martian regolith at the time of crater formation are given and briefly discussed

New very high resolution radar studies of the Moon

As part of an effort to further understand the geologic utility of radar studies of the terrestrial planets, investigators at the Hawaii Institute of Geophysics are collaborating with NEROC Haystack Observatory, MIT and the Jet Propulsion Laboratory in the analysis of existing 3.8 and 70 cm radar images of the Moon, and in the acquisition of new data for selected lunar targets. The intent is to obtain multi-polarization radar images at resolutions approaching 75 meters (3.8 cm wavelength) and 400 meters (70 cm wavelength) for the Apollo landing sites (thereby exploiting available ground truth) or regions covered by the metric camera and geochemical experiments onboard the command modules of Apollos 15, 16 and 17. These data were collected in both like- and cross-polarizations, and, in the case of the 70 cm data, permit the phase records to be used to assess the scattering properties of the surface. The distribution of surface units on the Moon that show a mismatch between the surface implied by like- and cross-polarized scattering data is being analyzed, based on the scattering models of Evans and Hagfors

The influence of oceans on Martian volcanism

Geomorphological evidence for episodic oceans on Mars has recently been identified. This idea of large bodies of water on Mars is innovative and controversial compared to the more generally accepted view of a 'dry Mars', but also enables some of the more enigmatic volcanic landforms to be reinterpreted in a self-consistent model. This hypothesis can be used to develop new models for the mode of formation of several volcanic landforms in the W. Tharsis and S.E. Elysium Planitia regions of Mars

Constraints on the depth and geometry of the magma chamber of the Olympus Mons Volcano, Mars

The summit caldera of the Olympus Mons volcano exhibits one of the clearest examples of tectonic processes associated with shield volcanism on Mars. The radial distance from the center of the transition from concentric ridges to concentric graben within the oldest crater provides a constraint on the geometry and depth of the subsurface magmatic reservoir at the time of subsidence. Here, researchers use this constraint to investigate the size, shape, and depth of the reservoir. Their approach consists of calculating radial surface stresses corresponding to the range of subsurface pressure distributions representing an evacuating magma chamber. They then compare stress patterns to the observed radial positions of concentric ridges and graben. The problem is solved by employing the finite element approach using the program TECTON

The Diversity of Martian Volcanic features as Seen in the MOC, THEMIS, and MOM Data Sets

This one-year project (which included one-year no-cost tension) focused on the evolution of the summit areas of Martian volcanoes. It extended the studies conducted under an earlier MDAP project (Grant NAG5-9576, Principal Investigator P. Mouginis- Mark). By using data collected from the Mars Orbiter Camera (MOC), Thermal Emission Imaging System (THEMIS), and the Mars Orbiter Laser Altimeter (MOLA) instruments, we tried to better understand the diversity of constructional volcanism on Mars, and hence further understand the eruption processes. By inspecting THEMIS and MOC data, we explored the following four questions: (1) Where might near-surface volatiles have been released at the summits of the Tharsis volcanoes? Is the trapping and subsequent remobilization of degassed volatiles [Scott and Wilson, 19991 adequate to produce eruptions responsible for extensive deposits such as the ones identified on Arsia Mons [Mouginis-Mark, 2002]? To answer this question, we investigated the diversity of eruption styles by studying the summit areas of Arsia, Pavonis and Ascraeus Montes. (2) What are the geomorphic characteristics of the valley system on Hecates Tholus, a volcano that we have previously proposed experienced explosive activity [Mouginis-Murk et al., 1982]? Our inspection of THEMIS data suggests that water release on the volcano took place over an extended period of time, suggesting that hydrothermal activity may have taken place here. (3) How similar are the collapse processes observed at Martian and terrestrial calderas? New THEMIS data provide a more complete view of the entire Olympus Mons caldera, thereby enabling the comparison with the collapse features at Masaya volcano, Nicaragua, to be investigated. (4) What can we learn about the emplacement of long lava flows in the lava plains of Eastern Tharsis? The result of this work provided a greater understanding of the temporal and spatial variations in the eruptive history of volcanoes on Mars, and the influence of the volatiles within the top few kilometers of the volcanic edifice. This relationship in turn pertains to the availability of volatiles (both juvenile magmatic volatiles and ground water contained within the near-surface rocks) and to magma supply rates at appreciable distances (tens to hundreds of kilometers) from the centers of volcanoes. Explosive volcanism on Mars, a major factor in the release of water at the surface, may have been driven not only by volatiles within the parental melt, but also by magma encountering water or ice at shallow depth within the volcano [Mouginis-Mark et al., 1982, 1988; Crown and Greeley, 1993; Robinson et al., 19931

Effects of Volcanoes on the Natural Environment

The primary focus of this project has been on the development of techniques to study the thermal and gas output of volcanoes, and to explore our options for the collection of vegetation and soil data to enable us to assess the impact of this volcanic activity on the environment. We originally selected several volcanoes that have persistent gas emissions and/or magma production. The investigation took an integrated look at the environmental effects of a volcano. Through their persistent activity, basaltic volcanoes such as Kilauea (Hawaii) and Masaya (Nicaragua) contribute significant amounts of sulfur dioxide and other gases to the lower atmosphere. Although primarily local rather than regional in its impact, the continuous nature of these eruptions means that they can have a major impact on the troposphere for years to decades. Since mid-1986, Kilauea has emitted about 2,000 tonnes of sulfur dioxide per day, while between 1995 and 2000 Masaya has emotted about 1,000 to 1,500 tonnes per day (Duffel1 et al., 2001; Delmelle et al., 2002; Sutton and Elias, 2002). These emissions have a significant effect on the local environment. The volcanic smog ("vog" ) that is produced affects the health of local residents, impacts the local ecology via acid rain deposition and the generation of acidic soils, and is a concern to local air traffic due to reduced visibility. Much of the work that was conducted under this NASA project was focused on the development of field validation techniques of volcano degassing and thermal output that could then be correlated with satellite observations. In this way, we strove to develop methods by which not only our study volcanoes, but also volcanoes in general worldwide (Wright and Flynn, 2004; Wright et al., 2004). Thus volcanoes could be routinely monitored for their effects on the environment. The selected volcanoes were: Kilauea (Hawaii; 19.425 N, 155.292 W); Masaya (Nicaragua; 11.984 N, 86.161 W); and Pods (Costa Rica; 10.2OoN, 84.233 W)

Evolution of the Olympus Mons Caldera, Mars

Extensive high-resolution (15 to 20 m/pixel) coverage of Olympus Mons volcano permits the investigation of the sequence of events associated with the evolution of the nested summit caldera. The sequence of the intra-caldera events is well illustrated by image data collected on orbits 473S and 474S of Viking Orbiter 1. These data cover both the oldest and youngest portions of the caldera floor. The chronology inferred from the observations is presented which in turn can be interpreted in terms of the internal structure of the volcano (i.e., magma chamber depth and the existence of dikes)

Report of the panel on volcanology, section 4

Two primary goals are identified as focal to NASA's research efforts in volcanology during the 1990s: to understand the eruption of lavas, gases, and aerosols from volcanoes, the dispersal of these materials on the Earth's surface and through the atmosphere, and the effects of these eruptions on the climate and environment; and to understand the physical processes that lead to the initiation of volcanic activity, that influence the styles of volcanic eruptions, and that dictate the morphology and evolution of volcanic landforms. Strategy and data requirements as well as research efforts are discussed

Late-stage intrusive activity at Olympus Mons, Mars:summit inflation and giant dike formation

By mapping the distribution of 351 lava flows at the summit area of Olympus Mons volcano on Mars, and correlating these flows with the current topography from the Mars Orbiter Laser Altimeter (MOLA), we have identified numerous flows which appear to have moved uphill. This disparity is most clearly seen to the south of the caldera rim, where the elevation increases by >200 m along the apparent path of the flow. Additional present day topographic anomalies have been identified, including the tilting down towards the north of the floors of Apollo and Hermes Paterae within the caldera, and an elevation difference of >400 m between the northern and southern portions of the floor of Zeus Patera. We conclude that inflation of the southern flank after the eruption of the youngest lava flows is the most plausible explanation, which implies that intrusive activity at Olympus Mons continued towards the present beyond the age of the youngest paterae ~200 – 300 Myr (Neukum et al., 2004; Robbins et al., 2011). We propose that intrusion of lateral dikes to radial distances >2,000 km is linked to the formation of the individual paterae at Olympus Mons. Two specific dikes to the SE of the volcano are inferred to have volumes of ~4,400 km3 and ~6,100 km3, greater than the volumes of individual calderas and implying triggering of both caldera collapse and lateral dike injection by the arrival of large inputs of magma from the mantle. A comparable disparity between lava flow direction and current topography, together with a tilted part of the caldera floor, has been identified at Ascraeus Mons

Current and future use of TOPSAR digital topographic data for volcanological research

In several investigations of volcanoes, high quality digital elevation models (DEM's) are required to study either the geometry of the volcano or to investigate temporal changes in relief due to eruptions. Examples include the analysis of volume changes of a volcanic dome, the prediction of flow paths for pyroclastic flows, and the quantitative investigation of the geometry of valleys carved by volcanic mudflows. Additionally, to provide input data for models of lava flow emplacement, accurate measurements are needed of the thickness of lava flows as a function of distance from the vent and local slope. Visualization of volcano morphology is also aided by the ability to view a DEM from oblique perspectives. Until recently, the generation of these DEM's has required either high resolution stereo air photographs or extensive field surveying using the Global Positioning System (GPS) and other field techniques. Through the use of data collected by the NASA/JPL TOPSAR system, it is now possible to remotely measure the topography of volcanoes using airborne radar interferometry. TOPSAR data can be collected day or night under any weather conditions, thereby avoiding the problems associated with the derivation of DEM's from air photographs that may often contain clouds. Here we describe some of our initial work on volcanoes using TOPSAR data for Mt. Hekla (Iceland) and Vesuvius (Italy). We also outline various TOPSAR topographic studies of volcanoes in the Galapagos and Hawaii that will be conducted in the near future, describe how TOPSAR complements the volcanology investigations to be conducted with orbital radars (SIR-C/X-SAR, JERS-1 and ERS-1), and place these studies into the broader context of NASA's Global Change Program