Imagine you find a cracked brick in your yard. You don't just see a brick — you see the kiln temperature in the grain size, the rain damage in the surface pitting, and the lawnmower strike in the fresh chip. A petrographer does the same thing with a thin-section slice of rock, except the kiln is Mars' mantle, the rain is Martian groundwater, and the lawnmower is an asteroid impact violent enough to launch debris to escape velocity. Teghaza 001 is one of the most ancient Martian meteorites ever recovered on Earth. Found in Algeria, the rock preserves a mineral record stretching back to the formation of Mars' earliest crust and mantle — roughly 4.4 billion years. NASA/JPL-Caltech's reflected-light imaging of a polished slice serves as the primary road map for directing more specialized instruments to regions of interest. The annotated image (Figure A) identifies four key mineral populations. Iron-titanium oxides appear as brighter grains — diagnostic of igneous crystallization conditions in Mars' interior. Pyroxene (medium gray) records the silicate chemistry of the parent magma. Together, these two mineral families constrain the temperature, pressure, and oxygen fugacity of early Martian differentiation. Shocked plagioclase (darker gray) tells a different story: extreme transient pressures from hypervelocity impact. This is the signature of the event that ejected Teghaza 001 from Mars and sent it on an interplanetary trajectory that ended in the Sahara. The degree of shock metamorphism helps constrain the impact energy and excavation depth. The alteration minerals — fine-grained carbonates, sulfates, and clays — are explicitly noted as having formed on Earth, not Mars. This distinction matters: terrestrial weathering overprints can easily be mistaken for Martian aqueous alteration if analysts aren't careful. The annotation prevents that misread. What makes Teghaza 001 significant within the Martian meteorite catalog is its age. Most Martian meteorites (the shergottites) are relatively young igneous rocks, 150–600 million years old. Teghaza 001 belongs to the rarer ancient cohort that samples Mars' earliest geological epoch — material that Mars Sample Return missions are specifically designed to collect but have not yet delivered. This image release is a methods demonstration, not a standalone research paper. No new isotopic ages, no new chemical analyses, no new claims about Mars are presented. The value is in the mineral map itself: a publicly available guide that other researchers can use to target follow-up analyses with electron microprobes, ion probes, or laser-ablation mass spectrometry. It's infrastructure, not a result.
