Formation of the layered deposits in the Valles Marineris, Mars

Evidence is presented for large standing bodies of water on Mars during past epochs. It is noted that the origin of the horizontally-layered deposits in the Valles Marineris can be best explained by formation in standing bodies of water. These lakes, if they existed, were most likely covered by ice. There are several geologically feasible mechanisms that could have led to formation to thick deposits in ice covered paleolakes in the Valles Marineris. Present data are insufficient to choose conclusively among the various possibilities

Formation of the layered deposits in the Valles Marineris, Mars

Thick sequences of layered deposits are found in the Valles Marineris, which exhibit fine, nearly horizontal layering, and are present as isolated plateaus of what were once more extensive deposits. It was argued that the morphology of the deposits is most consistent with origin in standing bodies of water. The conditions necessary for the existence of ice-covered Martian paleolakes are examined in detail and mechanisms for sediment deposition in them are considered. It was concluded that there are several geologically feasible mechanisms that could have led to the formation of thick deposits in ice-covered paleolakes in the Valles Marineris. Present data are insufficient to choose conclusively among the various possibilities. Several types of data from the Mars Observer mission will be useful in further characterizing the deposits and clarifying the process of their origin. The deposits should be considered important targets for a future Mars sample return mission

Part 2: Sedimentary geology of the Valles, Marineris, Mars and Antarctic dry valley lakes

Detailed mapping of the layered deposits in the Valles Marineris, Mars from high-resolution Viking orbiter images revealed that they from plateaus of rhythmically layered material whose bases are in the lowest elevations of the canyon floors, and whose tops are within a few hundred meters in elevation of the surrounding plateaus. Four hypotheses for the origin of the layered deposits were considered: that they are eolian deposits; that they are remnants of the same material as the canyon walls; that they are explosive volcanic deposits; or that they were deposited in standing bodies of water. There are serious morphologic objections to each of the first three. The deposition of the layered deposits in standing bodies of water best explains their lateral continuity, horizontality, great thickness, rhythmic nature, and stratigraphic relationships with other units within the canyons. The Martian climatic history indicated that any ancient lakes were ice covered. Two methods for transporting sediment through a cover of ice on a martian lake appear to be feasible. Based on the presently available data, along with the theoretical calculations presented, it appears most likely that the layered deposits in the Valles Marineris were laid down in standing bodies of water

Mars rover sample return: An exobiology science scenario

A mission designed to collect and return samples from Mars will provide information regarding its composition, history, and evolution. At the same time, a sample return mission generates a technical challenge. Sophisticated, semi-autonomous, robotic spacecraft systems must be developed in order to carry out complex operations at the surface of a very distant planet. An interdisciplinary effort was conducted to consider how much a Mars mission can be realistically structured to maximize the planetary science return. The focus was to concentrate on a particular set of scientific objectives (exobiology), to determine the instrumentation and analyses required to search for biological signatures, and to evaluate what analyses and decision making can be effectively performed by the rover in order to minimize the overhead of constant communication between Mars and the Earth. Investigations were also begun in the area of machine vision to determine whether layered sedimentary structures can be recognized autonomously, and preliminary results are encouraging

Mars Rover Sample Return: A sample collection and analysis strategy for exobiology

For reasons defined elsewhere it is reasonable to search for biological signatures, both chemical and morphological, of extinct life on Mars. Life on Earth requries the presence of liquid water, therefore, it is important to explore sites on Mars where standing bodies of water may have once existed. Outcrops of layered deposits within the Valles Marineris appear to be ancient lake beds. Because the outcrops are well exposed, relatively shallow core samples would be very informative. The most important biological signature to detect would be organics, microfossils, or larger stromato-like structures, although the presence of cherts, carbonates, clays, and shales would be significant. In spite of the limitations of current robotics and pattern recognition, and the limitations of rover power, computation, Earth communication bandwidth, and time delays, a partial scenario was developed to implement such a scientific investigation. The rover instrumentation and the procedures and decisions and IR spectrometer are described in detail. Preliminary results from a collaborative effort are described, which indicate the rover will be able to autonomously detect stratification, and hence will ease the interpretation burden and lead to greater scientific productivity during the rover's lifetime

Advances in Planetary Geology

The surface of Mars displays a broad range of channel and valley features. There is as great a range in morphology as in scale. Some of the features of Martian geography are examined. Geomorphic mapping, crater counts on selected surfaces, and a detailed study of drainage basins are used to trace the geologic evolution of the Margaritifer Sinus Quandrangle. The layered deposits in the Valles Marineris are described in detail and the geologic processes that could have led to their formation are analyzed

Challenges in Achieving Trajectory-Based Operations

In the past few years much of the global ATM research community has proposed advanced systems based on Trajectory-Based Operations (TBO). The concept of TBO uses four-dimensional aircraft trajectories as the base information for managing safety and capacity. Both the US and European advanced ATM programs call for the sharing of trajectory data across different decision support tools for successful operations. However, the actual integration of TBO systems presents many challenges. Trajectory predictors are built to meet the specific needs of a particular system and are not always compatible with others. Two case studies are presented which examine the challenges of introducing a new concept into two legacy systems in regards to their trajectory prediction software. The first case describes the issues with integrating a new decision support tool with a legacy operational system which overlap in domain space. These tools perform similar functions but are driven by different requirements. The difference in the resulting trajectories can lead to conflicting advisories. The second case looks at integrating this same new tool with a legacy system originally developed as an integrated system, but diverged many years ago. Both cases illustrate how the lack of common architecture concepts for the trajectory predictors added cost and complexity to the integration efforts

One size does not fit all: Preferences for HIV care delivery among out-of-care people living with HIV in the Southeastern United States.

Approximately half of the people with HIV (PWH) in the United States are retained in HIV care and only 57% have achieved viral suppression, due to barriers including transportation access, stigma, poor mental health, substance use, and medical mistrust. Community-based HIV care models have potential to address the diverse needs of patients and to improve retention in care, but their success is contingent on acceptance by patients and key community stakeholders. Recognizing that the preferences of PWH who are out-of-care (PWH-OOC) likely differ from those retained in care, we conducted a mixed-methods study from June 2019 to May 2021 composed of surveys with PWH-OOC (n = 50) and in-depth interviews with key clinic and community stakeholders (n = 41) to examine the relative preference and perceived advantages and disadvantages for six different community-based HIV care models versus the traditional fixed-clinic model. Survey data was analyzed to assess average rank preference for each care model and interview transcripts were thematically coded to examine factors influencing model acceptance. The highest preference for care delivery was via a mobile clinic, followed by community-based peer navigation, primary care clinics, telemedicine, traditional HIV subspeciality clinic, homeless shelter, and drug treatment center. Common factors influencing preference included convenience, accessibility, potential to preserve confidentiality, quality of care assurance, opportunity to develop rapport with their HIV care provider, access to a smart device, and potential to alleviate versus exacerbate HIV stigma. Participants discussed need for integration of care models and for individuals to choose different care models at different times. Providers and patients differed in preference for care model and weighting of relative advantages and disadvantages of each. Findings highlight the need to integrate alternative, community-based care models into the national plan to end the HIV epidemic and to allow for PWH-OOC to choose the model most fitting based on individual circumstances

Perceived advantages and disadvantages of community-based HIV care models across HIV care stakeholders (n = 41 key informants).

Perceived advantages and disadvantages of community-based HIV care models across HIV care stakeholders (n = 41 key informants).</p