by Richard Pelisson
Translated by Sally Sutton
In the 19th century, when explorers first began to cross the Sahara, no journey was considered more hazardous. Today, the GPS and the precision of satellite maps make it possible to venture off the beaten track, right into the heart of the biggest desert on the face of the Earth. The Sahara alone covers 9,000,000 sq km (3,500,000 sq mi), extending 4800 km (3000 mi) east to west and 1900 km (1200 mi) north to south across North Africa. Daytime temperatures have been recorded at over 57° C (135° F) in the shade. The surface of the desert ranges from sand dunes (erg), covering about 15%, to stone plateaus (hammada) and gravel surfaces (reg), covering about 70%, to several deeply dissected mountain massifs.
The desert has held a special attraction for my brother and me for many years now. Mauritania, Algeria, the Hoggar Massif - all are destinations filled with memories. Today, a car ferry takes us towards Libya, a country where, three years ago, a tiny meteorite discovered on a dune awakened in us the curiosity which was soon to become a passionate obsession.
The crossing is an opportunity to unwind a little. The final days before departure are always very important. There is a lot to do to prepare our two 4WDs for the expedition: a mechanical check, equipment, food supplies, various belongings: a great many small details that will become all-important if we strike a problem in the desert. We have to do our best to avoid nasty surprises; we want to be completely self-sufficient and equipped to combat any problems. At the same time though, we know that the unpredictable will catch up with us sooner or later - risk and adventure are part of travelling, after all!
Hammada al Hamra
Nalut, a fortified village on the cliff, Derdj... The road south often dwindles to a long straight line between two filling stations. In front of us, the horizon is dark grey. Little by little, the Sun is disappearing, and the temperature has risen by ten degrees in just a few kilometers. It's the Ghibli - a hot, very dry, sand-laden wind, which will accompany us until evening. It is our first day in the desert, and already the dust is everywhere - it has got into our cases, our belongings, and even the engines' air filters.
Ghadames, the southernmost outpost of Roman times, is a beautiful oasis town famed for its unique desert architecture. It is also the last opportunity to refuel before approaching the first target of our journey, Hammada al Hamra (the red plateau), which extends 300 km from west to east. It has been prospected regularly since 1986, and with the discovery of over 450 meteorites, remains, after Dar al Gani, one of the top spots of the Sahara, along with Acfer in Algeria.
This part of the Sahara is a huge, calcareous expanse, the site of ancient marine deposits recalling the oceans which covered it several tens of millions of years ago in the Cretaceous Period. It is chiefly a stony landscape, with only a few grassy zones surviving in depressions and oueds: dry river-beds or wadis. The southern region ends with a cliff overlooking the dunes, which spread out as far as the eye can see: the Awbary erg, an immense sea of undulating sand which seems never to end. The ever-changing colors at sunset have a magical effect; this is a desert landscape which provokes not only fascination, but also awe.
There is no real need for watches in this place. The bivouac lights up as soon as the first rays of sun touch the dunes. Then we have a few more minutes to enjoy the freshness of the morning: moments of privilege, when the Sun is still a friend, the wind non-existent and the temperature perfect.
The terrain seems more favorable today, with little or no vegetation and fewer boulders. I am working my way along the side of a gentle butte when I notice a black spot 50 meters to my left. In the time it takes to get there, I dream up several possibilities: it is a shadow, a piece of dark limestone or a nodule of limonite, perhaps even a tin can which has been patinated by the desert. But the closer I get, the clearer it becomes: it is a meteorite all right, lying there on the ground as if it wanted me to find it.
My first reflex is to take photos and coordinates, to reach for my note-book. Only then do I permit myself to pick up the first find of the expedition. It is about 400 g, rather smooth, very rounded in shape and weakly magnetic, but leaving no doubt as to its origins. Its crust is darker in some places than in others and there is a break... There is a piece missing! A few minutes are all it takes to locate the second fragment about a hundred meters away. It is a perfect fit.
Some months later, after analysis and classification by a specialist laboratory, the meteorite will be given an official name by the Meteoritical Society. It will be named after the zone in which it was discovered: Hammada al Hamra, often abbreviated to HaH, followed by the number 001 for the first one classified, and 002 for the second.
In a terrain carved by gentle valleys, the range of my radio is not good enough to communicate the good news to my brother, who will be prospecting several kilometers further south, searching for new zones. We usually split up when hunting, but come together once or twice a day at a time and place determined each morning. When I get there, I'm alone. There is no sign of my brother, the horizon is empty. My imagination is working overtime when his 4WD finally appears, heading full speed in my direction, and accompanied by a cloud of dust.
A meteorite is run over
Today is a day to be remembered. I may have found the first meteorite of our expedition, but the ten or so fragments which Roland is busy reassembling for me weigh at least 30 kg. It is a chondrite, discovered right in the middle of the track leading south. My brother's excitement still hasn't worn off, and he tells me how surprised he was to come face to face with this incredible discovery. When he first saw the large black rock right in front of the 4WD, he thought it was basalt. How could it be anything else, given that the track had already been worked over by other prospectors? He decided there would not be any point in slowing down to have a closer look, and started to lose interest. But at the last moment, he had noticed an abnormal fracturing which made him decide to carry out a routine inspection of the sort we do dozens of times a day, whenever we see a rock which looks promising. This time, there was no fusion crust, but it did show a slight magnetic attraction. Disbelief was replaced with uncertainty. One of the fragments detached, allowing him to file down the inner part a little, and revealing a speck of metal. Now the digging could begin in earnest - too bad for the track!
Now entirely reassembled, the meteorite has a nice rounded shape. The part which was buried has kept its fusion crust. We have decided to give it a name alongside its field number: "Willy" - saved from a tragic end, and still safe and sound today.
There are times when civilization makes its presence felt at inopportune moments. I'm driving eastwards along a track so rocky that progress is difficult. I have to focus my attention just ahead of the wheels of the 4WD, avoiding the big, sharp blocks which might damage the tires or the mechanics. The terrain has got progressively worse. I could always do a U-turn, but I keep thinking there will be a smoother track soon, perhaps even a large meteorite hiding in the middle of this field of rocks. A long, dark ribbon at ground-level blocks out the horizon - it is a pipe. Or, more precisely, a pipeline - Libya is an oil-producing country. Out here in the desert, it hasn't occurred to them that someone might actually want to cross the line, and the pipe remains unburied.
We have got into the habit of driving off-piste without restriction. The map informs us of the important variations in elevation and any major difficulties, and we improvise the rest. The situation I now find myself in is rather amusing. It is impossible to get over the pipeline, as it is nearly a meter in diameter, with Tripoli at one end, and the oil field of wadi Irawan at the other. I decide to drive along it northwards, so that I'll have the sun at my back and better lighting in which to continue prospecting. My saviour comes at last in the form of a ramp of earth, appearing on the horizon like a mirage and enabling me to clear the obstacle. One last acrobatic feat, and it is time to meet up at the rendezvous point recorded in the GPS. These navigational aids have become real on-board computers, telling us which point to follow, estimating the time it takes to reach a certain position, memorizing routes and establishing when the Sun will set. A piece of advice: always copy out your route on to a good old map!
By the time I make it back to the bivouac, the shadows are lengthening disproportionately and the Sun is level with the horizon. The essentials for camping are already in place: a board serving as a table, two spare wheels as chairs, and most importantly, sparkling mineral water, our pre-dinner drink. The bottle is wrapped in a damp cloth: simple evaporation will lower the water's temperature, providing us with a cool, refreshing drink in half an hour. If three liters of water per person per day is enough at this time of year, in summer the daily requirement could easily exceed five liters.
The landscape on the eastern border is more mountainous; there are fossil deposits and rock carvings. But for now, it is time to head for the second destination of our journey: the Dar al Gani plateau.
It has taken us one week to cover 1500 km on the Hammada al Hamra and to collect 20 meteorites originating from at least six different falls, including an HED and a type 3 chondrite. There is every reason to expect many more discoveries. The distribution of meteorites currently stands at one for every 200 sq km for the entire western region. However, the most favorable prospecting zone, which is very clear and subject to erosion, is situated to the south-east, and shows a distribution close to one for every 20 sq km. Here, on a plateau which covers 60,000 sq km (23,000 sq mi) and has seen prospecting for almost 15 years, the ground is best observed with the naked eye. Even so, picking out an abnormal or very black rock amongst thousands of grey, beige or brown ones is no easy task.
Dar al Gani
Small in size at 80 x 50 km (50 x 30 mi), Dar al Gani is the most important Saharan strewnfield, with nearly a thousand itemized meteorites, Lunar and Martian rocks, various achondrites, etc. At least 150 different falls are represented. When you approach Dar al Gani from the west, the first thing to strike you is its whiteness, as if you were looking out over mountain-tops covered in snow: a mirage in the desert. First comes a succession of terraces which then open on to a smooth, rolling expanse of white, without rocks or vegetation. Meteorites have been falling here for thousands of years, and it goes without saying that strewnfields like this one are of scientific interest. Unlike Antarctica, where ice shifts concentrate meteorites and wind scatters the fragments, things here stay in the same place from one millennium to the next. I often think of Dar al Gani as a photographic plate recording all falls over a significant time-scale of 20,000 years or more. The terrain is gentle and preserving, so that thousands of years worth of data are at present accessible.
Within a one-year period, Dar al Gani yielded 210 kg of meteorites, as opposed to 74 kg in Antarctica, the diversity of the finds being at least as important (Met. Bull. N° 84, July 2000). Moreover, it is estimated that there is one fall for every 25 sq km, fragmentation in the atmosphere being capable of producing several individual meteorites from the same fall, associated distribution ellipses are intersecting on the plateau. Just one complete analysis of each find can result in the discovery of pairings, and it is common to find a pairing of two meteorites 30 km apart. On the other hand, two individuals just a few meters apart could originate from different falls, having landed in the same place, but at a different time.
Since 1995, groups have been taking it in turns not only to carry out meticulous prospecting work, but also to record as much information as possible about the terrain. This data, in particular the exact coordinates of the discoveries, will allow us to provide future generations with a complete map of meteorite distribution, and therefore to widen our knowledge about the frequency of falls, along with other statistics. Given the plundering which has been orchestrated in other North African countries, this is an example to us all.
You might be tempted to think that prospecting such a smooth, obstacle-free terrain is easy. But then you would be forgetting that the desert always has a surprise up its sleeve... a storm, for instance. Wind, flashes of lightning, driving rain... In just a few minutes, the landscape is completely transformed. Puddles the size of small lakes form around us. Usually firm, the ground drinks up the rain and creates traps where the 4WD sticks like glue. You really need to concentrate to zigzag between these sebkhas (salt water lakes). It is flat as far as the eye can see, and a third of the ground is soon covered in water, making it impassable. I glance at the map, studying the contour lines and looking for a raised area. When I have time, I enter the coordinates in the GPS and head in the appropriate direction. The ground does indeed become progressively less flooded, the puddles less frequent. Five kilometers further east, Roland is mopping up in vain. At least the rain has refreshed the air. And tonight, we will be camping on the shores of a lake!
Trajectory of the CO3
The next morning, we are forced to change our plans. The rain of the day before has completely altered the ground of the entire eastern region, all the way to the volcanic, basalt massif of the djebel Haruj. We are left with the western part of the plateau, which has been spared from the rain, but not from meteorite hunters. The evidence is there in the form of tire-tracks, some fresh, perhaps only a month old, and others obviously dating back a year or more. Every parcel of land must have been searched at least three times. Under these circumstances, it is futile to hope for a meteorite any bigger than a nut. A number of prospectors would have already been attracted to the area by the discovery of a carbonaceous chondrite in the same south-western part of Dar al Gani four years ago (DaG 005), followed by 34 other CO3 individuals within a radius of just a few kilometers. Despite all this, we decide to risk it.
We have access to information about the positions of all carbonaceous meteorites found and analysed since 1995. This data shows a vague distribution ellipse, with the majority of small pieces in the south-eastern part of the oval, and specimens weighing one kilo or more in the north-western part. We also keep in mind a 130 g piece which I discovered last year. What makes the DaG 601 distinctive is the place where I found it: more than 2 km south-east of the established ellipse.
We begin with two hypotheses: firstly, that the principal mass of the fall was more significant than the 28 kilos already collected. The history of discoveries such as Allende or Millbillillie only goes to show that many are multiple falls which turn out to be more important than first predicted. Secondly, that the axis given by aligning the epicentre of the individuals discovered to the northwest and DaG 601 to the southeast could show us a trajectory.
In the zone prospected by the teams before us, the ground is so clear and light-colored that a very black carbonaceous meteorite, even a small one, would be seen 100 m away. This type of pale, stoneless ground is every prospector's dream - provided he's the first on the scene. Needless to say, we are not. It is midday by the time we head towards the north-west. Our goal is simple: to find something which would confirm our hypothesis. In a few minutes, we reach the far end of the zone where the discoveries of past years were made. The plateau ends just in front of us, the small cliff which marks its edge overlooking a lightly undulating landscape with an old oued bed, alluvial deposits and fech fech, a very fine powder caused by erosion of the clay-limestone terrain: a real trap for 4WDs! If a meteorite has fallen here, by now it will be buried under the alluvium, never to be found.
Even though our theory is a good one, and seems to be confirmed by the fact that several pieces were found a few meters from the edge of the plateau, we need to face facts. To all appearances, finding anything beyond the plateau will be impossible. Even so, neither one of us is prepared to abandon the hope of adding a CO3 to our list of successes. My brother does not want to because he narrowly missed smashing a meteorite on a track of the Hammada al Hamra, and is beginning to think that anything is possible, and I do not want to either, as I have just begun prospecting, on foot, a very small rocky area full of fossilized wood. It seems that I am the first to have looked here, because I spot a nice individual of 500 g. Discovering a 500 g carbonaceous is not something that happens every day, and there is a moment of intense joy. I celebrate the event accordingly, allowing myself a break to enjoy a fruit juice. The discovery has a stimulating effect on Roland, who has been scouting around in the oued, and he decides to try to reach a gara, a small, flat-topped butte standing out from the landscape two kilometers away. Good luck to him! I track his manoeuvres through field glasses for a moment or two - and then decide to follow in his footsteps.
The nearest oasis is 100 km (60 mi) away as the crow flies, and there are indeed a pair of crows circling over-head, as well as some small black and white wheatears (a type of bird with a conspicuous white rump) searching for signs of human beings. It might as well be said that when exploring a new zone which bears no signs of having ever being touched, you always proceed with caution. Each of our vehicles carries more than 600 kg of water, gasoline and other materials, a minimum requirement for self-sufficiency in the desert. Descending rocky slopes and driving over soft ground demands a good amount of experience and skill if you do not want to end the day with an overheated motor, or a shovel in your hand. Ahead of me, Roland's 4WD is sending up a huge cloud of dust several meters in height. A bad sign! I'll have to tow him out. He does indeed call me by radio, but not to ask for help. When he realized he was trapped in the fech fech, he accelerated deeper into it, and actually managed to reach a small raised terrace which helped him to get out. His call is to tell me that he has come face to face with a carbonaceous chondrite weighing 4 kg.
It is there on the butte: a large black stone lying on white gravel. It takes me a while to realize the importance of the discovery. Not only has our hypothesis proven to be correct, but we are once again on favorable ground. We can see more similar little buttes and terraces of limestone in front of us. By the time evening falls and we are forced to stop our searching, we have 15 kg of CO3, as well as a one-kilo chondrite clearly originating from a separate fall.
The changing colors of the desert are intensified by the final rays of the Sun. In the distance, the plateau of Dar al Gani is bathed in splendid ochre. It is a photographer's dream as evening shadows cling to the contours of the landscape, and the fading light paints the desert in pastels.
Looking towards the southeast, we imagine a meteor heading straight for us: the light, one or more fracturings, the explosions, the whistling above us, and the impact of blocks around us. It is not just a fantasy: it really did happen in this very landscape, maybe 4000 years ago. Today's specimens lead us to believe that the meteor had an oriented, inclined trajectory 309° north. The pieces discovered in this area all weigh more than 2500 g. Some of them broke up on impact, but all originated from a fracturing in the atmosphere. The most interesting of all is an elongated individual shaped like a rocket which broke into three on impact. The initial block must have been very large to produce a fragment shaped like this. Where is it?
Some days we take our time preparing and cooking our evening meal, but tonight we are the ones simmering - with understandable excitement! The stars are bright by the time we finally settle into our sleeping bags, full of hope for the next day. We have decided that one of us will continue northwest for at least 5 or 6 km to look for the missing mass, while the other will widen the search around the camp.
The desert landscape can change radically in just a short distance, and this part of Dar al Gani is a prime example. Progressing further on the axis of the trajectory, the landscape changes kilometer by kilometer. First come the tumuli: small mounds or hillocks, some topped with large blocks of stone. Searching behind these mounds requires us to zigzag through a real labyrinth. Next, our path is blocked by large canyons. The wind blows the sand into drifts which cover the slopes, allowing the 4WDs to slip smoothly to the bottom of the gullies. Getting back up the other side, however, is much more difficult. We have to look for a place where we can climb the scree-covered cliffs, usually a steep slope which will need all the power of the 8-cylinder motor to scale. When we manage to clamber up to little plateaus, they turn out to be covered with limestone slabs which shatter under the tires, producing dry noises which make us anxious. The sharp edges shred pieces of rubber, and we can think of nothing but the agony suffered by our poor tires. Prospecting in such an area, far from all civilization, requires tenacity as well as a good mastery of your vehicle.
We look in all the nooks and crannies of the desert, and our perseverance is rewarded. Today, we collected more than 36 kg, the nicest individuals being an extremely attractive complete piece of 8,300 g, and a 15,500 g piece which we were able to rebuild in its original form, the majority of fragments being scattered over a few square meters following an impact on rock. These 15 kg, situated on the trajectory which we had calculated ourselves most certainly represent the final mass of the fall, and so also the culmination of our research. It is time to let the engines rest while we take stock for the first time: our efforts of the last two days have been rewarded far beyond any expectation.
"In nature... nothing is impossible, one must be prepared for anything, and assume that anything which could be true, is true." (G. Buffon, French naturalist, 1788).
A similar thought keeps running through our heads in the morning of the third day: perhaps the distribution ellipse is longer than we thought. We are already 30 km from DaG 601, but a meteor with an inclined trajectory could easily lose fragments over a wider distance. The thought of embarking on a search for a meteorite weighing dozens of kilos is so exciting that we decide to follow a course of 309°. We are all the keener because the ground we will be covering has never been prospected before. You really need a good reason to lose yourself willingly in this tortured, inhospitable lunar landscape.
Up ahead, there is one more cliff to go down before we reach the foot of the plateau; a rapid descent down a slope of sand, and we have made it to the bottom. Since this morning, we have been driving without losing sight of each other, following parallel routes. The distance is displayed on the dial of the GPS: first 35 km, then 40 km. Our motivation drains away with the hours; we have not found a single thing and, worse, the terrain is becoming less favorable. The sand here is everywhere and covers everything. Our chances of discovery diminish, but the desert around us is so magnificent, and our pleasure at driving across the sand so great, that we continue mechanically. The formations to my left appear to be covered in a white crust: ancient lake deposits, perhaps. As they are slightly elevated, the sand is absent. The Sun is at its zenith, and I let my thoughts wander... The Sahara will always be a country of adventure and discovery; a fascinating mineral universe, full of contrasts, reminding us every step of the way that water and life are vital, inestimable treasures.
"I'm afraid we have a problem, what we feared most has come true!" calls Roland over the radio. I drive in his direction, knowing full well what to expect. But even so, I am more than a little surprised. There on the ground is a 95 kg meteorite, broken into a thousand pieces. It is a striking image: a pile as black as ink on a background of white.
We stand there, dumbfounded, trying to take it in. We are conscious that this is a unique moment in our lives, that we have made an important discovery. This type of meteorite containing carbon is among the most primitive material in the solar system. What was unthinkable three days ago is now here before our very eyes.
The ground is covered with thousands of fragments, some of which have been thrown quite a distance. The impact must have been very violent to have shattered the meteorite like this. We cautiously begin a meticulous and laborious recovery operation, recording as much information as possible. The nose of the meteorite has sunk 20 cm into the ground. It is a very fractured block of about 22 kg, the frontal part reduced to powder. The ground alongside is strewn with fragments of all sizes. The largest weighs 25 kg, its buried face, which has been protected from the wind and sand, clearly showing a fusion crust. The surface fragments however, have been exposed to the desert winds for hundreds or thousands of years, and have a polished appearance and blunted shapes.
After a few hours of work, crawling around like ants under the hot sun, we clear the ground of all traces of black, leaving behind a desert of immaculate whiteness.
Before leaving Dar al Gani, we have a rendezvous with a friend we met two years ago. If you ever have the opportunity to drop in, bring him a few biscuits or seeds. He lives at the edge of the plateau, and he's a friendly jerboa. This little rodent will come to pay you a visit when night has fallen. Here in the desert, what could be more natural than sharing your meal? His cheeks bulging, he will head off to feed his little family.
The rain which fell several days ago over the east of the plateau has brought about much seed germination. Beneath the Sun, the last pools of water reflect the blue of the sky, and all around burgeoning grasses add a note of green. We have never seen Dar al Gani like this. From a dry, inhospitable desert has been born a place you could almost call pleasant!
All the meteorites discovered on our expeditions have been documented in great detail, with photos of the principal mass, analysis results, and images of cuttings showing their internal structure. All this information is stored on CD-ROM.
The principal mass of the 95 kg CO3, which still remains the largest meteorite ever found in Libya, has been analyzed by Professor P. Sipiera of the Planetary Studies Foundation. From now on, it will be known officially under the name of Dar al Gani 749. The principal fragment of 25 kg has been kept for the Libyan government and will be exhibited in their museum.
On January 18, 2000 another carbonaceous meteorite fell on Earth, near Tagish Lake, Canada. "An asteroid weighing 200 tonnes and approximately five metres across had impacted the Earth's atmosphere... A field effort consisting of 234 person field days is now over. This recovery effort is believed unique in the history of meteoritics." (University of Western Ontario, news release, May 31, 2000). Ten kilograms of this "school bus size" meteorite have been recovered by scientists!