Welcome to GeoUnion, the graduate student body of the Department of Earth, Environmental and Planetary Sciences. GeoUnion  strives to supplement the overall graduate student experience at Rice and DEEPS. GeoUnion represents DEEPS in the overall Rice grad student community, acts as a liaison between students and faculty and organizes a number of intra- and inter-departmental events throughout the academic year.

Date Event
August 19-23O-Week
September 6-8Overnight Camping at San Marcos
September 13Welcome Barbecue
Cancelled because of ImeldaPre-GSA talk
October 12-15Field Trip to Big Bend
October 25Halloween Kickball Tournament
November 26Multicultural Thanksgiving!
Dec 6Pre-AGU practice session

Here’s a list of the resources  that you would need to use frequently as graduate students at Rice. The websites of the Rice Graduate Student Association (GSA), Office of International Students and Scholars (OISS), Graduate and Postdoctoral Studies (GPS) are platforms which graduate students can use to keep track of upcoming events, funding opportunities, changes in rules and regulations, etc.

Living in a vast city like Houston and exploring a new place can also be challenging, and so we have compiled a list of recommendations for housing and fun things to do in the Space City!

Debadrita Jana



Jackson Borchardt



Yi Hou



David Valerio

David Valerio



Tanyel Baykut

Social Chair


Alana Semple

Alana Semple

Faculty Liaison


Eric Barefoot

GSA Representative


google sphere of Arches hike

The Astrophysical Journal: The effect of a strong pressure bump in the Sun’s natal disk: Terrestrial planet formation via planetesimal accretion rather than pebble accretion

The effect of a strong pressure bump in the Sun’s natal disk: Terrestrial planet formation via planetesimal accretion rather than pebble accretion

André Izidoro, Bertram Bitsch, Rajdeep Dasgupta


Mass-independent isotopic anomalies of carbonaceous and noncarbonaceous meteorites show a clear dichotomy suggesting an efficient separation of the inner and outer solar system. Observations show that ring-like structures in the distribution of millimeter-sized pebbles in protoplanetary disks are common. These structures are often associated with drifting pebbles being trapped by local pressure maxima in the gas disk. Similar structures may also have existed in the Sun’s natal disk, which could naturally explain the meteorite/planetary isotopic dichotomy. Here, we test the effects of a strong pressure bump in the outer disk (e.g., ~5 au) on the formation of the inner solar system. We model dust coagulation and evolution, planetesimal formation, as well as embryo growth via planetesimal and pebble accretion. Our results show that terrestrial embryos formed via planetesimal accretion rather than pebble accretion. In our model, the radial drift of pebbles fosters planetesimal formation. However, once a pressure bump forms, pebbles in the inner disk are lost via drift before they can be efficiently accreted by embryos growing at gap1 au. Embryos inside ~0.5–1.0 au grow relatively faster and can accrete pebbles more efficiently. However, these same embryos grow to larger masses so they should migrate inwards substantially, which is inconsistent with the current solar system. Therefore, terrestrial planets most likely accreted from giant impacts of Moon to roughly Mars-mass planetary embryos formed around gap1.0 au. Finally, our simulations produce a steep radial mass distribution of planetesimals in the terrestrial region, which is qualitatively aligned with formation models suggesting that the asteroid belt was born low mass.

Izidoro, A., Bitsch, B. & Dasgupta, R. (2021). The effect of a strong pressure bump in the Sun’s natal disk: Terrestrial planet formation via planetesimal accretion rather than pebble accretion. The Astrophysical Journal 915, 62. doi:10.3847/1538-4357/abfe0b

JGR Atmospheres: Effects of ozone isotopologue formation on the clumped-isotope composition of atmospheric O2

Laurence Y. Yeung, Lee T. Murray, Asmita Banerjee, Xin Tie, Yuzhen Yan, Elliot L. Atlas, Sue M. Schuaffler, and Kristie A. Boering

doi: 10.1029/2021JD034770


Tropospheric 18O18O is an emerging proxy for past tropospheric ozone and free-tropospheric temperatures. The basis of these applications is the idea that isotope-exchange reactions in the atmosphere drive 18O18O abundances toward isotopic equilibrium. However, previous work used an offline box-model framework to explain the 18O18O budget, approximating the interplay of atmospheric chemistry and transport. This approach, while convenient, has poorly characterized uncertainties. To investigate these uncertainties, and to broaden the applicability of the 18O18O proxy, we developed a scheme to simulate atmospheric 18O18O abundances (quantified as ∆36 values) online within the GEOS-Chem chemical transport model. These results are compared to both new and previously published atmospheric observations from the surface to 33 km. Simulations using a simplified O2 isotopic equilibration scheme within GEOS-Chem show quantitative agreement with measurements only in the middle stratosphere; modeled ∆36 values are too high elsewhere. Investigations using a comprehensive model of the O-O2-O3 isotopic photochemical system and proof-of-principle experiments suggest that the simple equilibration scheme omits an important pressure dependence to ∆36 values: the anomalously efficient titration of 18O18O to form ozone. Incorporating these effects into the online ∆36 calculation scheme in GEOS-Chem yields quantitative agreement for all available observations. While this previously unidentified bias affects the atmospheric budget of 18O18O in O2, the modeled change in the mean tropospheric ∆36 value since 1850 C.E. is only slightly altered; it is still quantitatively consistent with the ice-core ∆36 record, implying that the tropospheric ozone burden increased less than ∼40% over the twentieth century.

Plain-language summary

Oxygen in the air is constantly being broken apart and remade. Its constituent atoms are shuffled around by light-induced chemical reactions, which cause changes in the number of heavy oxygen atoms that are bound together. The number of these heavy-atom “clumps” is sensitive to air temperatures and the presence of air pollution; hence, their variations are being used to understand past high-altitude temperatures and atmospheric chemistry. This study incorporates oxygen clumping into an atmospheric chemistry model and compares the results to measurements of oxygen clumping in the atmosphere. We find that the model can explain all the modern-day measurements (from the surface to 33 km altitude), but only if the broader fates of oxygen atoms―i.e., their incorporation into other molecules beyond O2―are considered. Simulations of the preindustrial atmosphere are also generally consistent with snapshots of the ancient atmosphere obtained from O2 trapped in ice cores. The developments described herein will thus enable models to simulate heavy oxygen-atom clumping in past cold and warm climates and enable simulated high-altitude atmospheric changes to be evaluated directly against ice-core snapshots of the ancient atmosphere.


Because of COVID-19, the field trip is being postponed to later (date TBD) this year.   The seminar will continue via remote meetings through the end of the Spring 2020 semester.

As earth scientists we seek to understand the natural processes that have shaped the world around us through time. The most fundamental requirement to acquiring a deeper understanding of these mechanisms is through observation.  EEPS has a strong heritage in field-based research that when combined with analytical excellence, produces skilled scientists with a broad view of Earth as a system.  While Rice University is well placed to take advantage of a broad array of research resources, students in Houston do not always have immediate access to nearby geological sites that represent Earth as a system.  

A generous gift from Mike Johnson enables EEPS students the opportunity to observe classic and fundamental geologic concepts in the field.  Students are in charge of proposing, selecting and managing a field excursion that will benefit everyone in the department. A year-long seminar-based class run by the students prepares them to visit the locality they have selected.  Papers are selected, presented and discussed, followed by activities that educate the students on how to run a field-based project. During the field excursion, elected stops will be led and presented by individual students.  The knowledge gained before and during the field trip will cumulate into a multi-media field guide that will be made available to the department and public following the trips conclusion.

A significant benefit of a department-wide field excursion is the interaction of students with scientists from various disciplines.  Many earth scientists only carry out field work with specialists in their own field. The real discoveries in modern earth science occur when the different disciplines are part of a collective discourse. This trip will have scientists with different backgrounds observe the same outcrops; fostering fruitful discussion that results in the generation of new and unique questions. In addition, this trip may inspire fellowship among EEPS graduate students that will hopefully create life-long collaborations and a cohesive department.


General route starting in Albuquerque, New Mexico

This year, EEPS elected to utilize Mike Johnson’s gift to lead graduate students on a 7 day field expedition to observe some of the most diverse and economically important geologic terrains in the United States.

In early June of 2020, EEPS will travel through New Mexico, Colorado and Utah, which have easily accessible exposures of metamorphic, sedimentary, and igneous rocks. Starting from Albuquerque, New Mexico they will explore the Rio Grande Rift, the San Juan Volcanic field, and the well exposed Mezozoic stratigraphy on the Colorado Plateau. Observing these diverse geologic terrains will give EEPS graduate students a chance to see how their research interests dovetail with what they observe in nature and provide opportunities to create new ideas.

Pre-Trip planning seminars

Fall semester:  The graduate student of the winning field trip proposal organizes a weekly reading group focusing on the regional geology of the four corners region and come up with potential stops.

Spring semester: The weekly reading group continues.  Students pick the final outcrops that they would like to visit.  Each student is assigned to be an expert on 1-3 stops. Before the field trip, each student will submit their description(s) of their stop for the field guide.

Spring 2020 Seminar Papers

Fall 2019 Seminar Papers