Research Training Program

Sharon A. Wilson
Middlebury College
Middlebury, Vermont

Ed Vicenzi, Ph.D.
Supervising Scientist
Department of Mineral Science

"The opportunity to research Martian meteorites at the Smithsonian has provided an invaluable introduction into the amazing field of planetary geology."

Microscopy and microchemistry of low temperature aqueous alteration in the Lafayette meteorite

Out of the 7500 meteorites that have been found on the surface of earth, only fifteen have been identified as Martian. These few rocks from this neighboring planet provide scientists with clues to interpret the active and dynamic geologic history of Mars. Lafayette is from a portion of Mars that formed 1.3 billion years ago and is thought to have fallen in Lafayette, Indiana prior to 1931. This 800-gram rock is igneous in origin, meaning it cooled from molten material akin to lava. Lafayette is a unique Martian meteorite because it contains an abundance of rust-like reddish-orange "alteration" material that formed on Mars. The chemistry of the alteration suggests that water was involved in its formation; therefore, the rock must have been subject to water whilst on Mars. A firm understanding of the alteration is crucial to determine whether the Martian subsurface was once suitable to sustain primitive lifeforms such as bacteria. In this study, the preterrestrial alteration was characterized through digital imaging techniques and detailed chemical microanalysis. The alteration is quite complex and possesses a delicate microtexture consisting of silica-rich and iron-rich glass, clay and carbonate, all materials known to form in watery environments on Earth. A sensitive X-ray microanalyzer was used to quantify the concentrations of sodium, sulfur and chlorine within the alteration. The presence of sulfur is important regarding the search for life on Mars because it can be present in a form that allows bacteria to use it as an energy source. The presence of chlorine in the alteration suggests that the water at or near the surface of Mars was slightly saline. The saline component would decrease the freezing temperature of liquid water, extending the conditions suitable for life on Mars.

This research was supported by a grant from the Smithsonian Director's Office.

Letter of Gratitude