We present a thermal model to calculate the total thermal flux for lava flowing in tubes, on the surface, or under shallow water. Once defined, we use the total thermal flux to estimate effusion rates for active flows at Kilauea, Hawaii, on two dates. Input parameters were derived from Landsat Thematic Mapper (TM), field and laboratory measurements. Using these parameters we obtain effusion rates of 1.76B0.57 and 0.78B0.27 m 3 s -1 on 23 July and 11 October 1991, respectively. These rates are corroborated by field measurements of 1.36B0.14 and 0.89B0.09 m 3 s -1 for the same dates (Kauahikaua et al. 1996). Using weather satellite (AVHRR) data of lower spatial resolution, we obtain similar effusion rates for an additional 26 dates between the two TM-derived measurements. We assume that, although total effusion rates at the source declined over the period, the shut down of the ocean entry meant that effusion rates for the surface flows alone remained stable. Such synergetic use of remotely sensed data provides measurements that can (a) contribute to monitoring flow-field evolution, and (b) provide reliable numerical data for input into rheological and thermal models. We look forward to being able to produce estimates for effusion rates using data from high-spatial-resolution sensors in the earth observing system (EOS) era, such as Landsat 7, the hyperspectral imager, the advanced spaceborne thermal emission spectrometer, and the advanced land imager.

On the basis of morphology of the exterior deposits of 1558 fresh Martian impact craters, 6 crater types are defined, and the incidence of each crater type on 10 different geological units is documented. It is shown that several crater types are preferentially associated with specific target materials: radial textured craters are found primarily on Tharsis and Elysium lavas, a type of crater here called 'pancake craters' on fractured terrain, old lavas, and channel materials. The occurrence of secondary craters is also strongly terrain dependent. Three times as many craters on young lavas have secondary craters as compared to those craters on ridged and cratered plains materials, and 10 times as many have secondary craters when compared to primary craters on ancient terrain materials. The maximum radial extent of fluidized ejecta blankets is demonstrated to be a function of both crater altitude and latitude. The most extensive ejecta units are found at low altitudes and high latitudes, while the least mobile ejecta is located at high elevations and close to the equator. Only pancake craters exhibit any pronounced latitudinal variation in their distribution. These craters are almost exclusively located poleward of latitudes 40øN and 40øS. For the majority of the sample craters (N = 1333), there is no such systematic latitudinal variation in crater occurrence.

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[1] The Thermal Emission Imaging System (THEMIS) visible (VIS) images provide new insight into the nature and development of the unique ejecta deposits of Martian craters. This study focuses on double-layered ejecta (DLE) craters. To date, over 100 DLE craters have been examined using mainly THEMIS VIS data. Our observations suggest that emplacement of DLE crater ejecta occurred in two stages, with the inner ejecta layer emplaced similar to single-layered ejecta (SLE) crater ejecta. This may have involved both ballistic and flow processes. In contrast, the outer ejecta layer of DLE craters appears to have been emplaced through the high-velocity outflow of materials from tornadic winds generated by the advancing ejecta curtain or base surge. Remarkably, DLE craters lack secondary craters, which suggests that the large ejecta blocks that normally produce such craters may have either been entrained and/or crushed by these winds or fragmented as a result of the presence of water in the target materials. These observations suggest that volatiles (either trapped in the subsurface or in the atmosphere) have played a key role in the emplacement of the ejecta of DLE craters and leaves open the question as to what role volatiles play in the emplacement of ejecta of other types of fluidized ejecta craters (i.e., SLE and MLE craters). Because DLE craters are found in many different regions of Mars, often in close proximity to other types of craters, conditions (e.g., atmospheric density) that produce DLE craters must fluctuate or the Martian crust must be unexpectedly heterogeneous (laterally and vertically). While the degree of heterogeneity has yet to be recognized, recent suggestions about possible Martian climate change raises the possibility of impact into target materials that are periodically wet or that a significantly higher atmospheric pressure may be periodically present.