This March 18, 2015, view from the Mast Camera (Mastcam) on NASA’s Curiosity rover shows a network of two-tone mineral veins at an area called Garden City on lower Mount Sharp.
This view from Curiosity rover’s Mastcam shows a network of 2-tone mineral veins at the Garden City area on lower Mount Sharp, Mars. This is a mosaic combining 28 images taken with Mastcam’s right-eye camera, which has a telephoto lens with a focal length of 100 mm. The component images were taken on March 18, 2015, during the 929th Martian day of Curiosity’s work on the Red Planet. The color has been approximately white-balanced to resemble how the scene would appear under daytime lighting conditions on Earth. Image credit: NASA / JPL-Caltech / MSSS.
The veins combine light and dark material, and appear as a network of ridges left standing above the now eroded-away bedrock in which they formed. They jut to heights of up to 6 cm above the surrounding rock, and their widths range up to 4 cm.
“Some of them look like ice-cream sandwiches: dark on both edges and white in the middle,” said Dr Linda Kah, a researcher at the University of Tennessee, Knoxville, and a member of the Curiosity team.
Mineral veins such as these form where fluids move through fractured rocks, depositing minerals in the fractures and affecting chemistry of the surrounding rock. In this case, the veins have been more resistant to erosion than the surrounding host rock.
The veins at the Garden City area offer clues about multiple episodes of fluid movement. These episodes occurred later than the wet environmental conditions that formed lake-bed deposits Curiosity examined at the base of Mount Sharp.
“These materials tell us about secondary fluids that were transported through the region after the host rock formed,” Dr Kah said.
The rover has analyzed rock samples drilled from 3 targets lower on the mountain in the past 7 months.
It found a different mineral composition at each, including a silica mineral named cristobalite in the most recent sample. These differences, together with the mineral veins, illustrate how the layers of Mount Sharp provide a record of different stages in the evolution of the area’s ancient environment.
Curiosity has found bright veins composed of calcium sulfate at several previous locations. The dark material preserved here presents an opportunity to learn more.
“At least two secondary fluids have left evidence here. We want to understand the chemistry of the different fluids that were here and the sequence of events,” Dr Kah said.
