2015 Annual Science Report
Massachusetts Institute of Technology Reporting | JAN 2015 – DEC 2015
The MSL Mission to Mars
The overall scientific goal of the Mars Science Laboratory (MSL) mission is to explore and quantitatively assess a local region on Mars’ surface as a potential habitat for life, past or present. The MSL rover carries ten scientific instruments and a sample acquisition, processing, and distribution system. The various payload elements work together to detect and study potential sampling targets with remote and in situ measurements; acquires samples of rock, soil, and atmosphere and analyze them in onboard analytical instruments; and to observe the environment around the rover. MSL has been investigating a site that shows clear evidence for ancient aqueous processes based on orbital and ground-based data and has been undertaking a search for past and present habitable environments.
A long-standing goal of Mars environmental studies has been to understand the role of water throughout its geologic history. The presence of water is a strong indicator of potential habitability as well as of formerly different climatic conditions. Prior to studies by the Mars Exploration Rovers, most studies of water-related processes had been based on analysis of geomorphic attributes. However, we can now examine the record of past surface processes, including the role of water, through sedimentologic studies of the stratigraphic record of Mars. Many processes that operate at a planetary surface have the potential to create a record of sedimentary rocks. Sedimentary rocks can provide clues that allow past environmental conditions to be reconstructed. Therefore, the detection of sediment transport by water and wind in ancient sedimentary layers is important, because it provides insight into past climatic regimes and potential habitability.
Curiosity successfully completed its primary mission in 2014, and has had continued success in its extended mission. In the first years of operations, Curiosity traversed over stream-rounded pebbles to a site where mud accumulated from an ancient lake. The mudstones drilled and analyzed yielded evidence for long-lived fresh water, the major elemental building blocks of life, and a source of chemical energy capable of sustaining microbial life. Curiosity continues its traverse up the foothills of Mt. Sharp to study ancient environmental transitions and to identify habitable environments capable of preserving organic compounds.
At Caltech, John Grotzinger and his lab group have been working on landed operations since Curiosity touched down on Mars in 2012.
Jennifer Shechet’s Research:
Jen has been working landed operations as a Surface Properties Scientist (SPS), Keeper of the Plan (KOP), and mission Documentarian since the rover landed. Her research focuses on mapping terrain from orbit and correlating that to ground based observations in order to choose the safest traverse path with regards to wheel wear. We first noticed wheel damage in late 2013, so the Project set up a team of scientists and engineers to understand the terrain types and what causes wheel punctures in an attempt to pick routes that would not damage the wheels as severely, and be least likely to open up punctures that were already there. We mapped the route already driven and future terrain using HiRISE images (25 cm/pixel resolution) from orbit, along with Mastcams, Navcams, and Hazcam imagery from the rover to assess the locations where damage is thought to occur.
Kirsten Siebach’s Research:
Kirsten has been working with the database of sedimentary rocks analyzed by the Mars Science Laboratory using both the Alpha Particle X-Ray Spectrometer (APXS) for bulk compositional information and the Mars Hand Lens Imager (MAHLI) for high-resolution surface textures. Combining these two datasets has shown that there are significant compositional trends with sedimentary grain size, indicating that hydrodynamic sorting processes during sediment transport on Mars play a large role in defining the range of compositions of sedimentary rocks within the Bradbury group on Aeolus Palus (the floor of Gale Crater). Modeling the mineralogy of the different samples has further indicated that the igneous sources for the Aeolus Palus rocks are slightly more evolved and alkaline than average Mars, but there is not significant igneous variability within the primary source area except for a distinctive high-potassium source that contributed to select sedimentary intervals within Aeolus Palus. She is also using this database of compositional and textural information to begin to understand the Mount Sharp group rocks, which show very different diagenetic trends.
Nathan Stein’s research:
Nathan is studying the nature of sedimentary units surrounding the Curiosity rover to infer their deposition and subsequent evolution. To this end he is a participating student scientist on the Mars Science Laboratory (MSL) team, and works with the team to select targets and analyze downlinked data. Additionally he uses orbital data to provide context for in-situ rover observations. Nathan is also starting projects on sand grain analysis of the Bagnold Dunes using high-resolution images from Curiosity and correlating surface morphology with spectral features on the dwarf planet Ceres. Past work includes the development of image processing techniques to improve the spatial and spectral resolution of Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) along-track oversampled observations, spectral unmixing techniques for the derivation of compositional endmembers from Mars Exploration Rover (MER) and MSL Alpha Particle X-Ray Spectrometer (APXS) observations, and computational modeling of MSL mobility and terramechanics.
Jessica Watkins’ research:
Jessica’s current research focuses on using orbital and rover topographic and image data to investigate the stratigraphy, geology, and geomorphology of Mars. The goal is to use fundamental principles of processes on Earth to inform study of the evolution of various processes on the surface of Mars. As a collaborating member of the Mars Science Laboratory Science Team, she is particularly interested in characterizing and quantifying the stratigraphic context within Gale crater in order to reconstruct its depositional and erosional history. She participates in daily planning of rover activities, and analyzes rover data to ground-truth orbital observations.She is also interested in exploring the role of fractures as conduits for fluid flow, both in Gale crater and elsewhere on Mars, through image analysis and laboratory testing of mechanical analogs.
Ted Present’s research:
Ted looked at the sedimentology, petrography, and geochemistry of tube-shaped pyrite structures in the ~1.47Ga Newland Formation to test the hypotheses that they are extraordinarly early fossilized macroscopic organisms, or the result of abiotic hydrothermal accretion. We conclude the latter, and use the mineralogy and sulfur isotope geochemistry to constrain paleoenvironmental conditions such as Mesoproterozoic seawater sulfate composition (>2mM, ~10permil).
Daven Quinn’s research:
Daven is a structural geologist with an interest in targeting key regions that bear on the paleoenvironment of Earth and Mars. He is working in the Zebra Nappe of the Naukluft Nappe Complex in south-central Namibia. The Naukluft is a major plateau and tectonic klippe, comprising an outlying remnant of the Damara orogenic belt atop the Kalahari Craton and foreland basin.
The Zebra Nappe contains a singular carbonate/clastic stratigraphy which is likely Ediacaran in age, potentially bridging well-studied autochthonous sections of Marinoan cap carbonates and a Cambrian-boundary foreland basin (the Nama group). Though folded and faulted due to thrust tectonics, this stratigraphy is of high value to understanding the Neoproterozoic paleoenvironment. His project consists of mapping and measuring sections of the Zebra Nappe in order to record its structural architecture and stratigraphy.
At UC Davis, Dawn Sumner and her team have been also been working on landed operations since Curiosity touched down on Mars in 2012.
Francis Rivera-Hernandez (graduate student) has made significant progress developing facies models for sedimentation in ice covered lakes to help constrain our understanding of lacustrine environments on Mars. Specifically, she is developing criteria to determine whether or not ancient lakes were ice covered. This knowledge is critically important for reconstructing ancient climates. For example, if the ancient lakes in Gale Crater were covered in ice, the atmospheric temperature and density could have been much lower than if they were persistently open water lakes.
In 2015, much of Frances’ work focused on ice-covered Lake Joyce, Antarctica. During the reporting period, she described 14 cores of lake sediment; observed and collected sediment samples from the surface of the ice; and retrieved sediment traps deployed in 2014 that show both sand and mud accumulation patterns. She has discovered several processes that result in isolated sand grain deposition through the ice, as well as sorting by grain color (and thus composition). As Frances compiles and quantifies her results, she will develop a model for deposition that can and will be compared to observations of lacustrine sediments by the Curiosity rover. Additional analog work by the Sumner Lab is reported under a separate heading.
At Brown University, Ralph Milliken and his team have been also been working on landed operations since Curiosity touched down on Mars in 2012. Their research has focussed on organic spectroscopy as an aid to Mars exploration and is reported separately.
At MIT, Roger Summons and members of his team have been working on analog studies that are specifically aimed at validating the organic matter detection data gathered by the SAM instrument. For examples, experiments conducted by Kristen Miller, using a SAM-like instrument set-up at MIT showed that the hydrocarbon trap aboard SAM could not be responsible for the high abundances of chlorobenzene detected in the Cumberland mudstone. The exact precursor of this chlorobenzene is not identifiable but must be an organic compound indigenous to Mars.