GPS Event Calendar

"Searching for a Sixth Sense with Gurindji People"

Felicity Meakins, The University of Queensland

Abstract:

Like most First Nations languages, Gurindji expresses spatial relations according to cardinal directions rather than left/right terms, for example "put the flour north of the vegemite" or "there's a fly on your west shoulder". This attention to geocentric cues has cognitive effects that show that Gurindji people have an extraordinary mental map of the world anchored in the trajectory of the sun, but which is constantly in operation regardless of the time of day.

One question is whether this unique attention to geocentric cues is reflected neurologically, i.e. whether Gurindji people have a hard-wired magneto-reception ability. Human neurophysiology has been shown to contain a geomagnetic sensory system (Wang et al 2019). Small rotations in the magnetic field triggered drops in the brain's EEG alpha-wave power. However, no participants were consciously aware of these magnetic eld shifts. All participants tested spoke English, which uses a left/right system, with cardinal terms marginal in everyday speech. On the other hand, the Gurindji spatial orientation ability is so casual and accurate, we propose that they might be consciously aware of the geomagnetic field – a new human 6th sense.

Felicity Meakins (ASSA) is Professor of Linguistics at the University of Queensland and a CI in the ARC Centre of Excellence for the Dynamics of Language. She is a field linguist who specializes in the documentation of First Nations languages in northern Australia and the effect of English on these languages. She has worked as a community linguist as well as an academic over the past 20 years, facilitating language revitalization programs, consulting on Native Title claims and conducting research into First Nations languages. She has compiled a number of dictionaries and grammars, and has written numerous papers on language change in Australia.

"Investigation of Europa's Ocean with the Planetary Ice Chemistry Laboratory (PICL)"

William Denman, Graduate Student – Chemistry and Chemical Engineering, Caltech

Abstract: We have developed a laboratory for understanding the chemistry of icy bodies in our solar system. The first body of investigation is Europa, due to its radiolytic environment and the presence of a subsurface ocean. Europa has large differences in trailing and leading radiolytic environments. Europa's leading hemisphere is thought to possess endogenous material from the subsurface ocean while the trailing hemisphere undergoes intense ionic bombardment. By using existing observations from both ground and space-based telescopes, we are able to compare our lab-based measurements. PICL has led to more evidence for the presence of sodium chloride on Europa's leading hemisphere and is now turning its attention to Europa's trailing hemisphere and the sulfates that reside there.

"TBD"

Maria Camarca, Graduate Student, Planetary Science, Caltech

Michael Greklek-McKeon, Graduate Student, Planetary Science, Caltech

"TBD"

Ryleigh Davis, Graduate Student, Planetary Science, Caltech

Julie A. Inglis, Graduate Student, Planetary Science, Caltech

"A nutrient relay sustains subtropical ocean productivity"

Mukund Gupta, Postdoctoral Scholar, Caltech

Abstract: The ocean's subtropical gyres account for about half of the global flux of organic carbon sinking into the deep ocean. Biological production is limited by the availability of nutrients in these subtropical regions, because large-scale ocean circulation patterns push nutrient-rich waters away from the surface. The transfer of nutrients into the sunlit layer is achieved by fine-scale vertical nutrient transfers, at the expense of the layers beneath. We show that these sub-surface layers are replenished by the lateral turbulent transport of nutrients along density surfaces, on 10-100 km scales. This nutrient 'relay', involving both vertical and lateral transport, ultimately fuels biological production and sustains an associated sequestration of carbon in the subtropics.

"TBD"

Sally Pusedu, University of Virginia

"Lipidomic hydrogen stable isotope probing for quantification of slow microbial growth in situ"

Tristan Caro, Graduate Student, University of Colorado, Boulder

Abstract:

The ability to measure rates of microbial growth and productivity is fundamental to our understanding of ecosystems. However, many energy- and nutrient-limited environments are characterized by extremely slow rates of microbial growth that are difficult to directly measure. To quantify exceedingly slow microbial growth, we implemented a new taxa-agnostic approach: lipidomic hydrogen stable isotope probing (LH-SIP). For this method, a sample is amended with isotopically heavy water ( 2H2O) as a tracer of membrane lipid biosynthesis. The resulting 2H enrichment of microbially-produced lipids is measured by gas chromatography/pyrolysis/isotope ratio mass spectrometry (GC-P-IRMS). 2H2Ohas the advantage over many SIP tracers in that it is nutritionally passive and therefore does not stimulate the growth of certain taxa, especially copiotrophs/contaminants that may have enhanced growth capabilities. LH-SIP assigns compound-specific 2H values to intact polar lipids, allowing the coupling of microbial growth rates to distinct taxonomic groups.

In this work, we discuss our applications of LH-SIP to natural systems and specifically its utility in energy-limited subsurface biospheres. We describe LH-SIP measurements acquired in high alpine soils and desert regolith, noting that LH-SIP techniques are sensitive enough to capture 2H incorporation corresponding to as little as 1/1000 the of an organism's generation time in the presence of as little as 1% 2H2O tracer. We propose that LH-SIP is uniquely suited for capturing microbial growth in deep subsurface and energy-limited systems where microbial generation times are expected to be on the order of hundreds or thousands of years. In addition, we will share our efforts in now applying LH-SIP to subsurface permafrost and serpentinite rocks.

" The response of flexural isostasy to climatically driven sea-level changes on continental-scale deltaic depocenters "

Sara Palanco, University of Sydney

Abstract: The isostatic response to the last glacial maximum has long been identified in shoreline elevations and it has been extensively studied because of its impact on human coastal settlements and on sea-level change. In contrast, the response of flexural isostasy to climatically driven sea-level changes in passive margin deltas during deep time remains poorly understood. Deep-time load-induced vertical movements have a profound effect on delta shorelines and their effect might have been underestimated because subsequent, more recent isostatic adjustments have obscured their deep-seated signal. In this work, we use conceptual numerical models to explore the potential significance of bidirectional high-frequency flexural adjustments driven by deep time climate-forced sea-level changes and the associated responses of large fluvio-deltaic systems. Our approach is to model a large drainage basin that discharges to a continental margin to generate a deltaic depocenter, then prescribe synthetic and climatic-driven sea-level curves of different frequencies to assess flexural response. Results show that flexural isostatic adjustments are bidirectional and are in sync with the magnitude, frequency (100-1000 kyr) and direction of sea-level fluctuations, and that isostatic adjustments play an important role in driving along-strike and cross-shelf river-mouth migration and sediment accumulation. Our findings demonstrate that climate-forced sea-level changes set up a feedback mechanism that results in self-sustaining creation of accommodation into which sediment is deposited and plays a major role in delta morphology and stratigraphic architecture.

"The Chemistry of Europa and Venus, and Characterization of Earth-like exoplanets"

Members of the Ph.D. examining committee are: Katherine de Kleer (chair), Yuk Yung (thesis advisor), Mike Brown, Andy Ingersoll

"Exploring Earth's core-mantle boundary with multi-technique approaches"

Members of the Ph.D. examining committee are: Mike Gurnis (chair), Jennifer Jackson (thesis advisor) Paul Asimow, Zhongwen Zhan

"Mechanical interactions between water and the solid Earth: From quasi-static geodetic deformation to dynamic fault slip"

Members of the Ph.D. examining committee are: Zachary Ross (chair), Jean-Philippe Avouac, Nadia Lapusta (thesis co-advisors), Rob Clayton

"The Planet-Disk Connection: From Protoplanetary Disks to Planetary Atmospheres"

Members of the Ph.D. examining committee are: Geoff Blake (chair), Heather Knutson (thesis advisor), Dimitri Mawet, Konstantin Batygin, Yuk Yung