Four distinct classes of lineaments can be described on the basis of Galileo's improved spectral and spatial coverage of Europa: (1) incipient cracks are narrow (<1.6 km wide) and are generally colorless fractures which tend to crosscut other lineament types, (2) ridges have raised relief, tend to be wider (3–6 km) than the cracks, and are distinct in color from the icy plains they transect, (3) triple bands have dim medial stripes similar in color and width to the ridges and broad (8–12 km wide) diffuse low-albedo margins tainted by a red–brown nonice contaminant, and (4) ancient bands are generally similar in width to ridges and triple bands and have colors intermediate between those of triple bands and the undisturbed icy plains. They are only slightly darker than the plains at visible wavelengths—hence, they were largely undetected by Voyager—but are distinctly brighter than the plains in the infrared, precluding the possibility that they have simply faded from their formerly darker appearance. The morphologies, spectral properties, and orientations of the lineaments vary systematically with age, suggesting that these four classes represent different stages of development in an evolutionary sequence. Lineament formation appears to be the dominant resurfacing mechanism on Europa, and every landscape that has escaped erasure by heating from below is imprinted with generation after generation of intersecting ridges at various scales and orientations. Relatively recent fractures expose coarse-grained, clean ice in the shallow subsurface, possibly accounting for the distinctive color of the satellite in comparison to the other icy moons of Jupiter. The process of lineament formation may be continuing today; the bright band Agenor Linea is among the leading candidates for current activity.
The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration. Any lacustrine sediments that may exist at this location within Gusev apparently have been buried by lavas that have undergone subsequent impact disruption.
Although imaging radar is able to penetrate through sand to reveal subsurface geology in some areas, backscatter from the subsurface is influenced by attenuation of the signal by the sand. To study this modification of the backscatter, field measurements were coordinated with acquisition of AIRSAR images over the Mojave Desert, CA. Quad-polarized images at L- and C-bands were acquired along two orthogonal tracks over the Dumont Dunes area. A comparison of the backscatter at L-band to that at C-band for various areas reveals differences in the way that the sand affects the backscatter at the two wavelengths. To understand how radar attenuation by sand varies with radar frequency, a laboratory experiment was conducted to measure radar transmission through a sand target as a function of radar frequency and sand moisture. The frequency range covers X- through P-bands, and the moisture contents of the sand were 0.3, 4.7, and 10.7 percent by volume. Laboratory results quantify the difference in attenuation of the signal at L- and C-bands, allowing comparison AIRSAR data and field measurements in order to further understand how a sand cover modifies the radar signature of a surface.
The characteristics of aerolian (wind) activity as a surface modifying process on Earth, Mars, Venus, and appropriate satellites was determined. A combination of spacecraft data analysis, wind tunnel simulations, and terrestrial field analog studies were used to determine these characteristics. Wind tunnel experiments simulating Venusian surface conditions demonstrate that rolling of particles may be an important mode of transport by winds on Venus and that aerolian processes in the dense atmosphere may share attributes of both aerolian and aqueous environments on Earth.
Dust. It gets in our eyes, our shoes, even in our lungs, sometimes causing disease to those who breath it. Dust storms cause visibility problems on highways, resulting in many accidents and deaths each year. And soil erosion is a major worldwide problem where surfaces are disrupted through cultivation, overgrazing, mining, construction, vehicular traffic, or other activities which disturb the surface or destroy vegetation cover.
Research Article| December 01, 1973 Mariner 9 Photographs of Small Volcanic Structures on Mars Ronald Greeley Ronald Greeley 1Ames Research Center, NASA 245–5, Moffett Field, California 96053, and Department of Physics, University of Santa Clara, Santa Clara, California 95053 Search for other works by this author on: GSW Google Scholar Author and Article Information Ronald Greeley 1Ames Research Center, NASA 245–5, Moffett Field, California 96053, and Department of Physics, University of Santa Clara, Santa Clara, California 95053 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1973) 1 (4): 175–180. https://doi.org/10.1130/0091-7613(1973)1<175:MPOSVS>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Ronald Greeley; Mariner 9 Photographs of Small Volcanic Structures on Mars. Geology 1973;; 1 (4): 175–180. doi: https://doi.org/10.1130/0091-7613(1973)1<175:MPOSVS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Surface features on the flanks of martian shield volcanoes photographed by Mariner 9 are identified as lava flow channels, rift zones, and partly collapsed lava tubes by comparisons with similar structures on the flanks of Mauna Loa shield volcano, Hawaii. From these identifications, the composition of the martian lava flows is interpreted to be basaltic, with viscosities ranging from those of fluid pahoehoe to more viscous aa. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
