Martian Spiders, a paradox

By Greg M. Orme and Peter K. Ness

In consultation with

Sir Arthur C. Clarke




Following our paper in the Journal of the British Interplanetary Society[1] the following summer on Mars brought us more spider images[2]. This now means we can see nearly two full summer seasons of the spiders. We can only see them in summer because the sun doesn’t rise on the Martian South Pole during its winter.


This now enables us to test many of the observations put forward in the first paper. In order to do this we have assembled the total amount of spider photos in one table[3]  placed in order of Solar Longitude[4], which basically gives us a sequence of images in seasonal order. At the beginning of the table the images are early spring and at the end late autumn.


The table also shows us that some spider areas are highly imaged and so we can separate these areas into clusters, so that these areas can be more closely examined. Two main clusters[5] are examined. Also these are shown in the context of wide angle THEMIS[6] images and MOLA[7] maps. We also present information on seasonal temperatures, to show how temperature compares to spider positions. One problem is that we probably cannot tell what the spiders are at this stage, but we can see some things they are not. There are so many photos that common properties can be inferred and how these might compare to known geological formations and physical laws.




The story of the spiders so far has been an interesting one. The name “spiders” was coined by Malin Space Science Systems[8]. One of the first and most interesting spider photos was M0804688 which was found by Greg Orme in October 2000. Subsequent to this Sir Arthur C. Clarke[9] the well known author saw this image and decided it may represent good evidence of a form of life on Mars. Since then he has done many interviews and lectures on the subject, including Popular Science[10],,[11] the Smithsonian Institute[12], and the London Times.


The spiders and Sir Arthur himself have come in for their share of skepticism because of this. As it stands now the spider formations remain an enigma barely even mentioned in published papers on Mars.


This has lead to a highly unusual situation. Sir Arthur is very highly respected in the scientific community, for example as shown by the fact that a probe to Mars was named after one of his books[13]. Also Sir Arthur had written on the subject of plants on Mars in earlier times[14] and is widely respected as a visionary in science. Percival Lowell believed in his day that the South Pole of Mars might contain life from his observations.[15]


Most people’s reaction to images of the spiders is discomfort and confusion. They when viewed together[16] give an almost overpowering impression of some form of fungus, trees or coral. In fact it would be almost impossible to find someone who did not get this impression. On the other hand it is widely believed such life on Mars is all but impossible, and that even microbial life is barely conceivable.[17]


The situation then is we are confronted with something that looks like life but according to what we know about Mars almost certainly cannot be.


In our first paper on the subject we tried to explore the subject as thoroughly as possibly while sitting firmly on the fence as to what they are. We provided image numbers of all the spider photos known to us, explained some plausible geological models and even explored some basic biological ideas. Now this paper is beginning to be referenced we believe it is necessary to update those impressions, as some of the concepts in there have changed markedly since then.


This paper is in two sections. In the first we describe some of the problems that have arisen in the geological models on the spiders. Many of these were touched on in the first paper and some have been discovered since. The second part relies on a sequence of images combined from the two Martian years recorded by the MOC[18] to run from early spring to late autumn. Additional images show another area on the South Pole (called “Swiss Cheese” formations) that may have been a spider area. Also there are images of fluid flows, dunes, ejecta, layers, and ridges on Mars to compare to spiders, and some images of older possible spider formations at lower latitudes.




Figure 1 shows a main area of spider activity, Chasma Australe.[19] [20][21]Figures 2[22] and 3[23] show similar Chasma also apparently associated with spiders. Figure 4[24] shows a MOLA map of the area, Chasma Australe is at 270 degrees West. The Main spider areas seem concentrated on the right side of the pole, particularly around Chasma Australe.[25] [26] Figure 5 shows possible spider formations in Chasma Australe from THEMIS.[27] The main problems with geological models are shown below.


Fibonacci patterns


These were mentioned in our JBIS paper. The basis of this claim is that spiders seem to follow a well known mathematical formula called the Fibonacci sequence[28].  This is formed by adding numbers together to make a third number, e.g. 1+2=3, 2+3=5, 3+5=8,… This sequence is extremely well studied in mathematics and even has its own Journal[29]. One of the great unsolved problems in mathematics refers to this sequence, whether it contains an infinite number of primes.


This sequence has also been extensively studied in relation to the world around us, for example the planetary and satellite orbits of the solar system conform closely to the Fibonacci sequence[30] but so far this pattern is not known to be found in non living formations except by chance.


The reason is in the nature of how the pattern is formed, in adding each two preceding numbers to form the next, which is not something that can easily happen in non biological systems. If the spiders were being formed by a nonliving Fibonacci process it would be a new development in the study of Fibonacci numbers.


One counter argument heard on this is that rivers and deltas have patterns that approximate this shape[31] [32]. While they can approximate this sequence the argument revolves around whether the patterns on Mars are exactly this sequence often enough or they only approximate this occasionally and merely appear to be Fibonacci related. However even so the idea of fluids forming these shapes on Mars also runs into problems.


Fibonacci patterns are well known to us, virtually all plant life uses this as a template for its shape of branches, flowers and roots[33] [34]. Animals also use this template for blood vessels[35], nerves, and even the proportions of our limbs. On Earth it is almost a definition of life itself.


The problem is further increased by the positions of the spiders, concentrated in a relatively small area on the South Pole. Most of the other geological formations there are also seen in other areas of Mars. So if we believe there is some unknown inorganic process occurring uniquely to Mars then it should also be occurring at other parts of the planet, or at least at other parts of the South Pole and the North Pole. So far not a single spider has been seen on the North Pole where conditions are comparable, but somewhat colder in summer[36].


For example if the spiders are formed from a fluid flow then other fluid flows and remains of such should also look like spiders in some way, but they don’t. In fact, as will be shown later, ancient rivers on Mars look much like they do on Earth, as do craters, volcanoes, faults, troughs, etc[37]. This then means that not only would this unknown process have to occur on Mars and not ever on Earth, but it can only occur in parts of Mars. There only can these particularly geological and chemical processes form like this, and elsewhere on Mars act much as we would expect.


Against gravity


Another problem which will be seen later is that the spider branches and formation are not positioned as we would expect to find if something was influenced by gravity. Any kind of fluid naturally tends to follow a path to lower ground, which of course is why rivers don’t flow up hill. For example M0806802 is orientated so the channels seem to flow uphill which we would know to be impossible on Earth. On Mars this image has the channels flowing downhill. M0904327[38] also flows downhill only and doesn’t form branches like the spiders. M1102981 shows rock formations that can form from mass wasting but don’t point uphill like spiders.


Spiders however look as if fluids should be flowing uphill all the time[39], which is impossible. On Mars we also see perhaps millions of examples of former fluid flows[40] [41] [42] [43] [44], and all that we know of seem to follow this rule. Indeed from what we know of physics we would be confident that any fluid would always flow down hill with gravity. While there is still some debate whether these fluids that formed these channels are water or CO2 based[45] no one has ever asserted they should not follow gravity.


The models assert CO2 formed many of the crater channels that look like they may be formed from water are actually from CO2[46].  Here Hoffman[47] shows a model that Co2 may be actively forming crater gullies on the South Pole with CO2. The problem is if CO2 can mimic water so closely then the argument that spiders are formed by some unusual properties of CO2 seems less likely. If CO2 can flow in such a water like way it can’t also form unusual shapes like spiders, which are in comparable temperature areas on the Pole.


Many of these effects are thought to occur by avalanches of CO2[48] [49] [50]


The spiders on the other hand have branches that seem all but oblivious to the law of gravity. One could literally give thousands of examples from these images where branches point up hill in a delta shaped formation, and then have branches that also point down hill in the same shape. Studies on ancient deltas and rivers on Mars[51] [52] [53] [54]show no similarity to spiders or spider ravines[55].A fluid flow encountering a hill for example would at least tend to go around it, but branches almost invariable just go straight over them. A fluid would tend to flow into depressions but spiders either avoid them or skirt the rim of them in ways seemingly impossible for fluids to act.


Russell Crater is a good example of what is generally believed to be a current water flow on Mars[56] [57]. Note the channels flow straight downhill as they would on Earth[58] [59] [60] [61] [62] [63] [64] [65] [66], nothing like spider branches.


The only alternative to a fluid is a solid such as soil or sand forming dunes[67] [68] [69]  [70]. These also however are common at lower latitudes and don’t exhibit any tendency to form against gravity[71]. For example many dunes are found in gullies and craters but none seem to climb the walls or form anywhere but at the bottom. Known Martian[72] and Earth dunes also don’t look like spiders.[73] [74] [75] [76]


Some spider types also seem to follow the tops of ridges in a line, which is the opposite of what gravity should dictate.


Surface shape


Any kind of fluid flow should have a relatively flat surface whether subsequently frozen or not. The exception to this is surface tension but we are talking here about branches that are meters wide not millimeters. When we see the surface of a river on Earth, whether liquid or frozen the surface is almost invariably very flat. This again is simply a consequence of the law of gravity. So any fluids forming spider branches on Mars should have a flat upper surface, but we find the surface of spider branches can clearly be seen from the shadows as convex[77]. Also any fluid would naturally tend to pool unless there were existing channels holding the fluids but branches often clearly form on flat featureless ground with no visible terrain to stop them from simply forming a puddle. This is also the problem with models based on geysers and outflows. On Earth such formations don’t form any branches, just pools of mud, etc.[78] We don’t have any Earth examples of outflows of any material that would form any kind of branches like these.


Dense spider areas have a certain texture, but markedly different from other areas of Mars[79] [80].


Some spiders seem to leave behind ravines but others do not. If there was a tendency for a fluid or sand to accumulate in ravines to form spider shapes then one case seems to follow the law of gravity but the other ignores it. That is, ravines and spiders tend to imply that fluids or sand is accumulating in the ravines and somehow disappearing and then reappearing. The problem then is identical looking spiders are then seen leaving no trace of ravines so the ravine formation model must also account for spiders also forming as if the ravines are irrelevant.  So in one model the ravine is essential to the formation of spiders conforming to known physical laws and then in other images the spider just does the same thing ignoring all those same physical laws. Therefore ravines actually make it less likely for the spiders to be a fluid flow as they behave the same whether the ravine is there or not. This implies the spiders form the ravines but don’t need the ravines to form.


Known materials


Whatever the spiders are made of it stands to reason these are materials found elsewhere on the South Pole. For example if the spiders are made of CO2 or water ice then other known ice nearby should also be in similar unusual formations. However elsewhere on the pole all the ice we see seems to act as we would normally see on Earth. If the spiders were an unusual form of dune then known dune formations on Earth and Mars should exhibit occasional spider like characteristics but none of them do. As we shall see later the spiders tend to form in early spring and fade away in autumn, and so we should see dune formations in more amorphous patterns tend to follow this sequence. However we see the opposite of this. The spiders are forming as the CO2 is usually already gone and the ground becomes frost free, and the spiders are shrinking when ice and frost are returning to the ground. So if they are made of any kind of ice then it needs to be explained why they are affected by temperature in the opposite way to known ice.


Also the time of highest wind on the South Pole is in early spring when the CO2 sublimates and late autumn when the CO2 freezes. This is because in the spring for example the sublimating CO2 increases the air pressure compared to outside the pole creating a wind leading off the pole. This can be clearly seen in images where streaks form from the wind. In between these times the amount of streaking is minimal. So if the spiders are forms of dunes they must be forming when the wind is lowest which is impossible. Also if they were dunes they should be forming in the spring when the wind is stronger but they seem to form after the wind is gone. Not only then do they not obey the law of gravity but they also don’t obey the laws of friction and momentum either.




When the two Martian seasons are combined and the photos assembled in order of Solar Longitude there seems to be a clear progression in the nature of spider formation through the summer. While there are some models which could conceivably allow for formations to grow as the weather became warmer, they of course cannot overcome the conditions already described, as they cannot form Fibonacci patterns, cannot move against gravity, cannot act completely differently to the same materials nearby[81], and cannot form convex shapes.


Even if they could and somehow could grow[82] with the warmer weather they would also have to shrink[83] and often disappear as the weather grew cold and frost returned to the area. Any kind of rock or soil cannot just disappear, and any kind of fluid as it grew colder should have either sublimed months ago, and cannot just sublime now with the cold. In fact the cold should freeze them in place just as it forms frost on the ground. So spiders break another natural law, that increasing a temperature can cause evaporation, here lowering temperature causes evaporation.

Kieffer[84] believes the spiders are formed under a layer of clear CO2 ice. One problem with this is the spiders are often seen on slopes, and the branch pattern remains in all directions. If there was a pressure from below forming cracks this material would tend to form downhill so we should see a non radial pattern on slopes. Also the theory is based on dust settling in CO2 ice which makes it clearer in the top area. The problem here is the spiders as shown form when the temperatures are far above the sublimation point for CO2 so the CO2 should be long gone. We can also see this because the frost on the ground disappears as the spiders are forming. Looking at E1201762 for example, the ground is very undulating making it unlikely there is a clear layer of CO2 ice on top of it. Also this is autumn when any CO2 ice would have sublimated. 


Also spider branches are usually pale and not dark so any model that uses dark soil to form them remains at the wrong albedo.


The spiders only disappear when the temperatures start falling, which is when the CO2 is likely to be returning not disappearing.


The temperatures in the spider areas come close to zero Celsius in summer[85] [86] [87] [88] [89] [90] [91] [92] [93], and perhaps above zero. The South Pole has a warmer summer than the North because of eccentric Martian orbit[94].


Also because the sun doesn’t set in summer for many months the temperature is relatively even. During this time most signs of frost and ice disappear from the ground and return in many images in autumn. So the spiders cannot be made of CO2 or H2O ice as this sublimates away while the spiders are growing.


One argument that the spiders cannot be a life form is that it is too cold. However the temperatures are at least close to zero in summer and with dark materials absorbing heat, they could well be high enough for at least brines to be liquid for considerable lengths of time. The spiders might also be related to an ancient extinct life form, and the ravines are imprints of a warmer climate.




Spiders typically form as discrete types with their own characteristics[95] and in common kinds of terrain. If there were some material that could do all of this it would also have to appear looking very different in each of these cases, and act in ways particular to that terrain. It is hard to imagine though how a material would know where it was, and not to manifest randomly in different ways. This implies some rigid kind of structural identity, but each quite different from the other. We know of nothing on Earth that could meet this requirement so we are then faced with needing not one kind of cryptic process but perhaps as many as ten, all without any known mode of formation, and all breaking apparent known physical laws. Crystals and minerals typically only have a few kinds of appearances and cannot form wildly different appearances with only slight changes in conditions.


It is hard to estimate the number of spiders in these areas. The MOC has imaged only a small portion of the total and the number of spiders is enormous. It seems reasonable to conclude there are millions of these structures, which must indicate their mode of formation is robust. So many formations can hardly be the result of chance.




Spiders are often a different albedo to the ground, usually paler. They begin to form in times when the wind is clearly blowing dark soil around yet they maintain this lighter albedo as they grow, one that is different from known ice and frost. We know this because spiders can often be seen next to ice and frost forming or sublimating, and the ice has a different albedo. In an environment where a geological process was forming they should become dirty over perhaps thousands of years of dust storms and appear a similar albedo to the ground but they don’t. Some appear in the spring near dark streaks clearly being blown by the wind, and even being blown over the spiders, but they retain their different albedo. M0906428  E0901155 M1000071  show pale spiders surrounded by dark soil. The question then is where their different albedo comes from. The materials around them cannot be used in their current form because they have a different albedo already, and if there is an outflow from below we should be able to see ice, puddles, etc with the same albedo as the spiders but we don’t. So not only does a liquid need to form spider shapes but it needs to always form them and never act like a normal liquid. This implies some form of chemical reaction to change the albedo to that of the spiders, but then this should be forming elsewhere as well. If there were geysers for example there should be at least some that were a known shape we see on Earth with a pool of material but there are none.


Other spiders have the same albedo as the ground, but this is later in the season as they fall apart foe exampleM1003666  M1100222  M1100396 M1101739 M1102393M1104046 . The materials that make up spiders though should not be able to change albedo just because of the change in temperature. Normally a decrease in temperature slows chemical reactions not speeds them up. They start out pale and resist getting covered in dust from wind. Then only as they dwindle do they return to the soil albedo. Plants might be expected to return to the soil and indeed become the soil but a inorganic chemical reaction implies that they are made out of the surrounding soil to return to that albedo. So if an outflow occurs it should have a different albedo to form the spiders but then it has to lose that difference as it loses its structure and as the temperature drops.


So if there is a chemical reaction that makes the spiders a different albedo that is formed from the soil that reaction has to reverse itself because the temperature is dropping, but no known reactions in a situation like this are known. For example we should see areas that turn paler in the spring as the frost disappears, like in pools or sheets and that disappear in the autumn. We only see the spider shapes doing this however.  




Spiders are typically found in certain positions but not in others, with no clear reason why. For example many areas have features known as polar spots[96] [97] [98] [99] [100], and spiders are often found close to these. They have never been seen so far intermixed with them. This implies that either the spots and spiders form in the same process but manifest differently for some reason, or that they are different processes. Occasionally branches are seen growing out of spots.




Spiders when they first start forming seem to put out their first branches at right angles to the sun, and then afterwards form a more radial pattern. Any process would somehow have to recognize where the sun was coming from and yet later disregard this. This orientation seems to occur regardless of the slope of the ground, which is also movement against gravity. If this was controlled by some kinds of faults or cracks then they should be randomly aligned. A pressure from below causing a crack doesn’t know where the sun is, and tends to form a radial cracking pattern but not Fibonacci.


Bush material


Many spiders develop a bush like covering over the branches as the summer progresses, to the point of covering up the branches completely. Then they seem to lose this and the branches reappear. If this material was solid then it shouldn’t be able to go anywhere, which implies it is a 3D structure but with a lot of empty space. Such a material structure implies that something has to occupy these spaces and subsequently sublimate or leave somehow, or else the structure has to grow while leaving all these spaces. There seems to be no Earthly analogue for this. Many may totally dissipate and leave Swiss Cheese like shapes, a hollow with a ridge around the edges.


Also this bush material often covers large areas but also in parts forms clumps, though the ground in between looks the same. Gravity should dictate this material shouldn’t clump on flat ground.



Old fluid flows on Mars usually have signs of debris at the ends of the channels, perhaps from erosion. The spider branches have none of this. For example M0306110  M0302290  M1302043 have debris at the end of the channels, eroded by the fluid flow. Spiders though do not[101]. Also spiders seem to be able to disappear in autumn without leaving much if any debris at all. It seems impossible for a rock formation to just disappear because the weather became colder. Water ice might if the heat was increasing but not when it is going to well under zero Celsius.


Branch directions


Branches seem to avoid each other even when very close together[102]. Dunes would tend to join up and rivers should follow into a depression. Less than 1% of branches cross each other, and when they do they often don’t merge but go right over each other.




Active spiders are found in a very precise latitude of only a few degrees variation, though over nearly half of the pole. The sun however should be warming much more than this as it moves up and down in a circle in the sky in summer. If spiders are formed by pressures of CO2 gas underground it shouldn’t be so temperature sensitive there that only those positions are active. Inactive spiders are seen over a wider area, implying spiders may have been more common in the past.


Swiss Cheese


These formations[103] [104] [105]are very similar to bush areas[106] that are changing seasonally. It seems likely then that they represent either areas of spiders that are no longer active or that spiders are growing on Swiss cheese areas. They don’t look like anything we are aware of on Earth that would form in colder climates. They only seem to occur in selected areas and are intimately associated with spiders. So we have two kinds of mysterious formations, one that is active and seasonally changing and the other that is inactive but highly related.


This seems to imply spiders can become defunct in some areas and leave very specific relics of their activity. It might also imply these formations are also founding spider areas, and somehow the spiders alter them. Indeed on the opposite side of the pole there are many areas with spider ravines that show no sign of change, so this is a third mysterious formation.


There are 3 mysterious formations on the pole then, one active and two apparently defunct and all surrounded by formations that seem quite normal.


Possibly spiders have covered much more of the South Pole in the past at times of high obliquity and the Swiss Cheese and inactive ravines are relics of that time.




Many of the areas of polar spots bear a remarkable similarity to wetlands[107] [108] [109]. While there is no amount of water like that now perhaps they were much wetter when the axial tilt or obliquity was periodically much higher[110] [111].

Also the ground is perhaps half[112] [113]composed of ice so all that is needed is an additional temperature rise which obliquity could provide[114] [115]  [116] [117] [118] [119] [120] [121] [122] [123]. Also some brines may become liquid at lower temperatures than pure water,[124] [125] and water may take long periods to refreeze or sublimate[126] [127] [128]. A wetlands shape[129] would not necessarily imply life forms however.

Much of the spider terrain is familiar looking as Earth wetlands in appearance. Whether they were or not it further isolates the actual spiders, the Swiss cheese and ravines areas as formations not explainable by any known geological models.


Viking spiders


      Oddly enough Viking 2[130] landed[131] nearly in the middle of a sub polar 
area that seem truly spider like[132]. Interestingly some troughs perhaps related 
to spider ravines were found near Viking 2[133]. While other explanations were 
also suggested the presence of the spiders nearby and their association with 
sometimes polygonal ravines makes these troughs possibly from spiders. These 
“enigmatic troughs”[134] can be traced in a sequence of photos[135]. If they 
are spider ravines it might indicate when the spiders seasonally dissipate they 
might at times leave ravines too shallow to see. There are also pits[136] in 
the area of unknown origin. Figures 195[137],199[138], and 200[139] may also 
be troughs. Figures 290, 210 and 211[140] show paler areas devoid of rocks, 
which may also be related to spiders. Of course there are many other explanations 
but the proximity to the spiders makes these interesting. Spider branches in 
E0200503 are 1-3 pixels wide with a pixel width[141] here of 9.46 meters[142]. 
Since spiders typically have a paler albedo and a comparable branch width to 
these pale patches it is possible these may be spider remnants. Here[143] they 
also look like dunes. A mosaic[144] also has a good view of these troughs. If 
so they probably represent the only images that might contain them.





The spider features seems all but impossible to explain. They have no counterpart on Earth for them to compare them to, we know of no processes that could cause them. They are somewhat consistent with a life form, but Mars has an environment that seems impossible for any more than a few known microbes and perhaps tardigrades[145] to survive in. Certainly we cannot imagine any kind of large scale life we know of could live there. Overall the possibility they are a life form is negligible but not zero. For example they might be the imprints of an earlier life form when the pole was much warmer.


These features need to be closely studied to see if there are any unknown processes that could be causing them to occur. The spiders represent a genuine enigma, not only in their appearance but in their behavior.


There seems little point in speculating on what kind of life form they might be, have no real information about the spiders except images. They do seem to deserve much more attention in future Mars missions however. If they did turn out to be life forms that would be a great discovery. If they didn’t then a lot of exciting science is waiting to be found there. Either way they merit much closer examination.

[1] “Spider Ravine Models and Plant Like Features on Mars- Possible Geophysical and Biogeophysical Modes of Origins” Journal of the British Interplanetary Society,

8 February 2002. Vol 55 No 3/4, March-April Edition, Pp 85-108.





Figure number refers to our JPIS paper, Comparisons are reimaged photos also at:

Groups are clusters of images close to each other. Groups 1 and 8 are shown here in detail.



[5] Marked in one column as Groups 1 and 8.





[8] “these have been termed black spiders by the MOC team”


[9] “Arthur C. Clarke is one of the most celebrated science fiction authors of our time. He is the author of more than sixty books with more than 50 million copies in print, winner of all the field's highest honors. He was named Grand Master by the Science Fiction Writers of America in 1986. His numerous awards include the 1962 Kalinga prize for science writing, which is administred by UNESCO; the 1969 AAAS-Westinghouse science-writing prize; the Bradford Washbur Award; and the Hugo (2 times), Nebula and John W. Campbell Awards. His bestsellers include Childhood's End; 2001:A Space Odyssey; 2010: Odyssey Two; 2061: Odyssey Three and most recently, 3001: The Final Odyssey, Rama II, The Garden of Rama and Rama Revealed (with Gentry Lee).”



[10] "I'm now convinced that Mars is inhabited by a race of demented landscape gardeners," Sir Arthur C. Clarke announced recently.

The author of 2001: A Space Odyssey was only half-joking. He claims that an image produced by the Mars Global Surveyor satellite shows "large areas of vegetation . . . like banyan trees."


[11] "I'm quite serious when I say have a really good look at these new Mars images," Clarke said. "Something is actually moving and changing with the seasons that suggests, at least, vegetation,"


[12] "I am flying over Mars, thanks to the Mars orbital surveyor," Sir Arthur said at the onset. "I'm now convinced that Mars is inhabited by demented landscape gardeners."
Touting that there is organic vegetation on Mars, Sir Arthur urged that "We should continue the search" for intelligent life elsewhere in the universe, by hunting for artifacts.”,%20June%202001.htm


[13]“ The name "2001 Mars Odyssey" was selected as a tribute to the vision and spirit of space exploration as embodied in the works of renowned science fiction author Arthur C. Clarke.”


[14]“For a science fiction book written in the late 1940s, this is an amazingly undated piece of work. Oh, sure, there are a few anachronisms ~ vacuum tubes and the possibility of vegetation on Mars are the most obvious to my non-scientific mind ~ and we are not as close to having a colony there at the end of the Twentieth Century as Clarke expected, but almost nothing else is out of place.”



“”On May 1, then, Martian time, the cap was already in rapid process of melting; and the speed with which it proceeded to dwindle showed that hundreds of square miles of it were disappearing daily. As it melted, a dark band appeared surrounding it on all sides. Except, as I have since learned, at Arequipa, this band has never, I believe, been distinctively noted or commented on before, which is singular, considering how conspicuous it was at Flagstaff. It is specially remarkable that it should never have been remarked upon elsewhere, in that a similar one girdling the north polar cap was seen by Beer and Madler as far back as 1830. For it is, as we shall shortly see, a most significant phenomenon. In the first place, it was the darkest marking upon the disk, and was of a blue color. It was of different widths at different longitudes, and was especially pronounced in tint where it was widest, notably in two spots where it expanded into great bays, one in longitude 270 degrees and one in longitude 330 degrees. The former of these was very striking for its color, a deep blue, like some other-world grotto of Capri. The band was bounded on the north, that is, on the side toward the equator, by the bluish-green areas of the disk. It was contrasted with those both in tone and tint. It was both darker and more blue.


[16] e.g. at


[17] People may be interested in reading these papers on the possibilities of life on Mars:








[21] This area is also roughly known as the cryptic region:

“One of the most dominant albedo features on the seasonal cap is a region that appears almost as dark as bare ground, but yet remains cold. (See Figure 1.) We refer to this region, generally located between latitudes 85°S and 75°S and longitudes 150°W and 310°W, as the Cryptic region.”








[25] Here are some papers on Chasma Australe:


Chasma Australe is the most remarkable of the Martian south pole erosional

reentrants carved in the Polar Layered Deposits. This Chasma originates near the south pole and runs across the polar troughs over a distance of c. 500 km. Its width varies between 20 and 80 km and, with a depth up to 1,000 m, it reaches the bedrock.”


[26] Cavi Augusti also has some spider signs:




[28] For example: E1201762  E0800043 M0900157 M0900528 E0801158  M0806244  M0901352 M0901567 M0903082  E1003496 M1102393





[30]“ That the attested, ubiquitous, and long-revered constant Phi = 1.61803398875... - The Golden Mean provides the underlying foundations for these exponential planetary functions should surprise no one. The value is known to occur in many diverse contexts that range from the structure of quasi-crystals, 3 Penrose Tiles,4 the closely related Phi and Fibonacci series, growth functions and even the structure of spiral galaxies.”


[31] For example:



[32] For example

M0302290 M0802316 M0806802 M0804758 M0902382 M1000886



[33] For example:


[34] This was also covered in our first spider paper: note Figures 10 a,b,c, and d.



“”The branching (bifurcating) structure of roots, shoots, veins on leaves of plants, etc., have similarity in form to branched lightning strokes, tributaries of rivers, physiological networks of blood vessels, nerves and ducts in lungs, heart, liver, kidney, brain etc. Such seemingly complex network structure is associated with exquisitely ordered beautiful patterns exhibited in flowers and arrangement of leaves in the plant kingdom.


[36] “Near the tail end of the dusty season, the atmosphere has cooled off again, but now, the warmest place on the planet is over the south pole! That is because it is sunny all day long there at this time of year.”

“though temperatures are somewhat colder due to a 20% increase in the distance from Mars to the Sun.”

“However, the eccentricity of Mars' orbit causes the solar input to be significantly different when one pole is in sunlight than when the other pole is in sunlight.”




[38] Also see M1900054


[39] For example: M1103950 M1200159 M1200397 M1200456 E0800043 E1004220 E1102247 E1200329 














[43] “Images from the visible light camera on NASA's Mars Odyssey spacecraft, combined with images from NASA's Mars Global Surveyor, suggest melting snow is the likely cause of the numerous eroded gullies first documented on Mars in 2000 by Global Surveyor.”








[47] “Many examples of the Malin and Edgett gullies are to be found here - the southernmost location noted to date. Malin and Edgett included an example from this area in their summary of gully morphologies and occurrences.

Unlike examples in more temperate zones, the gullies are not so restricted to poleward-facing slopes. Here, gullies occur frequently on east- and west-facing as well as on south-facing slopes. This alone suggests that mechanisms for gully formation are more active here then elsewhere on Mars.

… It has some unusual gully forms that were first drawn to my attention by Greg Orme, an amateur observer of the planet. ”





“Hoffman [7] posited that Martian gullies result from

release of liquid CO2 , but it is very unclear that such

release would produce tidy gullies instead of explosive



[50] “Over thousands of springtime thaws, the kilometre-long channels we see today can be carved by repeated small flows of this nature.”

















“Narrow gullies interpreted as the result of liquid flows

on frozen dunes are observed on 6 MOC images in the

latitudes of 40 to 60°S. Among these dunes, a large

scale sand dunes reaching an elevation of 600 m above

surrounding plains covers the floor of Russel crater

(Fig. 1).”








“The study of Earth-like planetary surfaces — geomorphology — is not a disjointed collection of observational facts solely with which to test, or against which to constrain, theoretical models. Rather, such scientific inquiry proceeds from the informed colligation of landform observations to the discovery of consistency and coherence, and, ultimately, to consilience5 in the theoretical accounting (explanation) of those observations. The key element of this inquiry is the formulation of one or more working hypotheses6, which are most often suggested (but not proved) by analogies of form and context among landscapes of known origin and those under scrutiny7. In the retroductive inferences of geomorphology8, 9, analogy serves merely to suggest fruitful working hypotheses, thereby leading to completely new theories that bind together any newly discovered facts. Mars' landscape provides particularly stimulating opportunities to practise geomorphological reasoning, generating hypotheses that may initially strike some researchers as outrageous10. Nevertheless, it is the productive pursuit of such hypotheses that leads ultimately to new understanding, not only of Mars, but also of Earth itself.”
























“Characteristics of buried surfaces: A study of Earth

analogs will facilitate a clearer understanding of the

evolution of surface landforms and provide a subset of

geomorphic signatures that has the potential to deter-mine

the characteristics of buried surfaces (e.g., the

original extent of the deposit).”



“Wind is currently the dominant geological agent acting on the surface of Mars. A study of Martian aeolian activity leads to an understanding of the forces that have sculpted the planet’s face over the past billion years or more and to the potential discovery of climate shifts recorded in surface wind features that reflect ancient wind patterns.”






[70] This refers to wind speeds on the South Pole:




[72] For example: M0802949 M1000911 M1200409 M1700797 M1701178 M20001670










[77] For example: E1003496 




[79] Here lobate debris aprons are very different from spiders.



“Introduction: High resolution Viking images (or-bit

724A, 14m/pixel) show evidence for ancient glaci-ation

in parts of southeastern Elysium Planitia. While

previous authors have mapped the materials as thin

lacustrine and fluvial deposits [1], we present evidence

for erosional and depositional processes associated

with glacial environments. The previous ice sheet

formed hummocky goundmoraines, eskers, and possi-bly



[81] For example these are a different albedo to the frost still on the ground: M1002495 



[82] For example: E0700758 E0800043 M0900157 E0801158 M0900528 


[83] For example: M1104046 M1200543 E1200911 




[85] See Figure 2:


[86] This shows the shrinking of the polar cap at the same time as the spiders are increasing, Figure 2:


[87] “The seasons in Mars's southern hemisphere include short, very hot summers, and longer, cold winters. The Martian orbit is less circular and more elliptical than Earth's, which means for part of the year the planet is a lot closer to the sun. The southern hemisphere, tilted towards the sun when Mars is closest, has a hotter summer than the other hemisphere. The northern hemisphere is tilted towards the sun when Mars is farther away, and so its summers are not as hot.”


[88] Here the spider areas (mainly on the right side of the inner circle) show a temperature of yellow to orange at Ls 253 degrees, which is -30 to -15 degrees Celsius.!Uo!NC).gif


[89] Here at Ls 251 degrees the temperatures show -40 degrees Celsius. Bolometric readings according to Titus can underestimate the temperature by around 20 degrees Celsius if the ground is frost free.


[90] Here the temperatures in green get to near zero from 250 to 300 degrees Ls, which is when the spiders are growing.


[91] Here the shrinking of the polar cap is shown to favor the spider areas, which are on the right:


[92] Here Figure 4 shows the temperatures at Ls 309 degrees. The spider areas are very patchy with some areas still very cold but other areas much warmer. The yellow and orange spots in the bottom right part of the inner circle correspond roughly to spider clusters:


[93] “Dark spots appeared as the surface began defrosting in August. Winds occasionally moved the darker material across the surface, leading to dark streaks, NASA said. But all the frost and streaks disappeared by February.”


[94]The large eccentricity of Mars' orbit also affects the seasons. The current configuration means aphelion occurs during northern-hemisphere summer; as a result, northern summer is up to 30 degrees colder than southern summer, and the amplitude of the seasonal cycle is 110 K in southern midlatitudes but only 55 K in the north.”


[95] The different types are outlined in our fist spider paper:



“Introduction:The recent finding of abundant,appar-

ently young,Martian gullies with morphologies indicative of

groundwater seepage and surface runoff processes (1)was

surprising in that volumes of near-surface liquid water of

sufficient quantity to modify the surface geology were not

thought possible under current conditions (2,3).This discov-

ery has therefore called into question our current understand-

ing of the stability,transport processes,and geologic role of

water on Mars.Reported here are observations of dark spots

in the seasonal frost cap confined to Martian gully channels

that indicate a surface with distinct thermophysical proper-




“But one hint that continues to fuel visual detective work centers on the waxing and waning of dark 'colony-like' blotches recorded by the Mars Orbital Camera. The heated discussion has become known as "the dark dunes" debate. The ESA meeting agreed that the seasonal variation in dark and light spots seen on Mars are certainly fascinating. They concluded that the dark dunes might well be worth a detailed look by Mars Express, the European Space Agency's Mars mission, when it goes into orbit around the Red Planet in late 2003.”



“In craters of the Southern polar region (-50° to -82°) of Mars

dark dunes (DD) are apparent, which are covered by white

snow/ice during the Martian winter, and on which character-

istic, growing splotches, called dark dune spots (DDSs)

appear at the end of the winter. Malin et al. explain the ap-

pearance and temporal development of these spots by de-

frosting processes. Based on the images of the Mars Global

Surveyor (MGS), we show here that solely sublimation proc-

esses cannot explain the shape, development and characteris-

tic features of these spots; other processes must also be in-

voked. We list the supporting evidence and the associated




“Synopsis: Changes in the appearance of a de-frosting

dune field in the martian southern hemisphere

are tracked from late winter into early summer.

Changes become noticeable shortly after the dune

field emerges into sunlight as winter transitions to

spring. These changes, in the form of small dark

spots formed on and along the base of the dunes, oc-cur

while surface temperatures are still around the

freezing point of CO2 (~148 K). Most of the changes

occur over the course of spring, while temperatures

are transitioning from those of frozen CO2 toward the

H2 O freezing point (~273 K). Late spring and early

summer views acquired ~2 a.m. local time exhibit

higher albedos than ~2 p.m. views obtained during

the same period, suggesting that frost forms on these

surfaces as the sun dips toward the horizon during

early morning hours in these seasons.”



“(4) Small dark features that appear in

spring on the seasonal frost outside the resid-ual

cap. Some of the features have parallel

tails that are clearly shaped by the wind. Oth-ers

are more symmetric, like dark snowflakes,

with multiple branching arms. After the CO2

frost has disappeared the arms are seen as

troughs and the centers as topographic lows.”


[101] None of these for example have debris at the ends of the channels:



[102] For example: E1201762


[103] For example:



“In general, as discussed above, they have circular or

near circular shapes, flat floors and steep walls. They

appear only on the residual cap itself (as mapped by

Viking [2]). They show no noticeable changes as the

southern summer season progresses. Each depression

appears to have an interior moat of constant width.

The moat width is independent of the lateral size of

the depression. Inside the moat, at the center of the

depressions, are elevated areas approximately 2 meters

above moat level, which are possibly lag deposits remaining

after sublimation of the interior [1]. One of

the most intriguing observed properties is the exis-tence

of four or more layers within the medium in

which the depressions are incised [1]. Figure 2 (as

shown in the Thomas et al [1] article) shows a more

detailed view of the layering, each layer is roughly two

meters thick and so when slopes are this steep can

only be discerned in the highest resolution MOC images.”



“The current sizes and expansion rates

seem to preclude the initiation of these features

being associated with the anomalous

1969 water vapor observation. For features in

the region of 350° to 360°E, 86.5°S, our

modeling results indicate the year of initiation

to be in the range of 1600 to 1920, with

the most likely case being _1900. The spread

of ages reflects both the range of current sizes

and the range of expansion rates.”


[106] For example: M1000935  M1003277  M1100580 M1101351 M1101643 




[107] For example:



[108] For example M1001115 M0807198 E0900232 M1103505 M1103919 M1201448 


[109] For example M1001115






[111] “Figure 1. Phase diagram of the AI system which il-lustrates

conditions for multiple solutions. The hori-zontal

axis is the total amount of CO2 in the AI sys-tem,

and the vertical axis is the effective solar con-stant.”


[112]  “(Left) This diagram shows a possible

configuration of ice-rich and dry soil in

the upper meter (3 feet) of Mars. The ice-rich

soil was detected by the gamma-ray

spectrometer suite of instruments aboard

Mars Odyssey.”


[113] “The scientists then looked at TES data that overlapped the THEMIS images and found that in one area, called Unit I, the water ice warmed up slowly in the summer after the dry ice covering had sublimated away. (Under Martian conditions water ice does not melt, it goes directly from solid to a gaseous state, a process called sublimation.) The temperature remained under about -90 degrees Fahrenheit, the hottest Martian ice gets and about the temperature of the northern summer ice cap on Mars, which is composed of dirty water ice (ice mixed with dirt and dust).

"On the southern polar ice caps, the differences between daytime and nighttime temperatures were small, which also suggested to us that the "stuff" might be water ice," Titus said.

Titus and his colleagues also examined unit S, located adjacent to unit I. It showed a different trend in temperatures than unit I. In unit S, as temperatures warmed early in the Mars summer, the dry ice covering changed from solid ice to gas much earlier than in unit I, and in a matter of a few days or so. Suddenly, said Titus, daytime temperatures jumped and the nighttime temperature stayed the same, which told us that as the dry ice sublimated, probably what was left behind was a 2-7 mm layer of dust over ice.

"This suggests that the top layer changed from dirty water ice to dry dust," Titus said. "The cool nighttime temperatures are what one would expect from having a layer of water ice underneath the thin layer of dust."


[114] “The obliquity change could cause a climate jump in

the Martian climate system on short timescale. Figure

2 shows the annual mean atmospheric pressure as a

function of the obliquity. The present solar constant

and 2.0 bar of the total amount of CO2 in the system

are assumed for a nominal example. There are two

branches of the solution. One is a “cold” residual-cap

solution branch, and the other is a “warm” no-ice-cap

solution branch. It is noted that the residual-cap solu-tion

branch disappears in higher obliquity region. On

the other hand, the no-ice-cap solution branch does not

exist in lower obliquity region. Therefore, climate

jumps should occur at the ends of two branches. “



“The Etched Terrain (=Etched Material)

which occurs in the immediate vicinity of the

martian South Pole Cap is one of the most

enigmatic landscapes of the entire planet.

However, if one takes into consideration the

possibility that the South Pole Cap got

thawed at least one time [1], then the origin

of the Etched Material turns out to be a logic




“A large number of observations of the surface, at-mosphere,

geophysical properties, and solar-wind in-teractions

of Mars, along with analysis of martian me-teorites,

are relevant to understanding the history of

martian volatiles and climate. Our goal here is two-fold:

First, to examine the different observations and

to determine which ones provide the key constraints to

understanding the nature of the martian climate system.

Second, to examine all of the observational constraints

together and to see if there is a scenario of volatile

history with which they would be consistent; although

this scenario may not be unique, our goal is to see if at

least one exists. To this end, we have sorted the obser-vations

into (i) those relevant to the nature of the earli-est

atmosphere and climate, and the connections be-tween

the early climate and the geology and geophysics

of the planet, (ii) understanding the processes by which

the atmosphere can (and has) evolved and the timing of

the changes, (iii) the geological evidence for crustal

liquid water, (iv) and the nature of the present-day cli-mate.

Each of these topics is discussed below, and

includes a list of the relevant observations and their

implications; at the end, we summarize with a scenario

that is consistent with all of the observations and with

suggestions for new observations that would provide

key additional constraints.”



“Introduction: Several lines of evidence suggest that

Mars have experienced climate changes intermittently

in its history. Mars might have had a denser atmos-

phere and warmer climate in the Noachian period [1].

Cyclic and episodic climate changes might have oc-

curred in later epochs after the Noachian [2].”



“Introduction: Martian polar caps (PCs) consist of

residual ice deposits and layered terrains distinctive

from any other terrains on Mars. PCs are thought to be

made of water ice, solid CO2, CO2 clathrate hydrates

and dust in unknown proportions [e.g., 1]. Basal melt-ing

of these deposits could occur due to geothermal

heating [e.g., 2]. It was suggested [2] that several fea-tures

in the PCs, including Chasma Boreale and

Chasma Australe, were formed by the catastrophic dis-charge

of a large subglacial reservoir of basal meltwa-ter.

Recent studies [3-5] added new evidence for melt-water

discharge from PCs. In this study we consider

energy and timing constraints related to basal melting

of the PCs.”



“Introduction: The objective of this investigation is

to explore a new model of the coupled evolution of

climate and rotation, as applied to Mars. It has long

been appreciated that changes in the orbital and rota-tional

geometry of Mars will influence the seasonal

and latitudinal pattern of insolation [1-5], and this

will likely dominate climatic fluctuations on time

scales of 10 5 to 10 7 years [6-9].”



“Introduction: The origin of the layering charac-teristic

of the Polar Layered Deposits (PLD) of Mars is

generally not thought to arise from the flow of the

water ice presumed (along with dust) to comprise

these layers, since rheological modeling indicates that

Mars is presently too cold to permit substantial ice

flow in the polar regions.

However, Martian obliquity deviates chaotically

from its current Earth-like value of 25º, surpassing 45º

within the last several Myr. Not only will the polar

regions receive additional insolation at these high

obliquities, but the resulting increase in H2O sublima-tion

from the ice caps will initiate a water vapor

greenhouse heating effect. Hence, surface and subsur-face

temperatures will be elevated at high obliquity,

leading to dramatic increases in ice flow velocities.”



“Results: In general, the model results suggest that

seepage and runoff features can be explained by the

melting of near-surface ground ice during periods of

high obliquity in virtually all the locations and settings

that they have been observed. However, special cir-cumstances

are generally required to produce liquid

running water, and this provides an explanation of

sorts, for why these features are not more widespread

than they apparently are.

During Mars’ present orbital configuration, night-time

temperatures everywhere on the planet are always

well below 273K, which effectively prevents sub-surface

temperatures from reaching the melting point

for sustained periods. However, when Mars’ obliquity

approaches 45°, its eccentricity approaches 0.11, and

summer solstice in one of Mars’ hemispheres coincides

with perihelion, the model results show that middle and

high-latitude surface temperatures during summer can

in fact remain well above the melting temperature

throughout the day.”







“Long-term climate change: Like earth, the polar

regions are the most sensitive regions of the planet to

climate change. The polar layered deposits may record

climate and atmospheric variations related to orbital

changes, intense volcanic activity, impacts, and per-

haps other phenomena.”






“Introduction: Geochemical thermodynamic reaction

modeling allows one to predict the equilibrium com-

position of fluid and rock resulting from water-rock

interactions. Geochemical modeling has been used

here to predict fluid compositions resulting from

brine-basalt interactions as analogs for possible liquid

water-rock interactions near the surface of Mars.

Given the low temperatures and pressures at the sur-

face of Mars, pure water is not stable in its liquid

state. However, the addition of salts to liquid water

depresses the triple point, allowing liquid to be stable

at lower temperatures and pressures. Salts have been

reported to be important components in Mars surface

chemistry based on evidence from lander soil analyses

[1],[2],[3],[4],[5] as well as Mars meteorites [6].

Water-salt brines could form near the surface of Mars

through dissolution of soil duricrusts, input of vol-

canic salts from the atmosphere and/or through water-

rock interactions.”



“of water.At martian average temperature and

pressure,the existence of a body of water

competes with loss by evaporation,frost and

sublimation.Assuming a maximum water height

of 50-m (corresponding to the highest eroded

terrace in the platform),it would first take

between 5 to 10 years for this depth of water to

freeze solid in current martian conditions at the

relatively low latitude of Newton.This assumes a

freezing rate of 5-10 m per year (Carr 1996).

Sublimation rates are likely to be low because of

the low temperatures on the surface of the ice,and

because of the logarithmic dependence of the

vapor pressure of water on temperature (Carr

1996).Assuming an ice sublimation rate of 0.01-

0.1 cm yr -1 (Carr 1990),and no recharge,it would

take between 5 ·10 4 to 5 ·10 5 years for the frozen

lake to completely disappear.”



“Introduction: The phrase "liquid water is not sta-ble

on present-day Mars" introduces many publications

on water-related features. While technically correct, the

statement is misleading. On Earth or Mars, water is

ordinarily metastable, slowly evaporating or freezing.

An exception is found on Earth when the relative hu-midity

reaches 100%. On Mars, water will crust over

with ice when the atmospheric pressure falls below

approximately 6.1 mbar.

It has long been known that water could conceiva-bly

flow and ice could conceivably melt on Mars as a

transient event. Such an event need not be catastrophic,

as the re-freezing rates are on the scale of hours or


This talk reviews reasonable spatial and temporal

scales for such melting and flowing events, and relates

them to plausible Martian conditions. It is shown that

seasonal accumulation of snow and ice on cold peaks

could melt and flow in the summer sun, explaining

gullies recently observed by Malin & Edgett [1]. Fur-ther,

it can be concluded that summer wetting may fre-quently

occur where seasonal ice is present.”



“Mars has water as ice in the polar caps and as vapor in the atmosphere. The atmosphere often contains enough water to be saturated at nighttime temperatures. Frost was observed on the ground at the Viking 2 Lander site at 48°N and presumably forms at other high-latitude sites as well (2). Water as liquid on the surface of Mars has not been observed, and theoretical considerations suggest liquid water would not form on the surface because of low pressures and temperatures (3, 4). However, the pressures (5) at the Viking sites were always above the triple point of liquid water [6.1 millibar (1 millibar = 100 Pa)], and surface temperatures on Mars have been observed to rise above freezing (6). Thus it is expected that pressure and temperature combinations exist on Mars that would allow liquid water. A map of such sites might reveal locations of the most recent liquid water activity or sites of possible transient liquid formation at the present epoch.”


[129] For example:





“Location of Mars Pathfinder landing site in MOC image 25603. The lander is located in the center of the white box. The original resolution of the MOC image was about 3.3 meters (11 feet) per pixel; however, because the region was hazy at the time the picture was taken, the effective resolution is only about 5 meters (16.4 feet) per pixel. Thus, the lander and rover are too small to actually be seen in the image. The colored box, 120 m (just under 400 ft) on a side, is the topographic map of the landing site.”



E0200503 E0600815 M1501410



[133] “Within a few meters of the spacecraft are some interconnected, drift-filled troughs, 1 m across and 10 cm deep. They appear to form a polygonal pattern that mimics the pattern observed on a much larger scale in the orbiter photographs. Their origin is unknown.”



Figure 100 is one of the more instructive pictures taken at the Viking 2 site. A linear depression, or trench, can be traced across the middle of the picture. The bottom of the trench is 10 to 15 cm lower than bordering lips. The trench can be traced more than 10 m (figs. 103 to 106), trending generally east west and descending slightly to the east. It is partly filled with sediment finer than on adjacent surfaces.”


[135] Figures 103 to 106



 ibid “Oblique lighting in figure 134 accentuates pits so large they look like small craters. Indeed, if Mars lacked a shielding atmosphere that destroyed small meteoroids, an impact origin for the pits probably would be favored.”













[142]Scaled pixel width:      9.46   meters







Even more astonishing is the fact that a species of mite called tardigrades, less than half a millimetre long has been found to be able to survive boiling, freezing and exposure to a vacuum.

The results show that these microscopic animals, can withstand pressures of up to 6000 atmospheres by entering a state of suspended animation, which can be maintained for more than a century.

To accomplish this they reduce their body weight by 50% or more, accompanied by an almost total loss of water using a sugar called trehalose to stabilise their cell membranes. Such evidence points towards a re-evaluation of our current beliefs on how essential liquid water is to the development and preservation of life.

Examination of terrestrial biota reveals that life-forms have invaded an enormous variety of 'non-optimum' niches, for example cold polar regions and desert belts, where the essential ingredients for life are rare.

The simple conclusion therefore is that one of life's most conspicuous properties is its aggressive versatility, which arises from its fundamental ability to create new experimental organisms during evolution. Life on modern Mars would admittedly be very challenging, the largest obstacle being the lack of ample liquid water which would hinder metabolism, mobility and reproduction.”