Antonio Macias Canizares
(Advisor: Prof. Dimitri Mavris)

will propose a doctoral thesis entitled,

Volatile Molecular Species and their Role in Planetary Surface Morphology and Spacecraft Design and Performance

On

Tuesday, November 7 at 10:00 a.m. EST
Collaborative Visualization Environment (CoVE)

Weber Space Science and Technology Building (SST III)

Abstract
               The geologic processes that govern the surface morphology of ice-covered, airless (i.e., without atmospheres) bodies in the Solar System have gained increasing interest over the past several decades, both for the scientific questions such worlds present, and for the relevance for future in-situ exploration. Though engineering capabilities for landing spacecraft, such as terrain relative navigation and hazard avoidance, can mitigate against meter and sub-meter scale hazards, it is nevertheless important to understand the morphological evolution and steady state of the surface ice on these worlds. Considerable work has been dedicated to the large- and small-scale geology of these worlds, but much remains to be understood about the centimeter- to meter-scale morphology of these icy, cryogenic (~100 K) surfaces.

One specific hypothesis, is that blade-like structures, called penitentes, form on the surface of Europa, and rise up to 15 meters in height, though it has been argued that the physics of penitente formation, as applied for such a hypothesis, does not apply to the exosphere and surface conditions of Europa. Interestingly, penitente-like structures have been observed on Pluto, which does have a significant, albeit seasonal, atmosphere. Penitentes are also predicted to form under certain conditions on Mars though they have yet to be observed. On Earth, penitentes are made from compact snow or ice and achieve quasi-stability in high-altitude, low-latitude regions, as the result of sublimation and melting processes, and importantly, they only occur in regions of net sublimation (or melting) loss of water. Penitentes are erosional features that form as a series of corrugated ridges and troughs that run parallel to the path of the Sun across the sky, and mature structures often yield fields of individual spikes or blades, which bear some resemblance to a pair of hands praying toward the Sun, hence the name 'penitentes.'

To advance our understanding of the surface morphology of airless, ice-covered worlds, and to address the limitations of current models, we have developed numerical models that accurately represent the irradiance and physical evolution of ice on such worlds, and we have constructed experiments against which such models can be validated. It is important to emphasize the focus on sublimation erosional morphologies, such as penitentes, and thus a key condition is that the region of interest experiences a net loss of water molecules. On Earth, wind and melting carry away water. On worlds like Europa, regions exposed to more diurnal or seasonal solar irradiance may experience a net loss of water, while colder, less-illuminated regions could serve as sites of net accumulation. Despite the physics of Europa, which would most likely deter the formation of penitentes, the possible presence of penitentes could pose a hazard for a future lander on Europa.

Committee

• Prof. Dimitri Mavris – School of Aerospace Engineering (advisor)
• Prof. Christopher Carr – School of Aerospace Engineering
• Prof. John Dec – School of Aerospace Engineering
• Prof. David Goldstein – Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin
• Prof. Philip Varghese – Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin
• Dr. Kevin Hand – NASA Jet Propulsion Laboratory