Mars Exploration: Surface
& Orbital Reconnaissance

Introduction: Is There Life On Mars? continued

He continues: "we are justified in believing in life on Mars – hardy plant life" because the "colour changes" on Mars he considers to be most logically and simply explained by vegetation: the Tibetan landscape is believed to offer a "good idea of what to expect," essentially, a desert, bleak, empty, bare and with no mountains. (For more details click here)

*(Later, in his book The Exploration of Space (1951), Clarke spoke similarly of Venus, believing that humans would probably require no more than a supply of oxygen to survive there.)
**(We now know that Mars' polar caps comprise both carbon-dioxide and water-ice, the former sublimating or evaporating from ice to vapour during the Martian summer whilst leaving the water-ice behind: during the Martian winter this carbon dioxide vapour returns to the poles either as snow or condenses on the surface as frost gradually increasing the size of the polar cap once again.)

Importantly, in the time between the publication of Lasser's book The Conquest of Space in 1931 and the publication of Ley’s book in 1949, a crucial turnaround had occurred in the world of planetary science. Specifically, Jeans's tidal hypothesis implying the extreme rarity of planetary systems had fallen, in part due to its inability to adequately address issues raised in 1935 by Henry Norris Russell concerning the dynamics and structure of our solar system. From the 1940's, astronomers, including Jeans, were once again willing to believe in the abundance of other planetary systems and in turn the possibility of life on other worlds. This change was partly fuelled by two claims made in 1943 for the detection of planetary or planet-like bodies around two other stars (K. Strand; D. Reuyl/E. Holmberg). Russell himself quickly responded to these apparent discoveries by claiming that they argued against the rarity of planetary systems. Then, in 1944, Carl Friedrich Weizsäcker published his modified version of the nebular hypothesis of planetary formation that would finally both lay the tidal theory to rest and fill the void that it left behind. According to physicist George Gamow, "...if the Weizsäcker theory holds, planetary systems of a wide variety of types must be the rule rather than the exception." Life too, said physicist Thornton L. Page in 1948, could be expected on millions of worlds, including other civilizations. Astronomy was returning to the notion that the Earth and life on Earth were nothing special, for scientists a philosophically far more appealing position.

By the late 1950's biology and biochemistry had realized a vision of a structural unity underlying all life on Earth. The geneticist Joshua Lederberg stated:

Throughout the living world we see a common set of structural units - amino acids, coenzymes, nucleins, carbohydrates and so forth - from which every living organism builds itself. The same holds for the fundamental processes of biosynthesis and of energy metabolism.

This global perspective of the unity of life on Earth, together with the