The rock target called "Mojave" at Gale Crater displays copious slender features - slightly smaller than grains of rice - that appear to be mineral crystals.
"The crystal shapes are apparent in the earlier images of Mojave but we do not know what they represent," said Curiosity project scientist Ashwin Vasavada at Nasa's Jet Propulsion Laboratory, Pasadena, California.
"We are hoping that mineral identifications we get from the rover's laboratory will shed more light than we got from just the images and bulk chemistry," he added.
To begin with, Curiosity is beginning a "mini-drill" test to assess the rock's suitability for deeper drilling which collects a sample for on board laboratory analysis.
This is the fourth new version of the on board software since the rover's August 2012 landing.
The "Mojave" drilling begins Curiosity's third round of investigating the basal layer of Mount Sharp exposed at an area called "Pahrump Hills".
Curiosity's Chemistry and Mineralogy instrument (CheMin) can identify specific minerals in rock powder from a drilled sample.
Analysis of the drill hole and drill tailings may also reveal whether the crystals are only at the surface, like a salty crust, or are also deeper in the rock.
There could be a fairly involved story here.
"Are the salt crystals left from a drying lake? Or are they more pervasive through the rock, formed by fluids moving through the rock? In either case, a later fluid may have removed or replaced the original minerals with something else," Vasavada asked.