|
Evidence of possible terracing in the Twin Peaks The peak on the right has been suggested to show evidence of horizontal terracing, an effect commonly associated with water on the Earth. There is little doubt that the Sagan Station sits in the midst of a large flood plain, not unlike the broad arroyos and playas that are often common just below mountain bajadas in deserts on the Earth. The flood that created Ares Vallis was almost certainly a transient event, similar to the flash floods that create arroyos, but on a far grander scale. The most likely scenario for the occurrence of the flood was a general warming of Mars, possibly due to orbital precession, and the subsequent collapse of the permafrost layer over a large highland region. Permafrost is a rock-ice matrix that tends to catastrophically "squeegee" out its water in a gush when warmed to a point that the permafrost can no longer mechanically support its own weight. Terracing is often associated with the action of water on Earth. One mechanism that creates such terraces is the differential deposition of sediments over extended period of times. If the Ares Vallis flood was transient, this explanation can be ruled out. A second terracing mechanism is the action of waves, leaving a sequence of high water marks on an upland area (much like a bathtub ring), primarily by surface wave erosion and the deposition of salts due to evaporation. But terraced landscapes can also be created volcanically. Subsequent sequential eruptions of a volcano may generate a series of ash tuffs of different colors and mechanical strengths. In the presence of only aeolian (wind) erosion, without water at all, a slope may be differentially worn away, creating a terraced structure. And the "terraces" may not be there at all, but are more the result of the eye's desire to connect a series of dots. When more time is available, better image processing will almost certainly allow a greater assessment of the likelihood that the terraces are real.
|