Research
My current area of research is understanding the structure and composition of the dust grains that are observed in comet coma. The dust grains are believed to be micron-sized porous aggregates of amorphous silicates, ices/volatiles, glassy carbons, and organics with submicron crystalline silicate inclusions. When observing these grains in the infrared from 3-40 um, we clearly see both amorphous silicate features and crystalline silicate features, but of varying strength within individual comets of a certain class and between the classes of Ecliptic Comets (ECs) and Nearly Isotropic Comets (NICs). The strength of these features can be changed by increasing the grain size, crystalline content, or by increasing the porosity making this problem degenerate. It is of utmost importance to break this degeneracy in order to understand the abundances of cometary dust grains.
To date, computational limitations have only allowed for scattering and absorption models to be done with approximations that allow for quick calculations, but poorly match the physical structure of an aggregate grain. My work includes using DDSCAT, a publicly available Discrete Dipole Approximation (DDA) code developed by Draine and Flatau, to model the absorption and scattering properties of micron-sized aggregate dust grains with submicron crystalline inclusions. The distinct advantage of using a DDA code is that it allows for irregularly shaped grains, while methods such as Continuous Distributions of Ellipsoids with Effective Medium Theory and Mie Scattering are limited to more regular shaped grains such as spheres and ellipsoids. The drawback of a DDA code is that is very computationally intensive, so to run my models, I use NASA's supercomputer, Pleiades. Once absorption properties for a grain size distribution of the crystals has been calculated with DDA, they are piped into thermal models to match Spitzer spectra of the Deep Impact spectra of comet 9P/Tempel 1. Currently, I have modeled the crystalline forsterite component of the grains with moderate success for a single grain shape. Inclusion of multiple grain shapes into the absorption properties of the forsterite component to match the irregularity of grains should drastically improve upon these results.
What is of particular interest is that crystalline silicates are only seen in low abundance in the ISM, which means that are not primordial nebula materials, but have been processed during the early stages of our Solar System in the dusty disk around our the forming Sun. Temperatures in excess of 1000 K are required to either anneal or condense crystalline silicates from the amorphous population in the ISM. This indicates that the silicates formed in the inner regions of the disk where temperatures were high enough for these processes to take place. Comets, however, contain large amounts of volatiles that do not survive over 50 K, so the presence of these hot relic crystalline silicates embedded in the cold storage of comets implies that there was significant radial mixing between the inner and outer regions of the protoplanetary disk. So, if we can develop a rigorous way of identifying and quantifying the amount of these crystalline silicates in comets, we can provide strong constraints to current disk models for our forming Solar System. Further, understanding the structure of these dust grains will tell us something of the dynamics of the comet forming areas of the disk itself providing even more information towards understand the formation of comets and protoplanets. The past decade has also shown that planetary systems are common in the universe with a wide variety of planetary arrangements, so better understanding the origins of our own Solar System's formation is an integral piece to planetary formation theory.
This work is being done in under the advising of Dr. Jim Murphy of NMSU and Diane Wooden of the NASA Ames Research Center. Collaborators for various aspects of my current and future projects include Mike Kelley, Chic Woodward, Denis Richards, and David Harker.
I would like to thank NASA Ames Research Center and the NASA GSRP Fellowship for providing the funding for this project.
I have also worked with Dr. Jim Murphy on better understanding and extracting the modes of the thermal tides within the Martian atmosphere using both simulated data, Mars Global Survery Thermal Emission Spectrometer (MGS TES), and MGS Mars Horizon Sensor Assembly. This work has included running a global climate model for Mars's atmosphere that was developed at NASA Ames, as well as analysis of the data from the afore mentioned MGS instruments.
Previously, I worked with Dr. Nancy Chanover to analyze infrared spectra
of the planet Saturn taken with the NASA Infrared Telescope Facility, during
the summer of 2005. We extracted spectra based on longitudinal and
latitudinal positions across the planet, to examine the differences and
similarities in the chemical composition of the zones and belts.
Teaching
For two years, I was an Astronomy 105G: The Planets teaching assistant. Over those two years, I taught eight lab sections, and discovered that I am not only passionate about astronomy, but also about teaching. It is my hope that I will be given the opportunity to teach once again in the future.
Further, during the school year, I work as Science Tutor for Mayfield High School. My responsibilities here are to assist high school students in better understanding the fundamentals of Physical Science, Chemistry, and Physics.
I am also a volunteer for a local group called SCIAD (SCIence ADvisors), where I will participate in events such as astronomy talks in classrooms for all grades, work as a science fair judge, or assist teachers with the best way to teach certain scientific topics.
Awards
2008: Recipient of the NASA GSRP Fellowship.
