Climbing up Mt. Sharp in the middle of Gale Crater, NASA’s Curiosity rover has discovered two-tone mineral veins on a layered mountain which provides new clues of multiple fluid movement episodes on Mars, including some that occurred later than the wet conditions that formed after lake-bed deposits at its base.
Curiosity has analyzed rock samples drilled from three targets lower on the mountain in the past seven 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 prominent veins seen in image taken a little farther uphill, illustrate how the layers of Mount Sharp provide a record of different stages in the evolution of the area’s ancient environment.
The two-tone veins are located at a site known as Garden City in the Pahrump Hills region of Mount Sharp, and the US space agency explained that they look like a network of ridges which stands above the now-eroded bedrock in which they were formed.
The ridges, some of which are approximately 2.5 inches (6 centimeters) high and 1.25 inches (3 centimeters) wide, bear both bright and dark materials. NASA scientists believe that those layers indicate how Mount Sharp shows the geologic history of that region of Mars.
“Some of [the mineral veins] look like ice-cream sandwiches: dark on both edges and white in the middle,” said Curiosity science team member Linda Kah from the University of Tennessee, Knoxville’s Department of Earth and Planetary Science. “These materials tell us about secondary fluids that were transported through the region after the host rock formed.”
Veins such as these form where fluids move through cracked rock and leave minerals in the fractures, often affecting the chemistry of the rock surrounding the fractures. Kah said, “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. How have later fluids affected the host rock?.”
Curiosity, which landed on Mars in 2012, has already found environments with the right chemical ingredients for life, as well as not-too-salty, not-too-acidic water. It has also turned up evidence of a lake that may have drained and filled over time. Curiosity is now exploring different layers of Mount Sharp in the hope of finding more clues to the red planet’s history.
Bottom line: NASA’s Mars Science Laboratory Project is using Curiosity to examine environments that offered favorable conditions for microbial life on ancient Mars, if the planet ever has hosted microbes, and the changes from those environments to drier conditions that have prevailed on Mars for more than three billion years.
JPL, a division of the California Institute of Technology in Pasadena, built the rover and manages the project for NASA’s Science Mission Directorate in Washington.