A newly released image from a Mars satellite offers a glimpse into the complex and mysterious past of the now dry and dusty world.
From above the surface of Mars, the High Resolution Imaging Experiment (HiRISE) orbits in Danielson Crater, north of the Martian equator. This is an area of great interest to space geologists, due to the stratigraphic sediments that line the crater.
Layered sediments can be found all over Mars, but Danielson Crater contains the best preserved. Even more impressively, they appear to be evenly spaced, with varying levels of wear: stronger layers form steps, with layers of weaker material inside.
The equality of these layers means that they cannot be created by random processes, such as impact events. Instead, scientists believe that a regular, repetitive process led to the deposition of the strata.
The NASA blog explained: “The rocks were formed millions or billions of years ago when loose sediments settled into the crater, one layer at a time, and subsequently cemented in place. Periodic variations in the sediment properties have made some layers more resistant to erosion than others. After eons, these tougher layers protrude outward like the steps of a ladder. Through these steps, the wind disperses the sand, which leads to the appearance of patterns that resemble zebra stripes.”
On a small scale, there are large areas of highly fractured rock. Scientists studied these fractures and determined that because the pieces fit perfectly together, this happened after the sediments had already turned into rock.
It is not clear exactly how the deposits formed, but it is possible that the deposits were on annual timescales, or even longer.