How to make a comet

The primary mandate of NASA is the study of the nature and origin of the solar system. The study of the comets provide information about conditions and processes at the beginning of the solar system. Short period comets and their relatives, the near Earth asteroids may prove to be second only to the sun in importance to the long term survival of civilization for two reasons. The short period comets and the near Earth asteroids are a possible candidate for the cause of mass extinctions of life on Earth; and they may provide the material means for the expansion of civilization into the solar system and beyond. The comets and near Earth asteroids almost certainly represent the most primitive material of the solar system, still tantalizingly unavailable until spacecraft bring first-hand information. In the meantime comets must be studied by remote means. Laboratory investigations using synthetic cometary materials may add to the knowledge of these interesting objects. Experimentation on comet synthesis is briefly discussed

Mars Structural and Stratigraphic Mapping along the Coprates Rise

This geologic mapping project supports a topical study of structures in east Thaumasia associated with the Coprates rise. The study examines cuesta-like features on the east flank of the Coprates rise first identified by Saunders et al. [1]. Mapping combines detailed local stratigraphy, structural geology and topography. Hogbacks and cuestas indicate erosion of tilted rock units. The extent of the erosion will be determined in the course of the mapping. The region of interest lies along the eastern margin of Thaumasia bounded by latitudes -15 and -35 and longitudes 50 to 70 W (Figure 1). Three MTM geologic quadrangles are being compiled for publication by the USGS (-20057, -25057, -30057). All existing data sources are used including THEMIS, MOC, CTX, HiRISE, MOLA and gravity, as well as higher level data available through the PDS data nodes at ASU, UA and Washington University. The extremely valuable ASU JMARS tools are used for analysis of many of the data sets. ArcGIS software has been obtained and is being learned for the map compilation

Magellan: Principal Venus science findings

This is a brief summary of the science findings of the Magellan mission, principally based on data from the radar system. Future plans for Magellan include acquisition of high resolution gravity data from a nearly circular orbit and atmospheric drag and occultation experiments. The Magellan science results represent the combined effort of more than 100 Magellan investigators and their students and colleagues. More extensive discussions can be found in the August and October, 1992 issues of the Journal of Geophysical Research, Planets. The Magellan mission's scientific objectives were to provide a global characterization of landforms and tectonic features; to distinguish and understand impact processes; to define and explain erosion, deposition, and chemical processes; and to model the interior density distribution. All but the last objective, which requires new global gravity data, have been accomplished, or we have acquired the data that are required to accomplish them

Person-related and Treatment-related Barriers to Alcohol Treatment

Treatment underutilization by persons with alcohol use disorder is well-documented. This study examined barriers to treatment at the latter stages of the treatment-seeking process, which was conceptualized as recognizing the problem, deciding that change is necessary, deciding that professional help is required, and seeking care. All participants identified themselves as having a drinking problem that was severe enough to warrant treatment. Differences between those who had (Treatment Seekers) and those who had not (Comparison Controls) sought treatment were evaluated, including the experience of person-related (e.g., shame) and treatment-related (e.g., cost) barriers. Person-related barriers were more commonly endorsed by both groups than treatment-related barriers. Comparison Controls were more likely to endorse both types of barriers, especially the preference for handling the problem without treatment. Treatment-related barriers were less relevant than person-related barriers at the latter stage of help seeking. The significance of barriers endured after accounting for other differences, such as drinking-related negative consequences. Treatment implications are discussed

Overview of Venus geology: Preliminary description of terrain units for Venus global geological mapping

Venus terrain units can be categorized on the basis of morphology, reflectivity, backscatter, roughness, and emissivity. Morphology can be inferred from Magellan left-looking nominal incidence angle image mosaics, right-looking coverage, and more limited left-looking stereo. The typical resolution is about 300 m down to about 120 m near periapsis in the cycle one nominal coverage. The scale of geologic mapping governs definition of mappable terrain units. Initial global mapping is being compiled at a scale of 1:50 million. At this scale, the smallest individual features that can be mapped are about 125 km. The categories of terrain types are plains, complex ridge terrain, features with morphology suggesting volcanic or volcano-tectonic origin, features interpreted to be tectonic in origin, crater units, and surficial units such as splotches and streaks. Brief descriptions of terrain units are provided

In Situ Resource Utilization (ISRU II) Technical Interchange Meeting

This volume contains extended abstracts that have been accepted for presentation at the In Situ Resource Utilization (ISRU II) Technical Interchange Meeting, November 18-19, 1997, at the Lunar and Planetary Institute, Houston, Texas. Included are topics which include: Extraterrestrial resources, in situ propellant production, sampling of planetary surfaces, oxygen production, water vapor extraction from the Martian atmosphere, gas generation, cryogenic refrigeration, and propellant transport and storage

Geomorphic evidence for ancient seas on Mars

Geomorphic evidence is presented for ancient seas on Mars. Several features, similar to terrestrial lacustrine and coastal features, were identified along the northern plains periphery from Viking images. The nature of these features argues for formation in a predominantly liquid, shallow body of standing water. Such a shallow sea would require either relatively rapid development of shoreline morphologies or a warmer than present climate at the time of outflow channel formation

Curvilinear ridges and related features in southwest Cydonia Mensae, Mars

Examined is a region on Mars in southwest Cydonia Mensae (32 deg lat., 17 deg long.) just northwest of the lowland/upland boundary escarpment. The dominant morphological features in this region are the clusters of large massifs and plateau outliers (PI), knobby material (K), and smooth lowland plains (Ps). Surrounding the clusters and linking many isolated knobs is a system of curvilinear ridges and arcuate terrain boundaries which tend to separate the massifs and knobs from the smooth plains. Curvilinear ridges are arcuate to nearly linear and smoother in plan than wrinkle ridges and show no apparent correlation with regional structural grain. They are typically 5 to 10 km long but can range from as little as 2 or 3 km to greater than 50 km long. The widths vary from about 100 m to as much as 2 km. Curvilinear ridges are most numerous within 100 km of the lowland/upland boundary escarpment and are associated with massifs and knobby terrain. Arcuate terrain boundaries appear between units of different apparent albedo or arcuate breaks in slope

Geomorphic evidence for ancient seas in west Deuteronilus Mensae, Mars-2: From very high resolution Viking Orbiter images

Very high resolution Viking Orbiter images of the Martian surface, though rare, make it possible to examine specific areas at image scales approaching those of high altitude terrestrial aerial photographs. Twenty three clear images lie within west Deuteronilus Mensae. The northernmost images which constitute an almost unbroken mosaic of the west wall of a long fingerlike canyon are examined. Morphological details on the plateau surface within zone B, not detectable at low resolution, make it possible to divide the zone into two distinct subzones separated by an east-west escarpment. The morphology of the canyon floor is described in detail

Geomorphic evidence for ancient seas in west Deuteronilus Mensae, Mars-1: Regional geomorphology

The fretted terrain in west Deuteronilus Mensae consists of extensive cratered upland penninsulas or isolated plateaus cut by long, finger-like canyons typically 10 to 20 km wide and upwards of 300 km long. The longest of these canyons trend roughly north-south to north-northeast, which may reflect some local structural and/or topographic control. At least three geomorphic zones roughly parallel to the lowland/upland boundary, suggestive of increasing modification northward, can be recognized on the fretted region of the region. The southern-most zone (zone A) consists of sharply defined fretted terrain. The middle zone (zone B) consists of well defined fretted terrain in which the plateau surfaces appear smoother, with a somewhat darker and much less varied albedo surface than those of zone A. The northern-most zone (zone C) consists of rounded or softened fretted terrain. The zones were interpreted as surface exposures of successively lower stratigraphic units