FRACTURE NETWORKS ON MARS: Preservation of Surface and Subsurface Environments at Mawrth Vallis Student Author Mentor Phoebe Kinzelman is a rising Briony Horgan is an assistant senior at Purdue University professor in the Department majoring in planetary science of Earth, Atmospheric, and with a minor in global liberal Planetary Sciences at Purdue arts studies. She is especially University. She received her BS interested in planetary geology in physics from Oregon State and public science policy and University in 2005 and her worked as a space policy intern PhD in astronomy and space at the National Academy of Sciences in Washington, sciences from Cornell University in 2010, then was D.C., for the summer of 2019. Kinzelman currently an Exploration Postdoctoral Fellow at Arizona State works as an ambassador for both the College of University until joining EAPS in 2014. Horgan’s Science and the Department of Earth, Atmospheric, research program uses data from NASA satellites and and Planetary Sciences (EAPS) in addition to rovers, along with lab and fieldwork back on Earth, undergraduate research and enjoys rock climbing in to understand the surface processes that have shaped her spare time. In the future, she hopes to become an Mars and the moon. She is particularly interested astronaut on Mars. in using mineralogy to investigate weathering and past surface environments on Mars as well as volcanic, sedimentary, and impact processes on both planets. Horgan is a participating scientist on NASA’s Mars Science Laboratory rover mission and a coinvestigator on NASA’s upcoming Mars 2020 rover mission, the first step toward the Mars sample return mission. 42 Journal of Purdue Undergraduate Research: Volume 9, Fall 2019 http://dx.doi.org/https://doi.org/10.5703/1288284316931 INTRODUCTION Abstract Modern Mars is cold and hyperarid, but there are Mawrth Vallis is an outfl ow channel on Mars abundant physical signs of past fl owing water, that cuts through some of the planet’s most such as valleys, deltas, outfl ow channels, and lake ancient terrains, which contain many diff erent sediments. One such sign of fl uvial activity is types of fractures. The ExoMars rover mission Mawrth Vallis, an outfl ow channel that cuts through will search for biosignatures on Mars, and some of the most ancient terrains on Mars. This this site was proposed as one of the two kind of channel formation most likely occurred fi nal candidate landing sites for the rover. A during the late Noachian era due to rare fl ooding biosignature is any object that shows evidence episodes (e.g., Carr & Head, 2010). As shown in of past or present life. Fracture networks are Figure 1, the channel is situated on the dichotomy a high priority for the mission because they boundary between the Martian highlands and might contain minerals precipitated by fl uid lowlands at ~25°N, 20°W (Bishop et al., 2008). The interaction, and these minerals could trap area around Mawrth Vallis is composed of a thick and preserve biosignatures, critical for our sequence of light-toned sedimentary layers dating understanding of ancient processes. In this from the Noachian era (~3.7 billion to 4.0 billion project, we seek to determine the distribution years ago). Orbital spectroscopy has shown that and origin of large fractures in the Mawrth these layers are clay rich, with Al-phyllosilicates and Vallis region. The Java Mission-Planning hydrated silica layered on top of Fe/Mg smectites and Analysis for Remote Sensing (JMARS) and overlaid by a partially eroded dark capping program and satellite images from the High unit (Loizeau et al., 2015). Most of the layered clay Resolution Imaging Science Experiment deposits in the area are over 200 meters thick. The (HiRISE) orbiter were both used to map clays appear to be inconsistent with hydrothermal fractures at Mawrth Vallis. Based on similar activity or groundwater, and regional extent and fractures on Earth, we have interpreted that lack of topographic infl uence suggest a surface all of the large fractures formed due to water weathering origin for the clays (Noe Dobrea et al., loss, but a rectangular shape suggests that the 2010). This layering of Al-phyllosilicates and Fe/Mg fractures formed when rocks contracted at the smectites can be attributed to a semiarid climate and surface, while curvilinear fractures formed weathering by rain that produced the paleosols seen in subaqueous sediments. After contraction, in the area today (Carter, Loizeau, Mangold, Poulet, the fractures were fi lled in by precipitated & Bibring, 2015). minerals, causing them to appear bright. These fractures on Mars imply some sort of fl uid These ancient Martian rocks were likely formed in fl ow, and precipitated minerals in the fractures aqueous environments that were habitable for ancient may preserve evidence of the environment and microbial life. Bishop et al. (2008, 2013) showed ancient life that once existed in that area. that an Fe2+ mineral layer appears at the areas of transition from Al-phyllosilicates to Fe/Mg smectites. Kinzelman, P. (2019). Fracture networks on On Earth, Fe2+ typically exists in sedimentary rocks Mars: Preservation of surface and subsurface environments at Mawrth Vallis. Journal of Networks on Mars Fracture Purdue Undergraduate Research, 9, 42–48. https://doi.org/10.5703/1288284316931 Keywords Mawrth Vallis, Mars, fractures, biosignatures, Al-phyllosilicates and hydrated silica, Fe/Mg smectites, fl uvial activity Figure 1. Global MOLA map of Mars with Mawrth Vallis denoted by a white star. 43 because it precipitated out of reducing fluids (Bishop in the clay layers at Mawrth are a high priority for et al., 2008). The presence of strong redox gradients this mission because they might contain minerals in the subsurface is a key discovery in the study of precipitated by fluid interaction, and these minerals the history of Mawrth Vallis, as it could indicate a could trap and preserve biosignatures, critical habitable environment with significant microbial for our understanding of ancient processes and energy sources (Horgan, Rice, Farrand, Sheldon, & environmental conditions of the planet. However, no Bishop, 2015). In addition, on Earth, organic material map currently exists of the distribution of fractures and/or microbes are often necessary to reduce Fe, in the proposed Mawrth Vallis landing ellipse for the and paleosols have a high preservation potential ExoMars rover. for this kind of material (Hays et al., 2017). Thus, the clays at Mawrth Vallis have the potential of The objective of our study was to map the preserving biosignatures from ancient microbial life. distribution and morphologic properties of fractures within a region of Mawrth Vallis as outlined by two The clay-rich terrain in Mawrth Vallis also hosts a potential landing ellipses for the ExoMars rover. One diverse suite of large fractures and fracture networks, ellipse was centered at 341.567E, 22.372N and the some of which are further indications of subsurface other at 342.055E, 22.156N. We used HiRISE orbital fluid flow in the area. Loizeau et al. (2015) identified imagery to look for fractures and fracture patterns, four different types of fractures at Mawrth Vallis: and the physical features of each fracture were small and thin, thick, short, and parallel fractures. analyzed once it was recorded. We identified three According to Loizeau et al. (2015), fracturing of the key fracture morphologies within the mapping area: clay unit occurred after the clay had lithified into rectangular, irregular (linear and curvilinear), and solid rock. This process broke the newly formed rock halo-bounded fractures. into blocks, and then groundwater flowed through the fractures and left behind precipitated minerals. We hypothesize that the variety of fracture “Halo-bounded” fractures (a subset of thick and short morphologies present at Mawrth Vallis represents fractures) were created in this way. Loizeau et al. different formation environments, and any (2015) also found that the Al clay unit holds the most precipitated minerals in the fractures could be potential for preserving biosignatures because it is accessed by a future rover mission such as ExoMars protectively covered by the capping unit and has not in the search for preserved Martian biosignatures. been subject to erosional surface processes. Thus, the earlier discovery of at least two watery episodes MATERIALS AND METHODS (surface water that lithified the clay, then subsurface water that filled fractures with precipitated minerals) This research project began in July 2018 and leaves the possibility of multiple areas for trapped eventually extended into the fall semester. Three biosignatures. However, the depth and environment undergraduate students (Phoebe Kinzelman, (surface vs. subsurface) of the large fractures in the Jonathan Forss, and Madison Van Buskirk) along Mawrth Vallis region are not well understood. with faculty adviser Professor Briony Horgan were contributors to this project. Each student was The ExoMars program is a European Space Agency responsible for mapping a third of the total outlined project tasked with investigating the possibility of landing ellipses and recording all mapped data into a past microbial life on Mars. ExoMars consists of fracture database. The JMARS software application the Schiaparelli lander, a Trace Gas Orbiter (both was used to view images, create maps, and build launched in 2016), and a rover that will launch in the fracture database. JMARS is an open-source 2020. The Trace Gas Orbiter will analyze gases geospatial information system created at Arizona in the Martian atmosphere, and Schiaparelli was State University and designed to assist researchers meant to test landing sequences on the planet but has with mission planning and data analysis on the since crashed. The ExoMars rover, now colloquially surface of other planets. The information system named after Rosalind Franklin, will visit different contains a wealth of Martian orbiter data and maps sites that are important to the investigation for use in a variety of scientific research projects.