Implications of Viking color data for evolution of the Amenthes Region, Mars

In the Eastern Hemisphere of Mars, where the hemispheric dichotomy is not overlain by relatively recent flows from the Tharsis volcanoes, the Mars cratered terrain boundary (CTB) now exists as highly fractured terrain juxtaposed with the smooth plains of the Northern Hemisphere. Based on Mariner 9 photography, the southern cratered terrain in the Amenthes region (0 to 30 deg N, 225 to 270 deg W) is approximately 3 to 4 km above the northern plains, and the transition zone is marked by both broad plateaus and knobby terrain. In the Amenthes Southest quadrangle, in particular, the continuum between large detached plateaus, smaller smooth topped plateaus and knobby hills can be seen. To define the previous position and evolution of the boundary, the distribution of cratered terrain, characteristic landforms (knobby terrain and detached plateaus) have been mapped, as well as structural features across the boundary. Structural mapping indicates that geological formations parallel the boundary in the Eastern Hemisphere with the conclusion that CTB evolution involved normal faulting through extension perpendicular to the boundary

Geologic mapping of northern Lunae Planun, Mars

Lunae Planum is an elevated region east of the Tharsis rise, and ridged plains containing numerous Sacra Dorsa wrinkle ridges, cross-cutting Sacra Fossae grabens, and lobate scarps compose this Martian Plateau. Geologic mapping of the northern Lunae Planum region was undertaken to better understand to emplacement history of the ridge plains, the structural history of deformation, and the periods of fluvial processes that have modified the region. These investigations are important for several reasons: (1) the history of plains emplacement yields information valuable for understanding the evolution of Tharsis volcanism; (2) interpretation of structural deformation has implications on the lithology of the Martian crust; and (3) determining the history and fate of Martian volatiles is dependent upon knowing the periods of outflow activity. A discussion of the findings is presented

Ancient fluvial processes in the equatorial highlands of Mars

Martian highland craters typically lack ejecta deposits, have no noticeable rim, and are flat floored. In addition, crater size frequency distribution curves show that highland craters have depleted populations less than 20 km in diameter. A variety of processes have been suggested to explain these observations including deposition of aeolian or volcanic materials up to the crater rim crests, thermal creep, terrain softening, and mass wasting. However, none of these processes adequately explains both the crater morphology and population distribution. In order to explain both the Martian highland crater morphology and population distribution, a fluvial process is proposed which is capable of removing the loose crater rim material. The resulting effect is to decrease the crater diameter, thereby causing the population curves to bendover. The eroded material is redistributed, burying or partially burying smaller diameter craters before complete erosion. This material may also be deposited into local topographic lows, creating the depositional basins observed. A fluvial process explains both sets of observations: crater morphology and crater population distribution curves

Directory of research projects, 1991. Planetary geology and geophysics program

Information is provided about currently funded scientific research within the Planetary Geology and Geophysics Program. The directory consists of the proposal summary sheet from each proposal funded by the program during fiscal year 1991. Information is provided on the research topic, principal investigator, institution, summary of research objectives, past accomplishments, and proposed investigators

MECA Symposium on Mars: Evolution of its Climate and Atmosphere

The geological, atmospheric, and climatic history of Mars is explored in reviews and reports of recent observational and interpretive investigations. Topics addressed include evidence for a warm wet climate on early Mars, volatiles on Earth and on Mars, CO2 adsorption on palagonite and its implications for Martian regolith partitioning, and the effect of spatial resolution on interpretations of Martian subsurface volatiles. Consideration is given to high resolution observations of rampart craters, ring furrows in highland terrains, the interannual variability of the south polar cap, telescopic observations of the north polar cap and circumpolar clouds, and dynamical modeling of a planetary wave polar warming mechanism

Signs of a vector's adaptive choice: on the evasion of infectious hosts and parasite-induced mortality

Laboratory and field experiments have demonstrated in many cases that malaria vectors do not feed randomly, but show important preferences either for infected or non-infected hosts. These preferences are likely in part shaped by the costs imposed by the parasites on both their vertebrate and dipteran hosts. However, the effect of changes in vector behaviour on actual parasite transmission remains a debated issue. We used the natural associations between a malaria-like parasite Polychromophilus murinus, the bat fly Nycteribia kolenatii and a vertebrate host the Daubenton's bat Myotis daubentonii to test the vector's feeding preference based on the host's infection status using two different approaches: 1) controlled behavioural assays in the laboratory where bat flies could choose between a pair of hosts; 2) natural bat fly abundance data from wild-caught bats, serving as an approximation of realised feeding preference of the bat flies. Hosts with the fewest infectious stages of the parasite were most attractive to the bat flies that did switch in the behavioural assay. In line with the hypothesis of costs imposed by parasites on their vectors, bat flies carrying parasites had higher mortality. However, in wild populations, bat flies were found feeding more based on the bat's body condition, rather than its infection level. Though the absolute frequency of host switches performed by the bat flies during the assays was low, in the context of potential parasite transmission they were extremely high. The decreased survival of infected bat flies suggests that the preference for less infected hosts is an adaptive trait. Nonetheless, other ecological processes ultimately determine the vector's biting rate and thus transmission. Inherent vector preferences therefore play only a marginal role in parasite transmission in the field. The ecological processes rather than preferences per se need to be identified for successful epidemiological predictions

Diet diversity in pastoral and agro-pastoral households in Ugandan rangeland ecosystems

We explore how diet diversity differs with agricultural seasons and between households within pastoral and agro-pastoral livelihood systems, using variety of foods consumed as a less complex proxy indicator of food insecurity than benchmark indicators like anthropometry and serum nutrients. The study was in the central part of the rangelands in Uganda. Seventy nine households were monitored for three seasons, and eight food groups consumed during a 24 hour diet recall period used to create a household diet diversity score (HDDS). Mean HDDS was 3.2, varied significantly with gender, age, livelihood system and season (p < .001, F = 15.04), but not with household size or household head’s education level. Agro-pastoralists exhibited lower mean diet diversity than pastoralists (p < .01, F = 7.84) and among agro-pastoralists, households headed by persons over 65 years were most vulnerable (mean HDDS 2.1). This exploratory study raises issues requiring further investigation to inform policies on nutrition security in the two communities

Scintillation Observations and Response of The Ionosphere to Electrodynamics (SORTIE) Mission First Light

At low and middle latitudes, wave-like plasma perturbations are thought to provide the seeds for larger perturbations that may evolve non-linearly to produce irregularities, which in turn have deleterious effects on HF communications and global positioning systems. Unfortunately, there is currently no comprehensive atlas of measurements describing the global spatial or temporal distribution of wave-like perturbations in the ionosphere. The SORTIE mission, a CubeSat experiment with team members from ASTRA, AFRL, UTD, and Boston College, was designed to help map and further understand the wave-like plasma perturbation distributions throughout the ionosphere. The SORTIE 6U CubeSat sensor package measures key in-situ plasma parameters, and includes an ion velocity meter and a planar Langmuir probe. SORTIE will provide (1) the initial spectrum of wave perturbations which are the starting point for plasma instabilities; (2) measured electric fields which determine the magnitude of the instability growth rate near the region where plasma bubbles are generated; (3) initial observations of irregularities in plasma density which result from plasma instability growth. The SORTIE spacecraft was deployed from the ISS in February 2020 and began data collections shortly after orbit insertion. The measurements are expected to continue for at least a year. In this presentation we present the first light results of the SORTIE mission, as well as reviewing the science objectives and providing an overview of the spacecraft and instruments