Background and motivation the upper atmosphere of mars has an important role in mediating atmospheric escape processes. Measuring the composition, density and dynamics of the upper atmosphere is key…

This federal contract award, NNX16AJ42G, was granted by the National Aeronautics and Space Administration (NASA) to the Regents of the University of California, doing business as the University of California, Berkeley. The $100,962.89 grant will fund a two-year study to analyze data from NASA's MAVEN (Mars Atmosphere and Volatile Evolution) mission, with the objective of characterizing the structure and composition of Mars' upper atmosphere and understanding the impact of atmospheric tides on atmospheric composition. The research is highly relevant to the Mars Exploration Program Analysis Group's goal of characterizing the present Martian climate and underlying processes. No set-aside designation was used for this award.

Background and motivation the upper atmosphere of mars has an important role in mediating atmospheric escape processes. Measuring the composition, density and dynamics of the upper atmosphere is key to understanding the role this region plays in the various processes responsible for atmospheric loss and evolution. Pioneering observations by viking 1 and 2 revealed the basic composition of mars atmosphere, however the manner in which this varies in response to upper atmosphere dynamics and energetics has yet to be determined. Maven measures the densities of various atmospheric species (including CO2, AR, O2, N2, CO and o) in mars upper atmosphere over different geographical regions and at varying local times, providing a dataset of atmospheric density and composition that is substantially larger than all those previously obtained combined. These measurements also allow for the important atmospheric parameters of temperatures, pressures, scale heights etc. To be derived. Moreover, repeating full longitudinal coverage of these data enables the identification of planetary-scale structures associated with atmospheric tidal waves (tides). Here we propose a limited, focused, two-year study to analyze the available maven data to first: objective 1: characterize the structure of mars upper atmosphere in terms of densities, scale heights and temperatures over different regions and local times. Then we shall use this dataset to address the following science question: objective 2: what is the compositional change caused by atmospheric tides in mars upper atmosphere? Maven nimgs and iuvs data key density observations of mars upper atmosphere are made both in situ and via remote limb-scans by maven s ngims and iuvs instruments, respectively. The ngims level 2 and iuvs level 1C data obtained from october 2014-may 2015 were publicly available on the planetary data system (PDS) more than 30 days prior to the mdap proposal due date. Owing to maven s changing orbital geometry, these data sample many different altitudes and latitudes, allowing for identification of upper atmosphere composition changes in relation to atmospheric tides at various conditions. Methodology towards objective 1: as the altitude of the periapsis of maven varies with time, and given that atmospheric dynamics is organized more closely around constant pressure surfaces than constant altitude surfaces, we will translate the in situ ngims observations to a constant pressure level to allow for comparison between orbits. This will be done with a simple 1D semi-empirical model that assumes local hydrostatic balance. While this assumption may not be valid 100 % of the time, IT is valid over the spatial scales relevant to atmospheric tides (low integer fractions of the planet s circumference). Towards objective 2: as various species are measured, we will investigate whether the longitudinal structures associated with atmospheric tides remain similar between different species, both heavy and light. The broad vertical range of the data will be used to study the propagation of tides throughout the upper atmosphere. By looking at different vertical levels, and assessing the coherence of these structures across a range of levels, we will be able to examine changes in composition in a region where atmospheric tides are dissipating. By looking at variability with latitude, we will determine how the impact of atmospheric tides depends on background atmospheric conditions. Relevance to NASA mdap we will analyze only maven data that are publicly available on the planetary data system (PDS). This proposed research is highly relevant to the mars data analysis program (mdap) because the research directly addresses goal II of the mars exploration program analysis group (mepag) 2015 goals document, which is to characterize the state of the present climate of mars atmosphere and the underlying processes.