REPRESENTATIVE PROJECTS

1. Examining MARSIS Radar Sounding Data for Evidence of Subpermafrost Groundwater
Advisors: Dr. Steve Clifford and Dr. Essam Heggy

One of the primary objectives of the MARSIS orbital radar sounding investigation, on ESA’s Mars Express mission, is the potential detection of subpermafrost groundwater, at depths of a kilometer or more beneath the surface. MARSIS operates much like a traditional ground-penetrating radar (GPR).  When a radar pulse, emitted from orbit by MARSIS, reaches the boundary between two materials of differing dielectric properties (such as the atmosphere and the planet’s surface), a portion of the incident energy is reflected back to the sounder–while the remainder continues to propagate into the subsurface, where it may suffer additional losses due to scattering by imbedded objects and absorption due to the electromagnetic properties of the host material.  As successive dielectric interfaces are encountered, the signal experiences additional reflections and losses by absorption and scattering (affecting both the transmitted and reflected portions of the signal).  As the reflected signals are received by the orbital sounder, the depth of the corresponding interface can be determined by the time delay between transmission and reception (assuming that the returned signal is still detectable above the ambient noise).  MARSIS is using this approach to acquire the first global dataset of martian subsurface radar properties, attempting to assess the three-dimensional distribution and state of subsurface water by its high dielectric contrast (as a liquid) with ice and rock.

This intern project will examine the MARSIS data, acquired in selected areas, and analyze it for evidence of deep reflections that might be indicative of the presence of subpermafrost groundwater.  As a complement to this investigation, the intern will also conduct Finite Difference Time Domain simulations of MARSIS radar propagation into the martian subsurface, based on the latest mineralogical information about the composition of the surface, laboratory measurements of the associated electromagnetic properties of these materials, and subsurface conditions found in analogous terrestrial environments. Regardless of whether evidence of subpermafrost groundwater is detected, this project is expected to yield an improved understanding of the lithology, stratigraphy, and structure of the martian crust that may assist in addressing a broad range of scientific questions related to the geologic and hydrologic evolution of Mars.

 

2. Cooling Rates of Impact Melts on Asteroids as Determined by Metal Compositions in Meteorites
Advisor: Dr. David Kring

Impact cratering is the dominant geologic process affecting planetary surfaces.  One way to unravel the collisional evolution of the Solar System is to study meteoritic samples from impact-cratered asteroids. These types of samples can be used to study the ages of impact events on asteroids (and, thus, the impact flux), how those impact events affect asteroids, and also provide insights into the structural integrity of asteroids.  The latter will be critically important in the future when we need to deflect a hazardous asteroid on a collision course with Earth.  A particularly important subset of the meteorite samples from asteroid impact craters are impact melts and impact melt breccias.  To properly interpret impact ages of these samples, however, we need to determine peak temperatures created in these samples when the impact events occurred and the subsequent cooling rate of these samples.  This data can also be used to determine the size of the impact event on the parent asteroid.

To address these issues, the student will analyze meteorite samples from impact craters on asteroids.  The student will begin by examining the samples using a petrographic microscope at LPI to identify metal that is entrained in the impact melt breccias.  Those metal particles will then be analyzed using an electron microprobe at JSC to determine chemical compositions.  Those chemical compositions will then be used in simple calculations to determine the cooling rate of the impact melt.  In addition to these specific scientific outcomes, the student will learn about meteorites, impact cratering, and asteroids.  Many of the lessons learned will also provide the foundation needed to understand the impact cratering of asteroids on other planetary surfaces like Earth, the Moon, and Mars.

 

3. Forensic Engineering of Lunar Dust
Advisor: Dr. John Lindsay

A layer of soil and dust covers the entire surface of the Moon.  During the Apollo missions the dust proved to be a problem for spacecraft operation and crew health. Over the summer we will be studying a series of dust samples peeled from two Apollo space suits, Alan Bean’s suit from Apollo 12 and Jack Schmitt’s suit from Apollo 17.  Using a scanning electron microscope we will determine the size and shape distribution of the dust and study the composition of the grains. The results of our work will be used in future mission planning and in establishing standards for crew health.