2024 LPL Graduate Student Colloquium Day

Understanding the diversity of carbonates in carbonaceous chondrites through a coordinated microanalysis endeavour

The presence of secondary altered phases such as carbonates and magnetites are used as proxies to the presence of aqueous fluid on asteroids. Initial mineralogical and petrological from a coordinated microanalysis study of a recent fall meteorite, Winchcombe, will be reported. This endeavour will serve to not only provide contextual evidence for degree of hydrothermal alteration but also assist in interpretation of the isotopic data.

Constraining the Martian Planum Boreum Basal Unit Extent and Stratigraphy from Orbital Radar Data

The basal unit (BU) is a sedimentary deposit formed by water ice and fine lithic material buried within Planum Boreum at the north pole of Mars. The BU comprises two subunits, the rupēs and cavi units, and it lies between the Vastitas Borealis interior unit and the North Polar Layered Deposits (NPLD). There are still several unanswered questions about the stratigraphic structure and the characteristics and timing of the events documented within the strata of the BU. Observations from high-resolution images suggest that the rupēs unit accumulated as a dome-shaped deposit. However, we haven’t explored rupēs unit internal stratigraphy, morphology, geometry, and composition in detail, leaving us with a lack of knowledge in the understanding of the evolution of this unit. To target this problem, we take advantage of MARSIS radar data and new data processing analysis techniques that led to the development of the SHARAD 3D data set which provides better visualization of the Planum Boreum’s internal structure. Using Seisware, a software designed for 2D and 3D seismic interpretation we identified the contact between the rupēs and cavi units by following the continuation of the top of the rupēs unit under cavi material and the contact between the basal unit with the NPLD to delineate the morphology of the basal unit in new regions that were previously characterized by excessive clutter in 2D profiles, providing greater detail into the distribution and characteristics of the BU within Planum Boreum.

With radiometric age dates in excess of 4.567 billion years, calcium-aluminum-rich inclusions (CAIs) are widely accepted to be the first solids to have condensed from the solar protoplanetary disk. These assemblages, which are mainly composed of Ca-Al-rich mineral phases, are mm- to cm-sized refractory inclusions that occur in primitive chondritic meteorites. They represent time zero for solar-system origins and point to a high-temperature origin for at least some of the materials that were incorporated into the planets. The transport and large-scale (tens of A.U.) convective mixing of CAIs within the protoplanetary disk subjected them to a wide array of thermodynamic conditions, influencing their mineralogical and isotopic characteristics. Fluffy type-A (FTA) CAIs are believed to have formed via gas-solid condensation from the nebular vapor, though workers have argued that some FTAs experienced post-condensation thermal processing that affected their mineralogy. Thus, another set of CAIs, referred to as fine-grained CAIs (FGIs), were suggested to be more representative of the first condensed objects. Here we identify and analyze FTA and fine-grained CAIs across a range of petrologic type 3 chondrites, meteorites that have largely escaped secondary processing. The CAIs will be probed for detailed composition, phase association(s), and structure from the micron scale down to the atomic level to assess solid-solution and defect chemistry. These experimental data will be combined with thermodynamic modeling to provide new insights into the condensation and thermal history of some of the earliest formed solids in the solar protoplanetary disk.

Carbonate minerals are present in the OSIRIS-REx returned sample. These minerals indicate a history of aqueous alteration at some point in Bennu's parent body. Here, we report initial petrographic observations of carbonate minerals in Bennu samples. 

Diversity of carbonates identified in Bennu samples. The different petrographic context within which these carbonates are found will provide contextual evidence for interpretation of carbon and oxygen isotope analysis.

Reconstructing the Cavi Unit Internal Stratigraphy with the SHARAD 3D Radar Volume

The cavi unit, is one of the two subunits within the basal unit (BU) at the north pole of Mars. It can be found stratigraphically on top of the rupēs unit (also part of the BU) and the Vastitas Borealis interior unit and has an approximate middle to late Amazonian age. The cavi unit is composed of sand-sized material that forms aeolian features cemented and mixed in varying proportions with water ice. The contact with the NPLD on top of the cavi unit presents various configurations, including conformable, erosional, unconformable, gradational, and transgressive. Studies using SHARAD radar data have revealed the internal stratigraphy of fragments of cavi unit. We used the SHARAD 3D data set that was developed from new data processing analysis techniques to gain a better visualization of the Planum Boreum’s internal structure and map the geometry of the cavi unit in unprecedented detail. Using Seisware, we delineated the contacts between the cavi unit and the rupēs unit, Vastitas Borealis interior unit (VBIU), and North Polar Layered Deposits (NPLD), providing detailed insights into the internal stratigraphy of the cavi unit and its contact with the rupēs unit.