Erika Gibb

Research

I consider myself to be an astrobiologist, or one who studies the the Origins of Life. This is a booming multidisciplinary, collaborative, worldwide effort to get scientists from widely different fields (biology, geology, astronomy, chemistry, physics, etc) talking together to get a big picture understanding of the development/emergence/evolution of life.

By furthering our understanding of the complicated interactions between solid and gas phase chemistry in the interstellar medium, we may begin to understand what materials were available for forming planetary bodies in young star systems. My research investigates one small piece of the puzzle of how life began on Earth and may begin on other worlds in our galaxy. See my research pages for more information.

Organic Volatiles Toward Star Forming Regions and in Comets

Between the stars are large areas of vacuum with very little in the way of dust or gas. On average, the density of this material is 19 orders of magnitude less than that of Earth's atmosphere at sea level! There are regions of much higher density (which are still better than the best vacuums on Earth) which we call dark molecular clouds. The image above is one example of such a dark cloud. Even though the number of dust particles per cubic meter is incredibly small by earthly standards, there is still enough dust in these objects to block the light from the stars behind the cloud, making the sky in that region appear dark. Fortunately, these submicron (< one millionth of a meter) dust particles are relatively transparent to long wavelengths like infrared and radio, and we can use observations at these wavelengths to investigate the interiors of these dark clouds. These clouds aren't made of just dust, however. In fact, dust only makes up about 1% of the mass. The rest of it is gas, primarily hydrogen.

In these very cold (as cold as only 10 Kelvin above absolute zero!), dark clouds, dust grains composed of silicate cores, with perhaps an organic refractory mantle or other refractory carbon component (such as graphite), accrete ices on their surfaces. Essentially, the grains are so cold that anything other than hydrogen and helium will stick when it collides with a grain. Molecules will stick, but just as important (or perhaps moreso) are the atoms that collide and stick, such as carbon and oxygen. A light atom like hydrogen can collide with a dust grain and then move around the surface for a while before escaping from the grain. If it happens to hit an oxygen atom, it could bond to it. If a second hydrogen atom comes along, a water molecule can be formed. This is the process by which most of the water is believed to be formed in the interstellar medium. Likewise, CH4 (methane) may be formed by adding H atoms to carbon. Other molecules, like CO, form primarily in the gas phase. When the temperatures are cold enough, these ices will stick to grains as well. Essentially, a silicate core with a layer of "polar" (water-rich) ice and a layer of "apolar" or "nonpolar" ice (rich in CO2 and CO) is formed. Note that at this point, with cold temperatures, neutral chemical species, and relatively few collisions we have primarily very simple molecules.

When a core in a dark cloud gets to a certain density, known as the critical density, collapse can begin. The gravitational attraction pulls matter inward. By conservation of energy, we know that the initial potential energy of the cloud is converted into kinetic energy. As the dust and gas fall inward, they collide with other particles, transferring their energy and raising the temperature of the infalling material. The extended matter far away from the collapsing core stays cold, below 50 K or so, while the core can reach temperatures much higher, say above 150 K or so. During collapse, a complex chemistry occurs both in the gas phase and on the grain that leads to the formation of many "large" molecules (astrophysically speaking), including such organics as methanol, formaldehyde, and many nitriles. The interactions between solid and gas phase chemistry are still being studied by observers and experimenters. If these species survive the star formation process, they could be incorporated into the excess material in the disk around the young star and possibly eventually into planets and comets. This is one way to provide an early earth with sufficient organics to begin the complicated chemical processes that eventually led to the origin of life.

That's the big picture--how did life form on Earth, and, by extension, how could it happen on other planetary bodies?

Disks

Gas (and Ice) in Disks Around Young Stars

My current research concentrates on searching for and characterizing volatiles in disks and envelopes around young stars. We primarily use the high dispersion echelle spectrograph NIRSPEC on Keck II located on Mauna Kea, HI for gas phase work. Ice studies are performed using the SpeX spectrometer on the Infrared Telescope Facility (also on Mauna Kea) and archival Spitzer Space Telescope data. I am looking for (among other things) CH4 gas in disks surrounding low mass young stars. Why? Well, we know CH4 gas is on interstellar ices towards massive young stellar objects like NGC7538 IRS9 where it is about 2% or so as abundant as water. Warm CH4 gas is also seen in these regions. It is also one of the principle parent volatiles in comets, usually found to be about 1% as abundant as water. And, afterall, comets formed under what should be similar to conditions in disks around low mass young stars.

It is thought that methane forms primarily by addition of H atoms one by one onto a C atom that is sticking to a cold dust grain in a dark cloud. This is the same way water forms (adding 2 H to an O atom). CH4 should be part of the initial ice/gas composition around lower mass stars too and as the ices are heated (close to the young star) the CH4 should be in the gas phase.

We are also looking for other common volatiles, including HCN, acetylene (C2H2), ethane (C2H6), that are found in comets and ices and should be detectable in disks around young stars.

Below is a list of my Interstellar Ice and Gas Publications:

(Publications can be viewed at the NASA Astrophysics Data System)

Brown, L. R., Troutman, M. R., Gibb, E. L., 2013, ApJ, 770, L14. “A Spectro-Astrometric Study of Water in DR Tauri”

Horne, D., Gibb, E. L., Brittain, S. D., Rettig, T., Tilley, D., 2012, ApJ, 754, 64-73. “The gas/dust ratio of circumstellar disks: Testing models of planetesimal formation”

Wilking, B. A., Marvel, K. B., Claussen, M. J., Gerling, B. M., Wootten, A., Gibb, E. L. 2012, ApJ, 753, 143. “A Proper Motion Study of the Haro 6-10 Outflow”

Gibb, E. L., Brittain, S. D., Rettig, T. W., Troutman, M., Simon, T., Kulesa, C. 2010, ApJ, 715, 757. “CO and H3+ Toward MWC 1080, MWC 349, and LkHa 101”. Gibb2010_MWC.pdf

Brittain, S. D., Rettig, T. W., Simon, Theodore, Gibb, E. L., Liskowsky, J. 2010, ApJ, 708, 109. “Near Infrared Spectroscopic Study of V1647 Ori”

Gibb, E. L., Van Brunt, K. A., Brittain, S. D., Rettig, T. 2008, ApJ, 660, 1572. Erratum: “Warm HCN, C2H2, and CO in the Disk of GV Tau” Gibb2007_GVTau.pdf

Note: See Erratum: Gibb, E. L., Van Brunt, K. A., Brittain, S. D., Rettig, T. 2008, ApJ, 686, 748. Erratum: “Warm HCN, C2H2, and CO in the Disk of GV Tau”

Brittain, S. D., Rettig, T. W., Simon, T., Balsara, D. S., Tilley, D., Gibb, E. L., Hinkle, K. H. 2007, ApJL, 670, L29-32. “Post-Outburst Observations of V1647 Ori: Detection of a Brief, Warm Molecular Outflow” Brittain2007_MNO.pdf

Whittet, D. C. B., Shenoy, S. S., Bergin, E. A., Chiar, J. E., Gerakines, P. A., Gibb, E. L., Melnick, G. J., Neufeld, D. A. 2007, ApJ, 655, 332. “The Abundance of Carbon Dioxide Ice in the Quiescent Intracloud Medium” Whittet2007_CO2.pdf

Rettig, T., Brittain, S.D., Gibb, E.L., Simon, T., Balsara, D.S., Tilley, D.A., Kulesa, C. 2006, ApJ, 646, 342, “Gas and Dust Stratification in Young Disks” Rettig2006_DiskStrat.pdf

Gibb, E.L., Rettig, T., Brittain, S.D., Simon, T., Vacca, W.D., Cushing, M.C., & Kulesa, C. 2006, ApJ, 641, 383, “Post-Outburst Infrared Spectra of V1647 Ori, the Illuminating Source of McNeil’s Nebula” Gibb2006_MNO.pdf

Rettig, T., Brittain, S.D., Gibb, E.L., Simon, T., & Kulesa, C. 2005, ApJ, 626, 245. “CO Emission and Absorption toward v1647 Ori (McNeil’s Nebula)” Rettig2005_MNO.pdf

Rettig, T., Haywood, J., Simon, T., Brittain, S.D., & Gibb, E.L. 2004, ApJL, 616, 163. "Discovery of CO gas in the inner disk of TW Hydrae” Rettig2004_TWHya.pdf

Gibb, E.L., Brittain, S.D., Rettig, T., Haywood, R., Simon, T., Kulesa, C., 2004, ApJ, 610, L113. “Upper Limit for CH4 in the Protostellar Disk towards HL Tau" Gibb2004_HLTau.pdf

Gibb, E.L., Whittet, D.C.B., Boogert, A.C.A., Tielens, A.G.G.M. 2004, ApJS, 151, 35. “Interstellar ice: The ISO legacy” Gibb2004_ISO.pdf

Gibb, E.L. & Whittet, D.C.B., 2002, ApJL, 556, 113. “The 6 μm Feature in Protostars: Evidence for Organic Refractory Material.” Gibb2002_Org.pdf

Chiar, J.E., Adamson, A.J., Pendleton, Y.J., Whittet, D.C.B., Caldwell, D. A., & Gibb, E.L. 2002, ApJ, 570, 198. “Hydrocarbons, Ices, and “XCN” in the Line of Sight Toward the Galactic Center” Chiar2002_GC.pdf

Gibb, E.L., Whittet, D.C.B. & Chiar, J.E. 2001, ApJ, 558, 702. “Searching for Ammonia in Grain Mantles Toward Massive YSOs.” Gibb2001_NH3.pdf

Nummelin, A., Whittet, D.C.B., Gibb, E.L., Gerakines, P.A. & Chiar, J.E. 2001, ApJ, 558, 185. “Solid Carbon Dioxide in Regions of Low-Mass Star Formation” Nummelin2001_CO2.pdf

Whittet, D.C.B., Pendleton, Y.J., Gibb, E.L., Boogert, A.C.A., Chiar, J.E. & Nummelin, A. 2001, ApJ, 550, 793. “Observational Constraints on the Abundance of ‘XCN’ in Interstellar Grain Mantles” Whittet2001_XCN.pdf

Whittet, D.C.B., Gibb, E.L., & Nummelin, A. 2001, Origins of Life Evol. Biosphere, 21, 157. “Interstellar Ices as a Source of CN-Bearing Molecules in Protoplanetary Disks” Whittet2001_OLEB.pdf

Gibb, E.L., Nummelin, A., Bergman, P., Irvine, W. & Whittet, D.C.B. 2000, ApJ, 545, 309. “Chemistry of the Organic-Rich Hot Core G327.3-0.6” Gibb2000_G327.pdf

Gibb, E.L., Whittet, D.C.B., Schutte, W.A., Boogert, A.C.A., Chiar, J.E., Ehrenfreund, P., Gerakines, P.A., Keane, J.V., Tielens, A.G.G.M., van Dishoeck, E.F. & Kerkhof, O. 2000, ApJ, 536, 347. “An Inventory of Interstellar Ices Toward the Embedded Protostar W33A” Gibb2000_W33a.pdf

Comets

Volatiles in Comet Comae

Comets are the most pristine objects in our solar system (though not completely pristine). I am interested in the overall volatile composition, which we determine by measuring gas that is evaporating and expanding into the coma when a comet approaches the Sun. I use high-resolution, near infrared spectroscopy to measure ro-vibrational transitions of simple molecules like water (H2O), methane (CH4), ethane (C2H6), and carbon monoxide (CO).

Currently, I am particularly interested in what contribution comets may have made to the Earth’s oceans and biosphere. In order to answer this, I am collaborating with scientists at NASA Goddard Space Flight Center and Rowan University to search for deuterated water (HDO) an methane (CH3D). The HDO/H2O ratio in Earth’s oceans is well known. How similar is the cometary HDO/H2O ratio? Can this be used to infer what percentage of Earth’s water originated in the outer solar system?

Comet Publications:

Gibb, E. L., Bonev, B. P., Villanueva, G. L., DiSanti, M. A., Mumma, M. J., 2013, Journal of Molecular Spectroscopy, in press. “Solar Fluorescence Model of CH3D as Applied to Comet Emission”

Bonev, B. P., Villanueva, G. L., Paganini, L., DiSanti, M. A., Gibb, E. L., Keane, J., Meech, K., Mumma, M. J., 2013, Icarus, 222, 740-751. “Water Outflow in Comet 103P/Hartley 2: Distribution of Column Density, Rotational Temperatures, and Ortho-Para Ratio”

Gibb, E. L., Bonev, B. P., Villauneva, G., DiSanti, M. A., Mumma, M. J., Sudholt, E., Radeva, Y., ApJ, 750, 102. “Chemical Composition of comet C/2007 N3 (Lulin): another “atypical” comet”

Villanueva, G. L., Mumma, M. J., DiSanti, M. A., Bonev, B. P., Gibb, E. L., Magee-Suaer, K., Blake, G. A., Salyk, C. 2011, Icarus, 216, 227. “The molecular comporition of Comet C/2007 W1 (Boattini): Evidence of a peculiar outgassing and a rich chemistry”

Mumma, M. J., Bonev, B. P., Villanueva, G. L. and 10 coathors, 2011, ApJ, 734, 7. “Temporal and Spatial Aspects of Gas Release During the 2010 Apparition of Comet 103P/Hartley 2”

Meech, K. J. and 196 coauthors, 2011, ApJ, 734, 1. “EPOXI: Comet 103P/Hartley2 Observations from a Worldwide Campaign”

Radeva, Y. L., Mumma, M. J., Bonev, B. P., DiSanti, M. A., Villanueva, G. L., Magee-Sauer, K., Gibb, E. L., Weaver, H. A. 2010, Icarus, 206, 764. “The organic composition of Comet C/2000 WM1 (LINEAR) revealed through infrared spectroscopy”

Bonev, B. P., Mumma, M. J., Gibb, E. L., DiSanti, M. A., Magee-Sauer, K., Villanueva, G. L., Ellis, R. 2009, ApJ, 699, 1563, “Comet C/2002 Q2 (Machholz): Parent Volatiles, A Search For Deuterated Methane, and Constraint on the CH4 Spin Temperature”

Villanueva, G. L., Mumma, M. J., Bonev, B. P., DiSanti, M. A., Gibb, E. L., Bonhardt, H., Lippi, M. 2009, ApJ, 690, 5L, “A Sensitive Search for Deuterated Water in Comet 8P/Tuttle” Villanueva2008_TuttleHDO.pdf

Bonev, B. P., Mumma, M. J., Radeva, Y. L., DiSanti, M. A., Gibb, E. L., Villanueva, G. L., 2008, ApJ, 680, 61, “The Peculiar Volatile Composition of Comet 8P/Tuttle: A Contact Binary of Chemically Distinct Cometesimals?” Bonev2008_Tuttle.pdf

Magee-Sauer, K., Mumma, M. J., DiSanti, M. A., Dello Russo, N., Gibb, E. L., Bonev, B. P., 2008, Icarus, 194, 347, “The Organic Composition of Comet C/2001 A2 (LINEAR): I - The Unusual Chemistry of this Comet Revealed at Infrared Wavelengths” MageeSauer2008_A2.pdf

DiSanti, M. A., Anderson, W. M., Villanueva, G. L., Bonev, B. P., Magee-Sauer, K., Gibb, E. L., Mumma, M. J. 2007, ApJ, 661, L101, “Depleted Carbon Monoxide in the Jupiter-family comet 73P/Schwassmann-Wachmann 3-C” DiSanti2007_CO_SW3.pdf

Gibb, E. L., DiSanti, M. A., Magee-Sauer, K., Dello Russo, N., Bonev, B. P., Mumma, M. J., 2007, Icarus, 188, 224, “The Organic Composition of C/2001 A2 (LINEAR). II - Search for Heterogeneity within a Comet Nucleus” Gibb2007_A2.pdf

Dello Russo, N., Mumma, M.J., DiSanti, M.A., Magee-Sauer, K., Gibb, E.L., Bonev, B.P., McLean, I.S., Xu, L.-H. 2006, Icarus, 184, 255, “A High-Resolution Infrared Spectral Survey of Comet C/1999 H1 Lee” dellorusso2006_leesurvey.pdf

Mumma, M. J., DiSanti, M. A., Magee-Sauer, K., Bonev, B. P., Villanueva, G. L., Kawakita, H., Dello Russo, N., Gibb, E. L., Blake, G. A., Lyke, J. E., Campbell, R. D., Aycock, J., Conrad, A., Hill, G. M. 2005, Science, 310, 270. “Parent Volatiles in Comet 9P/Tempel 1: Before and After Impact.” Mumma2005_DeepImpact.pdf

Dello Russo, N.,Bonev, B.P., DiSanti, M.A., Mumma, M.J., Gibb, E.L., Magee-Sauer, K., Barber, R.J., & Tennyson, J. 2005, ApJ, 621, 537. "Water Production Rates, Rotational Temperatures and Spin Temperatures in Comets C/1999 H1 (Lee), C/1999 S4, and C/2001 A2” DelloRusso2005.pdf

Bonev, B.P., Mumma, M.J., Dello Russo, N., Gibb, E.L., DiSanti, M.A., & Magee-Sauer, K. 2004, ApJ, 615, 1048. “Infrared OH Prompt Emission as a Proxy of Water Production in Comets: Quantitative analysis of the multiplet near 3046 cm-1 in Comets C/1999 H1 (Lee) and C/2001 A2 (LINEAR)” Bonev2004_OH.pdf

Dello Russo, N., DiSanti, M.A., Magee-Sauer, K., Gibb, E.L., Mumma, M.J., Barber, R.J., & Tennyson, J. 2004, Icarus, 168, 186. "Water production and release in comet 153P/Ikeya Zhang (C/2001 C1): Accurate rotational temperature retrievals from hot-band lines near 2.9-μm." DelloRusso2004_IZ.pdf

Mumma, M.J., Disanti, M.A., Dello Russo, N., Magee-Sauer, K., Gibb, E., & Novak, R. 2003, AdSpR, 31, 2563. "Remote infrared observations of parent volatiles in comets: A window on the early solar system"

Gibb, E.L., Mumma, M.J., Dello Russo, N., DiSanti, M.A., Magee-Sauer, K. 2003, Icarus, 165, 391. "Methane in Oort Cloud Comets" Gibb2003_CH4.pdf

Gibb, E.L., Mumma, M.J., DiSanti, M.A., Dello Russo, N., Magee-Sauer, K. 2002, In the Proceedings for the Asteroids, Comets, & Meteors Conference, Berlin, Germany (ESA SP-500), pp. 705-708. "An Infrared Search for HDO in Comets" Gibb2002_HDO.pdf

Interested in an Undergraduate Research Experience?

I often have undergraduate students working with me on various research projects. This involves learning how to reduce and analyze spectroscopic data. Opportunities are limited to UMSL students. Interested students must be physics majors and should have taken their basic introductory physics and math courses (PHYS 2111 & 2112, College Algebra and Calculus are required). Students are also encouraged to take AST 1050 and 1051 concurrent with research (these courses are also required for the astrophysics emphasis option of the physics degree). Students may request to do research during the semester for credit (usually 1 credit of PHYS 3390) or a summer research project. Students are encouraged to present their results at the UMSL Undergraduate Research Symposium held each spring. There may also be opportunities to present at professional meetings. Current sources of Stipends: NASA Space Grant, NSF Planetary Astronomy Program: Information is available in mygateway under Physics Majors