Antarctica (18 page)

Back at the Johnson Space Center, this was the first meteorite that year to be opened, earning it the sobriquet ALH84001. At first and even second glance it looked like a visitor from the asteroid belt. For one thing it was at least four billion years old—very much older than the SNCs. The curators decided that it had come from an asteroid called Vesta—which was interesting, though not Earth-shattering. Suitably identified and labelled, it was safely filed away.

Seven years later, while fiddling around with a sample of this same meteorite, a researcher named David Mittlefehldt from the JSC saw something that puzzled him. Though it was supposed to have come from Vesta, ALH84001 contained a few minerals that were more like the ones found in some of the SNCs. Could it actually have come from Mars? If so, that would be really exciting. This would be the first Martian meteorite from that early, old, wet period, when there was the best chance that there had been Martian life.

There was one way to find out. The element oxygen comes in several flavours, called isotopes, with slightly different weights, and their ratio in a rock works as a sort of fingerprint, showing exactly where the rock came from. David requested an analysis and the results came back with astonishing news. ALH84001 had the classic characteristic fingerprint of the Red Planet.

On the much closer inspection that it now received, ALH84001 turned out to have a very interesting history. It had been formed several miles below the Martian surface in the planet's earliest days. As the crust of Mars bucked and heaved, our rock worked its way upwards. About four billion years ago, it received its first big shock, when parts of it shattered as something hit the surface above its head, very hard. But the smack wasn't quite enough to dislodge the rock and it stayed put. It may, though, have felt trickles of early Martian water passing through its fractured veins.

Nothing much happened for the next few billion years until something else hit the Martian surface even harder, and the rock that was to become ALH84001 was flung out into space. It roamed the Solar System for seventeen million years and then finally, 13,000 years ago, it fell on to the Antarctic ice and lay there, unnoticed and unsung.

This awakened the interest of a colleague of David Mittlefehldt's—another David, but this time called McKay. The most interesting stage from David McKay's point of view was the early part. He decided to see whether ALH84001 had really been in touch with Martian water, and if so whether there had been anything alive in the water. First, he found orangey-red carbonates in the rock. That was promising. Carbonates form out of water, often with something living involved in the process. Next, he found something even more intriguing: certain organic chemicals that form when living things indulge in chemistry. And then came the most intriguing finding of all. When David and his team sliced off a piece of the meteorite and put it into their most powerful microscope, they saw something astonishing. Within the matrix of the rock were tiny worm-like shapes that looked like bacteria. They weren't alive, that was for sure. But they might once have been.

Quickly, David's team prepared a scientific paper,
¹²
but before they could publish, the news started leaking out. On 6 August 1996, NASA head Dan Goldin issued a statement announcing a press conference the following day:

 

NASA has made a startling discovery that points to the possibility that a primitive form of microscopic life may have existed on Mars more than three billion years ago . . . I want everyone to understand that we are not talking about little green men. These are extremely small, single-cell structures that somewhat resemble bacteria on Earth . . . The NASA scientists and researchers who made this discovery will be available at a news conference tomorrow to discuss their findings.

 

The world went wild. Headlines around the planet broke the news. President Bill Clinton himself stepped out on to the South Lawn of the White House at 1:15 p.m. on 7 August 1996 to address the jostling crowd of journalists. He spoke of how NASA's announcement had vindicated the US scientific and space programmes and how he intended to pursue the study of Mars more aggressively than ever. And then, he said this:

 

Today, rock 84001 speaks to us across all those billions of years and millions of miles. It speaks of the possibility of life. If this discovery is confirmed, it will surely be one of the most stunning insights into our universe that science has ever uncovered. Its implications are as far-reaching and awe-inspiring as can be imagined. Even as it promises answers to some of our oldest questions, it poses still others even more fundamental. We will continue to listen closely to what it has to say as we continue the search for answers and for knowledge that is as old as humanity itself but essential to our people's future
.
¹³

 

More than a decade later, debate is still raging. But although most scientists remain sceptical about the claims for Martian life in the rock, nobody has yet managed to prove beyond all doubt that ALH84001 has no traces of life. At first it seemed as though the carbonates must have formed at temperatures that were far too high to allow the existence of life, but, no, they could also have formed at comfortably low temperatures. The wiggles that looked like worms were too small to be bacteria, except that we have now found similarly small ‘nanobacteria' on Earth. The organic chemicals could easily be formed by perfectly normal chemistry that has nothing to do with life. But they are also a natural by-product of life itself. ALH84001 is far from conclusive. But it is still the most intriguing evidence to date that life might have existed elsewhere in space, that we humans may not be alone.

And if this proves to be right, there is a fascinating corollary. The earliest days of the Solar System were like a celestial billiards game with half-formed planetoids slamming into each other. Most scientists agree that life could not begin on Earth until this early bombardment had calmed down, and the rocks had stopped melting and the atmosphere had stopped boiling away. However, the evidence suggests that life started on Earth
immediately
after the bombardment ended. Which begs the question: how did life get its toehold on Earth the very moment that conditions were right?

Perhaps the answer lies elsewhere in the Solar System. Mars is much smaller than the Earth, and its weaker gravitational pull would have attracted fewer incoming missiles. For it, the bombardment would have finished earlier, and thus life could have arisen earlier. And if life did appear on Mars in its earliest days and if (as we now know to be true) meteorites can be chipped off Mars and carried to Earth, could some of those rocks from space have brought Martian life along with them? If so, life might have evolved just once in the Solar System—on the planet Mars—and then come belatedly to Earth on the wings of an incoming rock or two. If that is true, and thanks to all that we have learned from Antarctica, we might all of us be Martians.

 

Mars, Mars, Mars: you hear about it everywhere in the Dry Valleys. But the most Mars-like of all is a remote valley tucked up against the edge of the ice sheet, almost level with the Allan Hills. It is hard to reach, almost hidden by the bright white ice that all but surrounds it.

Beacon Valley is an elongated horseshoe, protected by a semicircle of mountains, its flat northern edge disappearing seamlessly into the interlocking system of valleys and glaciers that stretches all the way down to the sea. It lies in the upland region of the Dry Valleys, the coldest, driest, most desolate part. And it is not just the closest place to Mars that humans have ever seen. It is also a valley where time stands still.

From above, Beacon Valley's floor looks like the scaly skin of a crocodile, or perhaps the cracked mud from a dried-out river bed. While the other Dry Valleys are smooth, this one is shot through with many-sided shapes that look too regular to have formed by chance. They are called ‘contraction-crack polygons' and they show up in small patches in many cold, bleak parts of the world. But here they stretch for miles, the defining characteristic of an otherwise bare valley floor.

Through my helicopter window the polygons looked so small and tidy that it was a shock to land and find that they were metres wide; so wide, in fact, that at eye level you could no longer make out the patterns. They seemed instead like random jumbles of rocks, set in shifting gravel and silt, with no discernible purpose but to turn your ankles and bar your way. The pilot had been in radio contact with my hosts and told me they were expecting me. ‘They're over there somewhere,' he said with a grin and a jerk of his thumb.

As I watched him take off, I was feeling a bit bleak myself. The helicopter pad was just a small square in the middle of a polygon, with some of the biggest stones removed to make it flat. In the centre was an ‘x' formed of yellow sandstones that stood out against the grey; the edges were marked with red tent bags weighted down with more stones. Just beyond were three pyramidal Scott tents, two yellow, one white, a few smaller dome tents and a large, brightly striped Endurance model that was probably where they cooked. There was no sign of anyone in camp. I was tempted for a moment just to stay there and wait for the end of the day, but I resolutely dumped my sleeping gear and stumbled off in search of the field party.

I'd come to meet a double act of scientists, a partnership that Peter Doran described to me as a ‘match made in heaven'. The leader of this expedition was Dave Marchant from Boston University.
¹⁴
Dave was an expert on geomorphology—the shape and structure of ice-formed landscapes—and he knew this particular landscape as well as anyone alive. With him would be Jim Head, from Brown University in Rhode Island, who was a world expert on Mars. According to both of them, Beacon Valley was the most Martian of the Dry Valleys, the closest you could get to the Red Planet without leaving Earth.
¹⁵

To be sure, the rocks I was stumbling over reminded me of the famous pictures from NASA's missions to Mars. There were boulders everywhere, with polished sides like gemstones, and slightly rounded edges where they had been shaped by the wind. The winds must be strong here. Some of the more exposed ones had a scooped-out hollow in the gravel in front of them, and a long drawn-out gravel tail behind. Many of the rocks were pitted with holes that had been scoured by a combination of wind, salt and sand. I watched, fascinated, as a stray flake of snow landed on one of these pits and bounced from one side to the next before it finally settled and melted.

The polishing by the wind had varnished these boulders, giving them a rust colour that looked even redder through my sunglasses. I sat for a moment with my back against a boulder and imagined that I was on Mars. The gravity was too strong, but I tried to let go of that. I pictured a pink sky, alien moons, Earth as a distant neighbour. The first overwhelming impression was one of loneliness. I shook myself and stood up. Maybe I overdid it. But now, a feeling of responsibility had kicked in. If I were really on Mars, then anything I touched had never been touched before. I started jumping from rock to rock like a child avoiding the cracks, so that I didn't leave any footprints on the soft gravel. On this ridged landscape, I could see nobody else in the entire valley. It was foolish, but I suddenly needed to climb up on to one of the highest ridges of the nearest polygon and peer out ahead until I caught sight of a handful of red coats in the distance and felt a rush of relief.

As I stumbled over the polygon rocks towards them I heard a mighty thwack. A figure in a red parka and jaunty green hat had slammed a sledgehammer against a small square of aluminium on the ground in front of him. The plate rose into the air with a silver flash like a leaping salmon and from where I was standing I heard two distinct ‘tings' as the sound reached me first through the ground and then through the air. Two other figures were operating monitoring equipment and a handful more were looking on. The man with the hammer turned out to be Dave Marchant. When he saw me, he put the hammer on the ground. ‘OK, men!' he barked in a mock-military tone though there were clearly women in his team. ‘Five minutes. Smoke if you've got 'em. Check your socks. If you've got a buddy make sure he's OK.' His students were clearly used to this. They grinned, stood down from the equipment and started pulling chocolate bars out of their backpacks.

Dave was an odd combination of the light-hearted and intense. He was in his forties, his face deeply tanned and crinkled with laughter lines. His eyes were strikingly blue. He worked so hard and relentlessly that his students called him, to his face, ‘Cyborg'. But he required little persuasion to tear open his parka and fleece and show off the T-shirt he often wore underneath, bearing a picture of his infant son with the same striking blue eyes.

While the rest of the crew took their break, Dave climbed with me over the boulders, pointing out his favourite features of this, his favourite valley. The main thing he wanted to show me was how it defied the normal rules. The one constant on earthly landscapes is usually change. Our home planet is restless and the continual assault of wind and weather, water and ice, is what shapes its surface.

But not here. Dave calls this landscape ‘paralysed'. There has been no running water in Beacon Valley for fourteen million years. Most of the snow on the ground has blown in from elsewhere rather than fallen from the clouds. The wind may scoop and pit the boulders but it doesn't move them. ‘You see that rockfall over there?' He was pointing to a large skirt of rocks and boulders that had tumbled down from the mountain across the way. The rocks lay neatly where they had fallen, just as you'd expect from a fresh young landslide. If it had happened long ago, they should have been shuffled and shifted, confusing that neatly sloping pattern. ‘It looks recent, doesn't it?' said Dave. ‘Well, we've dated it and it's a million years old!'