From the Editor

Our topic this issue is the stuff of novels and movies. Is or was there extraterrestrial life and can we find evidence on Mars? But it is even better than that! This time we are sending two rovers to land on and explore two martian sites that have been meticulously chosen for geologic features indicative of water, hence the possibility of life.

In our lead article, “Landing the Mars Exploration Rovers,” Matthew Golombek and colleagues describe how the entire surface area of Mars was narrowed down to two landing sites, Meridiani Planum and Gusev crater, based on operational considerations and scientific criteria. Never before has so much site selection data been available, drawing on Earth-based observations, satellites and earlier landing sites. “This information has resulted in the best-imaged, best studied locations in the history of Mars exploration,” the authors write. These sites offer the promise that the vehicle can safely land, the rovers can successfully operate, and that the observations will significantly sharpen our confidence that water and life were or are present on Mars. For all this to happen the sites must hit the geologic bull’s eye and not be too dusty, too far from the geoid, too shaded, too rocky, too steep or too hilly. Don’t you feel the suspense building?

Much of the success of the mission will depend on the performance of the twin rovers, built to do what a geologist would do if dropped into the same location. Writing in our third feature, Lisa Pinsker describes the “affection” the designers express for the 395-pound rovers, each equipped with an extendable arm that has capabilities comparable to a hand lens and a rock hammer. There the similarity ends however, because the rovers also have a Mössbauer Spectrometer and an Alpha Particle X-Ray Spectrometer for elemental analysis.

Interpreting the geologic and organic history of virtually inaccessible sites, such as those on Mars, relies upon whatever direct observation we have of the place, embellished by our greater understanding of other places that seem to be analogous. This process of building analogs, or models, is the heartbeat of research and exploration. The remainder of our feature stories in this issue are of this genre, predicting martian processes, features and history based on similarities between martian an earthly observations.

An example is work going on at the Center for Earth and Planetary Studies at the Smithsonian Institution, National Air and Space Museum. Dark and light streaks have been observed in the deserts of both Egypt and Mars (in our second feature, see “Egypt: Rivers of Sand” by Christina Reed). In the Egyptian desert, field work has identified paleo-river channels, now largely covered by sand, that play a role in the dark-light patterns. The planned Mars Express and Mars Reconnaissance Orbiter missions are slated to carry ground penetrating radar to search for similar buried features on Mars.

This second feature wraps up with four more vignettes of this genre. In the first, similarities and dissimilarities between the Nanedi Vallis of Mars’ Xanthe Terra region and Earth’s Grand Canyon are considered in studying Mars’ past climate. How much, if any, of the latter’s history is applicable to the former? The focus then shifts to similarities between the unusually long-wavelength dune ripples at Great Dunes National Monument, Colorado and Edwards Air Force Base, California and similar features on Mars. What do the environments of the unusual earth features tell us about Martian conditions of formation? Finally, strongly acidic lakes in Australia sport features that bear resemblance to features noted on Mars. Could it be that acidic waters are basic to understanding Mars’ surficial geology?

If all this suspense and mystery leave your nerves a’jangle, thumb back to the Geologic Column for a good belly-laugh, especially if your name is Steve.

Believe your compass,

Samuel S. Adams
Geotimes Editor-in-Chief

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