Engineering topics

Jakosky, Bruce M.

Publications and source records attributed to Jakosky, Bruce M..

61 records · Page 4

NASA NTRS1988

The behavior of water vapor in the Mars atmosphere

The behavior of water vapor in the atmosphere of Mars is important to understanding the Mars climate and its evolution as well as the nature of ongoing seasonal processes of exchange and transport. On the seasonal timescales, exchange of water between the atmosphere, regolith, and polar caps combine with advection of water and the possible saturation at some locations and seasons in order to produce the observed distribution of water. A summary of the observations made by the Mariner and Viking spacecraft and analyses of the seasonal cycle of water is presented, along with a brief discussion of the implications for the long term variability of water. The upcoming Mars Observer mission is also briefly discussed.

Jakosky, Bruce M.↗

NASA NTRS1988

Solar Mesosphere Explorer observations of stratospheric and mesospheric water vapor

It is noted that while the SME (Solar Mesosphere Explorer) data is consistent with the earlier LIMS (Limb Infrared Monitor of the Stratosphere) results, its interpretation is complicated by aerosol contamination, particularly at altitudes below 35 km. This contamination arose from several volcanic eruptions, including that of El Chichon. Analyses are reported of a subset of data from the SME satellite, concentrating primarily on the period January through March 1982 so as to avoid contamination from the El Chichon volcanic aerosol. The SME observations of water vapor between 20 and 60 km were inverted for the first three months of 1982 as well as for selected additional periods. Reasonable results are obtained at locations where no contamination by aerosol is suspected.

Jakosky, Bruce M.↗

NASA NTRS1987

Mars - North-Polar atmospheric warming during dust storms

Viking observations of the two 1977 dust storms on Mars yield winter polar atmosphere temperature measurements that indicate a strong spatial and temporal dependence in the process of polar warming. Very little dust appears to be contained in the upper atmosphere; the data do not allow a determination of dust abundance in the lower atmosphere to be made. Surges appear in the polar warming that are prevalent only on one side of the pole, corresponding to the evening side of the 1977 observations. The polar atmospheric warming occurred during the second, but not the first, of the 1977 global dust storms.

Jakosky, Bruce M.↗

NASA NTRS1987

The evolution of topography on a comet

The evolution of cometary surface topography is presently modeled in terms of a focusing of thermal energy due to topographical concavity. The model encompasses incident sunlight, shadowing, molecular sublimation, and mutual radiative heating by the walls of a circle-segment cross section trench, which has a 'lensing' effect. After a large number of perihelion passages, the net effect of trench bottom sublimation losses will be the accentuation of topographical concavities. The comet surface sublimation, comet-splitting, and comet surface jet-formation consequences of this model are discussed.

Colwell, Joshua E.↗

NASA NTRS1987

Mars - VLA observations of the northern hemisphere and the north polar region at wavelengths of 2 and 6 cm

Calculations based on 2- and 6-cm observations of Mars with the A configuration of the VLA have yielded a whole-disk effective dielectric constant of 2.34 + or - 0.05, implying a subsurface density of 1.24 + or - 0.11 g/cu cm at 2 cm, as well as 1.45 + or - 0.10 g/cu cm effective density and 2.70 + or - 0.10 dielectric constant at 6 cm. These parameters have also been estimated as a function of latitude over the 15 deg S - 60 deg N range; subsurface radio absorption length was estimated to be about 15 wavelengths at most of these latitudes. Most of the subsurface density calculations yielded results in the 1-2-g/cu cm range, implying that the subsurface is not very different from the surface observed by Viking and Mariner spacecraft; the decrease in correlation with depth is in keeping with slow variation of the subsurface in the near-subsurface region.

Rudy, Donald J.↗

NASA NTRS1987

The behavior of water on Mars

The recent focus in Mars research was in the area of the seasonal behavior of water in the atmosphere, surface, and polar caps, and exchange of water between these reservoirs. Results of recent work is summarized.

Jakosky, Bruce M.↗

NASA NTRS1987

The observed day-to-day variability of Mars water vapor

The diurnal variability of atmospheric water vapor as derived from the Viking MAWD data is discussed. The detection of day to day variability of atmospheric water would be a significant finding since it would place constraints on the nature of surface reservoirs. Unfortunately, the diurnal variability seen by the MAWD experiment is well correlated with the occurrence of dust and/or ice hazes, making it difficult to separate real variations from observational effects. Analysis of the day to day variability of water vapor in the Martian atmosphere suggests that the observations are, at certain locations and seasons, significantly affected by the presence of water-ice hazes. Because such effects are generally limited to specific locations, such as Tharsis, Lunae Planum, and the polar cap edge during the spring, the seasonal and latitudinal trends in water vapor that have been previously reported are not significantly affected.

Jakosky, Bruce M.↗