Greg M. Orme and Peter K. Ness (In consultation with Sir Arthur C. Clarke)
publication of our paper in the
of the British Interplanetary Society
the following summer on Mars revealled more "spider" images
With nearly two full summer seasons of the spiders, we are able to test many of
the observations put forward in our first paper. To this end, we have compiled
of spider photos in seasonal order
beginning in early spring and ending in late autumn. The table shows that some
spider areas are highly imaged. We separate these areas into clusters so that
they can be more closely examined. Two main clusters
are considered. They are shown in the context of wide-angle THEMIS
images and MOLA
maps. We present information on seasonal temperatures to show how temperature
is correlated with spider positions. Although we do not know what the spiders
are at this stage of the investigation, it is possible to say what they are not
based on inferred properties, interpretation of physical laws, and comparisons
to known geological formations. Additional evidence is support of our arguments can
be found on our web site at
story of the spiders is an interesting one. The term "black spiders" was coined
by the MOC team
One of the first and most interesting spider photos is M0804688
which was found by Greg Orme in October 2000. Subsequently, Sir Arthur C. Clarke
saw this image and decided it might represent evidence of a form of life on
Mars. This has lead to an unusual situation: Sir Arthur is highly respected in
the scientific community
A science visionary, Sir Arthur wrote about the possibility of plants on Mars
over fifty years ago
(Percival Lowell also believed in his day that the South Pole of Mars might
contain life from his observations
Although he has done many interviews and lectures on the subject (including
the Smithsonian Institute
and the London Times
the spider formations remain an enigma that is hardly mentioned in published
papers on Mars.
people's reaction to images of the spiders is discomfort and confusion. When
they 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.
The situation is that we are confronted with something that looks like life,
but according to what we know about Mars, cannot be life.
our first paper on the subject, we explored the subject as thoroughly as
possibly while remaining neutral as to what the spiders might be. We provided
image numbers of all spider photos known to us, explained plausible geological
models and even explored basic biological ideas. Now that this paper is
beginning to be referenced, we believe it is necessary to update those
impressions, as some of the concepts have changed markedly since then.
this paper, we describe some of the problems that have arisen in geological
models of the spiders. Many of these were touched upon in the first paper and
some have been discovered since. In a future paper we will present a
compilation of images over two Martian years recorded by the MOC
to run from early spring to late autumn. These 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 with spiders, and images of older possible spider formations at
1 MOLA image showing main area of spider activity
1 is a MOLA map of Mars' South Pole
The main spider areas seem concentrated on the right side of the pole,
particularly around Chasma Australe
There are other similar chasma also apparently associated with spiders
all plant life uses Fibonacci patterns
as templates for the shape of branches, flowers and roots
Animals also use them as templates for blood vessels
nerves, and the proportions of limbs. On Earth, Fibonacci patterns are almost a
signature of life itself. It is our claim that the structure of spiders seems
to follow a Fibonacci pattern (Figure 2).
2 The structure of some spiders resembles a Fibonacci pattern
patterns are never found in non-biological phenomena. In particular they are
not found in the branching pattern of rivers and deltas
except by chance. The chance argument for spiders runs into enormous
difficulties since each time the pattern follows a Fibonacci relationship
instead of random branching it becomes increasingly less likely to not have an
underlying cause. There are literally hundreds of thousands of branches just in
the photos we have examined. and of the ones we can see, clearly the
overwhelming majority appear to be Fibonacci branching.
a Fibonacci branching happens 10 times in a row then the odds would be 1:2
roughly one chance in a thousand. There are so many instances of Fibonacci
patterns that the odds of their occuring by chance is far larger number than
the number of atoms in the universe! Since we often regard polls of only a few
hundred people as being representative, it is almost certainly not credible to
say these patterns form by chance. This highlights a major problem with other
(non-organic) theories on the spiders -- that recognized faults in these
theories are glossed over as being unimportant, so we end up with impossible
improbabilities in branch distributions, fluids apparently flowing uphill
unaware of the law of gravity, and spiders that grow and shrink through the
summer as if these things were somehow accepted because they are on Mars.
idea of fluids forming these shapes on Mars runs into other problems as well.
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
The problem with the fluid-flow interpretation is further compounded 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 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
kind of fluid naturally tends to follow a path to lower ground, which of course
is why rivers don't flow up hill. If spider branches and formations were
related to fluid flows they would have to defy gravity. Channels flow downhill
but don't form branches like spiders
Rock formations that look like spiders
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
which is impossible. On Mars, we also see perhaps millions of examples of
former fluid flows
-- all of which flow down hill. Indeed, from physics we know that any fluid
would always flow down hill with gravity. The only exception would be when the
fluids were expelled with some force to temporarily move up the hill, but there
is no sign of this happening, especially over hundreds of meters in some cases.
If a liquid did exhibit such behavior we would expect to see signs of where it
went up the hill but also where it came down again. We wouldn't see river
branches perched up the hill against gravity seemingly full of fluids that
managed to freeze solid before they came down again. While there is still some
debate whether the fluids that formed these channels are water or CO2 based
no one has ever asserted they should not follow gravity.
of the crater channels that look like they may have been formed from water were
actually formed from CO2
shows a model that CO2 may be actively forming crater gullies on the South
Pole. The problem is if CO2 can mimic water so closely then the argument that
spiders are formed by some unusual properties of CO2 seems unlikely. If CO2 can
flow like water, why 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
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 have
branches that also point down hill in the same formation. Studies on ancient
deltas and rivers on Mars
show no similarity to spiders or spider ravines
A fluid flow encountering a hill, for example, would at least tend to go around
it, but spider branches almost invariably 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 that are seemingly impossible for fluids to act. (Russell Crater
is a good example of what is generally believed to be a current water flow on
Note the channels flow straight downhill as they would on Earth
nothing like spider branches.)
only alternative to a fluid is a solid, such as soil or sand, forming dunes
These also do not exhibit any tendency to form against gravity
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
and terrestrial dunes also don't look like spiders
Some spider types also seem to follow the tops of ridges in a line, which is
the opposite of what gravity should dictate.
we see the surface of a river on Earth, whether liquid or frozen, the surface
is almost invariably flat. This is simply a consequence of the law of gravity.
Fluids forming spider branches on Mars should have a flat upper surface, but
the surface shape of spider branches can clearly be seen from their shadows as
Any fluid would naturally tend to pool unless there were existing channels
holding the fluid. Spider branches on the other hand often form on flat
featureless ground with no visible terrain to stop them spreading out into 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.
On Earth there are no examples of outflows of any material that would form
branches like these. Dense spider areas have a certain texture, but markedly
different from other areas of Mars
spiders seem to leave behind ravines but others do not. If there were 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 with spiders imply that fluids or sand is accumulating in the
ravines, somehow disappearing, and then reappearing. The problem is that
identical looking spiders are seen leaving no trace of ravines. In one model
the ravine is essential to the formation of spiders conforming to known
physical laws, while in another the spider just does the same thing ignoring
the same physical laws. This implies the spiders form the ravines but don't
need the ravines to form.
the spiders are made of, it stands to reason that the same materials must be
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 in other places the ice 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 amorphous patterns tending to follow this sequence as well.
However, we see the opposite. 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. If they are made of ice, then
it needs to be explained why they are affected by temperature in the opposite
way known to ice.
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
the sublimating CO2 increases the air pressure compared to outside the pole
creating a wind blowing away from the pole.) This can be clearly seen in
images, where streaks form from the wind. Between these times, the amount of
streaking is minimal. If the spiders are dunes they must be forming when the
wind is lowest, which is impossible. If they were dunes, they should be forming
in the spring when the wind is stronger, but they seem to form after the wind
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
cannot overcome the conditions already described -- they cannot form Fibonacci
patterns, cannot move against gravity, cannot act completely differently to the
same materials nearby
and cannot form convex shapes.
Even if they could behave in these ways and could somehow grow
with the warmer weather, they would have to shrink
and 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 grows colder
should freeze. In fact, the cold should freeze them in place just as it forms
frost on the ground. So, spiders seem to break another natural law -- that they
"evaporate" as the temperature decreases.
believes the spiders are formed under a layer of clear CO2 ice. The theory is
based on dust settling in CO2 ice, which makes it clearer near the top. The
problem is that spiders form when the temperatures are far above the
sublimation point for CO2. We can also see this because the frost on the ground
disappears as the spiders are forming. Looking at one image
for example, the ground is highly undulated making it unlikely that there is a
clear layer of CO2 ice on top. Also, it is autumn when any CO2 ice would have
sublimated. Another problem with this explanation is in their shape. In
spiders seen on sloped terrain, their branches spread out in all directions. If
pressure from below was forming cracks, the material would tend to form
downhill so we should see a non-radial pattern on slopes.
stated above, spiders disappear when the temperatures start falling, which is
when the CO2 is likely to be returning not disappearing. The South Pole has a
warmer summer than the North Pole because of the eccentricity of Mars' orbit
The temperature in spider areas is close to zero deg. C in the summer
perhaps even above zero. 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 autumn. So the spiders cannot be
made of CO2 or H2O ice as this sublimates away while the spiders are growing.
has been argued that the spiders cannot be a life form because it is too cold
on Mars. But as noted above, temperatures are close to zero in summer. With
dark materials absorbing heat, they could well be hot enough for brines to
exist for considerable lengths of time.
typically form as discrete types with their own characteristics
and in common kinds of terrain. If there were some material that could do all
of this, it would 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 and so are faced with needing not one kind of unknown 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.
is hard to estimate the number of spiders. The MOC has imaged only a small
portion of the total and the number found thusfar is enormous. It seems
reasonable to conclude there are millions of these structures, which must
indicate their mode of formation is robust. The presence of so many formations
can hardly be the result of chance.
differ in albedo from the ground, usually paler. They begin to form at 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. 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. Some images
show pale spiders surrounded by dark soil. Why is their albedo different? It
can't be from materials around them because in their current form they have a
different albedo already. If they were from an outflow from below we should be
able to see ice, puddles, and so forth with the same albedo as the spiders, but
spiders have the same albedo as the ground, but this is later in the season as
they fall apart
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
becoming covered in dust from the wind. Then only as they dwindle do they
return to the albedo of the soil. Plants might be expected to return to the
soil and indeed become the soil but an inorganic chemical reaction implies that
they must be made out of the soil in order to return to its albedo. So if an
outflow of a different material 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 the temperature drops.
there is a chemical reaction that makes the spiders a different albedo, that
reaction has to reverse itself because the temperature is dropping, but no
known reactions in a situation like this are known to exist. 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.
are typically found in certain places but not in others, with no clear reason
why. For example, many areas have features known as polar spots
and spiders are often found close to them. They have never been seen 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
they first start forming, spiders seem to put out their first branches at right
angles to the sun, and then later form in a radial pattern. Any process would
somehow have to recognize where the sun was coming from and then disregard it.
This orientation seems to occur regardless of the slope of the ground. If this
were controlled by 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 one with a Fibonacci form.
3 Example of bush material
spiders develop a bush like covering (Figure 3) over the branches as the summer
progresses to the point of covering up the branches completely
Then, they seem to lose this material and the branches reappear. It is possible
that this material may have a 3-D structure with a lot of empty spaces inside.
Something would either have to occupy these spaces and subsequently sublimate
or leave somehow, or the structure would have to "grow" around the spaces. Many
may totally dissipate and leave "Swiss Cheese" like shapes -- a hollow with a
ridge around the edges. Bush material often covers large areas, but in parts
forms clumps, even though the ground in between looks the same.
fluid flows on Mars usually have signs of debris at the ends of the channels,
perhaps from erosion. The spider branches have none of these signs. For
example, some images
show debris at the end of the channels, eroded by the fluid flow. Spiders do not
Spiders disappear in autumn without leaving much, if any, debris behind. It
seems impossible for a rock formation to simply disappear just because the
weather becomes colder. Ice might if the temperture were increasing, but in
fact, it is doing just the opposite.
seem to avoid each other even when very close together
Dunes would tend to join up and rivers should merge. Less than 1% of branches
cross each other, and when they do they often don't merge but go right over
spiders are found in a very narrow latitude range of only a few degrees, 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 great circle in the summer sky. If spiders
are formed by the pressure of underground CO2 gases, why are they so sensitive
to temperature? Inactive spiders are seen over a wider area, implying spiders
may have occured more frequently in the past.
is a test for life developed by Frank Corsetti of MIT
Preliminary results indicate that spider images compress at consistently
different rates to dunes and fluid channels.
are very similar to bush areas that are changing seasonally. It seems likely
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 seemingly related.
is possible that spiders might have covered much more of the South Pole in the
past at times of high obliquity with the Swiss Cheese and inactive ravines
being relics of that time. 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 finding 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
are three mysterious formations on the pole then, one active and two apparently
defunct and all surrounded by formations that seem quite normal.
a wetlands shape
does not necessarily imply the presence of life, it is interesting to note that
many of the areas of polar spots bear a remarkable similarity to wetlands
While there is little surface water now, perhaps they were wet when the axial
tilt or obliquity was periodically much higher
(The ground is perhaps half ice
so all that is needed is an additional temperature rise which obliquity could
Some brines become liquid at lower temperatures than pure water,
and water may take long periods to refreeze or sublimate
enough, Viking 2
nearly in the middle of a sub polar area that seems truly spider like
Interestingly, some troughs were found near Viking 2
While other explanations have been suggested, the presence of the spiders
nearby and their association with sometimes polygonal ravines makes these
troughs possibly spider ravines. These "enigmatic troughs"
can be traced in a sequence of photos
If they are spider ravines, it might indicate that when the spiders seasonally
dissipate, they might leave ravines that are too shallow to see. There are also
in the area of unknown origin. In
may also be troughs. Figures 290, 210 and 211
show paler areas devoid of rocks, which may be related to spiders. Of course,
there are many other explanations but the proximity to the spiders makes these
interesting. In imagery of the landing site
spider branches are 1-3 pixels wide where a pixel's width
is 9.46 meters
Since spiders typically have a paler albedo and a comparable branch width to
these pale patches, it is possible that they might be spider remnants.
spiders represent a genuine enigma in terms of their appearance and behavior.
They have no known counterpart on Earth. We know of no physical processes
capable of explaning them. Although their behavior is consistent with a life
form, Mars has an environment that seems impossible for anything other than a
few known microbes and perhaps tardigrades
to survive. Certainly, no large-scale life could live there.
the spiders turn out to be a new kind of life form, it will be a great
discovery. If not, a lot of exciting science is ahead of us. Either way, the
spiders merit much closer examination.
number refers to our JBIS paper, Comparisons are reimaged photos also at:
are clusters of images close to each other. Groups 1 and 8 are shown here in
Marked in one column as Groups 1 and 8.
"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,
Rama II, The Garden of Rama and Rama Revealed (with Gentry Lee)."
example, "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.”
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
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
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.
"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,"
People may be interested in reading these papers on the possibilities of life
"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."
"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."
Cavi Augusti also has some spider signs:
This was also covered in our first spider paper:
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.
"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."
temperatures are somewhat colder due to a 20% increase in the distance from
Mars to the Sun."
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."
"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."
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.
"Hoffman  posited that Martian gullies result from release of liquid CO2 ,
but it is very unclear that such release would produce tidy gullies instead of
"Over thousands of springtime thaws, the kilometre-long channels we see today
can be carved by repeated small flows of this nature."
"SPRING DEFROSTING IN THE RUSSELL CRATER DUNE FIELD -RECENT SURFACE RUNOFF
WITHIN THE LAST MARTIAN YEAR ?"
"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 dune reaching an elevation of 600 m above surrounding
plains covers the floor of Russel crater."
"SIBERIAN RIVERS AND MARTIAN OUTFLOW CHANNELS: AN ANALOGY."
"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."
"SNOW AND ICE MELT FLOW FEATURES ON DEVON ISLAND, NUNAVUT, ARCTIC CANADA AS
POSSIBLE ANALOGS FOR RECENT SLOPE FLOW FEATURES ON MARS"
"THE AUSTRALIAN PALEOFLOOD MODEL FOR UNCONFINED FLUVIAL DEPOSITION ON MARS."
"COMPARISON OF ICELANDIC AND MARTIAN HILLSIDE GULLIES."
"GULLIES ON MARS: CLUES TO THEIR FORMATION TIMESCALE FROM POSSIBLE ANALOGS
FROM DEVON ISLAND, NUNAVUT, ARCTIC CANADA."
"SELECTIVE FLUVIAL EROSION ON MARS: GLACIAL SELECTIVE LINEAR EROSION ON DEVON
ISLAND, NUNAVUT, ARCTIC CANADA, AS A POSSIBLE ANALOG."
"SMALL VALLEYS NETWORKS ON MARS: THE GLACIAL MELTWATER CHANNEL NETWORKS OF
DEVON ISLAND, NUNAVUT TERRITORY, ARCTIC CANADA, AS POSSIBLE ANALOGS."
"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 determine 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."
"AEOLIAN AND PLUVIAL FEATURES IN THE EASTERN MOJAVE DESERT AS POTENTIAL ANALOGS
FOR FEATURES ON MARS."
This refers to wind speeds on the South Pole:
Here lobate debris aprons are very different from spiders.
"Introduction: High resolution Viking images (orbit 724A, 14m/pixel) show
evidence for ancient glaciation in parts of southeastern Elysium Planitia.
While previous authors have mapped the materials as thin lacustrine and fluvial
deposits , we present evidence for erosional and depositional processes
associated with glacial environments. The previous ice sheet formed hummocky
goundmoraines, eskers, and possibly pingos."
These are a different albedo to the frost still on the ground.
"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."
This shows the shrinking of the polar cap at the same time as the spiders are
increasing, Figure 2:
"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
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
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.
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:
"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."
"Introduction: The recent finding of abundant,apparently 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 discovery has therefore called into
question our current understanding 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 properties."
"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
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 characteristic, growing splotches, called dark dune spots
(DDSs) appear at the end of the winter. Malin et al. explain the appearance and
temporal development of these spots by defrosting processes. Based on the
images of the Mars Global Surveyor (MGS), we show here that solely sublimation
processes cannot explain the shape, development and characteristic features of
these spots; other processes must also be invoked. We list the supporting
evidence and the associated explanations."
"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, occur 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 H2O 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
Some of the features have parallel tails that are clearly shaped by the wind.
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
None of these for example have debris at the ends of the channels
"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 ). 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 . One of the most intriguing
observed properties is the existence of four or more layers within the medium
in which the depressions are incised . Figure 2 (as shown in the Thomas et
al  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."
"RECENT LIQUID WATER IN THE POLAR REGIONS OF MARS."
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).
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.
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.
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."
"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
solution branch disappears in higher obliquity region. On the other hand, the
no-ice-cap solution branch does notexist 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 , then the origin of the
Etched Material turns out to be a logical event."
large number of observations of the surface, atmosphere, geophysical
properties, and solar-wind interactions of Mars, along with analysis of martian
meteorites, 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 observations into (i) those relevant to the nature of the
earliest atmosphere and climate, and the connections between 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 climate. 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
Several lines of evidence suggest that Mars have experienced climate changes
intermittently in its history. Mars might have had a denser atmosphere and
warmer climate in the Noachian period . Cyclic and episodic climate changes
might have occurred in later epochs after the Noachian ."
"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 melting of these deposits could occur due to geothermal heating [e.g., 2]. It was suggested  that several features in the PCs, including Chasma Boreale and Chasma Australe, were formed by the catastrophic discharge
a large subglacial reservoir of basal melt-water. 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 rotational 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 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 receive additional insolation at these high obliquities, but the resulting increase in H2O sublimation from the ice caps will initiate a water vapor greenhouse heating effect. Hence, surface and subsurface 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 circumstances 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 perhaps other phenomena."
"Introduction: Geochemical thermodynamic reaction modeling allows one to predict the equilibrium composition 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 surface 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 ,,,, as well as Mars meteorites . Water-salt brines could form near the surface of Mars through dissolution of soil duricrusts, input of volcanic salts from the atmosphere and/or through water-rock interactions."
"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
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 stable 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 humidity 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 conceivably 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 days.
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 recently observed by Malin & Edgett . Fur-ther, it can be concluded that summer wetting may frequently 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."
"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."
"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."
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."
"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.
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."