Introduction: Under the general category of the "quest for life" on Mars a search for possible remnants of an intelligent prior habitation cannot be reasonably excluded. As established by Freitas and Valdes1, a Search for Extraterrestrial Artifacts (SETA) is a relevant field of inquiry, especially in light of NASA plans to consider long term human habitation of Mars. Recent release of Mars Global Surveyor images to the Internet has revealed a number of unusual features that do not seem to adhere to established geologic mechanisms. When compared to terrestrial satellite photography at comparable resolutions, at least two specific types of features bear a stronger resemblance to architectural structures than to any accepted natural geologic process. These features are preferentially found close to, but are not confined to, canyon walls near the line of dichotomy on the Martian surface, and along the margins and within broad planes of former sea beds. A third type of feature has been found on a large northern latitude caldera (and is similar to other features found in planar and mountainous areas). It shows a regular, geometric pattern similar to a terrestrial city as viewed from orbit. Various possible geo-logic explanations, such as fluvial erosion, wind sculpting, frost wedging and volcanic flows, are considered but seem inadequate to explain observable features. A tentative model is proposed with regard to the possible relative age of these features, working within assumptions made concerning the dating of catastrophic events in Mars Ancient History. Finally, recommendations are made for the best candidate sites for lander and rover exploration with an eye toward detailed exploration of these anomalies, as well as establishing the most desirable location for a permanent, self-sufficient human base on Mars. The three specific types of features will be examined in detail. Images provided within the abstract are for pre-view. Larger, full resolution images are included in the text.

Feature Type 1: An example of the first type of anomalous feature can be seen on Mars Orbiter Cam-era image MO4-002912, a narrow angle image taken in the Mare Acidalium region. This region is considered a probable location of an ancient ocean3. The image, (Fig.1) taken with a resolution of 3.07 meters per pixel, shows a number of large plates with a rift between them. Inside the rifts are regularly spaced brightly colored parallel features. In some parts of the image, the stripes or arches are mostly buried, but in other portions they are almost fully exposed. The "arches" are solid, individual features that stand out from the

background by their shape, regularity and albedo properties, which imply they are composed of a different material than the surrounding terrain. 

Fig.1 M04-00291

 One section of the rift contains what appears to be coherent, semi-translucent tubular structure, of which the "arches" are a structural component. The edge of the tube can be clearly defined against the darker background material, and the arches are cylindrical in shape and follow the contour of the "tube." The translucent-reflective quality of the "tube" is reinforced by a specular reflection off an exposed portion of the object, which is in phase with the Orbiter camera. Fluvial processes would not preferentially produce parallel arch-like features, especially ones that are 90 to the projected flow of water through the channel. They further would not be restricted to the channel itself. Likewise, wind erosion, even if confined to the rifts or channels, are not likely to produce parallel features with such regular spacing or sharply defined cylindrical shapes. Sand dunes on Mars display similar characteristics as those on Earth. To ascribe these features to sand dune-like processes requires ignoring the 3-D shape, spacing and extreme regularity of the form.

Feature Type 2: The second type of anomalous feature is

  found most commonly along canyon walls or floors. Images taken of the Valles Marineris system and along other canyon walls (like Ares Vallis image FHA00818 Fig. 2) reveal a tiered or "stepped" structure. Anomalous features are distinguished by a repetitive pattern of exposed geometric cellular structure in the vertical walls and regular, cylindrical "tubing" on the tapered slope faces.

Fig. 2 FHA00818

The tubes themselves (image FHA00818, close-up-- Fig. 3) have a coherent structure and seem to emerge from the valley wall at right angles to the proposed channel flow. They then extend under the soil, implying they are the exposed portions of a larger network. The tubes bear a strong resemblance to terrestrial plumbing or structural "rebar."

These patterns repeat over and over in several visible layers in the image. Again, conventional volcanic, wind or liquid processes seem inadequate to explain these features.

Fig. 3 FHA00818

Feature Type 3: The third type of anomaly is a set of large block like formations on the Alba Patera Caldera (image M02-00351 -- Fig. 4). The blocks appear to be distributed in a highly organized fashion, and appear comparable to a terrestrial cityscape at equivalent (1.5 meters per pixel) resolution. Specifically defined objects range in size from typical suburban housing to roughly the size of a small football stadium or warehouse. The blocks extend essentially the entire length of the 7km image, with some sections buried under sand or debris. Even so, the same rectilinear pattern can be seen beneath the sand. Although a well-developed high-angle joint set could provide such a rectilinear pattern, that explanation seems lacking for the following reason. Joint sets are a series of cracks, or openings, whereas the subject features display positive relief. The joints would have had to be filled in with more resistant materials and then the surrounding materials eroded to provide the observable relief. Not impossible, but also not very likely.

Fig. 4 M02-00351