The following picture, taken by the Curiosity rover in the Gale Crater on Mars in 2016 shows what appears to be a cracked Martian surface, with the Egg Rock nickel-iron meteorite. Ignoring the meteorite, the cracks appear to be infilled with a white substance. Has the white crack infill material ever been identified and if so, what is it?
These can be interpreted as desiccation cracks, filled with calcium- and/or magnesium sulfate (Ca-/Mg-SO4, seen as white material).
Methods used, for brevity citing from the below pop science link:
"... The team took a close physical and chemical look at those polygons using Curiosity's Mastcam, Mars Hand Lens Imager, ChemCam Laser Induced Breakdown Spectrometer (LIBS), and Alpha-Particle X-Ray Spectrometer (APXS) ..."
I believe this setting has led to the hypothesis of a once dried out lake on Mars.