Mad Vallis is a vallis (valley) in the Hellas quadrangle of Mars, with its location centered at 56.5° S and 283.9° W. It is 524 km long and was named after the Mad River in Vermont, USA.[1]
 Mad Vallis, as seen by HiRISE. Picture on right is an enlargement of part of the other picture. | |
| Coordinates | 56°30′S 283°54′W / 56.5°S 283.9°W |
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