Antarctica is sometimes described as otherworldly. As it turns out, this is actually quite close to the truth. Geologists’ knowledge of the origin and nature of certain features in the Mars-like Antarctic Dry Valleys (ADV) can be applied to regions of the Martian surface to improve our understanding of the Red Planet’s geology, climate, orbital history, and potential for exploration.In the equatorial region of Mars, numerous volcanoes known as the Tharsis Montes contain geomorphic evidence for past climate change. The northwest flanks of at least three of these volcanoes are marked by distinct surface features that closely parallel landforms and features in the climatically similar ADV; these features, it turns out, are indicative of the presence of glacial ice over the past several hundred (plus) million years.
|Shaded image of Olympus Mons and the Tharsis Montes volcanoes. Image Credit: NASA|
|Arsia Mons-- one of the Tharsis Montes|
volcanoes. Image Credit: NASA
The landforms and features observed on the Tharsis Montes are grouped into three distinct facies. To a geologist, a facies is an assemblage of things that share a common affinity. The outermost facies, which marks the farthest extent of former glaciers from their respective volcanoes, is characterized by a series of ridges called moraines, formed by glaciers carrying debris toward ice margins. The intermediate “knobby” facies features many hills, or knobs, interpreted to represent the uneven sublimation (change from solid to ice) of debris-covered ice. Finally, the innermost smooth facies is believed to contain glacial ice still buried by debris. Using highly similar features in Antarctica for guidance, geologists analyze the relative position and the extent of the three facies, which indicates glacial advance and recession, to study Mars’ climatic history. This is important for several reasons. First, it enables geologists to develop an accurate timeline of Mars’ climatic history. Moreover, by studying Mars’ climate, scientists can better understand its past orbital obliquity—the orientation of its axis of rotation with respect to its orbit around the sun. This is important to astronomers and planetary scientists because computer models of Martian orbital obliquity are only accurate for the past ~20 million years. However, because the presence of ice at certain latitudes is dependent on orbital obliquity, and this ice leaves lasting geological features that can be dated, scientists can study Martian climate for hundreds of millions of years or more into the past. The presence of ice suggested by the smooth facies may improve scientists’ knowledge of the ancient Martian atmosphere, when the currently frozen water may have been in the atmosphere. This ice may also be important to the continued exploration of Mars by robots, and eventually humans. Water ice could potentially be used as a component of rocket propellant for ships leaving Mars, and ancient sites of ice melting have been suggested as optimal locations for the search for extinct bacterial life. By continuing to study both Martian and Antarctic glaciers, geologists are improving our understanding of our place in the solar system—past, present, and future.