Nasa.gov White rock fingers like structure in Mars image:38720:5::0

The object initially looked like salt deposit remains on the lakebed, but further studies of the fingers in that location proved they are incorrect.

NASA scientists think this structure appears to have eroded away from the surrounding area, indicating a very low-density composition, possibly consistent with volcanic ash or windblown dust.

Erosion from the surroundings has exposed finger-like structures.

The sand in the lakebed is mostly composed of volcanic ash material, which is the reason they appear darker than the exposed rocks.

Here is a further detailed image of the fingers in the lakebed.



The image spans a distance of 10 kilometers (6.21 miles) and the surrounding lakebed is many times longer than this distance (100 kilometers).

This picture was chosen as the Astronomy picture of the day and it was taken by the European Space Agency's Mars Express, which is currently orbiting Mars and mapping its features.

If you want further detailed information about this feature, read planetary scientist Emily Lakdawalla’s report in the Planetary Society Weblog.