Placing Terrestrial Constraints on Past Mars Lava Flow Eruption Conditions
National Aeronautics and Space Administration Solar System Workings Program
Subaward to PSI from University of Pittsburgh
PI: Michael Ramsey (University of Pittsburgh)
Project Description
The surface of Mars is composed primarily of igneous rocks derived from extrusive volcanism, which has been a dominant geologic process throughout the history of the planet. Understanding the volcanic evolution and specific emplacement conditions of lava flows at Martian volcanoes is critical for determining the timing and duration of heat sources below these centers. However, detailed analysis and modeling of individual lava flows has been hindered in the past by the low spatial resolution of older orbital instruments. With higher resolution data from THEMIS, CTX and HiRISE and developments in lava flow modeling based on observations of active terrestrial volcanoes, we now have the ability to examine changes in morphology, petrology and emplacement conditions for individual Martian lava flows. This study is designed to answer specific volcanological questions regarding flow fields on Mars, including: 1) How can terrestrial flow propagation models be validated for Mars applications?; 2) What were the eruption conditions that produced Martian lava flows and did they vary across a given flow field and over time?; 3) Do Martian flows exhibit differences in modeled down-flow viscosity and crystal content, are these detected using other datasets, and can rheological parameters be associated with specific aspects of flow morphology?; and 4) What do the results of modeling volcanic processes imply regarding the larger volcano-tectonic evolution of the Tharsis region?
The overarching goal of the proposed work is to first test and refine well-developed terrestrial discharge rate and flow propagation models (developed for active flows) at a terrestrial analog site the 2012-2013 Tolbachik eruption in Russia. This eruption was the largest and most thermally intense flow field-forming volcanic event in the past fifty years. As such, it produced a terrestrial flow field that is perhaps the most similar to those seen in the Tharsis region. Furthermore, an unprecedented amount of satellite data coverage was acquired during the Tolbachik eruption leading to the ability to test the accuracy of thermorheologic models of discharge rate versus flow size/direction. The second phase of the study will then apply these refined models to extract eruption rates and examine down-flow variations of individual lava flows in the southwest flow field of Arsia Mons. This unique terrestrial eruption and dataset should allow us, for the first time, to connect planetary flow surface morphology to exact eruption conditions by constraining the thermorheologic models of flow formation. In a preliminary test of this approach, an individual flow in the Arsia Mons flow field was modeled as having a predicted effusion rate of 2600 m3/s, an initial velocity of 4-5 m/s, and a down-flow increase in crystal content of 23%. However, the accuracy of these results is not known and will be greatly improved using the terrestrial dataset and flow modeling.
