Meteor Crater of Arizona, three-quarters of a mile across and' six hundred feet deep,, with its walls of tilted and faulted strata and its encircling high rim of pulverized and brecciated rock, is a spectacle for the student of land forms, of geologic structures, and of katamorphic processes. Standing on its rim, one is imp,ressed by the fact that craterforming meteorites are extraterrestrial a...

Introduction: Both α-amino acids and α-hydroxy acids occur in aqueous extracts of the Murchison carbonaceous meteorite. The Strecker-cyanohydrin reaction, the reaction of carbonyl compounds, cyanide, and ammonia to produce amino and hydroxy acids, has been proposed as a source of such organic acids in meteorites [1]. Such syntheses are consistent with the suggestion [2] that interstellar precur...

Al Huwaysah 010 is an ungrouped achondrite meteorite, recently referred to as a brachinite-like meteorite. This showing fine-grained assemblage of low-Ca pyroxene and opaque phases, strongly reduced in comparison other brachinites. The occurrence some tiny plates graphite oldhamite this meteorite suggests that partial melt residue has experienced further reduction process. Olivine, the most abu...

The existence of numerous iron meteorite groups indicates that some planetesimals underwent melting led to metal-silicate segregation, sometimes producing metallic cores. Meteorite paleomagnetic records suggest crystallization these cores generated dynamo magnetic fields. Here we describe the history partially differentiated IIE parent body. This is first planetesimal for which have a time-reso...

MgSiO3 tetragonal garnet, which is the last of the missing phases of experimentally predicted high-pressure polymorphs of pyroxene, has been discovered in a shocked meteorite. The garnet is formed from low-Ca pyroxene in the host rock through a solid-state transformation at 17 to 20 GPa and 1900° to 2000°C. On the basis of the degree of cation ordering in its crystal structure, which can be ded...

Unraveling a planet's geologic evolution requires knowing what happened and when it happened. Two recent studies of the ages of Martian meteorites illuminate the early and late stages of Martian crust formation. One, by Munir Humayun (Florida State University) and colleagues in Australia and France studied Martian meteorite NWA 7533, an impact melt breccia composed of alkali-rich basalt similar...

Indirect evidence for life on Mars has been reported from the study of meteorite ALH84001. The formation temperature of the carbonates is controversial; some estimates suggest 20 degrees to 80 degrees C, whereas others exceed 650 degrees C. Paleomagnetism can be used to distinguish between these possibilities because heating can remagnetize ferrimagnetic minerals. Study of two adjacent pyroxene...

Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globule...

Background and Introduction: The question of the origin of nanophase magnetite in Martian meteorite ALH84001 has been widely debated for nearly a decade. Golden et al. [1] have reported producing nearly chemically pure magnetite from thermal decomposition of chemically impure siderite [(Fe, Mg, Mn)CO3]. This claim is significant for three reasons: first, it has been argued that chemically pure ...

Despite evidence for liquid water at the surface of Mars during the Noachian epoch, the temperature of early aqueous environments has been impossible to establish, raising questions of whether the surface of Mars was ever warmer than today. We address this problem by determining the precipitation temperature of secondary carbonate minerals preserved in the oldest known sample of Mars’ crust—the...