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Home , Earth, Earth mass, Moon, Wegener (lunar crater), Wegener (Martian crater)

INTERNATIONAL INSTITUTE No 5, June 2000 SPATIUM Published by the Association Pro ISSI

Earth,, Moon andand MarsMars Editorial

Mankind finds itself thrown into grateful for his kind permission Impressum a hostile . While our bod- to publish herewith an adapted ver- ies are subject to the soulless laws sion of his address at the Fourth of chemistry and govern- Anniversary of the ISSI founda- ing physical processes on even the tion. SPATIUM most distant , our minds, our Published by the hopes and fears find no spiritual Association Pro ISSI equivalent. The intriguing sketch- Bern, June 2000 twice a es on the walls of the Altamira Hansjörg Schlaepfer , for example, may have been the attempt of our early ancestors INTERNATIONAL SPACE to create humanlike beings simply SCIENCE in order to alleviate their spiritual INSTITUTE loneliness. The Greeks later filled Association Pro ISSI their with a great variety Hallerstrasse 6, CH-3012 Bern of who, by virtue of their Phone ++41 31 631 48 96 features, clearly betray the Fax ++41 31 631 48 97 intent of their creators. President Little has changed since. The past Prof. Debrunner, two thousand have seen man- University of Bern kind struggling to find a rationale Publisher for its existence, hopefully given Dr. Hansjörg Schlaepfer, by an entity beyond its transitory Contraves Space, Zurich existence. These days, evidence Layout seems to take precedence over be- Marcel Künzi, marketing · kom- lief. Hence, modern science seeks munikation, CH-8483 Kollbrunn to provide answers to these age- Printing old questions. It is only logical to Drucklade AG, CH-8008 Zurich begin with the nearby celestial bodies, i.e. with the Earth, Moon and , to which the present issue of Spatium is devoted, and to search there for traces of . But, while this has provided us with deep into the his- tory of our own , the feasi- bility of life on the Moon has meanwhile been excluded, and corroboratory proof of has not yet been found. We are still alone.

Prof. Johannes Geiss is the spiritus rector of the International Space Frontcover Science Institute in Bern and its Mars: of Candor Executive Director. We are (NASA/JPL)

SPATIUM 5 2 Earth,Moon and Mars *)

Johannes Geiss,International Space Science Institute,Bern

Introduction of geologic epochs from the In the second half of the 20th cen- Cambrian to the Quarternary was tury, and other pro- identified. Then, at the turn to the grammes enabled scientists to use , radioactivity was dis- the experience gained from the The ultimate goal of planetary re- covered, opening up a new era for earth sciences and apply their con- search is to find answers to the big many , includ- cepts and methodstotheinvestiga- questions: What happened when ing the earth sciences. The decay tion of the Moon. By combining 4’600 million years ago the of uranium, and potassi- observations at the lunar and the formed out of an um was found to be the and from with the chemical interstellar ? What were the source of in the inte- data obtained from the analyses of external circumstances and specif- rior of the Earth, maintaining there lunar rocks brought to Earth, ic processes that governed the ori- a high and driving scientists reconstructed a large gin of the Earth and determined geological processes. The applica- part of lunar history. its evolution to the present ? tion of for meas- Is there – or was there – life in the uring ages of rocks was an equally Thirty years after set past on another planet or on one important breakthrough. By using foot on the Moon and explored its of the in the solar ? various “radioactive clocks”, the , scientists and space agen- From the presence or absence of age of the Earth was derived and cies are turning their attention in- signs of life outside the Earth, can an absolute scale was estab- creasingly to Mars, the Red Planet we draw conclusions about the lished for the larger part of its (Figure 1). Let me emphasise that origin of life on our own planet? history (Figure 2). Thus, it became the of Mars for quite a possible to gain a quantitative while will be by robots. Human To an interplanetary traveller, understanding of the causes of exploration will be a great chal- Earth, Moon and Mars would geological evolution and identify lenge, because Mars is at least 200 present themselves as entirely dif- the underlying physical processes. more distant than the Moon. ferent (Figure 1). For earth and planetary scientists, however, these three members of the have important similari- ties. Their , their chemical compositions and their distances to the Sun are relatively similar, so that comparative studies yield results on their origin and their evolution. Moreover, Earth, Moon and Mars are the only objects in the universe where we have detailed geological observations and at the same time possess rock samples for laboratory analysis. Figure 1 Nineteenth century scientists real- Earth, Moon and Mars. The “Blue Planet" Earth, the “Red Planet” Mars and the ised that evolution is central to bi- Moon. The relative sizes are to scale. We have evidence that on Mars there were large quantities of at some time in the past. Today we see only small caps of ology and geology. On the basis of CO2 and H2O, which are seasonally distilled from pole to pole, giving rise to strong characteristic , the sequence .

*) Keynote address at the Fourth Anniversary of the International Space Science Institute, 21th October 1999

SPATIUM 5 3 We have on Earth a Mar- The Early Days tian . There is little doubt that their origin is the Red of the Planet, but we do not know the exact location they came from. Solar System The Mars meteorites were ex- pelled from the planet by a large impact, as a result of which they were badly shocked. This makes Sun and planets radioactive dating difficult. Still, ages of Mars meteorites have are created when an inter- given us a general idea of the stellar collapses. times of formation of geological We can observe this process in the features on Mars. However, sam- , where star forma- ples returned by spacecraft from a tion is presently going on. The few well-defined geological units Sun was 4’600 million years will probably be needed to obtain ago in a collapsing interstellar a definite time scale for Martian cloud that was dispersed long ago. geology. Once initiated, it took only a few million years to form the Sun and to allow the nuclear fusion pro- cess in its interior to start working and hence for the Sun to shine. Ages of Rocks Mars 6’860 km As predicted by Pierre Laplace Moon early in the 19th century, a portion 3’476 km Earth of the gas and dust of the protoso- 12’756 km lar cloud remained in a rotating

4’600 disc from which the planets were

0 1’000 2’000 3’000 4’000 5’000 formed by (Figure 3).This Million Years process followed the principle of Figure 2 “big fish eats small fish", well The ages of Earth, Moon and Mars. known in the behavioural and This diagram shows the distribution of social sciences. It began with dust ages of rocks from Earth, Moon and The Earth Mars. Earth has been geologically very attaching to each other. active throughout history. As a result, After they reached a certain , the geological record of the early times gravitation took over, and larger In the case of the Earth, the accre- has largely been overwritten. The Moon bodies attracted and swallowed tion process did not go so smooth- is much smaller than the Earth, and con- sequently, the geological activity of the smaller ones. In the end, a number ly. A second object, about the size Moon ended about 3’000 million years of planets were left, most of them of Mars, formed on a nearby orbit, ago. We have, however, a good geologi- well separated from each other, so so that the two were bound to col- cal record with absolute times by radio- active dating for the 4’100–3’200 that they could safely orbit the lide.All the evidence indicates that million years ago for our companion. Sun for more than four billion this did occur, and it cre- For 3’000 million years, the Moon has years. ated the pair of Earth and Moon as been geologically dead. For Mars, we we know it, circling around the have only a rudimentary time scale of geological events, since we only have 13 common center of , thus Mars meteorites for radioactive dating. avoiding any further collision.

SPATIUM 5 4 The Origin of the time of their formation. The exceptional size of our Moon, the Earth–Moon however, calls for an entirely dif- System ferent origin. The Giant Collision

For centuries, scientists have won- Among the various hypotheses dered about the large size of the about the origin of our Moon, Moon. Many planets in the solar there is only one, the “Giant Col- system are circled by moons, but, lision Theory" that explains all with the exception of the relevant observations. This theory of Earth and , all these was originally proposed by Wil- moons are tiny in comparison to liam K. and colleagues the planet they accompany (Figure in the .The sequence 4). The giant planets, and (Figures 5 to 7) depicting three stages , have con- of the creation of the Earth–Moon sisting of more than ten moons system were painted by him. They each. They were probably formed are based on quantitative model- from protoplanetary discs that ling by A.G.W.,W. Benz surrounded Jupiter and Saturn at and others.

Figure 3 Our Sun is born. The Sun was born by a collapse of an 4’600 million years ago. Some of the material could not be collected into the central star, the Sun, due to the law of physics, which requires conservation of . This material eventually accreted into planets (painting by Wil- liam K. Hartmann).

Figure 4 Jupiter with its moons and . The Jupiter with two of its moons, Io (reddish) and Europa (). While Io and Europa are nearly the same size as our Moon, they are tiny in comparison to the planet they orbit.

SPATIUM 5 5 Figure 5 Figure 6 Figure 7 A Giant Collision created the Moon: Five after the Giant Colli- 1’000 Years after the Collision: The half an after impact. All evi- sion: Because of the enormous formation of the Moon is essentially dence indicates that our Moon was cre- created by the impact, all volatiles complete. In its early history, the Moon ated by a collision between Earth and escaped, so that only non-volatile mate- was molten (“ ”). The another large object, ten percent of the rial remained in Earth orbit (painting by “tidal ” at that time were more Earth’s mass, formed in a nearby orbit William K.Hartmann). than a thousand times stronger than (painting by William K.Hartmann). they are today and contributed to heat- ing the Moon. Data from the Apollo missions showed us that the Moon is covered by a of light material. Thus, the Moon is chemically highly differentiated, and this could only have happened if the Moon was molten early on (painting by William K.Hartmann).

The Giant CollisionTheory is con- pictures taken from orbit and – The relative abundances of the sistent with all the relevant pieces on the lunar surface did not three isotopes of show of evidence we have. In particular, reveal any traces of past water small characteristic differences it explains in a natural way some flows or products of sedimenta- in the material of different unexpected results of the analyses tion. The complete lack of objects in the solar system. Thus of lunar rocks and some obser- volatile material and the rela- meteorites coming from differ- vations made by the Apollo astro- tively low abundances of sodi- ent , meteorites com- nauts and by photogeologists. um, and other alkalis ing from Mars and rocks on These are: are readily explained by the Earth all have their characteris- extremely high of tic, but different isotopic signa- the material ejected by the giant ture. The exception is that oxy- collision. gen in terrestrial and in lunar — The lunar rocks are completely rocks has exactly the same iso- free of crystalline water and – Relative to the Earth and mete- topic composition. The Giant -containing minerals, orites, the Moon has much less Collision Theory explains this such as or minerals . This would be expected, if finding, because most of the (Figure 8). Not only hydrogen, the giant impact occurred after lunar material was originally but also the other volatile ele- the Earth had formed its iron part of the Earth. Moreover, the ments such as and nitro- core and if the impact ejected two collision partners accreted gen are virtually absent. Astro- only material from the Earth’s from the same in the naut observations and all the crust and . protosolar disc.

SPATIUM 5 6 Figure 8 on the Moon: This beautiful landscape in was visited by the crew. Like everywhere else on the Moon, the rocks in this mare plain and in the distant highlands are extremely dry. There is no trace of past water flows nor have we found crystalline water in rocks. The rocks and the are also devoid of carbon and . Thus, there was never any chance for life on the Moon. Small amounts of water ice or other condensates exist in polar areas. They are probably mostly secondary, stemming perhaps from impacting (NASA Photo AS-15 9212430).

SPATIUM 5 7 The accretion process likely left Evolution we always see the same side of it. behind some sizeable objects that With the receding of the Moon were bound to collide at the end of the Moon to its present distance, the tidal of the epoch of planet formation. forces lost most of their strength. There are indeed indications that Dangerous occur only in a large happened else- The time scale of evolution of the few coastal , but there may where in the solar system, though Moon was reconstructed from the be another important effect: it has the collision producing our Moon radioactive ages of lunar rocks been calculated that the orbiting may have been the most violent. It determined by several laborato- Moon has stabilized the has been postulated that the high ries in the United States and in axis of the Earth, and this in turn of and the high . has a stabilising effect on the inclination of the rotation axis of Earth’s . were caused by large colli- Accretion of the Moon from the sions at the end of the accretion material circling the Earth proba- Using various ‘radioactive clocks’, process. bly took only a few years. The laboratories in the United States original heat content, the gravita- and Europe measured the abso- According to the Austrian-British tional energy liberated in the lute ages of numerous lunar rocks philosopher Karl Popper science accretion process and heating brought back by the Apollo astro- progresses by falsification of theo- from the extremely strong tidal nauts and reconstructed the time ries. The story of the origin of the forces caused by the proximity of scale of lunar evolution. The fig- Moon is a good example of this the Earth combined to melt the ures 9, 10 and 11 show the Moon at postulate.As data,observations and Moon in its early history. Chem- the end of important epochs in its theory increased in quality and ical differentiation set in and pro- evolution. quantity, one hypothesis after the duced a crust of light material that other about the Moon’s origin has been preserved up to today, The accretion process in the solar encountered severe difficulties, especially in the oldest region on system did not end abruptly: large the giant collision theory being the Moon, the highlands on its chunks of material were still the only one that remained con- backside. roaming around in the sistent with observation.Of course, between the planets, even several we do not know what kind of new hundred million years after the evidence may turn up, but most of The early Moon Sun was born. On the Moon, us think that with the giant colli- the last major impacts occurred in sion theory we have the right sce- Initially, the tidal forces between the time-span 4’050–3’850 mil- nario for the . Earth and Moon were more than lion years ago (Figure 9). These late a thousand times stronger than impacts excavated the large mare they are today, causing significant basins that were later filled with heating of the Moon and enor- basaltic rising up from below. mous tides on Earth. These tidal More than ten impacts, forming forces led to a transfer of angular craters with of more momentum from the rotation of than 500 km, occurred during this Earth and Moon to the orbital time-span. On Earth, we have no motion of the Moon. When record of this catastrophic epoch. Moon and Earth were close, the However, taking into account the transfer was fast; the Moon reced- larger size and of the ed quickly from Earth, the days Earth, we estimate that more than lengthened, and soon the Moon’s a hundred craters of these dimen- rotation slowed down, so that sions were excavated on our plan-

SPATIUM 5 8 Figure 9 The Moon 3’800 million years ago. Figure 10 500 to 700 million years after its forma- The Moon 3’000 million years ago. tion, the Moon was still bombarded by At about 3’800 million years ago, the large chunks of material, forming the basins began to fill with lava. Shown are huge basins that are still distinguishable. the ages of the local mare in mil- Within about 200 million years, more lion years, determined by radioactive than ten craters with diameters of more clocks. From to : Oceanus than 500 km were formed. On Earth Procellarum (3'200 million years), Mare the record of this bombardment has Imbrium (3'300), Figure 11 been lost, but we can estimate that more (3'800), (3'600– The Moon today. About 3’000 million than 100 such craters were formed on 3'800), (3'600). These years ago, the Moon cooled down suffi- Earth during the same epoch. This must ages show that this process was largely ciently, so that geological activity after- have been a fantastically catastrophic completed 3’000 million years ago. The wards did not change the face of the in the Earth’s history, at a time large plains, which called Maria, Moon very much. The main changes when and were in have existed on the Moon since that are from occasional impacts. On the an early stage. We would not know time. We know now that their dark front side of the Moon, the largest about this catastrophe if we had not colour is due to a -iron mineral ‘fresh’ crater is Copernicus, which was investigated lunar rocks in Earth-bound that is relatively abundant in the mare created by an impact about 900 million laboratories. basalts. years ago.

The Moon 3’800 million years ago The Moon 3’000 million years ago The Moon today

3’300 3’850 3’890 3’800 3’890 3’600

900 3’600–3’800 3’200 3’910

Time of Impact (million years) Mare Basalts Age of Copernicus (million years) (Formation of Basin) Ages in million years (Note: Age of Cambrium is 500 million years) et during that period. For the is due to minerals containing these ther east there may be some areas emerging atmosphere and oceans, elements, in particular the titani- covered with even younger basalts, this must have been a catastrophic um-iron called ilmenite. but there are no samples and no epoch. absolute ages from this region. In The ages of the mare basalts any case, the formation of mare Even before the last mare basins brought back by the Apollo astro- basalts that marks the last major were excavated on the Moon, lava nauts and Russian Lunar missions geologic epoch on the Moon had begun to rise and fill these were found to range from 3’800 ended not much later than 3’000 basins. These were basaltic , to 3’200 million years (Figure 10). million years ago. Since then, the richer than the crust in iron, mag- A few small rock pieces in the Moon has been geologically in- nesium and titanium. The dark were as active, its energy reserves exhaust- colour of the Maria on the Moon as 3’000 million years. Fur- ed.

SPATIUM 5 9 Figure 13 The of Neil . There are neither winds nor on the Moon and is very slow. Thus, the chances are good that this footprint of , the first man on the 10 µm Moon, will still be visible a million years from now. There is, of course, a minute statistical chance that this foot- Figure 12 print will be impacted by a larger A microcrater in a piece of lunar glass. In the present epoch, small impacts are the object, but then other of main cause of erosion, “gardening” and lateral transport (photo by Norbert Grögler, the Apollo crews would survive (NASA University of Bern). photo).

cess is extremely slow, so that mental difference in the evolution The serene Moon even small surface features last for of Earth and Moon. Copernicus a long time (Figure 13). Major im- was formed before the Cambrian, In the absence of geological pro- pacts were very rare during the the earliest of the classical geolog- cesses and without water or last . On the frontside ic epochs. Since on Earth plate tec- winds, the face of the Moon has of the Moon, the impact creating tonics and continue to not changed very much during the Copernicus crater is the most the present time, the effect of im- the last 3’000 million years, as a prominent among them. It oc- pacts on the geologic evolution is comparison of figure 11 with fig- curred about 900 million years minor. However, the catastrophes ure 10 shows. Erosion at the lunar ago (Figure 11). Sometimes Coper- caused by large impacts have had a surface is now mainly caused by nicus is called a young crater. This major influence on biological evo- small impacts (Figure 12). This pro- expression illustrates the funda- lution (Figure 14).

SPATIUM 5 10 Mars ten as much as on Earth. This is in line with the size of Mars, which is in between the sizes of Earth and Moon (Figure 1). Mars is intermediate in size be- tween Earth and Moon, and it seems to be intermediate as well in the degree of geological evolu- The tion (Figure 2). This is to be expect- ed: Small bodies cool faster than The radioactive dating of Martian large bodies, since energy produc- meteorites gives a general idea of tion and energy content are basi- the absolute ages of geologic fea- cally proportional to the , tures on the Red Planet. A relative whereas energy losses are propor- time scale of the sequence of geo- Figure 14 tional to the surface. It is for the logic epochs identifiable on Mars The Cretaceous/Tertiary boundary. same reason that warm-blooded is being set up by scientific groups On Earth, impacts did not have a large need a minimum size to at the Deutsches Zentrum für effect on the geological or geographical evolution of the surface, because vol- be able to maintain a body tem- Luft- und Raumfahrt, Berlin, and canism and were domi- perature that is above the ambient the Institute in nant. Impacts of meteorites, however, temperature. Tucson, . The method is had a major effect on the biological evo- by counting craters, which has lution. The best-documented case is the event that occurred 65 million years Asteroids have diameters below been successfully applied on the ago, marking the boundary between the 1’000 km. Thus, they cooled Moon. Cretaceous and the Tertiary age. At that down and became geologically time, a large impact – probably located at the edge of the – inactive only one or two hundred Presently, earth and planetary sci- caused the of many , million years after they were entists are engaged in reconstruct- giving way to the evolution of new formed. This has been confirmed ing the geological evolution of species. Thus, in sedimentary deposits, by radioactive dating of mete- Mars and in estimating absolute the CT boundary is marked not only by impact-specific materials (, orites that are rock pieces from time scales for the most promi- soot), but also by an abruptly changing asteroids. The Moon, with a diam- nent events in the Martian history. micro- over a very short interval eter of 3’476 km, became geologi- These issues were discussed in a (Figure by O.Eugster). cally inactive about 3’000 million recent workshop on “the Evol- years ago. Because of its size, the ution of Mars” at the International Earth has remained geologically Space Science Institute. The active throughout its history. As a results from Martian meteorites consequence, the geological rec- were compared with photogeo- ord of the first 1’000 million years logical evidence obtained from of its lifetime is essentially lost. orbit and with the data obtained by the Sojourner, the vehicle - The ages of the few Mars mete- ed by NASA on the Martian sur- orites range from 4’500 to 150 face on July 4, 1997. The whole million years. Apparently, some watched as the Jet Pro- rock-forming processes have been pulsion Laboratory in Pasadena going on quite recently. On the steered the Sojourner to some other hand, the old ages indicate nearby rocks, so that the chemical that the record of the early sensor of the Max--Institut Martian history was not overwrit- für Chemie, Mainz could analyse

SPATIUM 5 11 The evolution of Mars

The two most outstanding geo- logical features on the are the huge volcanoes and the evidence of the existence of liquid water in a past epoch. The largest of the Martian volca- noes, , is shown in Figure 15. It came as a great surprise that the volcanoes on Mars are higher and more massive than the highest on Earth (Fig- ure 16). The principal reason is de- picted in Figure 17. On Earth, plate tectonics causes continental drifts as predicted by Alfred early in the 20th century. Thus, plate tectonics determines the global on Earth, and it produces the high continental ranges. On Mars, the internal energy is not sufficient to drive plate tectonics. Thus, volca- noes are the dominant mountains, Figure 15 The Olympus Mons. The most outstanding geographical feature on Mars is the and they can grow without being large volcanoes (photo by Viking Orbiter, NASA). cut off from their hot spots below. them. At first, the outcome seemed surprising: the chemical Olympus Mons 15 high abundances were completely dif- 45 miles ferent from the abundances in the Martian meteorites. However, the Sojourner investigated rocks

1 in one of the dry riverbeds, the 5 /2 miles high Ares , whereas most of 1 the Martian meteorites probably Mauna Kea 6 /3 miles high come from volcanic highlands. Level Thanks to the Sojourner we now Ocean know of the very large variety in Floor Vertical Scale exaggerated 2 times the composition of Martian rocks. This indicates that chemical dif- Figure 16 ferentiation was much more Olympus Mons versus Mauna Kea: Olympus Mons and other volcanoes on Mars are much higher than the largest volcanoes on Earth, even if we measure these from intense on Mars than on the the bottom of the ocean. This may seem surprising, since one might expect less in- Moon. tense volcanic activity on Mars than on Earth, because of the difference in size.

SPATIUM 3 12 the rivers shown in blue. The exact

Niihau Kauai Motion of the Plate extension of this temporary ocean Oahu Molokai is still debated, but all indications N Pacific Maui are that it covered a significant Lanai Hawaii Ocean Kilauea Kahoolawe portion of the Martian surface. Jim of University, 5 Phillip Masson of the Université relative position3 of hot spot (million years) hot spot de Paris and other photogeol- 1.5 ogists are working to identify the plate moving over the hot spot in the mantle today ancient shorelines. If successful, we can quantitatively determine the amount of water that was present.

Figure 17 Where did these water go? Origin of the Hawaiian volcanic : Plate tectonics (“continental drift”) on A considerable fraction has proba- Earth is the answer to the apparent contradiction shown in Figure 16. The oceanic bly been lost, but some must have plate moves with a of a few centimetres per year over a hot spot in the mantle, creating a chain of volcanic islands. On Mars such plate motions are absent and, leaked through the ocean bottom therefore, the lava coming from a hot region in the mantle is piled up in one place and is preserved as a over a long period of time. layer.

Life on Mars?

Liquid water is a prerequisite for Figure 18 Figure 19 the emergence of life, at least of River system on Mars: Sometime in The : On the Moon there the form of life we know. Since the history of Mars there was a fluvial is no indication of liquid water, present water is liquid only in the tem- period. The extensive river systems are or past. But how do we know this? ° evidence of this. Hadley Rille and the other lunar rills perature range of about 0 C to have no tributaries: they were probably 100 °C, we could expect life on made by lava flows. On Mars, the tribu- a planet only in a narrow range of Contrary to the Moon, where tary systems of valleys are the most - distances from the central star. vious proof that they are dry riverbeds. there are no traces of past water Thus in the solar system, we have flows, we see large dry riverbeds presently only one body, the on Mars. The difference between The larger riverbeds on Mars com- Earth, with liquid water on its sur- the lunar rills and the Martian pare with the Nile valley. At some face. Because of radioactive heat- riverbeds is demonstrated in pic- –as yet–unknown time in the past, ing, planetary temperatures in- tures taken from orbit: Martian large amounts of water were trans- crease with depth, and therefore it riverbeds have extensive tributary ported, and they must have filled is believed that water could be liq- systems (Figure 18). The long lunar significant portions of the low uid at certain layers below the sur- rills on the Moon have no tribu- . Figure 20 is a topographic faces of Mars and some moons of taries, the rills are thought to stem map, with the area that might distant planets with icy , from lava flows (Figure 19). have been temporarily filled by such as Europa.

SPATIUM 5 13 We have strong evidence that dur- Traces of life in Martian ing an earlier epoch there were meteorites? large of liquid water on the surface of Mars. It is not yet Reports on the observation of long known during which epoch in straight “channels" on Mars were Martian history the rivers and the not confirmed by orbital photo- ocean existed (Figures 18 and 20), graphy. The Viking spacecraft, nor do we know whether there landed by NASA in the 1970s, did were several fluvial periods or only not turn up any evidence of life, Figure 21 one. In any case, since Mars is rel- although they were equipped with Buhwa iron deposit. atively close, the Red Planet offers some suitable instruments. Then, This sedimentary deposit in Zimbabwe is about three billion years the best chance for discovering a few years ago, a group of scien- old. The iron in this ore is highly oxi- or for identify- tists in the United States found dised. It is thought, that these are ing relics of extinct life. spherules in the oldest Martian the oldest indication for the presence of oxygen produced by of algae (photo by Jan D. , Uni- versity of Bern). –8 –4 0 4 8 180°

150° , and after elaborate mi- 210° croscopic investigations and chem- ical analyses, they concluded that these spherules could very well be

120° relics of life. The evidence is in-

240° triguing, but the discussion of its significance is continuing. Indeed, we cannot expect to have a con- sensus concerning the biological of these spherules unless corroborative evidence is found on Mars.

If life on a planet were confined to a limited area, a puddle of water or a cave, it would be extremely

300° difficult to discover. After all, the

60° surface of Mars is nearly as large as all on Earth taken to- gether. Fortunately, however, once created or imported, life seems to 330° 30° be extremely adaptable and pro- lific. This opens up another meth- 0° od of searching for life, which Figure 20 we may call the geochemical ap- Ancient ocean on Mars. The dry riverbeds on Mars with their tributaries go proach. On Earth, this approach towards the large low- plains in the north. Considering the amounts of water has proven to be valuable for that have cut the large valleys, the water masses must have fed large oceans. The estimated extent of the ocean is shown here in blue. is given in kilometers searching for early traces of life. (from J.W. Head, Science, 286, pp. 2134–2137, 1999). Large ferric iron deposits that

SPATIUM 5 14 formed only in the early Pre- ed to develop other equipment, and even some people at a dis- cambrium (Figure 21) are thought such as high-performance tele- tance. When the visitors cautious- to be the oldest evidence of life. scopes and sensitive detectors. ly approached, one of the earth- Most deposits, such as , when cruising in the lings began to talk, and it sounded those lifted to the top of Mount Mediterranean, found himself in a strange, but friendly. “So that is Everest or the Bernese Alps, are comparable situation. He had a the language of the people on this produced by life. If life existed on marvellous ship, but no , planet, for us impossible to under- Mars during a fluvial epoch, it poor maps, and no idea of the dan- stand”, they concluded. It was only would have spread over a large gers awaiting him. The spaceship much later that they found out area. Thus, searching for geo- with the extraterrestrials on board that almost nobody else on Earth chemical traces of life on Mars going towards the solar system understands these nice people liv- should be considered. G. Turner was successful. After short, unre- ing in the foothills of the Bernese and J.D. Gilmour of the Uni- warding visits to the Jovian moons Alps either. versity of Manchester proposed to and to Mars, they turned towards look for a life-specific iodine dis- the Earth. In a direct approach and tribution on Mars. without much “reconnaissance”, they chose to land on the western Acknowledgements flank of the Jungfrau, because the Life on Earth! Bernese Alps were among the few I am indebted to Hansjorg places that protruded through the Schlaepfer, the editor of Spatium, Let me finish this evening’s lecture cloud layer covering all Europe at for his help with the manuscript with a tale that may illuminate the the time of their landing. All they and his in getting geochemical search for life. The could see was and rocks this issue published. I thank Silvia society on a planet orbiting a near- (Figure 22). One of them tested the Wenger, Ursula Pfander and by star decided to explore their rock with a knife: “It’s limestone, Gabriela Indermuhle for their stellar neighbourhood. In a plan- there is life on this planet or at help with the manuscript and the et-wide effort, they built a fleet least there was in the past!” Cau- figures, and Diane Taylor for criti- of extraordinary spaceships that tiously, he opened his suit and cally reading the manuscript. With would enable them to reach a found he could breathe. So there this issue of Spatium I would like dozen or so stars in their neigh- was oxygen. On their home- to remember two distinguished bourhood during a crew’s life- planet the oxygen was produced colleagues and friends, Paul Gast time. However, by giving so much and continuously replenished by of Columbia University and priority to rocketry, they neglect- . This convinced them that NASA and there was a rich below the Norbert Grogler of the University Figure 22 .Slowly,they climbed down. of Bern, with whom I had close The Bernese Alps shown above the clouds From right to left: Jungfrau, Suddenly, the broke cooperation during the Apollo Mönch and Eiger. up, and there it was: grass, cows period. SPATIUM

The author

Prof. Johannes Geiss received his Johannes Geiss is co-founder of doctorate in 1953 from the Uni- the Association Pro ISSI and pres- versity of Göttingen and, after ently the Executive Director of several research positions in the the International Space Science USA, became a lecturer (“Hab- Institute, ISSI, in Bern. ISSI is ilitation") at the University of supported by a foundation of the Bern in 1957. After a professor- same name, endowed initially by ship in oceanic science at the Contraves Space in Zurich. The University of Miami, he returned Institute is primarily funded by to the University of Bern as a pro- ESA, the Swiss Confederation, fessor in 1960, where he was the Canton of Bern and the Swiss named director of the Physi- National Science Foundation. kalisches Institut in 1966. In ISSI is dedicated to interdiscipli- 1982 / 83 he was rector of the nary research of the solar system University of Bern, as well. and the universe, inviting scien- tists from around the world to During his tenure at the Uni- working group meetings and versity of Bern, he had extended workshops and offering them the stays as a visiting scientist in to exchange ideas and France and the USA. The public evaluate their newest research connects the name of Professor results. The basis for ISSI's re- Geiss with the solar experi- search activity is the data provided ment, the first experiment the by the scientific missions of the American astronauts set up on the space agencies of Europe, the US, Moon in 1969. and as well as labora- tory experiments and computer Since then, Professor Geiss has simulations. been heavily involved in scientific of NASA and the Euro- pean Space Agency, ESA.