Engineering topics

Betts, B. H.

Publications and source records attributed to Betts, B. H..

4 records

NASA NTRS1993

Thermal studies of Martian channels and valleys using Termoskan data

The Termoskan instrument on board the Phobos '88 spacecraft acquired the highest spatial resolution thermal data ever obtained for Mars. Included in the thermal images are 2 km per pixel observations of 4 major channel and valley systems: Shalbatana Vallis; Simud Vallis, Hydraotes Chaos, and the associated outflow channel connecting it with the eastern end of Vallis Marineris; Al-Qahira Vallis; and Ma'adim Vallis. Simultaneous broad band visible channel data were obtained for all but Ma'adim Vallis. We find that all 4 valley systems have higher inertias than their surroundings, consistent with previous thermal studies of Martian channels. We conclude that the higher inertia is likely due to some intrinsic difference associated with the channel floors, rather than due only to dark aeolian deposits as suggested by some previous studies. Our conclusion is based largely upon the localized nature of the dark deposits in contrast with the thermal homogeneity of the channel floors. Thus, these channels and valleys show an uncommon (for Mars) connection between morphology and inertia.

Betts, B. H.↗

NASA NTRS1993

Thermal studies of Martian channels and valleys using Termoskan data: New results

The Termoskan instrument onboard the Phobos '88 spacecraft acquired the highest-spatial-resolution thermal data ever obtained for Mars. Included in the thermal images are 2 km/pixel midday observations of several major channel and valley systems, including significant portions of Shalbatana Vallis, Ravi Vallis, Al-Qahira Vallis, Ma'adim Vallis, the channel connecting Valles Marineris with Hydraotes Chaos, and channel material in Eos Chasma. Termoskan also observed small portions of the southern beginnings of Simud, Tiu, and Ares Valles and some channel material in Gangis Chasma. Simultaneous broad band visible data were obtained for all but Ma'adim Vallis. We find that most of the channels and valleys have higher inertias than their surroundings, consistent with Viking IRTM-based thermal studies of Martian channels. We see for the first time that thermal inertia boundaries closely match all flat channel floor boundaries. Combining Termoskan thermal data, relative observations from Termoskan visible channel data, Viking absolute bolometric albedos, and a thermal model of the Mars surface, we have derived lower bounds on channel thermal inertias. Lower bounds on typical channel thermal inertias range from 8.4 to 12.5 (10(exp -3) cal cm(exp -2) s(exp -1/2)K(exp -1)) (352 to 523 in SI units). Lower bounds on inertia differences with the surrounding heavily cratered plains range from 1.1 to 3.5 (46 to 147 in SI units). Atmospheric and geometric effects are not sufficient to cause the inertia enhancements. We agree with previous researchers that localized, dark, high inertia areas within channels are likely eolian in nature. However, the Temloskan data show that eolian deposits do not fill the channels, nor are they responsible for the overall thermal inertia enhancement. Thermal homogeneity and strong correlation of thermal boundaries with the channel floor boundaries lead us to favor noneolian overall explanations.

Betts, B. H.↗

NASA NTRS1992

Thermally distinct ejecta blankets from Martian craters

The study of ejecta blankets on Mars gives information about the Martian surface, subsurface, geologic history, atmospheric history, and impact process. In Feb. and Mar. 1989, the Termoskan instrument on board the Phobos 1988 spacecraft of the USSR acquired the highest spatial resolution thermal data ever obtained for Mars, ranging in the resolution from 300 meters to 3 km per pixel. Termoskan simultaneously obtained broad band visible channel data. The data covers a large portion of the equatorial region from 30 degrees S latitude to 6 degrees N latitude. Utilizing the data set we have discovered tens of craters with thermal infrared distinct ejecta (TIDE) in the equatorial regions of Mars. In order to look for correlations within the data, we have compiled a database which currently consists of 110 craters in an area rich in TIDE's and geologic unit variations. For each crater, we include morphologic information from Barlow's Catalog of Large Martian Impact Craters in addition to geographic, geologic, and physical information and Termoskan thermal infrared and visible data.

Betts, B. H.↗

NASA NTRS1991

Preliminary assessment of Termoskan observations of Mars

The limited set of high-resolution observations of the 8-12 micron thermal emission from Mars' equatorial regions by the Termoskan instrument onboard the Phobos '88 spacecraft in February and March of 1989 is considered. Observations were also simultaneously acquired in the 0.5 to 1.0 micron region. A combined U.S. and Soviet scientific team made a preliminary quantitative evaluation of about 25 percent of the entire data set. It is found that there is a close agreement with the Viking Infrared Thermal Mapper brightness temperatures, confirming the accuracy of the Termoskan system and calibration. A novel pattern of emission from particles was observed in the morning and assumed to be water or ice. Thermal emission from surface features is varied and distinct down to the limit of resolution. The presence of unusually insulating material has been detected in the uppermost fraction of a millimeter of the Martian surface in places where the shadow of Phobos briefly eclipsed by the surface.

Murray, B.↗