The Soviet Union launched the first space probe towards Venus on 4 February 1961. However, this failed, and so did their next several attempts. The Americans, too, came unstuck on their first attempt. It was not to be expected that such a sophisticated endeavour as the first flight to another planet would be achieved easily, and both teams soon tried again. In the end, it was the Americans who got a working spacecraft to Venus first.

The Venus Mariners: the first close-up views

The US space agency NASA was set up in 1958 and among its first tasks was the development of the Pioneer series of small spacecraft to explore the interplanetary medium near the Earth. These were followed by the Surveyor series, which targeted the Moon. A larger spacecraft than these would be needed to go on to even the closest planets, and NASA gave the job to its newly acquired centre in Southern California, the Jet Propulsion Laboratory (JPL). Before this, JPL had been an Army Air Corps facility for the development of rocket engines, with the name dating back to 1943. The new series of spacecraft was called Mariner, and Venus was its first target.

The key to any discussion of the past and future state of the climate on Venus is an understanding of the production and loss processes for atmospheric gases, from the interior, at the surface, and at the top of the atmosphere where it merges into space. The balance between all of these determines the total mass of the atmosphere, and hence the surface pressure. This, in turn, is the principal factor controlling the temperature and hence the habitability and other characteristics of the surface environment.

At the heart of the problem is an almost complete lack of understanding of the various factors, summarised in Figure 11.1, related to volcanic activity on Venus. Volcanic emissions not only contribute to the mass and composition of the atmosphere, they also fuel cloud formation as part of a complicated cycle of atmospheric and surface chemistry involving various sulphur compounds. The surface itself is mainly of volcanic origin, although this leaves plenty of scope for puzzling about its composition and its capacity for absorbing, as well as emitting, atmospheric gases. The crust is dry and thin but evidently supports some huge volcanic mountains despite apparently being too weak to do so without convective upwelling which, if present, should also drive plate tectonics, although the observational evidence for the latter is elusive.

1. “Beside the Mare Crisium, that sea

2. Where water never was, sit down with me

3. And let us talk of Earth, where long ago

4. We drank the air and saw the rivers flow

5. Like comets through the green estates of man,

6. And fruit the color of Aldebaran

7. Weighted the curving boughs.”

A century ago water on the Moon began as an idea with the worst possible intellectual pedigree. In 1894 Hans Hörbiger, a successful engineer (who invented a valve to control blast furnaces’ airflow), had a curious vision of the Universe. His Glacial-Kosmogonie, published in 1912, propounded the Welteislehre (“World Ice”) theory, with the Moon, our Galaxy, and even space itself dominated by water ice, apparently inspired by the icelike appearance of the Moon in the night sky.

Hörbiger’s book was championed by respected German amateur selenographer Philipp Fauth, aided by Hörbiger and family. Public extravaganzas promoted the theory to common knowledge. Its cold, northerly tenor in opposition to Einstein’s relativity (and even Newtonian physics) attracted Nazi leaders. Welteislehre became party doctrine, and Fauth was promoted by S. S. Reichsführer Heinrich Himmler to university professor (having never taught at that level or conducted sufficient research). Fauth named a lunar crater Hörbiger (following his death in 1931). During and after the Third Reich, Hans Schindler wrote several books expanding the World Ice theory, soon discredited. In 1948 Hörbiger’s name was stripped from the crater (although a crater Fauth remains).

Long before the Cold War and the Space Race, people dreamed of traveling to places beyond Earth, like islands in a mythical sea, and they persist now that the Cold War is over. Dreams change, however, with the centuries’ achievements and the day’s technology and society. An odd mixture of myth, politics, and scientific knowledge sets the goals. More than five decades after the first robotic Moon missions, we have seen enough cycles of interest and dispassion about space exploration to see why we sometimes advance and at other times fail. To grasp the difference between the times in which Apollo was born versus later thrusts into space (and to understand why some succeed), momentarily let us return to the beginning.

Humans have dreamed of space flight for thousands of years. In second century AD Syria, Lucian of Samosata wrote of a sailing ship blown hundreds of kilometers skyward to an inhabited, cultivated, and luminescent island: the Moon. After war between the kings of the Moon and of the Sun, the ship and sailors return home to the Mediterranean. Before rocketry’s importance was realized, imaginative means were proposed to reach the Moon. In eleventh-century Persia, Firdausí wrote of King Kai-Kaus who “fetched four vigorous eagles and bound them firmly to the throne” to ride them to the Moon, much like the hero in Lucian’s other space fiction (Icaro-Menippus), whereas in 1630 the protagonist of Johannes Kepler’s Somnium is transported by demons. In Francis Godwin’s 1638 The Man in the Moone, the traveler exploits a flock of magic geese to find himself on the Moon with its human inhabitants (Christians, no less). In 1657 Cyrano de Bergerac’s hero reached the Moon propelled by rockets (fireworks, actually). In 1870 Edward Hale described a “brick moon” to be built in Earth’s orbit as a navigational aid for shipping.

Krafft Ehricke not only helped pioneer some of the earliest modern, liquid-propellant rockets, but also lived to develop workhorse boosters for the space age and concepts for lunar mining and planetary exploration now in the works. He envisioned the Moon as a stepping-stone, a role it played in several ways throughout humanity’s development starting long ago. He had a clever way of stating the profoundly obvious.

Ehricke’s life-span saw astounding human achievements: harnessing amazing new energy sources, traveling hundreds of times faster than ever before, probing scales millions of times larger and thousands of times smaller than imagined before, and transforming the Moon and planets from dreamlands to mapped worlds. We once ascribed romantic notions to the Moon; now we see how alien worlds differ from Earth and distant worlds of our imagination.