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.
Three Earth, Environmental and Planetary Sciences 2020 Ph.D. graduates are awarded prestigious National Science Foundation (NSF) Postdoctoral Fellowships – a record for the department. Brandee Carlson, Tian Dong and Andrew Moodie, all from the same laboratory group, receive the highly competitive grant after submitting research proposals to the Division of Earth Sciences at NSF. The scope of the evaluation considers the scientific merits of the proposal, and the potential for transformative research as well as professional development by training recipients for research and leadership positions. The grants provide two years of salary and research support at an institution of the fellows choosing.
These postdoctoral fellowships are only offered to early-career scientists, so student supervisors are relied upon to discuss fellowship opportunities with their students during their graduate careers. Assistant professor Jeff Nittrouer, primary advisor for Carlson, Dong, and Moodie, strongly encouraged them to apply to the NSF program and is thrilled with the results.
“I could not be more proud of them,” says Nittrouer. “Collectively, they’ve shown how a laboratory raises the bar and thrives, demonstrating that scientific success comes from collaborations with fellow students and colleagues, both here at Rice and globally.”
“In the past six years, Brandee, Andrew, Tian, and Chen Wu [PhD, 2020] have cultivated a special culture: inclusiveness and sharing of ideas and resources, typifying the mantra that the sum of the parts is greater than the whole.” -Dr. Jeff Nittrouer
In terms of their upcoming research ventures, they’ll rely on recent experiences, in particular, working in far-flung localities and remote environments.
Brandee Carlson heads to the University of Colorado, Boulder, to collaborate with Prof. Irina Overeem in the Institute of Arctic and Alpine Research. Dr. Carlson is exploring delta front processes of Arctic rivers, focusing research in Greenland, where under warming climate conditions, river sediment supply is increasing due to rapidly retreating glaciers and thawing permafrost. Dr. Carlson plans to investigate how failures on multiple Arctic deltas vary by water and sediment discharge. Her work includes several field campaigns combined with CU’s extensive remote sensing capabilities. The project dovetails with her previous work on the Yellow River delta but will ultimately expand her expertise to include sediment transport at a variety of delta fronts and climate conditions.
Tian Dong will study how physical processes shape river morphology, working with Dr. Timothy Goudge at the University of Texas at Austin. Tian will develop new metrics to distinguish between meandering and braided river patterns, from sediment deposits, drill cores, remote sensing, and the rock record. The goals are to identify the prevalence of these river types for the past eon of earth’s history and improve groundwater reservoir models. Ultimately, the metrics may be translatable to the paleoclimate record of other terrestrial planets, including Mars.
Andrew Moodie will collaborate between Stanford University and the University of Texas, working with Drs. Jef Caers and Paola Passalacqua, respectively. Dr. Moodie’s project seeks to improve an understanding of subsurface delta sediment distribution and ground fluid movement, using machine learning algorithms. The aim is to distinguish how multiple natural and anthropogenic factors, including as sea level change and infrastructure development, influence delta systems.
According to Andrew, “Our understanding of subsurface fluid transport in river deltas is limited. Improving our ability to manage water resources and mitigate pollutant transport lowers risk to societal health. And predicting ground-fluid transport relies on models to constrain subsurface composition, however due to the complexity of river-delta environments, accurate assessments are difficult. Using machine learning to better constrain environmental heterogeneity will benefit society and the cultures that live on deltas globally”.
Although the group splits at the end of the academic term, all agree that their experiences at Rice have collectively enhanced their future as scientists and mentors.
“Lessons learned abroad were brought back here” [to Rice] says Brandee. “Countless hours of discussion, sharing ideas on white boards and helping write each other’s codes all enhanced our scientific successes.”
Nittrouer concludes, “Rice’s motto is ‘Unconventional Wisdom’. When I view the accomplishments of these students, I can’t help but applaud their unconventional generosity, humility, and determination. These students selflessly helped one another, and thanks to the support here at Rice, there was no lack for opportunity”.
Shuo Ding, Rajdeep Dasgupta, Kyusei Tsuno
Abstract: We constrained the solidus of a model Martian composition with low bulk Mg# (molar MgO/(MgO + FeOT) × 100 ~75) and high total alkali (Na2O + K2O = 1.09 wt.%) concentration at 2 to 5 GPa by experiments. Based on the new solidus brackets, we provide a new parameterization of the solidus temperature as a function of pressure of Martian mantle: Ts (°C) = − 5P (GPa)2 + 107P(GPa) + 1,068. The newly constrained solidus of the Lodders and Fegley (1997; https://doi.org/10.1006/icar.1996.5653) model Martian composition (LF composition) is 20 to 90 °C lower than the previous solidus of model Martian mantle with lower total alkali (~0.54 wt.%). The supersolidus experiments yield an average isobaric melt productivity, dF/dT, of 20 ± 6 wt.%/100 °C. We also bracketed the solidi of model Martian mantle compositions with low Mg# (~75) and low alkali (~0.54 wt.%), and with high Mg# (~80) and low alkali (~0.54 wt.%) at a constant pressure of 3 GPa. We find that bulk Mg# enhances the solidus temperature and bulk total alkalis suppress it. A parameterization that estimates the effect of bulk Mg# and total alkalis on peridotite solidus, including Mars and Earth, at 3 GPa can be described as: Ts(°C) = 4.23Mg # − 85(Na2O(wt. %) + K2O(wt. %)) + 1,120. Based on the new solidus parameterizations, 10–40 km more Martian crust would be produced by columnar decompression melting for LF model composition compared to the low Mg#‐low alkali model composition. The quantitative constraints on the solidus shift with Mg# and total alkalis from this study can be used to assess the Martian mantle solidus change through melting and melt extraction over time and the role of mantle heterogeneity in crustal production.
Ding, S., Dasgupta, R. & Tsuno, K. (2020). The solidus and melt productivity of nominally anhydrous Martian mantle constrained by new high pressure-temperature experiments – Implications for crustal production and mantle source evolution. Journal of Geophysical Research – Planets 123, e2019JE006078. doi:10.1029/2019JE006078
Department of Earth, Environmental and Planetary Sciences
6100 Main Street
Houston, TX 77005 USA