Research & Projects
What I've been up to...
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Protoplanetary Disk
Gas Masses from Multiple Chemical Tracers
The bulk H2 gas in the disk cannot be observed directly. We instead rely on indirect tracers of the disk gas mass, mainly sub-mm dust and CO emission. However, the uncertainty in the ratios used to convert from these indirect tracers to a total H2 mass increases as the disk evolves. We are exploring additional gas species that could provide further constraints on this crucial quantity. But if disk gases aren't your thing, check out this paper on ices.
The Evolution of Protoplanetary Disk
Gas Compositions
The abundance of CO gas in the outer regions of disks can be up to 100x lower than that in the interstellar medium, even at distances interior to the expected CO snowline. We search for evidence of this CO depletion by comparing CO fluxes to those of N2H+. Forming from the protonation of N2 in ionized H2 gas, N2H+ acts as a tracer of both. We compare N2H+/CO ratios across disks to search for changes in gas composition with age or other properties.
JWST Predictions: C & O Carriers in Protoplanetary Disks at Mid-infrared Wavelengths
The James Webb Space Telescope (JWST) will characterize the inner regions of protoplanetary disks. These observations will be valuable for comparison with the outer disk gases probed by ALMA and the atmospheres of gas-giant extrasolar planets. We model the emission of C & O carriers observable in the mid-IR for various disk compositions and temperatures. In particular, we are interested in how this emission depends on the C/O ratio and the detectability of CH4 emission, which will be an exciting target for JWST.
Why is the Earth
carbon-poor?
Compared to the interstellar dust from which it formed, the Earth's carbon content is extremely low. The fact that primitive meteorites are also carbon-poor relative to interstellar dust could indicate that at least a portion of the carbon loss occurred prior to the formation of planetesimals. For this reason, we investigate processes that release carbon from refractory phases in protoplanetary disks.
Measuring Salts on Mars with Curiosity (ChemCam/LIBS)
A wealth of data is being collected by the Laser-Induced Breakdown Spectroscopy (LIBS) instrument, ChemCam, on the Martian rover Curiosity. Using an engineering model of the ChemCam instrument, we investigated its ability to detect and quantify carbonate, chloride, and sulfate salts in rock powder mixtures of Mars-like composition. Read more in the JGR Planets publication and LPSC abstracts on my Publications page. These results have contributed to ongoing ChemCam data analysis and studies of salts in Gale Crater, Mars.
Contact me to learn more about these projects.