My Research Page

Although they aren't as large as the major planets in the Solar System, there are a lot more comets than planets. Comets are important components of the Solar System, and studying comets is just as important as studying any other part of the Solar System to learn more about how it formed and developed. It is generally believed that the interiors of comet nuclei are the least processed materials in the Solar System, and as such, they could provide unique clues to understanding the formation of the Solar System. Furthermore, some studies of the formation of Earth have suggested that our planet, upon formation, could not have retained water and other chemicals necessary for life. While this subject is still hotly debated, there are some scientists who think that comets could have delivered these materials to the Earth.

From these statements, it is quite obvious that the ultimate goal of cometary science is to get at the nucleus. However, doing this is extremely difficult. When comets get close enough to perform ground-based observations, the nucleus is obscured by the coma. Therefore, most of what we know about comets comes from coma studies. While these studies have revealed a great deal of information, the full chemical inventory and the physical structure of nuclei are still not known.

To date, four cometary nuclei have been seen directly in detail: Halley (1986), Borrelly (2001), Wild 2 (2004), and Tempel 1 (2005). On the other hand, we are in an exciting time in cometary science. Within this decade, there have been two NASA missions geared to studies of comets. The Stardust mission has collected cometary dust samples from Comet Wild 2 and recently returned them to Earth. Additionally, Deep Impact has excavated a crater on the nucleus of comet Tempel 1 to examine interior chemistry and gauge the physical structure of the nucleus. The European Space Agency (ESA) also has a comet mission, Rosetta, which will visit Comet Churyumov-Gerasimenko and land on its surface.

NASA was supposed to have a third comet mission, CONTOUR, which would have visited comets Encke and Schwassmann-Wachmann 3 starting in 2003. However, the spacecraft met an unfortunate end. Hopefully this mission can be done again sometime in the future.

Nucleus of Comet Halley What I Do

I am collaborating with Anita Cochran at the University of Texas. We are examining the coma of comet Encke, a short-period comet that forms an unusually-shaped coma. More details will be posted as we complete more of this project.

My doctoral research focused on the formation and destruction of carbon monoxide in the coma. I examinined the impact of photochemistry and chemical reactions on the formation of CO, as well as influence of topography on these chemical reactions.

Here are abstract references relevant to my doctoral research -- they are available through ADS. Refereed publications are forthcoming now that I have recovered from my medical problems and have defended my thesis. As they make it to publication, I will post the references.

Pierce, D. M., and M. F. A'Hearn 2004. Formation and Destruction Mechanisms of Carbon Monoxide in Cometary Comae. Bull. Am. Astron. Soc. 36, 23.02
This was supposed to be presented at the 2004 DPS meeting, but I became severely ill and was unable to attend the meeting. However, the abstract is still available in ADS.

Pierce, D. M., and M. F. A'Hearn 2003. Formation of Carbon Monoxide in the Near Nucleus-Coma of Comets. Bull. Am. Astron. Soc. 35, 28.07.

For my full list of credentials, visit my CV page.

Asteroid 253 Mathilde Group Affiliations

I am now a faculty member in the Department of Physics and Astronomy at Mississippi State University, where I am continuing my research.

I held a brief postdoctoral appointment in the Department of Astronomy at the University of Texas at Austin. I was a part of the Planetary Systems Group. The group's research focuses on small bodies of the Solar System, as well as extrasolar planets.

I did my doctoral research with the Small Bodies Group at the University of Maryland. Group members do both observational and computational research. Team members Lucy McFadden and Dennis Wellnitz were active in the NEAR mission to the asteroid 433 Eros, and we were also an integral part of the Deep Impact mission, for which my advisor, Mike A'Hearn, was the Principal Investigator. Several of our group's researchers are also involved with the astrobiology group at NASA's Goddard Space Flight Center. Additionally, the group is home to the Small Bodies Node of the Planetary Data System.

Return to Main Page