Today's Image of Mars shows Danielson crater on the right and Kalocsa crater in the center, as imaged by Mars Express. Danielson crater is 60km in diameter, while Kalocsa crater is 33km in diameter and 1km shallower.
|Click image to see high resolution original from Mars Express. [See their article]
Within Danielson you can see some yardangs, which form when erosion is primarily caused by wind. Yardangs have multiple sharp ridges are oriented in a similar way. That orientation can help scientists determine the direction of the winds that created them. In this case the yardangs indicate that there were once very strong north, north-easterly winds.
Danielson Crater shows evidence that the climate went through periodic climate shifts as a result of changes to the rotational axis. The several layered deposits visible within Danielson have similar thickness and separation, which scientists speculate means the climate has changed on Mars in regular intervals. This can easily be explained by periodic changes in the rotational axis of the planet.
Kalocsa crater shows completely different features, with no layered sedimentary deposits . Scientists have two theories for how this could have occurred. The first is that because the floor of Kalocsa is at a higher altitude, it did not break into the suspected underground ancient reservoir. Since layered deposits usually require the presence of an abundance of water, this would make sense. The second hypothesis is that Kalocsa crater is much younger than Danielson and was formed at a time when water was no longer present on the surface.