The scientific paper is not due to be published until next week

The scientific paper is not due to be published until next week. The US astronomer Carl Sagan said the findings "are not evidence of life".John Kerridge, a planetary scientist at the University of California, San Diego, said "The conclusion is at best premature and more probably wrong. The PAHs are just not a reliable biomarker."Could the "Mars life" actually have come from Earth?The possibility that the meteorite was contaminated with Earth organisms was a major question for the Nasa scientists They provide a number of reasons refuting it. Many have been found in Earth sediments.Why weren't these signs found earlier?ALH84001 was discovered in 1984, but not recognised as being from Mars until 1994 It is one of only 12 Martian meteorites known. These fractures contain clear signs of molecules known as PAHs (polycyclic aromatic hydrocarbons) - the first such molecules ever seen in a Martian rock.

Scientists reckon that PAHs are formed either inside stars or by living organisms such as bacteria. In any case, belief in God and in aliens seems to co-exist quite easily: a majority of Americans, for example, believes firmly in both.. How do we know the meteorite came from Mars? The unusual balance of various elements in the meteorite (called ALH84001) indicates that it was not formed on Earth. Also, it must have spent some time in space because it contains radioactive versions of common elements not found on Earth. When did it arrive on Earth?About 13,000 years ago, after being thrown into space from Mars by a major asteroid impact about 15 million years ago.What exactly have the Nasa scientists found?The rock contains tiny fractures, thought to have occurred when it was on Mars. There was very little left to dream about.But just when it seemed that things had got about as factual and mechanical and circumscribed as they possibly could, the human mind executed an amazing double somersault, and with one leap it was free. God may be dead, and the Earth as good as, but with the advent of manned flight, suddenly there was a vast new frontier to dream about.There seems no reason to suppose that our fondness for dreaming about outer space and encountering its denizens will slacken now that a grain of truth has apparently been discovered in all the speculation: like the grit in an oyster, it can only encourage them.Likewise, it is unlikely to shake the religious belief of those whose faith has survived the assaults of science. There is a paradox here: the more breath- taking the discoveries and theories of the intellectual pioneers, the more arid, in consequence, grew the landscape of the popular imagination.Humanity evolved from the apes, and the rest of "creation" came about in the same way? Bang went God, and the angels and archangels with Him.

Character was formed through sexual experiences in infancy? That put paid to the soul, and doubtless to ghosts as well. History was a process of endless struggle between social classes? So much for the great heroes, the supermen of history.Meanwhile, modern navigation and transport ensured that no significant stone on the planet was left unturned, no nation or tribe undiscovered or undocumented. Even in a universe governed by the God of the Christians, there was plenty of room for enjoyably alarming speculation.With the maturing of knowledge in the 18th and 19th centuries, however, shades of the prison door fell across humanity's dreaming. Above were angels and archangels and all the company of heaven; across the sea beyond Finisterre and ultima Thule were lands unknown, full of inconceivable creatures and men with heads below their shoulders When night fell, the dark was populated by ghosts. But a modern obsession had been born.In 1898, HG Wells published The War of the Worlds; eight years later the American astronomer Percival Lowell published his theory that the surface of Mars was veined with canals which the Martians had constructed to irrigate their planet with water from the polar ice-caps.

The parallel projects, the literary and the scientific, were off the starting blocks.It was exactly the sort of imaginative adventure that the 20th century required. In humanity's infancy, heaven lay all about us: what we knew was so infinitesimal, what we could only dream about so vast, that the imagination was abundantly nourished. The objects, as happens with tedious regularity in such cases, were later removed by a mysterious stranger. If that's the company we've got through all eternity, one is entitled to say, it's a pretty minor mitigation of our loneliness.