Date of Award

2024

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Biological and Environmental Sciences

Specialization

Environmental and Earth Sciences

Department

Geosciences

First Advisor

Dawn Caradace

Abstract

Fundamental questions within Earth and Planetary Sciences, “Are we alone?” Remains chief among these major questions driving many areas of scientific research. The quest for life beyond Earth is still in its early stages and we are at a pivotal moment in this exploration, having discovered thousands of planets within our Milky Way galaxy and are searching within our own space neighborhood within the Solar System, from Mars to Enceladus, and beyond. Earth is the key planet to understanding the possibility of life elsewhere in the Solar System and beyond, in the many exoplanets that have been discovered that are similar to Earth. It is currently not known whether life has existed beyond Earth and Earth remains the only planet so far that is known to harbor life.

Planetary habitability, a planetary body’s ability to harbor life, is intimately connected to its geology, which can provide the necessary parameters to facilitate the proliferation of biology. “Does Mars Harbor environments suitable for biological processes; does Mars host life?” Terrestrial planets, like Earth and Mars, and other rocky worlds, can serve as massive chemical reservoirs to drive biological processes. Mars, the fourth rock from the Sun, is currently being explored for signs of biological activity and this exploration is largely within the surface and near-surface environments. Identifying how geology can drive life on Earth within similar environments, planetary analogs, can help constrain and better understand where to look to answer these broad questions. However, not all planetary analogs on Earth have been fully explored and linked to other terrestrial and rocky worlds.

Terrestrial planet lithospheres, such as the crust and mantle of both the Earth and Mars, are largely composed of mafic (crust) and ultramafic (mantle) rock units, with mineral assemblages that are dominated by olivine and pyroxene. When these mineralogies are exposed to water they experience metasomatism, and at near-surface geophysical conditions undergo serpentinization. Serpentinization, the mineral transformation from olivine- and pyroxene-rich protoliths to assemblages dominated by serpentine group minerals and secondary minerals is the most critical metamorphic hydration reaction in driving biological processes on Earth, and likely in the Solar System. These secondary minerals include magnetite (Fe3O4), talc, hydroxides, diverse clays, and often carbonates are also linked to biological processes in these environments.

The presence of these minerals in both terrestrial and extraterrestrial environments on rocky planets creates exciting opportunities for research into serpentinizing systems and their wider implications. I study significant terrestrial analogs sites of ultramafic systems found within the Coast Range Ophiolite in California, the Pine Hill Peridotite in Maine, and the Cumberlandite in Rhode Island using mineralogy, geochemistry, and magnetics. I connect and compare these Earth-based investigations and observations to data available for current sites on Mars using, new interdisciplinary modeling. Ophiolite units provide a window of observation into planetary mantles, which consist of primary minerals that undergo metasomatic reactions, chiefly serpentinization, that have major implications for both geobiology and astrobiology. Work completed here focuses on ultramafic rocks within a heterogenous section of the Coast Range Ophiolite to assess the extent of serpentinization by integrating magnetic, mineralogical, and geochemical data. The research aims to evaluate (1) the formation of magnetic minerals and the progression of serpentinization along with related fluid chemistry and (2) the sequence of serpentinization events and the broader tectonic history of the serpentinites, as interpreted from their geochemical signatures. In many thin sections, the dominant mineral phases are serpentine polymorphs of lizardite and antigorite. Some fibrous chrysotile has been identified as a minor component, based on texture and habit. Euhedral opaque minerals appear to be largely magnetite; however, many samples exhibit opaque minerals that exhibit a brown color tint. I performed a magnetic survey over the serpentinizing landscape of the Coast Range Ophiolite at the McLaughlin Research Reserve, in particular three outcrops and the locations of the CROMO groundwater monitoring wells. I employed both the KT-10 magnetic susceptibility meter and the G-864 cesium magnetometer to obtain magnetic property surveys of the sites of interest. Magnetic susceptibility observations ranged from 0 to 41.2*10E-3 across these outcrops. Further, superparamagnetic, ferromagnetic, and diamagnetic hysteresis were observed. Magnetometry surveys indicate that the magnetic subsurface of the Coast Range Ophiolite at the McLaughlin Research Reserve is heterogeneous, and that the concentrations of magnetite vary widely across the landscape.

I also examine two accessible ultramafic rock weathering sites in New England to contribute to the broader understanding of ultramafic rocks in diverse environments. I integrate magnetometry, mineralogy, and geochemistry to better define lithologic factors influencing serpentinization and magnetite production, as well as subsequent weathering stages, with potential applications for extraterrestrial serpentinization processes. The dominant minerals in these samples are euhedral opaque minerals, primarily identified as magnetite, which are common. However, some samples contain opaque minerals with a brownish tint. The common opaque minerals, typically dark in color, belong to the spinel group (A2+B23+O4), which could include magnetite (Fe3O4), chromite (FeCr2O4), hematite (Fe2O3), or possibly goethite (FeO(OH)). Titanomagnetites (Fe2TiO4) are also a plausible identification. The dark appearance suggests that most of these minerals are likely titanomagnetites or titanohematite solid solutions, rather than hematite or ilmenite, which would normally display a brownish hue. Olivine is the second most abundant mineral, exhibiting varying levels of alteration to serpentine group minerals. Minor plagioclase has also been identified, along with olivine grains altering to iddingsite, a mixture of residual olivine, various iron oxyhydroxides/oxides, and phyllosilicates. For the main outcrop of Cumberlandite, our observations of the volume magnetic susceptibility were between approximately 315.67*10E-3 to 907.00*10E-3 SI. Magnetic susceptibility measurements of the Pine Hill Peridotite Quarry Face Surface Sites were at the maximum 66.9*10E-3 SI with the minimum value is 13.9*10E-3 SI, and the average is approximately 45.36*10E-3 SI. The magnetometry surveys of both of these ultramafic systems indicates a diverse magnetic subsurface that likely has multiple zones of alteration and weathering fronts, and with the magnetization model-coupled to geochemical modeling, it is shown that these ultramafic systems are within range of magnetization of Mars locations.

I present new evidence supporting the existence of habitable microenvironments in the near-subsurface of Mars, specifically hosted within Fe- and Mg-rich rock formations. Additionally, I provide a list of minerals that can act as indicators of specific water-rock interactions in recent paleohabitats, which could be the focus of future studies. Using a thermodynamic modeling approach (without suppressing any phases) and Geochemist’s Workbench Ver. 12.0, I modeled reactions between published Martian meteorite compositions, Jezero Crater igneous rocks, and plausible Martian waters (saline, alkaline waters). The resulting mineral products, dominated by phyllosilicates like serpentine-group minerals, varied across reaction paths and included important indicator minerals. These products exhibited differences in physicochemical properties such as pH, Eh, and conductivity, along with major ion activities and gas fugacities, which have implications for the ecological potential of these environments. Using Gibbs Free Energy Minimization to evaluate microbial habitability in subsurface groundwater systems, it was found that models based on the Chassigny meteorite produced the highest H2 fugacity, while those using the "Rosy Red" soil-water analog achieved the highest sustained CH4 fugacity (with peak values seen using ALH 77005 as the reactant). Overall, the Chassigny meteorite protoliths provided the most favorable results in terms of Gibbs Free Energy, from an astrobiological perspective. The presence of serpentine and saponite, both of which have been observed via CRISM spectral data, is particularly important, as their formation through serpentinization suggests the potential for recent H2 and CH4 production, providing energy sources capable of supporting microbial life. I offer a list of index minerals to serve as diagnostic tools for paleo water-rock interactions that could have sustained microbial life in Mars’ recent geological past, and recommend these minerals be used as criteria for selecting future astrobiological study sites.

Download

Available for download on Friday, January 15, 2027

Share

COinS