Planetary Science Laboratory
Geology & Geophysics, LSU
Suniti Karunatillake
Assistant Professor
Louisiana State University
E235 Howe-Russell BLDG.
Geology and Geophysics
Louisiana State University
Baton Rouge, LA 70803
Email: wk43@cornell.edu
Past
Assistant Professor
Rider University
Postdoctoral Researcher
SUNY-Stony Brook Research Foundation
Graduate Research Assistant
Cornell University
Education
Cornell University
Cornell University
Wabash College
Science Themes
My dream of discovering life beyond Earth motivates me to explore Mars across several areas of planetary geoscience, with an emphasis on synthesizing in situ and regional observations to constrain geologic evolution, sedimentary processes, and aqueous alteration at the crust-atmosphere interface.
Longer-term, I hope to develop collaborations across exobiology and Europan investigations.
Chemical Provinces
Orbital missions yield mineralogically extensive data with insight into the evolution and surface processes of Mars. Chemical provinces provide a regional and decimeter depth context to these hundred-micron deep local observations.
This established regions of unusual chemical composition relative to average Mars primarily on the basis of Ca, Cl, Fe, H, K, Si, and Th. One overlaps with a radar Stealth region on Mars, with remarkable enrichment in Cl and depletion in Fe and Si relative to average Mars. Surface dust observed at the two rover sites mixed with and indurated by Ca/Mg-bearing sulfate salts would be a reasonable chemical and physical analog to meter-scale depths. The bulk dust component may be an air fall deposit of compositionally uniform dust as observed in situ. Sulfates may have been produced by low-temperature, regional-scale activity of ground ice–driven brine and/or regional-scale deposition of acidified H2O snowfall.
Martian Soil
Unlike soil on Earth, planetary soil remains poorly defined and described. However, on tectonically less active Mars, soil becomes the repository of processes between the atmosphere and crust over Ga time scales.
Three of my projects approach the question of Martian soil by evaluating hydration of bulk soil, potential for halogens to volatilize, and compositional trends by grain size. The latter expands more broadly into the sedimentology of Martian soil, while the first contributes to the exobiology potential in the Southern hemisphere of Mars.
Geological Evolution Models
Bulk compositional characterization can serve as a window to the geology of a planet. Mars provides an ideal case study in this, given the ready availability of bulk chemistry in the mid-to-low latitudes derived from neutron and gamma spectroscopy.
The geologic evolution of Mars can be considered in the context of chemical trends on the planet's shallow subsurface. The regolith may bear evidence of igneous processes despite impact gardening and the weathering regime on a planet across geologic time. Three examples highlight this theme. The first, on addressing the provenance of a swath of the northern lowlands of Mars, which bear a unique infrared spectral signature, named "surface type 2." Our work on this helped to show that a compositionally distinct mantle source, perhaps related to the magma ocean overturn model by Elkins-Tanton et al. [2005], may have contributed igneous rocks to this area. This contrasted with earlier interpretations suggesting basaltic andesites, which would have implied crustal recycling processes. Prior models on weathered basalts as contributing the infrared signature were also challenged by the chemical characterization. Elsewhere on Mars, the work by graduate student David Susko [2017] convolves a unique chemical signature of K and Th depletion in the southeastern lava fields of the Elysium volcanic province of Mars with crater-based ages and geomorphology. As a key outcome, this work demonstrated compositional variability of extrusive rocks for a single volcanic province on Mars at regional scale, advancing prior insight on variations across different volcanic provinces and local scale observations. The utility of regional chemistry was likewise demonstrated by graduate student Hood et al.'s [2016] work, reveavling that a continental-scale landslide model proposed for the geomorphology of the eastern area of Tharsis is not supported by compositional trends in geochemistry or mineralogy. Instead, this area, consisting of Syria, Solis, and Thaumasia planae, shows that the igneous rocks vary in composition by geologic age, perhaps coupled to mantle evolution.
GIS statistics, numerical methods, photoanalysis.
Fundamentally, the rigor of models developed for bulk and surface processes on planets hinge upon the suitability and accuracy of underlying compositional analyses. The limited compositional data of most planetary surfaces, compared to Earth, magnifies the importance of analytical methods, especially in synthesizing different datasets.
Two projects on numerical methods and two others on photoanalysis relate to my interest in this promising area of planetary data analyses. In one [2011], we focus on the spatial statistical methods that are best used with global datasets. Mars serves as the case study. Specifically, this identifies the primary statistical methods to use in answered five general queries that arise in planetary research: (1) Can we reject, to a desired degree of confidence, the null hypothesis that the data within one region are from the same distribution as the data within another? (2) How does the distribution of the attribute in one region compare qualitatively with that in another? (3) Can we reject, to a desired degree of confidence, the null hypothesis that the mean value of an attribute within one region is identical to that within another? (4) Is an attribute heterogeneous within a given region? (5) How are the solutions to the preceding questions altered when the ratio of two attributes is being investigated? By using a case-study approach, the associated project also provides the a recipe for future analyses with martian and other planetary data. The second project [2012] targets the specific case of applying hierarchical multivariate regression with spatially autocorrelated data. This is supported by method and fit diagnostics. Possible applications include chemical and mienralogic data from the MESSENGER missiona t Mercury, and Dawn at Vesta and Ceres. Data collected so far at Gale Crater form the Curiosity Mission could also be analyzed with these methods, complementing principal and independent component analyses.
The two projects on photonalyses approach the challenges unique to characterizing soil on other planets. In contrast to Earth, where soils are often physically accessible, soil analyses on Mars and other planets must often rely on images for granulometry. Our work, first developed a semi-automated algorithm [2013], coded in Mathematica as a template to expedite the laborious alternatives available from adaptations such as ImageJ. Importantly, the algorithm acquires the most intensive part of delineating the grains in an image, freeing sedimentologists to focus on qualitative adjustments to yield a realistic outcome. We subsequently quantified [2014] the accuracy and precision of the algorithm -- as implemented in Mathematica software platform -- so that future work using the software would have reliable estimates of associated uncertainty.