of 1,000 miles with relatively poor resolution, has been interpreted as being representative of a massive Sphinx-like face, about 1.6 miles long, 1.2 miles wide and just under 2,600 feet high. Other anomalies which have been cited in this region include pyramids, an ancient city and a fort. One alleged five-sided pyramid has naturally invited comparisons with Egypt’s Great Pyramid (see Bauval and Hancock, 1996: 40–2). The argument turns on whether these photographs represent artificial or natural phenomena. In a paper presented to the Department of Physics and Astronomy at the University of Leicester, Dr Tony Cook dismissed claims that there is evidence of an ancient civilization on Mars which is often claimed with reference to the famous ‘face’ formation. Cook suggested that this formation is similar to the mesas in the Arizona desert (Mobberley, 1994). This is the view echoed by NASA, who have been accused of concealing the truth about a former Martian civilization. The matter appears to have been resolved by the Mars Global Surveyor which went into orbit around Mars in September 1997, and took photographs of the surface and the surrounding terrain including the Cydonia region. The Surveyor employed a high precision camera which was more than ten times as sharp as the one which took the original Viking pictures. In April 1998, Surveyor released photographs which indicated that the ‘face’ was merely a hummocky hill with no facial features or signs of engineering at all. The Martian ‘face’ episode is a good example of the avoidance of Occam’s razor, which requires that plausible scientific explanations are examined before more exotic claims are made.
The two small Martian moons, Deimos and Phobos, were once speculated to have been spacecraft abandoned by the Martians, but early Mariner 9 photographs, which facilitated their mapping, dispelled this idea.
Venus
The planet Venus is close to the size of the Earth; its mass is about 82 per cent of the Earth’s. It has turbulent atmospheric conditions, rains of sulphuric acid and suffers from a runaway greenhouse effect caused by its dense carbon dioxide atmosphere. Its surface temperature is 475ºC, although there are protected regions with lower temperatures. There is no water there, and if there ever was any, it has long since evaporated. The atmosphere consists largely of carbon dioxide (about 97 per cent carbon dioxide with 1–2 per cent of carbon monoxide), with only traces of oxygen. Its surface pressure is one hundred times that of the Earth’s at sea level and the planet is covered by a sulphuric acid cloud. Infrared radiation is trapped by the atmosphere. It is an inhospitable place for life to emerge and offers no opportunity for the survival of life-forms generated elsewhere.
Has life ever existed on Venus? There is no evidence, but if there was a period with less CO2 and lower temperatures, possibly about 4 billion years ago, life might have developed. In fact, life might have developed on either Earth, Mars
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or Venus, and might even have been transferred by meteors from one planet to the other (Jakosky, 1998: 190).
Mercury
Mercury is too small to retain an atmosphere and its temperatures are too extreme to sustain life. A Mercury ‘day’ is 176 terrestrial days. Its hottest temperature, when close to perihelion, could be 430ºC, falling to -170ºC in its ‘night’ side. Its surface is dominated by impact craters, it has low surface gravity and an absence of water. The surface of Mercury has not shown any geological evolution for 3.5 billion years. It is the least hospitable of the inner planets.
Jupiter
The main problem with Jupiter is its size. Its surface gravity is 2.6 times as strong as Earth’s, which completely rules out the development of complex forms of life. Its atmosphere is composed mainly of hydrogen and helium with significant amounts of methane and ammonia. Organic compounds can be formed in such a mixture, a claim which has led to speculation of life-forms akin to jellyfish floating around in the more favourable temperature zones. The Galileo mission, which arrived at Jupiter on 7 December 1995, revealed details of Jupiter and its moons. It revealed the presence of water in the top layers of Jupiter’s clouds, which causes thunderstorms. Carl Sagan, in his book Cosmos, speculates on the form of Jovian life and imagines living balloons which can float at an appropriate level at which it is possible to survive. But this is unlikely. Microbes which can survive under severe pressure could exist there, were it not for other inhospitable features of the planet.
Jupiter has organic molecules within its atmosphe]bgbb re and there may be liquid water within its clouds, causing expectations of life within its atmosphere. Several years ago this speculation would have been ruled out as absurd. But towards the end of the twentieth century many species on Earth were discovered to be surviving in conditions which would formerly have been regarded as inimical to life. So, perhaps, organic development is possible in the Jovian atmosphere. However, it is very unlikely that Jovian life would emerge out of the prebiotic soup of warm liquid water, as species large enough for reproduction would be drawn by gravitation into the deeper, hotter regions of the Jovian atmosphere, where organic molecules would decompose.
Beneath the Jovian atmosphere there is no surface, either solid or liquid. Jupiter is also extremely hot; it radiates twice as much heat as it receives from the Sun. This is because heat energy is produced by the effect of gravitational contraction. There are, however, regions where temperatures are around 27ºC but any life-precursing molecules are unlikely to have developed as the strong winds would carry them into regions where they would be destroyed by intense heat as high as 1100ºC.
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