Mars Exploration: Surface
& Orbital Reconnaissance

Introduction: Is There Life On Mars? continued

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 common chemical origin of the planets, suggested the plausibility of life on other planets in the solar system. The discovery of life beyond Earth would also give biological theory a long-sought universality, whilst biology itself would at last be placed on a par with the physical sciences, which were known to be applicable to the rest of the universe and not to the Earth alone. The space age promised biology a "leg-up" in this direction. A panel of biologists commissioned by the US National Academy of Sciences (1964-1965) to evaluate the problem of life on Mars stated, "...The existence and accessibility of Martian life would mark the beginning of a true general biology, of which the terrestrial is a special case."

So far we have considered our estimate for the probability of life on other worlds in terms of the probability of the formation of planetary systems and how the prospect of that life in our own solar system has varied considerably from one observer to another, which, at the boundaries of human knowledge, is a common experience when speculation far outweighs the available data. As I suggested at the beginning, however, our view of the probability of life not only beyond our world or our solar system, but even beyond our galaxy depends upon how we view our Cosmos: what is the origin of the matter that forms the gas and dust from which stars and planets coalesce and from which life too might form? On what grounds do we assert that the same laws of physics apply universally rather than locally?

For some decades now the answers to these questions have been furnished by the ‘Big Bang’ theory of cosmogenesis according to which our universe began its emergence about 13 billion years ago: more precisely this was the emergence of space and time and the four fundamental forces that underpin the behaviour of all the material in the universe, both at the subatomic and macrocosmic levels (people, planets etc); I say in the whole universe because this is an expanding universe and so the physical laws established at its emergence preside in its farthest reaches too. The first atoms, from hydrogen to lithium – and perhaps beryllium - formed when our Cosmos was about 100 seconds old; heavier elements had to await the formation of stars that could provide the necessary temperatures and pressures to create these elements. Stars of sufficient size would explode at the end of their lives as supernovae and make available to a new generation of stars these heavier elements that might one day be used to form planets and even life, like you and me – and even perhaps life on Mars.