EUREKA - Snowball Earth - page 54

Dan and Paul both pounced on the idea and began to probe it. Did it work? Could it explain Paul's
other conundrums? First, the strange tube rocks and rose-coloured crystal fans. Both could have come
directly from the ocean's effervescent fury. The tubes might have formed when bubbles of gas shot
upward inside the fast-forming carbonates. The crystal fans might also be some weird by-product of
this frantic fizzing. In acidic hot springs like the ones at Yellowstone, you often find fan-shaped crys-
tals, their arms radiating outwards with the sheer pace of precipitation.
Next, the rapidity of the change. The contact between carbonate and glacial rocks was always
knife-sharp. That's just what you'd expect if the carbonate formed immediately after the ice melted.
What about the isotopes? Remember that the rocks showed a light, “lifeless” signal both before
the Snowball and then for a long time afterwards. To explain what happened before was easy. Living
things in the oceans pick out the light carbon atoms, the “red jelly beans”, and leave the heavier car-
bon behind for the carbonates. Paul had already suggested that before the Snowball, life's pace was
probably slowing down as a reaction to the growing ice. Fewer living things meant less pickiness, and
more light carbon left around to be bound up in the carbonates. That, Paul felt, was why the carbonates
grew steadily lighter as the ice approached.
But afterwards was trickier. Life must have rebounded quickly after the ice melted, but the light,
lifeless signal continued on in the carbonates for tens of thousands of years. Perhaps the “light” sig-
nal in the aftermath of the Snowball had nothing to do with whether or not life was flourishing. This
intense formation of carbonate rock would swamp any normal signal. Carbonates were madly precip-
itating everywhere. They would be grabbing so much of the ocean's carbon, both light and heavy, that
it wouldn't matter any more how picky the bacteria were being. It's as if you were sedately choosing
red jelly beans from the pile, when a greedy cousin came along and snatched handfuls of the lot, both
green and red, faster than you could eat any of them yourself. The post-Snowball carbonates were light
because they swamped the signal from the bacteria. It all made brilliant sense.
Back, forth, back, forth. Whatever piece of evidence Paul could think of, Dan managed to fit neatly
into his scheme. When they assumed a Snowball, all the pieces fell into place. The carbonates and the
isotopes weren't mysteries any more. They were just what you'd expect. They were predictions of this
new, improved Snowball theory.
The two of them grew more animated and excited. Try it this way and that. Look from every pos-
sible angle. The more they probed, the more Dan's idea really did seem to tie everything together.
Brian's ice rocks, Joe's volcanoes, Paul's isotopes and cap carbonates, all added up into one elegant
story. It was intoxicating. This, at last, was what Paul had been seeking. He could scarcely believe his
luck.
Dan didn't leave until nearly three. After he had gone, Paul sat in his office, staring at his computer
screen. At 3:04 a.m. he sent Dan an e-mail. The subject line was “funk in deep freeze” (the name of a
jazz album). The message said, “Muchas gracias for tonight. I needed it badly. Thanks for the kick in
the ass.”
The next day, Dan was back. He'd been thinking all night about the Snowball. He wanted to work
with Paul on a new paper. And he wanted to send it to Science , one of the world's most prestigious and
highest-profile journals. This was to be their first direct collaboration, and Paul was delighted. For the
next few weeks Paul and Dan wrote and rewrote and discussed and argued. They haunted each other's
offices. They fired ideas at each other, stopping wherever they happened to meet. Students going to
classes often had to step over them as they sat in the stairwells of the Geology Department, thrashing
out the latest details of their theory. Here's something I just thought of! Hey, I've just made another
connection! They both describe this period as the most exciting of their lives.