The Science of Discworld Revised Edition

bacteria-like chemical systems forming towers around the hot vents – much as Earthly bacteria do in the Baltic sea. More complicated creatures like amoebas and parameciums would be a pleasant surprise; anything beyond that, such as multicellular organisms, would be a bonus. Don’t expect plants – there’s not enough light that far from the sun, even if it could filter down through the layers of ice. Europan life would have to be powered by chemical energy, as it is around Earth’s underwater volcanic vents. Don’t expect Europan lifeforms to look like the ones round
our
vents, though: they will have evolved in a different chemical environment.
    In 2001 Brad Dalton, an astrogeophysicist (‘geologist’ for other worlds) wondered whether we might already have seen alien life. Europa’s surface is covered with red-brown marks, especially along what appear to be cracks in the ice. Dalton discovered that the infrared spectrum of these marks is very similar to that of Earthly bacteria that can survive in very cold environments. In fact, for three species of bacteria the spectrum is closer than that for the most likely alternative explanation of the marks: mineral salts seeping up through the cracks. Europa’s surface is too cold for even these bacteria, but they might thrive in the ocean and somehow be transported to the surface.

FIFTEEN
THE DAWN OF DAWN

    PONDER OPENED HIS Eyes and looked up into a face out of time. A mug of tea was thrust towards him.
    It had a banana stuck in it.
    ‘Ah … Librarian,’ said Ponder weakly, taking the cup. He drank, stabbing himself harmlessly in the left eye. The Librarian thought that practically everything could be improved by the addition of soft fruit, but apart from that he was a kindly soul, always ready with a helping hand and a banana. 1
    The wizards had put Ponder to sleep on a bench in the storeroom. Dusty items of magical gear were stacked from floor to ceiling. Most of it was broken, and all of it was covered in dust.
    Ponder sat up and yawned.
    ‘What time is it?’
    ‘Ook.’
    ‘Gosh, that late?’
    As the warm clouds of sleep ebbed, it dawned on Ponder that he had left the Project entirely in the hands of the senior faculty. The Librarian was impressed at how long the door kept swinging.
    Most of the main laboratory was empty, except for the pool of light around the Project.
    The Dean’s voice said, ‘Mappin Winterley … that’s a nice name?’
    ‘Shutup.’
    ‘Owen Houseworthy?’
    ‘Shutup.’
    ‘William.’
    ‘Shut
up
, Dean. That’s not funny. It never
was
funny.’ This was the voice of the Archchancellor.
    ‘Just as you say, Gertrude.’
    Ponder advanced towards the glowing Project.
    ‘Ah, Ponder,’ said the Senior Wrangler, stepping in front of it hurriedly. ‘Good to see you looking so –’
    ‘You’ve been … doing things, haven’t you,’ said Ponder, trying to see around him.
    ‘I’m sure everything can be mended,’ said the Lecturer in Recent Runes.
    ‘And it’s still
nearly
circular,’ said the Dean, ‘Just ask Charlie Grinder here. His name’s definitely not Mustrum Ridcully, I know that.’
    ‘I’m
warning
you, Dean –’
    ‘What have you
done
?’
    Ponder looked at his globe. It was certainly warmer now, and also rather less globular. There were livid red wounds across one side, and the other hemisphere was mainly one big fiery crater. It was spinning gently, wobbling as it did so.
    ‘We’ve saved most of the bits,’ said the Senior Wrangler, watching him hopefully.
    ‘What did you
do
?’
    ‘We were only trying to be helpful,’ said the Dean. ‘Gertrude here suggested we make a sun, and –’
    ‘Dean?’ said Ridcully.
    ‘Yes, Archchancellor?’
    ‘I would just like to point out, Dean, that it was not a very funny joke to begin with. It was a pathetic attempt, Dean, at dragging a sad laugh out of a simple figure of speech. Only four-year-olds and people with a serious humour deficiency keep
on
and
on
about it. I just wanted to bring this out into the open, Dean, calmly and in a spirit of reconciliation, for your own good, in the hope that you may be made well. We are all here for you, although I can’t imagine what
you
are here for.’ Ridcully turned to the horrified Ponder. ‘We made a sun –’
    ‘– some suns –’ muttered the Dean.
    ‘– some suns, yes, but … well, this “falling in circles” business is very difficult, isn’t it? Very hard to get the hang of.’
    ‘You crashed