Merging Particle Physics and Earth Science to develop a new tool to constrain the physical and chemical properties of LLSVPs

Regents Of The University Of Idaho, Moscow ID

Investigators

Abstract

Seismic mapping of Earth’s lowermost mantle reveals the presence of at least two continent-sized structures located just above the outer-core within the mantle. Due to these structures slow seismic wave speeds, they are commonly referred to as Large Low Velocity Provinces (LLVPs). LLVPs potentially influence deep-Earth dynamics, alter lower mantle circulation, decrease core heat flow, and consequently modify the planet’s magnetic field. The extent of these potential impacts depends on LLVP material properties, including their composition and density, among others. However, current geophysical methods do not directly measure composition and density. To address this, this project will leverage low-mass, elementary particles called neutrinos that have direct sensitivity to the composition and density of matter using a technique known as Neutrino Oscillation Tomography of the Earth (NOTE). The NOTE method can infer properties of the lower mantle by analyzing the characteristics of Earth-crossing neutrinos arriving at a detector (e.g., angles of arrival, energies, and neutrino types). To enhance the sensitivity of NOTE and complement existing geophysical methods, the researchers will create a new NOTE framework capable of integrating data from multiple neutrino detectors into a single analysis, providing new, independent estimates of the composition and density of LLVP. With several neutrino detectors online or in development, this project will develop tools to harness their collective capabilities, while also leveraging existing geophysical data toward new breakthroughs in understanding our planet. The goal is to build the tools necessary to demonstrate that with the use of multiple detectors, NOTE can provide a robust determination of LLSVP density and composition within a decade. This project will establish and strengthen international collaboration, while providing and training and mentoring for students, and facilitating outreach opportunities. The composition and density of an LLVP impact its viscosity and relative buoyancy, thereby governing its dynamic behavior and lifetime in the mantle. By developing a new tool to constrain the density and composition of LLVPs, this project will open new approaches for exploring the Earth’s deep interior. The researchers will create a novel multi-detector framework for NOTE and integrate it with existing geophysical constraints, yielding a unified method for estimating LLSVP properties. The project has three primary objectives: 1) incorporate multiple detectors into the NOTE code EarthProbe, 2) systematically assess the sensitivity of multi-detector NOTE to LLVP properties, and 3) integrate geophysical constraints into the proposed framework to improve data statistics and decrease required data collection times. To achieve Objective 1, the project team will modify the EarthProbe code and data structures to account for neutrinos arriving at multiple detectors, as well as the covariance matrix used by existing minimization algorithms to yield estimates of LLVP properties. Objective 2 will be accomplished through a series of systematic sensitivity tests of the new multi-detector framework across a range of anomalous LLSVP densities and compositional contrasts. Finally, for Objective 3, the team will incorporate existing geophysical estimates of either composition or density to quantify any reduction in data collection period required for NOTE analysis. This project will establish and strengthen international collaboration with a PhD student at the center, while providing and training and mentoring for students, and facilitate outreach opportunities. This project is jointly funded by Cooperative Studies for the Earth’s Deep Interior (CSEDI) and the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.