The gullies in this image are within the valley wall of an ancient channel—Nirgal Vallis—a testament to flowing water in Mars’ ancient past. However, the formation of gullies are still the subject of much debate with respect to their formation: “wet” vs. “dry” or even “dry” with the aid of some lubricating fluid.
Gullies most commonly form in the steep walls of simple craters . Gullies are common even in cold arctic deserts on Earth (e.g., the Haughton impact structure on Devon Island). This suggests that these provocative features can form on a mostly dry Mars that is only sporadically wet.
Regardless, these features bear a remarkable resemblance to flowers, including the blossom, petals, stem, and roots. Can you see it too?
Written by: Livio Tornabene and Kayle Hansen (audio: Tre Gibbs) (11 February 2015)
This is a stereo pair with ESP_019810_1515 .
More info and image formats at http://hirise.lpl.arizona.edu/ESP_020087_1515
Image: NASA/JPL/University of Arizona