The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater’s sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide–rich water under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks have been stored aboard Perseverance for potential return to Earth.

Before Perseverance, Jezero crater’s floor was variably hypothesized to have a lacustrine, lava, volcanic airfall, or aeolian origin. SuperCam observations in the first 286 Mars days on Mars revealed a volcanic and intrusive terrain with compositional and density stratification. The dominant lithology along the traverse is basaltic, with plagioclase enrichment in stratigraphically higher locations. Stratigraphically lower, layered rocks are richer in normative pyroxene. The lowest observed unit has the highest inferred density and is olivine-rich with coarse (1.5 millimeters) euhedral, relatively unweathered grains, suggesting a cumulate origin. This is the first martian cumulate and shows similarities to martian meteorites, which also express olivine disequilibrium. Alteration materials including carbonates, sulfates, perchlorates, hydrated silicates, and iron oxides are pervasive but low in abundance, suggesting relatively brief lacustrine conditions. Orbital observations link the Jezero floor lithology to the broader Nili-Syrtis region, suggesting that density-driven compositional stratification is a regional characteristic.

This review covers past and present developments of analytical chemistry in the field of Cultural Heritage (CH), from the methods of characterization of materials to the procedures aiming at diagnosing the state of conservation of CH assets. A large number of analytical methodologies and tools (molecular and elemental spectroscopic techniques, chemometrics, chemical reactivity and modeling, etc.) are now available to define: (a) the impacts of environmental stressors (natural and anthropogenic), (b) the decaying (chemical reactions) pathways of such materials in the surrounding environment, (c) the development of new remediation (cleaning, consolidation, rehabilitation, etc.) processes based on the chemical knowledge and (d) the transfer of such knowledge to conservation departments in museums and companies working in the field of CH. Two important issues are highlighted in this review. One is the important role of analytical chemistry in this field, although its role was forgotten until a few decades ago; nowadays there are hundreds of papers demonstrating the important role of analytical chemistry practitioners in many kinds of CH actions. The other is the societal impact of the issues related to the study of heritage (i.e., rock art paintings, Pompeii, paintings in medieval churches, famous artists, etc.) where analytical chemists are key professionals especially if portable instruments are used in field work. Finally a special consideration will be paid to future developments and how analytical chemistry can give added value to the research in CH.