The rationale for looking for prokaryote fossils in Martian materials is based on our present understanding of the environmental evolution of that planet in comparison to the history of the terrestrial environments and the development and evolution of life on Earth. On Earth we have clear, albeit indirect, evidence of life in 3.8 b.y.-old rocks

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We present high-resolution, near-infrared imaging of the circumnuclear region of the barred spiral galaxy M100 (NGC 4321), accompanied by near-infrared spectroscopy. We identify a total of 43 distinct regions in the K-band image, and determine magnitudes and colours for 41 of them. By comparison with other near-infrared maps we also derive colour

We present echelle spectroscopy in the 3500-10300 Å range of the Hourglass Nebula, which is embedded in the Galactic H II region M8. The data were obtained using the 2.1 m telescope at Observatorio Astronómico Nacional in San Pedro Mártir, Baja California. We have measured the intensities of 274 emission lines, in particular 88 permitted lines of C

Hay dos formalismos para el estudio de la evolución de estructuras a gran escala desde un punto de vista analítico: el Lagrangiano y el Euleriano. Los buenos resultados dados por el primero y lo farragoso de la presentación usual del segundo han hecho que este último haya recibido escasa atención. En este trabajo se muestra una presentación más

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