Richard Lyons

Graduate Student at University of Chicago

I am interested in the formation of planets and solar systems, like our own, and what processes are important in the early stages of formation. More specifically I am researching how impacts between planetesimals in the early Solar System resulted in the meteorites we have in collections today. To do this I utilize several numerical modeling techniques such as N-body models, impact shock physics code, and thermodynamic models.

Research

I aim to link the meteoritic record to dynamical models describing the conditions in the early Solar System. The common link between the two are impact events. If the conditions of an impact onto a meteoritic parent body (energy, timing) can be determined, then something can be learned about the dynamical environment that body experienced. Below are my current projects investigating this.

Current Research Projects

Impact Effects on Iron Meteorite Cooling Rates

With: Tim Bowling, Fred Ciesla, Tom Davison, Gareth Collins

Iron meteorites provide a record of the thermal evolution of their parent bodies, with cooling rates inferred from the structures of their minerals. While models have been developed to link cooling rates to sizes of parent bodies that they originate from, issues remain. In particular, some iron meteorite groups exhibit significant scatter in their cooling rates that require multiple parent bodies or appear to cool too rapidly to be consistent with ideas on sizes of planetesimals. Further, these models largely ignore high-energy impacts that are expected to occur when parent bodies still retain their radiogenic heat.
We've used numerical simulations to investigate the effects impacts have on cooling rates of the cores of differentiated planetesimals. We find that very early and late impacts will not significantly affect the recorded cooling rates. However, impacts that occur when the core is still largely fluid but the mantle has begun to solidify, can expose the cores leading to more rapid and non-uniform cooling (as seen in the video and figures to the left). These collisions should be considered when interpreting the histories of iron meteorite parent bodies.

Impact Effects on the Growth of the Widmanstätten Pattern in Iron Meteorites

With: Nicolas Daphaus, Fred Ciesla

The Widmanstätten Pattern is the exsolution of kamacite and taenite during the slow cooling of the core of a planetesimal. The nickel concentration across a kamacite-taenite band can be measured and fit using a nickel diffusion model. This is how cooling rates of iron meteorites have been determined. Thus far only constant cooling rates have been considered. Does an impact on a parent body effect the growth of these bands? I've developed a nickel diffusion model that can then be 'impacted,' changing its cooling rate during Widmanstätten formation to investigate if the impact would leave any observable characteristics. (image: Wikipedia)

Stony Iron Meteorite Formation

With: Tim Bowling, Fred Ciesla, Tom Davison, Gareth Collins

Early collisions (those occurring in the first 100 Myr of Solar System history) have been invoked in meteoritic studies to explain thermal evolution inconsistent with onion-shell models or the mixing of materials that appear to come from different regions of a planetesimal. The IAB and IIE groups are iron meteorites with silicate inclusions that are thought to have formed via catastrophic impacts during differentiation that mixed materials from different depths of their parent bodies. We have used a combination of impact models, N-body codes, thermal models, and material mixing models to understand the impact properties needed to create these meteortites.

Planetesimal Disruption in the Early Solar System

With: Tim Bowling, Fred Ciesla, Tom Davison, Gareth Collins

As planetesimals collide and grow, the efficiency of accretion is important for the timescales of planet formation as well as their resulting sizes. Bodies colliding with one another can result in catastrophic disruption. These catastrophic impacts can greatly affect the formation process. However, dynamical models of the early Solar System cannot fully quantitatively simulate all of these impacts because it would be computationally expensive. Therefore, parameterization of impacts must be employed to speed up the modeling. The energy of the impactor per unit mass of the target resulting in half of the target mass remaining has been used as a criterion for catastrophic disruption; Q*D. However, this criterion has not been determined for molten bodies which would be common in the dynamically active early Solar System. I will utilize differentiation models and impact models to understand how this parameterization may change in the first 100 Myr.

Publications

  • "Fast Litho-panspermia in the Habitable Zone of the TRAPPIST-1 System," Krijt, S., Bowling, T., Lyons, R., Ciesla, F.; 2017, The Astrophysical Journal Letters; arXiv:1704.01411
  • "Sloan Digital Sky Survey III Photometric Quasar Clustering: Probing the Initial Conditions of the Universe using the Largest Volume," Ho, S., Agarwal, N., Myers, A.D., Lyons, R.; 2015, Journal of Cosmology and Astroparticle Physics; arXiv:1311.2597

Professional Service

  • Co-Chair of the Gordon Research Seminar on the Origins of Solar Systems, 2017; GRS Program

Poster Presentations

  • Gordon Research Conference - Origin of Solar Systems, 2017
  • Lunar and Planetary Science Conference, 2017
  • Meeting of the Meteoritical Society, 2016
  • Lunar and Planetary Science Conference, 2016
  • Gordon Research Conference - Origin of Solar Systems, 2015
  • Lunar and Planetary Science Conference, 2015
  • Gordon Research Conference - Origin of Solar Systems, 2013
  • Meeting of the American Astronomical Society, 2013

Past Research Experience

Carnegie Mellon University, Bruce and Astrid McWilliams Center for Cosmology

  • Advisor: Dr. Shirley Ho
  • Researched the statistical correlations between the largest and second largest massed planets in every multiplanetary exoplanet system using Python. Generated simulations as well to identify what these correlations could mean for the planet formation process.
  • Researched multiplanetary exoplanet system characteristics involving the relative location of the snowline and Super Jupiter locations.
  • Performed photometric quasar clustering calculations using data from the Sloan Digital Sky Survey III to determined suitable cuts to outlaying data points. (Image: ESA)

Harvard-Smithsonian Center for Astrophysics, High Energy

  • Advisor: Dr. Eric Silver
  • Participated in an effort to increase the resolution of microcalorimeters compared to conventional spectrometers. The device was designed to be used by institutions such as NASA to analyze comet fragments to determine the composition.
  • Developed a program in C++ to determine the compounds that were detected and graphed their location in the material.
  • Created a thermal model to improve future iterations of the microcalorimeter. (Image: CFA HEA)

About Me

Education

University of Chicago (2014 - )
Ph.D in Geophysical Sciences (Expected June 2019)

Carnegie Mellon University (2010 - 2014)
Bachelor of Science in Physics, Astrophysics track

Research Experience

Graduate Student (2014 - )
University of Chicago, Department of Geophysical Sciences, Advisor: Dr. Fred Ciesla
Ph.D in Geophysical Sciences (Expected June 2019)

Research Assistant (August 2012 - May 2014)
Carnegie Mellon University, Bruce and Astrid McWilliams Center for Cosmology, Advisor: Dr. Shirley Ho

Research Assistant (May 2010 - August 2012)
Harvard-Smithsonian Center for Astrophysics, High Energy Astrophysics Lab, Advisor: Dr. Eric Silver

Contact Me

rjlyons at uchicago.edu

Department of Geophysical Sciences
University of Chicago
5734 S. Ellis Avenue
Chicago, Illinois 60637
(773) 702-8101