June 7, 2012
Mars Express Reveals Climate Evolution On Red Planet
Lee Rannals for redOrbit.com
ESA's spacecraft used its high-resolution stereo camera at the Arabia Terra region of Mars on June 19, 2011 to image the Danielson and Kalocsa craters.
Danielson crater is filled with layered sediments, and within the crater are peculiarly layered buttes, which are known as yardangs.
Yardangs are hills carved from bedrock or any consolidated or semi-consolidated material by abrasive dust and sand particles carried in the wind.
These structures are seen on Earth in desert regions, with examples in North Africa, Central Asia and Arizona.
ESA believes the sediments in Danielson crater were cemented by water, maybe from an ancient reservoir.
Scientists theorize that strong north-northeasterly winds both deposited the original sediments and then caused their subsequent erosion in a drier period later on in Martian history.
The 18.50 mile-long field of dunes can be seen bisecting the yardangs and is thought to have formed at a later epoch, according to ESA.
Danielson's crater floor shows evidence for a series of alternating sedimentary layers with uniform thickness and separation.
Some scientists believe this indicates periodic fluctuations in the climate of Mars, which is triggered by regular changes in the planet's axis of rotation.
According to ESA, the different layers would have been laid down during different epochs. The Kalocsa crater shows a different topography.
In the Kalocsa crater, no layered sediments can be seen, which is due to the higher altitude of its floor, ESA said.
The space agency said that another hypothesis is that the Kalocsa crater is younger than its neighbor, and was created when water was not present anymore.