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Sep 20, 2005
Craters, Trenches and Arcs

The overlapping of a crater and a trench on Mars reveals a wealth of electrical details

Was this crater excavated by a surge in the current that was digging the trench? Or did the arc that cut the crater touch down on a high point along the edge of the previously eroded rille? (Note that the crater seems to be centered on the edge of the rille.) Note also the small craters centered on the rim of the larger one as well as on the edges of the trench.

The left side of the trench below the crater appears to have a terrace cut into it, but as it nears the crater, the terrace becomes a shallow trench in its own right, separated from the main trench by a dike of material. The shallow trench then stops at a craterlet blasted into the rim of the large crater. On the opposite side of the main trench is another shallow trench that merges into the main trench at the point where the other shallow trench becomes a terrace.

Note also that, at the bottom of the image, the trench from the crater merges with another trench at an almost exact right angle. The terrace also turns the corner and continues along the edge of the other trench. Significantly, the transverse ridges on the floor of the trench also turn the corner, indicating that they were formed by the coronal filaments attending the primary arc that carved the channels.

David Talbott, Wallace Thornhill
Mel Acheson
  CONTRIBUTING EDITORS: Michael Armstrong, Dwardu Cardona, Ev Cochrane,
C.J. Ransom, Don Scott, Rens van der Sluijs, Ian Tresman
  WEBMASTER: Michael Armstrong

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