Lineated valley fill

Lineated valley fill (LVF), also called lineated floor deposit, is a feature of the floors of some channels on Mars, exhibiting ridges and grooves that seem to flow around obstacles. Shadow measurements show that at least some of the ridges are several metres high. LVF is believed to be ice-rich. Hundreds of metres of ice probably lie protected in LVF under a thin layer of debris. The debris consists of wind-borne dust, material from alcove walls, and lag material remaining after ice sublimated (changed from a solid directly to a gas) from a rock-ice mixture. Some glaciers on Earth show similar ridges. High-resolution pictures taken with HiRISE reveal that some of the surfaces of lineated valley fill are covered with strange patterns called closed-cell and open-cell brain terrain. The terrain resembles a human brain. It is believed to be caused by cracks in the surface accumulating dust and other debris, together with ice sublimating from some of the surfaces. The cracks are the result stress from gravity and seasonal heating and cooling. This same type of surface is present on Lobate debris aprons and Concentric crater fill so all three are believed to be related.

Wide CTX view of mesa showing lineated valley fill and lobate debris apron (LDA). Both are believed to be debris-covered glaciers. Location is Ismenius Lacus quadrangle.

Close-up of lobate debris apron from the previous CTX image of a mesa. Image shows open-cell brain terrain and closed-cell brain terrain, which is more common. Open-cell brain terrain is thought to hold a core of ice. Image is from HiRISE under HiWish program.

Closed-cell brain terrain, as seen by HiRISE under the HiWish program. This type of surface is common on lobate debris aprons, concentric crater fill, and lineated valley fill.

Open- and closed-cell brain terrain, as seen by HiRISE, under HiWish program.

Wide CTX view showing mesa and buttes with lobate debris aprons and lineated valley fill around them. Location is Ismenius Lacus quadrangle.

Close-up of lineated valley fill (LVF), as seen by HiRISE under HiWish program. Note: this is an enlargement of the previous CTX image.

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