Engineering topics

Rossbacher, L. A.

Publications and source records attributed to Rossbacher, L. A..

7 records

NASA NTRS1985

The problem of scale in planetary geomorphology

Recent planetary exploration has shown that specific landforms exhibit a significant range in size between planets. Similar features on Earth and Mars offer some of the best examples of this scale difference. The difference in heights of volcanic features between the two planets has been cited often; the Martian volcano Olympus Mons stands approximately 26 km high, but Mauna Loa rises only 11 km above the Pacific Ocean floor. Polygonally fractured ground in the northern plains of Mars has diameters up to 20 km across; the largest terrestrial polygons are only 500 m in diameter. Mars also has landslides, aeolian features, and apparent rift valleys larger than any known on Earth. No single factor can explain the variations in landform size between planets. Controls on variation on Earth, related to climate, lithology, or elevation, have seldom been considered in detail. The size differences between features on Earth and other planets seem to be caused by a complex group of interacting relationships. The major planetary parameters that may affect landform size are discussed.

Rossbacher, L. A.↗

NASA NTRS1985

Planetary perspective. Report of Working Group Number 4

The study of global megageomorphology from a planetary perspective requires that, philosophically, we view the Earth as a planet like any other; one among a number of bodies of varied size and composition which, together with the Sun, form the Solar System. A first step in the study of the Earth from the planetary perspective is the development of global distribution maps of surface factors as landforms, tectonics, and of key processes operating on Earth. Data of other types, such as gravity and magnetism, should also be included and, so far as possible, multiple data sets should be developed. The compilation of maps would serve as a catalyst for research and a basis for interpretation. They could be used scientifically to document changes such as glacial variations and their relationships to climate, volcanic eruptions and their effects, and coastal alterations. Slow and rapid changes should be studied together with the relationships between scale and the rapidity of change. A study of the relationship of geomorphology (i.e., surficial processes) to lithology and structure is needed. The planetary perspective can also help in the identification and investigation of exotic features such as suspect terrains.

Rossbacher, L. A.↗

NASA NTRS1985

Catastrophic-flood Features in Swedish Lapland as a Terrestrial Analog for Martian Channel Flows

Catastrophic flooding associated with deglaciation created unusual landscapes in several areas of northern Sweden. These areas in Swedish Lapland are distinguished by the large grain-size material that forms them. The presence of boulders at both Viking landing sites suggests the relevance of this analog. The Baldakatj area of Swedish Lapland offers terrestrial analogs for erosional remnants on Mars. Although the Baldakatj features are an order of magnitude or more smaller than the Martian forms, they created in boulder-rich till that may be a good approximation of the near-surface material on Mars. The Baldakatj area also includes other landforms that could reasonably be expected to occur with the Martian outflow channels, including boulder deltas, large transported blocks, and large-scale bedforms.

Rossbacher, L. A.↗

NASA NTRS1985

Terrestrial Analog Studies for Martian Patterned Ground

A recurring problem in understanding Martian patterned ground is explaining its large size. Terrestrial patterned ground in Swedish Lapland offers an analog that may help explain this. In cold, arid regions with strong winds, polygonal features are accentuated paralled to the dominant wind direction. Preliminary results of a comparison between Martian polygonal troughs and dominant wind directions suggests a good correlation. This evolutionary model involving aeolian modification of Martian polygonal ground helps explain the large size features without requiring multiple, deep freeze-thaw cycles. A well-established geographical technique, nearest neighbor analysis, can be modified and applied to the distribution of patterned ground on Earth and Mars. The procedure determines the R-statistic, which reflects the degree to which on observation departs from an expected random pattern. The R-statistic is independent of scale, and therefore it can be applied to any size of type of pattern. Preliminary results indicate that there may be a correlation between the R-statistic and the process that create the polygons.

Rossbacher, L. A.↗

NASA NTRS1984

Glacial and periglacial landforms in Denmark: Scandinavian analogs for Martian features

The geomorphology of Denmark is dominated by glacial deposits, including both end moraines and ground moraines. Many of these features have morphologies similar to features observed on Mars. A characteristic landscape complex in Denmark is a series of irregular mounds or parallel curvilinear ridges that outline the former ice margin. Many of these resemble curviliner features on Mars, and the Danish landforms occur at a similar scale. Another distinctive landform in Denmark is the hummocky moraine landscape found in parts of Sjaelland. Although their size is smaller, these areas resemble the hummocky terrain associated with some of the curvilinear features in the northern plains of Mars. The hummocky Danish terrain is probably caused by the melting of masses of dead ice left during glacial retreat. Similar landscapes observed developing during retreat of smaller glaciers were ice caps in Scandinavian mountains and in Greenland.

Rossbacher, L. A.↗

NASA NTRS1984

Curvilinear Ground on Mars: the Search for Terrestrial Analogs

Curvilinear features on Mars have dimensions ranging from 0.5 to 18.6 km in length and 0.2 to 2.0 km in width; these landforms can occur as curving ridges and troughs, rimless arcuate depressions, or features with no apparent relief. The Martian curvilinear ground has a relatively consistent relationship to both regional and local geomorphology. These landforms are one of a suite of features that occur near the base of the regional slope that marks the transition from the cratered uplands to the northern plains. Based on morphologic similarities, numerous terrestrial analogs were proposed for these Martian features. These include gilgai, backwasting scarps, solifluction lobes, ice-cored ridges and glacial moraines. Process models for the origin of the curvilinear ground suggest that its formation probably involved several processes, including scarp retreat by backwasting.

Rossbacher, L. A.↗

NASA NTRS1981

Ground ice on Mars - Inventory, distribution, and resulting landforms

A model is presented for the distribution of ground ice on Mars, and model predictions are compared with Viking Orbiter photographs of landforms possibly related to ground ice. Estimates of the amount of water originally outgassed on Mars and the amount of water presently on Mars are presented which show that approximately 90% of the estimated outgassed volume may be stored in the Martian subsurface as ground ice. The extent of the Martian cryosphere, the zone in which the temperature is below the freezing point of water and in which ground ice can exist, is examined, and it is shown that, in the presence of a protective surface layer approximately 10 m thick, ground ice may occur beneath the entire Martian surface. Observed features on the Martian surface considered most likely to reflect the presence of ground ice are discussed, including thermokarst-like pits and debris flows, and possibly polygonally patterned ground, curvilinear features and pingo-like mounds, and the geographic distributions of these features as seen in Viking photographs are examined. It is found that the possibly ice-related features are concentrated in the northern midlatitudes, the equatorial zone near Olympus Mons, and the Southern Hemisphere near the edge of the plains, indicating that subsurface ice may be present over the entire planet. The origin of the ice-related landforms is explained by a combination of volcanic heating and variations in insolation.

Rossbacher, L. A.↗