Digging in the Noise

This chapter highlights the emergence of the Martian methane saga from its hibernation in 1988 when Vladimir Krasnopolsky and his colleagues undertook a study of the Martian atmosphere. It explains how the methane gas in the Earth's atmosphere absorbs light at nearly the same wavelengths as the methane in the Martian atmosphere, obscuring any possible signature of Martian methane in telescopic observations. It also recounts Krasnopolsky and his colleagues' construction of computer models that allowed them to subtract the effects of the huge amount of terrestrial methane from their spectral observations of Mars. The chapter looks at the decision of Krasnopolsky's team to neither confirm nor contradict the Mariner 9 upper limit, even after they made a definitive detection of methane on Mars. It emphasizes that the attempt to measure the level of methane in the atmosphere of Mars using a telescope in Arizona in 1988 yielded only noise.

The Darkness between the Stars

In chapter 2, Bradbury enters the public debate over the curtailment of the Apollo program, beginning with his Los Angeles Times op-ed column, “Apollo Murdered: The Sun Goes Out.” For the moment, Bradbury placed more hope on unmanned Mars missions such as Mariner 9, and played a prominent role in the NASA Jet Propulsion Laboratory Mariner 9 events and book, Mars and the Mind of Man. Bradbury wrote the forward and the conclusion for this book, citing Arnold Toynbee’s concept of “challenge and response,” the need to face up to cultural challenges or face extinction, as the motivation for colonizing other worlds.

Mars before the Space Age

Mars has surely been scrutinised since the dawn of humankind. Its appearance every couple of years like a drop of blood in the sky led to warlike attributes in the ancient world. In the 16th century Tycho Brahe made accurate observations of the position of Mars that enabled Johannes Kepler to obtain his first two laws of planetary motion. These in turn were explained by Newton's laws of motion and gravity. In the 17th century the first telescope observations were made, but Mars is small and very little surface detail could be discerned.Throughout the 18th and 19th centuries telescopes improved, revealing many dark areas on the red tinted surface. During the close opposition of 1877 sufficient detail could be seen that enabled Giovanni Schiaparelli to announce that he could see about 40 canali on Mars. This led to the saga of the canals of Mars, finally laid to rest in 1971 when Mariner 9 made observations from Martian orbit showing that the canali/canals do not exist.Belief that there was life on Mars was widespread in the 19th century. However, the majority of astronomers never believed in Martian intelligence. Least controversial was the view that the dark areas were some form of plant life. This view persisted until Mariner 4 flew past Mars in 1965 and discovered a far thinner atmosphere than previously thought. This was a low point, with impact craters dominating the images. It was Mariner 9 that revealed much more promising landscapes, including volcanic features, and others indicating that water had flowed across the surface, particularly when Mars was young. Thus, the contemporary era of Mars exploration began.Our picture of Mars today is not only much more complete than that before Mariner 4, in several ways it is quite different. The belief, however, that there might be life on Mars persists – subsurface life cannot be ruled out and, failing that, there might be ancient fossils on Mars.

Les formes et dépôts nivéo-éoliens actuels en Antarctique et au Nouveau-Québec

En Antarctique, région de McMurdo, vallée de Victoria, des dépôts nivéo-éoliens, faits de lits alternants de neige et de sable entraînés par le vent, épais de 0 à 2 m, sont pérennes. Conjointement aux glaciers à sable inclus, ils sont peut-être apparentés aux dépôts stratifiés découverts par Mariner 9 dans la région polaire sud de la planète Mars. À Poste-de-la-Baleine, 55°17' Nord, 77°46' Ouest, les dépôts nivéo-éoliens sont annuels, toute la neige fondant chaque été. Ils contribuent à engraisser la première plage soulevée sableuse et certaines dunes. Sur le pied de glace, ils forment 1, 2 ou 3 remparts littoraux éphémères ; le plus haut est le plus proche du rivage. Sur la neige fraîche se forment des rides mixtes de sable et neige, dont le dessin ressemble à celui de champs de dunes vus d'avion (traverse, réticulé, lobé … etc.) et est beaucoup plus photogénique que celui des rides de neige sur neige ou de sable sur sable. Suivant la proportion relative de neige et de sable, l'albedo peut prendre toutes les valeurs entre celles de la neige pure et du sable pur : ainsi pourraient peut-être s'expliquer une partie des variations d'albedo, en fonction du temps, observées à la surface de Mars. Les formes de dénivation sont des cônes pointus, des mamelons doux dont la surface est craquelée typiquement, des boulettes de sable, des bourrelets de sable (micromoraines de dénivation) et des réseaux de sable. Sous les surplombs de la glace impure qui forme la base du nivéo-éolien sur l'estran, des gouttelettes tombent ; elles forment, si elles sont d'eau pure, des microcratères d'impact ; si elles sont de sable humide, des pastilles de sable ; dans les cas intermédiaires, des stalagmites de sable.