Thanks to very high resolution images taken by the Mars Global Surveyor (MGS) and Mars Orbital Camera (MOC), clues about the complex early history of Mars are just now beginning to come forth. Mars scientists are getting these clues by looking at Mars rocks and layers of sediment, which tell tales of the comings and goings of seas, mountain ranges, rivers, volcanoes, and deserts.
Recently NASA announced that ancient Mars may have featured numerous lakes and shallow seas. The scientists compare the rock layers on Mars to features seen in the American Southwest, such as the Grand Canyon and the Painted Desert of Arizona. According to Dr. Michael Malin, principal investigator for the Mars Orbiter Camera on NASAs Mars Global Surveyor spacecraft at Malin Space Science Systems (MSSS) in San Diego, CA, "These images tell us that early Mars was very dynamic and may have been a lot more like Earth than many of us had been thinking." NASA says it may be their most significant discovery yet.
The image above is the first image received by MOC scientists that began to hint at a larger story of layered sedimentary rock on Mars. The picture shows a 0.9 mi by 1.8 mi (1.5 km by 2.9 km) area in far southwestern Candor Chasma that was not previously expected to exhibit layers. What NASA says is most striking about the picture is the large number and uniformity of the layers, or beds. There are over 100 beds in this area, and each has about the same thickness, estimated to be about 11 yards (10 meters) thick. Each layer has a relatively smooth upper surface, and each is hard enough to form steep cliffs at its margins.
Layers indicate change. The uniform pattern seen herebeds of similar properties and thickness repeated over a hundred timessuggest that the deposition of materials that made the layers was interrupted at regular or episodic intervals. Patterns like this, when found on Earth, usually indicate the presence of sediment deposited in dynamic, energetic, underwater environments. On Mars, these same patterns could very well indicate that the materials were deposited in a lake or shallow sea.