(See description below)
Mars' Chasma Boreale
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The north polar layered deposits of Mars form a layered stack of
dusty ice up to 3 kilometers (2 miles) thick. The differences from layer to
layer are thought to reflect differences in the climate of Mars that existed
when the layers were formed.
We can see these internal layers exposed on the faces of the many troughs and
scarps that cut through these deposits. One of these scarp faces is shown here;
it is situated at the head of a large canyon (named Chasma
Boreale) that cuts
through these polar
layered deposits.
The terrain at the bottom of the image is higher and consists of the upper surface of the icy
layered deposits in this area, while the terrain at the top is lower and
consists of the rocky ground that underlies the layered deposits. The cliff that
separates these two areas runs down the center of the image with a relief of
about 700 meters (about 2300 feet).
The section of the layered deposits that is exposed on this cliff face is
unusual in that, as well layers of dusty ice, there are also layers of sand
present. Small structures, called cross-beds, visible in the sandy layers
indicate that each layer was originally a dune field that only later became
covered with ice. Some of this sandy material is being removed from the cliff
face and is forming new dunes at the foot of the cliff.