On the moon and other airless bodies, ballistically emplaced ejecta transitions from a thinning, continuous inner deposit to become discontinuous beyond approximately one crater radius from the crater rim and can further break into discrete rays and secondary craters. In contrast, on Mars, ejecta often form continuous, distinct, and sometimes thick deposits that transition to a low ridge or escarpment that may be circular or lobate. The Martian ejecta type has been variously termed pancake, rampart, lobate, or layered, and in this work we refer to it as abrupt termini ejecta (ATE). Two main formation mechanisms have been proposed, one requiring interaction of the ejecta with the atmosphere and the other mobilization of near-surface volatiles. ATE morphologies are also unambiguously seen on Ganymede, Europa, Dione, and Tethys, but they are not as common as on Mars. We have identified up to 38 craters on Charon that show signs of ATE, including possible distal ramparts and lobate margins. These ejecta show morphologic and morphometric similarities with other moons in the solar system, which are a subset of the properties observed on Mars. From comparison of these ejecta on Charon and other solar system bodies, we find the strongest support for subsurface volatile mobilization and ejecta fluidization as the main formation mechanism for the ATE, at least on airless, icy worlds. This conclusion comes from the bodies on which they are found, an apparent preference for certain terrains, and the observation that craters with ATE can be near to similarly sized craters that only have gradational ejecta.

The North Polar Layered Deposits (NPLD) of Mars contain a complex stratigraphy that has been suggested to retain a record of past eccentricity- and obliquity-forced climate changes. The surface accumulation rate in the current climate can be constrained by the crater retention age. We scale NPLD crater diameters to account for icy target strength and compare surface age using a new production function for recent small impacts on Mars to the previously used model of Hartmann (2005). Our results indicate that ice is accumulating in these craters several times faster than previously thought, with a 100m diameter crater being completely infilled within centuries. Craters appear to have a diameter-dependent lifetime, but the data also permit a complete resurfacing of the NPLD at similar to 1.5 ka.

Abstract Crater counting is a method which allows us to estimate the surface ages of the planetary bodies, from which the sampling and sample delivery to laboratories on Earth are difficult or impossible. Because the number of craters on a surface unit increases over the time the surface has been exposed to space, old, geologically stable units have more craters than young and active units. When the crater production rate as a function of time is known, the absolute age of the surface unit can be determined based on its crater density. The purpose of this thesis is to investigate the role of small impact craters in crater counts to find out how modern very high-resolution space images can be utilized in age determination of planetary surfaces. The thesis focuses on how reliable crater count based datings are, if only small craters and counting areas are used in age determination. The research is carried out by utilizing crater counts on the outflow channels of Dao, Niger, Harmakhis and Reull Valles, which all are located in the eastern rim region of the Hellas impact basin, on the southern hemisphere of Mars. Crater counts are performed mainly based on the images of ConTeXt Imager (CTX) and High Resolution Imaging Science Experiment (HiRISE) aboard Mars Reconnaissance Orbiter (MRO). The results show that small craters are a very valuable tool to get information about the surface age. Instead of the size-range of counted craters, or the size of counting areas, results are dependent on the variability and scale of the surface modification history. The more variable or larger scale the modification history is, the larger surface area and wider crater diameter range are typically needed to achieve comprehensive age estimations. The crater counts on the eastern Hellas outflow channels support the earlier theories according to which the valles formed during a relatively short time interval, ~ 3.4–3.7 Ga ago. The existence of terrace structures and smaller tributary channels indicate that the outflow channels were filled by several pulses of liquids. The major fluvial activity ended no later than ~ 0.8–1.9 Ga ago, and it was probably controlled by the activity of nearby highland volcanoes. Soon after the declined fluvial activity, the outflow channels were covered by ice-rich deposits. The major reason for this was probably the changed climatic conditions, although in places e.g. impact cratering seems to have contributed to the emplacement of the deposits. The region as a whole was also resurfaced several times because of changes in local climate conditions. The most significant of the resurfacing processes seem to be the episodes of thin ice-rich mantling deposits, the most recent of which dominated the regional modification less than 10 Ma ago. In addition, the region has experienced eolian activity during the last 1 Ma. / Original papers The original publications are not included in the electronic version of the dissertation. Kostama, V.-P., Kukkonen, S., & Raitala, J. (2017). Resurfacing event observed in Morpheos basin (Eridania Planitia) and the implications to the formation and timing of Waikato and Reull Valles, Mars. Planetary and Space Science, 140, 35–48. https://doi.org/10.1016/j.pss.2017.04.001 Kukkonen, S., & Kostama, V.-P. (2018). Modification history of the Harmakhis Vallis outflow channel, Mars, based on CTX-scale photogeologic mapping and crater count dating. Icarus, 299, 46–67. https://doi.org/10.1016/j.icarus.2017.07.014 Kukkonen, S., & Kostama, V.-P. (2018). Usability of small impact craters on small surface areas in crater count dating: Analysing examples from the Harmakhis Vallis outflow channel, Mars. Icarus, 305, 33–49. https://doi.org/10.1016/j.icarus.2018.01.004 Kukkonen, S., & Kostama, V.-P. (2018). Mapping and dating based evolution studies of the Niger Vallis outflow channel, Mars. Planetary and Space Science, 153, 54–71. https://doi.org/10.1016/j.pss.2017.12.012 Korteniemi, J., & Kukkonen, S. (2018). Volcanic Structures Within Niger and Dao Valles, Mars, and Implications for Outflow Channel Evolution and Hellas Basin Rim Development. Geophysical Research Letters, 45(7), 2934–2944. https://doi.org/10.1002/2018gl077067 http://jultika.oulu.fi/Record/nbnfi-fe201902226008

Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.

Pit crater and pit crater chains associated to the volcano Arsia Mons on Mars have been mapped to analyse their spatial pattern and to conclude about their formation. For the mapping, high resolution satellite data gathered during the Mars Express mission were used. The spatial distribution of the pit craters was then compared with typical patterns of magmatic sheet intrusions within volcanoes as they are known from Earth. The results show that the pattern of the mapped pit craters and pit crater chains are in good agreement with these sheet intrusions and are therefore likely related to Martian sheet intrusions. / Kollapskratrar och kraterkedjor relaterade till vulkanen Arsia Mons på Mars har karterats för att analysera deras spatiala mönster och för att komma till slutsatser för deras tillblivelse. Högupplösta satellitbilder tagna av Mars Express-sonden har använts för karteringen. Fördelningen av de karterade kraterkedjorna jämfördes med typiska fördelningar av magmatiska gångbergarter från vulkaner på jorden. Resultaten visar att fördelningen av kollapskratrar och kraterkedjor överensstämmer enligt förväntningarna och påvisar en relation mellan kollapskratrar och magmatiska gångbergarter på Mars.

Over the last fifty years, our knowledge of the Solar System has increased exponentially. Many planetary surfaces were seen for the first time through spacecraft observations. Yet the interiors of most planetary bodies remain poorly studied. This dissertation focuses on two main topics: the formation of central pit craters and what this reveals about the subsurface volatile content of the target material, and the mantle dynamics of Io and how they relate to the extensive volcanism on its surface. Central pit craters are seen on icy satellites, Mars, the Moon, and Mercury. They have terraced rims, flat floors, and a pit at or near their center. Several formation mechanisms have been suggested. This dissertation assesses the feasibility of central pit crater formation via drainage of impact melt through impact-generated fractures. For impacts on Ganymede, the expected volume of melt and volume of fracture space generated during the impact and the volume of melt able to drain before fractures freeze shut all exceed the observed central pit volumes on Ganymede. This suggests that drainage of impact melt could contribute to central pit crater formation on Ganymede. Molten rock draining through solid rock fractures will freeze shut more rapidly, so this work suggests that impact melt drainage is unlikely to be a significant factor in the formation of central pit craters on rocky bodies unless a significant amount of volatiles are present in the target. Io is the most volcanically active body in the Solar System. While volcanoes are most often associated with plate tectonics on Earth, Io shows no signs of plate tectonics. Previous work has suggested that Io could lose a significant fraction of its internal heat through volcanic eruptions. In this dissertation, I investigate the relationship between mantle convection and magma generation, migration by porous flow, and eruptions on Io. I couple convective scaling laws to a model solving the two-phase flow equations applied to a rising column of mantle. I show that Io has a partially molten upper mantle and loses the majority of its internal heat through volcanic eruption. Next, I present two-dimensional numerical simulations that self-consistently solve the two-phase flow equations including mantle convection and magma generation, migration by porous flow, and eruption. These simulations produce a high heat flux due to volcanic eruption, a thick lithosphere, a partially molten upper mantle, and a high eruption rate—all consistent with observations of Io. This model also reveals the eruption rate oscillates around the statistical steady state average eruption rate suggesting that the eruption rate and total heat flux measurements from the past 35 years may not be representative of Io's long term behavior.

Thesis (doctoral)--University of Tartu, 2008. / Vita. Includes bibliographical references.

abstract: Lunar Reconnaissance Orbiter (LRO) and MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft missions provide new data for investigating the youngest impact craters on Mercury and the Moon, along with lunar volcanic end-members: ancient silicic and young basaltic volcanism. The LRO Wide Angle Camera (WAC) and Narrow Angle Camera (NAC) in-flight absolute radiometric calibration used ground-based Robotic Lunar Observatory and Hubble Space Telescope data as standards. In-flight radiometric calibration is a small aspect of the entire calibration process but an important improvement upon the pre-flight measurements. Calibrated reflectance data are essential for comparing images from LRO to missions like MESSENGER, thus enabling science through engineering. Relative regolith optical maturation rates on Mercury and the Moon are estimated by comparing young impact crater densities and impact ejecta reflectance, thus empirically testing previous models of faster rates for Mercury relative to the Moon. Regolith maturation due to micrometeorite impacts and solar wind sputtering modies UV-VIS-NIR surface spectra, therefore understanding maturation rates is critical for interpreting remote sensing data from airless bodies. Results determined the regolith optical maturation rate on Mercury is 2 to 4 times faster than on the Moon. The Gruithuisen Domes, three lunar silicic volcanoes, represent relatively rare lunar lithologies possibly similar to rock fragments found in the Apollo sample collection. Lunar nonmare silicic volcanism has implications for lunar magmatic evolution. I estimated a rhyolitic composition using morphologic comparisons of the Gruithuisen Domes, measured from NAC 2-meter-per-pixel digital topographic models (DTMs), with terrestrial silicic dome morphologies and laboratory models of viscoplastic dome growth. Small, morphologically sharp irregular mare patches (IMPs) provide evidence for recent lunar volcanism widely distributed across the nearside lunar maria, which has implications for long-lived nearside magmatism. I identified 75 IMPs (100-5000 meters in dimension) in NAC images and DTMs, and determined stratigraphic relationships between units common to all IMPs. Crater counts give model ages from 18-58 Ma, and morphologic comparisons with young lunar features provided an additional age constraint of <100 Ma. The IMPs formed as low-volume basaltic eruptions significantly later than previous evidence of lunar mare basalt volcanism's end (1-1.2 Ga). / Dissertation/Thesis / Ph.D. Geological Sciences 2013

The purpose of the investigation was to map the geology of the north end of Craters of the Moon National Monument and surrounding area. A stratigraphic sequence of Late Paleozoic sedimentary and Tertiary volcanic rocks was compiles and the structures of these rocks and contact relationships with intrusions were delineated. Grade and facies of contact metamorphism were defined. The Snake River Plain basalts were also mapped. The sources of these flows were determined where possible. Preexisting structures and relationships of vents to earlier faulting were explored in ascertaining extensions of the Great Rift Zone into the Pioneer Mountains. Petrographic descriptions of the rock units were completed. Study of the economic geology was not undertaken. The interested reader is referred to Nelson (1969) for descriptions of the mineral deposits in the Lava Creek Mining District.

No description available.