Planetary Science Directorate


Upcoming SwRI Boulder Colloquia

Colloquia are normally on Tuesdays at 11:00 am in the 4th-floor conference room, except as indicated below in bold text.
Show previous colloquia

For questions or suggestions for speakers, please contact the SwRI colloquium organizers:
Hannah Kaplan, 720-208-7208 or kaplan(at)
Derek Lamb, 720-208-7207 or derek(at)
Katie Primm, 720-240-0124 or kprimm(at)
Raluca Rufu, 303-226-0879 or raluca(at)
Julien Salmon, 720-208-7203 or julien(at)
Kelsi Singer, 303-226-5910 or ksinger(at)

To be added to the SwRI Boulder Colloquia email list, please contact Kelsi Singer, ksinger(at)

Tue Dec 10, 201911:00 am Ron Ballouz University of Arizona LPL Surface refreshing of Martian moon Phobos by orbital eccentricity-driven grain motion
Abstract: The origin of the Martian moons Phobos and Deimos remains a prominent mystery in planetary science. It is unknown whether the moons are captured asteroids or if they formed in an accretion disk following a giant impact with Mars. A giant impact origin implies the presence of mafic minerals on Phobos and Deimos. However, there is an observed lack of diagnostic absorption features in near-IR spectra of the two moons. Furthermore, dynamical models of asteroid capture in the Mars system are unable to reproduce the near-circular orbits of Phobos and Deimos. A clue to the origin of the Martian moons are Phobos’ distinct red and blue geologic units. It is unclear whether these two units are compositionally distinct, or if spectral differences are due to space weathering, as there is an observed lack of strong absorption features in both units. In this talk, I will show how we used a combination of dynamical analyses and numerical simulations of particle dynamics to show that periodic variations in Phobos’ surface slopes, driven by its small orbital eccentricity, causes surface grain motion. Rather than the fast-flow of a landslide, a downslope creep of surface grains occurs every Phobos orbital period. Accumulated over many periods, this “cold-flow” mechanism can excavate the top layer of regolith in timescales < 1 Myr. Therefore, space weathering could be the driver of the dichotomy on the Phobos’ surface, reddening blue units that represent pristine endogenic material. If so, the regolith physical mechanical properties may constrain Phobos’ origin, and also potentially reveal the history of material exchange in the cis-Martian environment. Ultimately, these questions will be answered by JAXA’s next sample return mission, the Martian Moons eXploration mission (MMX). MMX will land on Phobos and return samples from its surface. Lab analysis of these samples may conclusively determine the origin of the Martian moons and shed light on the early history of the Martian system.
Tue Feb 25, 202011:00 am Kathryn Steakley NASA Ames TBD Impacts
Tue Mar 3, 202011:00 am Hakeem Oluseyi NASA Headquarters TBD Science Outreach
Tue Mar 31, 202011:00 am Hannah Jang-Condel University of Wyoming TBD