Cover

Cover: Upper left: High‐resolution mosaic of section ALH 84001,82 (~30 μm thick) from Martian meteorite Allan Hills 84001. Several highly detailed transmitted light images, obtained with a Zeiss Scope petrographic microscope at magnification of 500× and with crossed nicols (polarizers), were merged to create this mosaic. A grid was superimposed onto the image (square size is 1 mm²) to navigate around the section and (re)locate regions of interest. D5 and J7 are regions that contain a particularly high concentration of carbonates. The images were obtained at the Institute of Space Sciences (ICE, IEEC/CSIC) by Carles E. Moyano‐Cambero, who also created the mosaic. For details see the article on p. 1030. Upper right: Detail of region D5 in the mosaic. Cathodoluminescence image, obtained with a Nikon Eclipse LV100NPol petrographic microscope at 100× magnification, after applying electron bombardment in the sample with a Cambridge Image Technology Ltd. (CITL) Technosyn cold cathodoluminescent MK4 operated at a voltage of 20–24 kV and an intensity of 350–400 mA. The light emitted during electron bombardment of a mineral has intensity and wavelength that depends on its chemical composition and crystallographic structure, and even trace amounts of some elements can act as activators or quenchers of cathodoluminescence. Since iron is a typical quencher, iron‐free minerals can be particularly luminescent. In this case, bright red areas correspond to very Fe‐poor and Mn‐rich layers in the carbonates. This and the following images were obtained at the Universidad Complutense de Madrid by M. Isabel Benito. Lower left: Detail of the region D5 of the mosaic. Transmitted light image, obtained with a Nikon Eclipse LV100NPol petrographic microscope at 100× magnification and with crossed nicols. Carbonates are the brown‐to‐orange areas, while the large dark blue area is maskelynite (shock modified plagioclase). Lower right: BSE image of one of the spherical carbonates in D5 obtained with a JEOL JSM7600F SEM with a BSED (magnification 1,100×, voltage of 15 kV). The SEM was used to select regions and points of interest for subsequent chemical analysis by electron microprobe. The Fe‐rich and Mg‐rich rims of the carbonate can be clearly observed as bright and dark rims, respectively.