Imagine you find a geode at a flea market. The crystals inside are gorgeous, but you can't tell if they're the original mineral or a later impostor that quietly moved in and copied the shape. You could crack it open (destructive), or you could shine different lights at it, measure its density from multiple angles, and drill a tiny core. That's exactly what Curiosity is doing at a rock called Nazca — except the geode is on Mars, the flea market is Gale Crater, and the drill is a nuclear-powered robot arm. The rover has identified a block densely packed with disc- and needle-shaped features the team interprets as potential crystal forms — mineral growths whose shapes encode information about the temperature, salinity, and fluid availability at the time they formed. The central scientific question is whether these shapes represent original minerals or pseudomorphs: replacement minerals that inherit the geometry of their predecessors but not the chemistry. Resolving this distinction matters because it separates 'we know what was dissolved in ancient Martian water' from 'we know something crystallized here but not necessarily what.' To attack the problem, the planning block deploys a unusually rich instrument suite in a single sol window. MAHLI will execute a Quantitative Relief Model — five overlapping images at different geometries that enable construction of a 3D surface model — plus doubled focus-mechanism steps for higher-resolution depth-of-field compositing. This is the morphological arm of the investigation: what shape are these things, precisely? ChemCam's LIBS laser provides the compositional arm. Normally 150 shots are distributed across a five-point raster at 30 shots each. Here, all 150 shots are concentrated on a single spot on a nearby crystal-form-rich target called Toucan, creating a depth profile that penetrates roughly five times deeper than a standard observation. The rationale is straightforward: if the surface composition differs from the interior, that's evidence for either modern Martian weathering or original crystallization zoning — both scientifically productive outcomes. DRT brushing and APXS measurements round out the contact science on Nazca itself before the preload test, while a third LIBS observation targets Condor, a block showing fine layering. The diversity of targets within a few meters — disc-and-needle forms at Nazca, similar textures at Chiu Chiu, layered exposure at Condor — suggests the team is building a local stratigraphic picture, not just characterizing one rock. Meanwhile, the atmospheric science thread continues in parallel. Nighttime imaging of Phobos at full illumination exploits scattered sunlight in the Martian atmosphere to estimate cloud particle sizes — specifically targeting high-altitude CO2 clouds as twilight cloud season begins. This is a different measurement from solar observations because it samples later in the night, extending the temporal baseline for atmospheric particle-size data. The overall planning block is a clean example of multi-instrument convergence on a single scientific question (crystal identity) while maintaining an independent atmospheric monitoring cadence. No single instrument resolves the pseudomorph question alone; the answer requires morphology from MAHLI, surface chemistry from APXS, and depth-resolved chemistry from LIBS working together. The drill, when it comes, will add mineralogy from CheMin to close the loop.
