Subsurface Water Ice Mapping (SWIM) in the Northern Hemisphere of Mars
The goal of the SWIM project is to provide a set of mapping products using existing spacecraft data that delineate subsurface ice in the mid-latitudes of Mars. We aim to identify and map indicators of possible subsurface ice in each data set and use a combination of all data sets to assess the likelihood of ice being present in shallow (less than 5 m depth) and deep (more than 5 m depth) zones. In this, we are developing the SWIM Equation, styled after the famous Drake Equation, which will provide maps of how consistent the data are with the presence or absence of water ice resources in the subsurface.
Click here to learn more about the SWIM Project!
Radar response of lunar cryptomaria and pyroclastic deposits in Mini-RF data
I am investigating the monostatic and bistatic radar response of cryptomaria and pyroclastic deposits in Mini-RF data, a side-looking hybrid-polarization radar system onboard the Lunar Reconnaissance Orbiter. I am comparing and modeling the radar response of these terrains to other datasets (e.g. Clementine color ratios, Titanium map, etc.) and to the radar response of other terrains (e.g. Mare and Highlands).
Modeling and laboratory experiments of ice sintering processes in non-terrestrial environments
Our team, led by Dr. Jamie Molaro, is combining laboratory experiments and theoretical modeling to explore the role of sintering on the evolution of water ice on icy satellites, Mars, and across the solar system. I will be applying our experimentally-validated model to Mars to explore the role that diurnal and seasonal thermal cycling plays in sintering rates, and the formation of subsurface density gradients to explore how these processes may produce layering in martian ice deposits, and relate the results to spacecraft images and radar subsurface detections that show layering within Martian ice deposits.
My dissertation research focused on Mars mid-latitude ice and what it can tell us about the Martian climate system, particularly the stability of water (at least in ice and vapor form)
in the Amazonian period.
In 2015, I published my study on an ice sheet the size of California and Texas combined just underneath the surface of Mars that goes as deep as a 13-story building. To find this
ice, I used a high-resolution camera called HiRISE, which we operate here at the Lunar and Planetary Lab on campus, as well as a radar instrument called SHARAD. Both of these instruments are onboard NASA's Mars Reconnaissance Orbiter. Creating 3D Digital Terrain Models of terraced craters (above) allowed me to constrain the thicknesses of the ice layering, and by
combining these measurements with the time delays of the subsurface radar returns, I was able to estimate the dielectric constant of this deposit.
Bramson et al. (2015) Widespread excess ice in Arcadia Planitia, Mars. GRL, 42,
More recently, I have written a 1D thermal conduction model to look into how this ice could have been preserved. We find that decameters-thick ice sheets at the mid-latitudes of
Mars can be orders of magnitude older than the obliquity cycles that are typically thought to drive mid-latitude ice deposition and sublimation. Retreat of this ice in the last 4
Myr could have contributed ~6% of the volume of the North Polar Layered Deposits (NPLD) and more than 10% if the NPLD are older than 4 Myr.
Bramson et al. (2017) Preservation of Mid-Latitude Ice Sheets on Mars. JGR-Planets, 112,
Ice in the mid-latitudes exchanges with polar ice over geologic time so to understand the other half of the system, I applied my ice stability model to the migrating troughs of
Mars' North Polar Layered Deposits. This allowed me to investigate the role of sublimation on the migration of these troughs. The thickness of the sublimation lag is a key factor controlling sublimation rate and has been actively removed over time. We combine sublimation and accumulation conditions to reproduce migration at two adjacent troughs, demonstrating the viability of our new phenomenological model for spiral trough migration.
Bramson et al. (2019) A Migration Model for the Polar Spiral Troughs of Mars. JGR-Planets,
Additional topics and projects:
Radar and Remote Sensing
Newly-discovered scarps that expose the stratigraphy of mid-latitude ice sheets on Mars [Dundas et al. (2018)]
Radar detections of mid-latitude ice-rich deposits in the Southern hemisphere
I am currently mentoring an undergraduate astronomy major, Claire Cook, through the Arizona Space Grant Consortium on
this project for her senior honors thesis.
Application of super-resolution radar processing techniques to find thinner and shallower ice deposits on Mars (collaboration with Marco Mastrogiuseppe and Marìca Raguso)
Arecibo radar-based models of asteroid shapes and surface properties: a comparison of ground-based observations of Itokawa to the 'ground truth' from the Hayabusa spacecraft mission (collaboration with Mike Nolan, Ellen Howell and Patrick Taylor)
Theoretical Modeling of Icy Processes
iSALE modeling of the formation of terraced craters by impacts into icy targets (collaboration with Elena Martellato)
Temperature-dependent modification of possible cryovolcanic features
We predict a latitude-dependent asymmetry in equatorward vs. poleward facing slopes of cryovolcanic domes on Ceres due to temperature differences of these slopes
affecting the rates of viscous flow. Viscous flow rates are slow enough at the location of Ahuna Mons that it would remain identifiable as a cryovolcanic feature today,
given the expected young age of the dome [Sori et al. (2017a)] and can be used to constrain the cryovolcanic rates on Ceres throughout time [Sori et al. (2018)].
Carbon dioxide ice transport and stability on the Uranian moons
We predict the bright spot observed by Voyager 2 inside the crater Wunda is a deposit of CO2 ice.
[Sori et al. (2017b)]
Origin of geologically recent flow units in Hrad Vallis, Mars: mega-lahars or pāhoehoe-like lava flows?
We find evidence for both aqueous flooding and effusive volcanism suggesting the area has a complex hydrologic and geologic history. Pāhoehoe‐like lava flows could have interacted with ground ice in the region to generate meltwater and steam. [Hamilton et al. (2018)]