PSI Personnel
Non PSI Personnel: Colin Dundas (USGS), David Hollibaugh Baker (GSFC), James Dickson (Caltech)
Project Description
Motivation: Multiple lines of evidence support the widespread presence of subsurface ice across the high to mid-latitudes of Mars. Modeling efforts along with orbital data have shed light on the distribution and nature of such non-polar ice, and such knowledge is critical to reconstructing the climate history of Mars. However, deconvolving the origins and long-term stability of buried ice at lower latitudes remains a challenge.
Our current understanding of Martian climatology suggests large swaths of non-polar ice were deposited in the recent past (~1 Ma) during higher obliquity excursions. In contrast, many ice-rich assemblages return surface ages orders of magnitude older. The current reservoirs of non-polar ice therefore amount to a Smörgåsbord of relict deposits formed at different times that have undergone varying modification histories. Further compounding our efforts are large uncertainties in paleo-atmospheric conditions including dust content and humidity.
Approach: To unravel the complex history of ice deposition we will undertake a CTX based, near-global morphometric survey of glacial deposits termed Concentric Crater Fill (CCF), which as the name suggests, formed within impact structures. Since craters are ubiquitous features on Mars with well-defined geometries, surveying craters with and without CCF provides an excellent means to examine Martian glacial formation. An added dimension of our work will be exploring the range of textures/features exhibited by the CCF deposits. By systematically studying the distributions of each feature/texture as part of our survey we aim to explore the evolution of CCF deposits and consider whether landforms with distinct origins make up the CCF population.
The relationship between the distribution of glaciers and latitude has of course already been well established, but our approach will provide a more robust means to explore the extent to which insolation can account for the presence and properties of CCF. We will initially test the hypothesis that insolation alone can account for the formation of CCF by systematically exploring the latitudinal dependence of CCF crater onset diameter. Furthermore, we will also assess the onset diameters of craters containing CCF that exhibit azimuthally varying distribution/ orientations. Our detailed morphometric surveys will then be compared to insolation modeling of craters of different scales and under varying orbital parameters.
Implications: Good agreement between the survey and the models will not only further establish the importance of insolation in driving ice deposition on Mars, but it will also potentially provide important information regarding the role of the atmosphere (e.g. by placing constraints on the maximum atmospheric dust content at the time of glacial formation). Alternatively, if deviations from a purely insolation-controlled regime are identified, this will yield new insights into other controls at play. With such a wide range of CCF properties to explore, our comprehensive survey will provide key constraints on the local, regional, and global influences upon glacial formation.