Day: April 13, 2015

Curiosity is continuing its exploration and ascent of “Mount Sharp”, the huge mountain-like mound of deposited material occupying the centre of Gale Crater, which has been the rover’s home since it arrived on Mars in August 2012. And it is continuing to find curious and enigmatic hints about the past conditions in the crater, and about Mars as a whole.

The rover’s most recent discoveries come from an area of rock dubbed “Garden City”, which contains areas of two-tone mineral veins quite unlike anything so far encountered in the rover’s travels.

The veins appear as a network of ridges left standing above the now eroded-away bedrock in which they formed. Individual ridges range up to about  6 centimetres (2.5 inches) high and half that in width, and they bear both bright and dark material. They are strongly suggestive of multiple episodes of fluid movement which occurred much later than the wet environmental conditions that formed lake-bed deposits which gave rise to “Mount Sharp’s” formation.

“Some of [the veins] look like ice-cream sandwiches: dark on both edges and white in the middle,” said Linda Kah, a Curiosity science-team member at the University of Tennessee, Knoxville. “These materials tell us about secondary fluids that were transported through the region after the host rock formed.”

On Earth, veins of this kind form as a result of fluids moving through move through cracked rock, depositing minerals in the fractures which often affect the chemistry of the surrounding rock. Curiosity has found bright veins composed of calcium sulfate visible on the surface of rocks at several other locations, which appears to be the same with the lighter material found as “Garden City”,   but the dark material suggest something else.

“At least two secondary fluids have left evidence here,” Kah said. “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?”

While there are no plans to gather any samples form “Garden City”, analysis of the three sets of samples gathered from within “Pahrump Hills” reveal that mineral deposits within the area vary according to elevation, revealing a complex process may have been responsible for the formation of the area. Samples taken from the lowest elevation of the area revealed themselves to be rich in clays and hematite, both of which commonly form under wet conditions.

However, at just a 5 metre higher elevation, jarosite, an oxidized mineral containing iron and sulfur that forms in acidic conditions, was the dominant mineral, while towards the top of the area, at an elevation of 10 metres, clay minerals and hematite were almost non-existent, and traces of jarosite were greatly reduced, while the samples – from “Telegraph Peak” – were rich in cristobalite and quartz, both of which are mineral forms of silica.

Quite what the process may have been that gave rise to this spread of deposits is unclear – the science team have several options to choose from, and are continuing their investigation.

Continue reading “Space Sunday: ice-cream sandwiches, sniffing the air and targets of Opportunity” →