©2018 Rachel Sheppard

RESEARCH

 

THE EFFECT OF TEMPERATURE AND RELATIVE HUMIDITY ON MINERAL SPECTRA

2019-present

Using a small atmospheric chamber attached to an FTIR spectrometer, I am examining how diurnal cycling of temperature and relative humidity affect the VNIR spectra of several Mars-relevant hydrous minerals. In particular, I am interested in the speed and extent to which these cycles can cause phase and hydration state changes, which has implications for the martian hydrological cycle.

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MINERALOGY AND STRATIGRAPHY OF MT. SHARP

2018-2019

Using CRISM images processed using a new technique by our coauthors, we are revisiting parts of Mt. Sharp other than the rover traverse to understand how mineralogy changes across morphological contacts. These stratigraphic relationships and how they vary laterally can help constrain the crater's history, both during its lacustrine phase and long after.

ORBITAL MAPPING OF NAMIBIAN CAP CARBONATES

2018-present

After collecting samples from different units of Namibian cap carbonate, I am performing spectral mapping of the units using orbital and FTIR microscope data. I am also working with our coauthors who are performing the structural mapping of this complex region.

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LAKE TOWUTI: A TERRESTRIAL ANALOGUE FOR LAKE GALE?

2015-2018

Lake Towuti is a redox-stratified lake in ultramafic bedrock in Indonesia. This provides a rare opportunity to test the hypothesis that Lake Gale was redox-stratified. I have characterized the crystalline and amorphous mineralogy of the catchment, lake basin, and a 100 m long drill core to understand what signals can be uniquely linked to lake conditions.

DIAMOND COLOR ORIGIN USING FTIR AND RAMAN SPECTROSCOPY

2013-2015

Spectroscopy is a main tool to investigate whether diamonds are natural, lab-grown, and/or have had their color enhanced. My expertise at the Gemological Institute of America was in very small gems, or melee. I developed new analytical techniques for quickly determining the mineralogy and color origin of melee using FTIR spectroscopy.

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BIOMARKERS AND RAPID HEATING EXPERIMENTS

2011-2014

Methylphenanthrenes are organic molecules that can be used as a paleothermometer to understand past fault slip rates. We calibrated this technique using fault samples with pseudotachylite, a visible record of the most intensely heated part of the rock. To understand the kinetics of these reactions we also conducted rapid heating experiments to see how the molecules broke down under different time and temperature regimes.