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Volume 1415

The Real Primeval Mars
Den Valdron
Part of the Exploring Barsoom Series


In the beginning, we can imagine a Mars somewhat like early Earth.  A world with a thick reducing atmosphere, an active surface, high temperatures produced by greenhouse effects, and perhaps free water.   Martian water during this phase would have tended to collect at the poles, and there may have been small polar caps during this period.    Mars seems to have possessed a hot rotating core during this period, and a planetary magnetic field.

The planet was probably cooling during this time.  The crust had formed, and seemed to be stable.  There was nothing like terrestrial plate tectonics at work, which suggests either that the planet had cooled to the point where it simply wasn’t going to happen, or that the crust, like Venus’ was particularly thick.

Did life develop during this early period?   Were conditions for life even possible?   We probably may never know, except by going there.   But one thing was for sure.

Things were about to get a lot more interesting.

Mars history appears to have been shaped by two immense asteroid impacts perhaps three to four billion years ago, during the early formation of the planet.

The Argyre Impact

Argyre BasinMars landscape just beyond the Argyre rim

The first of these was probably Argyre, located in the southern Hemisphere.   To give you an idea of just how huge an impact Argyre was, its worth noting that we’ve never found anything comparable to this on any of the inner planets. 

The largest known craters on the Moon are about one hundredth the size of Argyre.    It’s possible that the moon received Argyre sized impacts so violent that they actually melted part of the surface and created a lunar Maria rather than a crater.  But this is not verified.   Nothing close to as a catastrophic as Argyre appears on either Venus or Mercury.

The Argyre impact left a crater roughly eleven hundred of miles in diameter, almost four miles deep and as almost a million square miles of area, and was so ferocious that the shockwave actually shook the entire planet, running completely through the planet’s core and crust, and discharging its energy on the opposite side of the planet, much like one of those ‘kinetic ball’ toys that litter executives desks.

The result was a small upwelling in the area in the northern hemisphere now called Elysium, and a complex of at least three volcanoes, including Elysium Montes, Albor Tholus and Hecates Tholus.

Meanwhile the Argyre impact deformed the surface where it hit, creating an immense depression, the crater, and pushing up the land around it into a series of rings of mountains. 

There was more.   The Argyre impact must have blown away a chunk of the atmosphere, the impact of the body hitting the atmosphere accelerating some Martian air into escape velocity.   The impact also kicked up hundreds of thousands, even millions of tons of debris.   Some of it immediately fell back as a huge splash of debris, dozens, even hundreds of feet thick.   This was thickest immediately around the impact area, and tended to thin out the further away you got.

But instead of being a fully round bloom, the debris field was distorted.   The hit was low in the southern hemisphere, not too far from Mars axis of rotation.  The swiftly rotating planet was moving as the debris fell, thus the debris pattern seemed to spread out and thin out towards the equator, as well as concentrate and thicken towards and at the pole. 

The phenomena is easy to grasp.   Imagine that the debris field is spreading out uniformly in a circle.   Now, the planet is rotating once every 24 hours.   The equator is moving fastest in relation to the falling debris.   The south pole is not moving at all.   As the debris falls north towards the equator, the equator is turning.   Thus debris which falls immediately, falls in a different spot than the debris which falls a few minutes later, or a few hours later.  The result is that the debris field starts to ‘stretch out’ towards the equator.   Meanwhile, the pole isn’t really moving at all.   Debris which falls a minute or an hour later towards the pole is still falling into the same general location.   So the result is a build up at the south pole, and a distorted smearing towards the equator.

Now, this means the south pole is covered thick with debris.   We don’t know whether or not there was an ice cap during this era of Martian history, but its quite possible that there was.  Any small ice cap at the southern pole would have been permanently buried, by a wave of rock and dust hundreds of feet thick, compressing into a hard rock shell.

Some debris made it into the upper atmosphere, even as high as low orbit, perhaps circling the planet a few times before falling to the surface.   Again, this concentrated in the southern hemisphere, but tended to spread more evenly.    Some of the debris of impact may have even reached escape velocity, becoming spaceborn.

But that was just the warm up act.   Hellas was coming.

The Hellas Impact

Part of the Hellas Basin

I’ve talked about just how colossal an impact Argyre was.  But compared to Hellas, Argyre was almost walk in the park.    This was a planet buster.    To give you some idea of scale, Hellas impact basin is about 1430 miles across, it was a dent in the planet six miles deep, with an area of approximately million, six hundred thousand square miles.   The primary ring of impact debris is almost 2500 miles across, and rises up to a mile and a half above the planetary mean (a sort of sea level).   It is the largest impact known of in the Solar System.

Only on a few smaller bodies, Jovian satellites, do we see impacts of this magnitude.   Literally, Hellas was close to as big an impact that a planet like Mars or Earth could sustain and not actually break apart.    The energy released by Hellas, equivalent to millions of hydrogen bombs, would have been sufficient to incinerate all life on the planet, if any existed then.

So what happened?   The same thing as Argyre, only bigger.   The impact created an immense round depression, a dimple or divot in the lower hemisphere.   The surrounding crust was distorted and displaced, pushed up all around the impact site in a broad circular highland.   In fact, it may well have distorted the shape of the entire planet, creating lowlands in the northern hemisphere, leaving a slightly ly pear shaped planet.

Once again, millions of tons of rock and debris were kicked up.   According to some estimates, if all of the Hellas debris fell on an area the size of the continental united states, it would have formed a blanket of rock two miles thick.   The result was a huge rather distorted looking ring.

Some of it fell back immediately in the same pattern as Argyre.   A kind of smear, concentrating thickly at the pole, stretching out towards the equator.   Argyre, caught in the debris field, was partially covered with debris, making it comparatively shallower.   In fact, Argyre’s relative shallowness and lack of contrast, compared to Hellas, is our tip that the Argyre impact probably came first.

The size of the impact was much more massive, so some of the debris even crossed the equator, where the planet’s rotation tended to smear it closest to the equator and concentrate it in higher latitudes.   This became the area known as the Syrtis Highlands of the northern Hemisphere.  Of course, orbital drift would leave it fairly wide towards the equator, with a pronounced drift or gradual slope in one direction.  As you went higher, the debris would tend to concentrate, the debris growing narrower, and the leading edge starting to bend in a sort of hook shape.

Of course, debris, because of rotation, would have tended to accumulate at the planetary poles.   The result, in the south pole, was another layer of debris and a remarkable bulge, which sat upon the debris resulting from Argyre.   If there was a southern ice cap, it was now definitely buried.  Mars may well have a ‘fossil’ Ice Cap buried at the South Pole, with water billions of years old, preserving a record of the early atmosphere and chemical composition of Mars. 

But Hellas also produced another bulge from collecting debris at the north pole, less impressive, but nevertheless, an odd bulge.   Again, this may leave us with a ‘fossil’ polar ice cap, though arguably, the debris layer was much less thick.   The frozen water here may well have been more accessible to the surface and melted or partially melted away at some point, leaving odd caverns, and perhaps a collapsed landscape.

Mars North Polar Ice Changing with the Seasons

By the way, just to be fair, I’m not aware of any scientists who argue that there may be ‘fossil’ ice caps of primeval Martian water buried at the poles.   This is just speculation on my part, in part because it dovetails with Burroughs Mars, but also because I think it makes sense in terms of the Martian history I am trying to reconstruct.

Actual photographs of the poles show mixed layers of light and dark material, ice and debris, carved into a spiral pattern (consistent with rotation on axis during debris fall.  The South Pole is more heavily mixed than the north pole, so I might well be onto something here.

Mars North Pole              ~           Mars South Pole

More debris reached the upper atmosphere or orbital reaches, even orbiting Mars before falling back to the ground.   This debris covered much of the southern hemisphere, but inevitably spread into the north, carpeting Mars with a layer of dust, gravel and rock.

Some of it, of course, managed to reach escape velocity, becoming meteorites.   And of course, once again, the impact must have blown a chunk of Martian atmosphere out into space.   This did not, however, leave us with the wafer thin atmosphere of the present day, or at least, not right away.   Things are still interesting, as we’ll see later.

There’s a couple of final effects of Hellas that have to be accounted for.   Like Argyre, the shockwave travelled through the core and around the crust, concentrating on the opposite side of the planet.   For Argyre, this had resulted in a small lifted area and a handful of volcanoes.   For Hellas, the result was the Tharsis bulge, a massive area of uplift the size of a small continent, the highest spot on the planet.   And the result was a series of volcanoes on Tharsis, including Olympus Montes, at 16 miles high and four hundred square miles, the largest mountain in the solar system.  Joining nix Olympica were a row of three volcanoes known as Tharsis Montes (individually, Arsia, Pavonis and Ascraeus Mons), as well as Tharsis Tholus and Alba Patera.

But even that did not account for the massive energies discharging from the opposite side of the world from the Hellas impact.   The titanic blast, or perhaps the resulting uplift of the Tharsis region literally caused a tear in the crust, a three thousand mile rip, up to ten miles deep in spots, that we’ve named Valles Marinis.   The scope of this feature is simply unique in the solar system.   There’s nothing like it that we know of anywhere else in the inner solar system, or in the giant moons of the outer system.  There may have been a similar tear on Tharsis itself, but this, in a far more active area, produced an upwelling, leaving a long, curving, rugged ridge near the equator.

And that should be it for Mars, you might think.   A couple of savage planet shaping impacts and there you go.   The Volcanoes will sputter and belch for a while, but that should be about it.   If there was an atmosphere, then the impacts should have blown it off, if there was water it was vapourized, if there was life, it was incinerated.

But that’s not the end of the story at all.   Nope, interesting things were still happening on Mars, believe it or not.

A Divided World
G ~ 70.5 S - 74.5 S / 250.1° W - 236.1° W
  Olympus Mons   ~    Burroughs Crater

In the 1960's, Earth sent its first space probes, the Pioneers, towards Mars.   These would be the first close up pictures received for any alien world, apart from the Moon.   To the dismay of romantics, the pictures revealed a heavily cratered surface, far closer to the Moon’s scarred visage than anything we imagined.   Mars, it seemed, was just a dry and dusty cratered ball.   No lost cities, no waters or seas, no belts of greenery, no canals or channels. 

Pioneer Probe      ~      Viking Probe 

In fact, the Pioneers were only getting pictures of the southern hemisphere.   In the 1970's, with the Viking Probes, we began to get pictures of the northern hemisphere....  And things got strange.    Because the northern hemisphere had barely any craters at all.   We were looking at two different planets.  A south which resembled the moon, and an oddly smooth and featureless north.    To make matters even more complicated, the north was actually at a lower average elevation than the south.   The south was, on average, kilometers higher than the north.

Now this was a puzzle.   In fact, the craters made sense.   The Moon, Mercury and even Venus were all heavily cratered.   Earth, because of the continuing sublimation of its surface through plate tectonics, and because of water and wind erosion, shows very few craters.   It shouldn’t have been surprising that Mars had lots of craters, and it wasn’t.

Current cosmological theory, by the way, now holds that the major waves of meteor impacts and the major period of crater formation for the Moon and inner world was probably around 3.2 billion years ago.   This gives us another clue as to the antiquity of the Hellas and Argyre impacts, which obviously must have taken place during or before the crater formation period.  (Although its possible that some of Mars cratering may have been the debris falling back from the impacts.)   Argyre is believed to be 3.9 billion years old. 

But still, this weirdly lopsided planet posed a problem.   There were smooth lowlands and cratered highlands.   How does that happen?   Normally, one assumes that the higher areas have been built up over a longer period and are more geologically active.   The Lunar Maria, are large smooth areas because they were geologically more active, their rocks are younger, and thus, less time and less opportunity for cratering.

This means that the highlands should be geologically younger than the lowlands.   So, under normal reasoning, one would expect severely cratered lowlands and smooth highlands.   The opposite of what we were getting.   Perhaps some force removed a few kilometers of the planet’s surface in the northern hemisphere, leaving a smooth area?   But there was no good explanation for how that could happen, or why those forces would be so comparatively neat in doing one side of the planet, and not the other.

It was only after we began to assemble detailed topographies in the 90's, that the processes created by Hellas and Argyre became clear.   We know now why Mars has its highlands and lowlands, and why they are shaped the way they are.   But that still didn’t answer the puzzle.   Why were the lowlands so smooth?

The Great Polar Ocean

The topic is still raging, but to my mind, there is only one reasonable explanation:    Water.   Since the 1980's, there has been speculation that Mars had an ocean filling much of its northern hemisphere, divided into three great lobes by land masses stretching up from the equator, including the Tharsis Bulge, the Syrtis highland and the Elysium plateau, and covering as much as a third of the planet.   Water processes eroded the north hemisphere craters.   Ocean currents filled them with silt.   Sedimentation buried features.   Lesser seas filled the Hellas and Argyre plateaus.

Ironically, we have returned full circle to the Astronomers of the 1890's with their belief in a vanished Martian ocean.   However, those astronomers located their ocean in the dark central and lower areas, and considered the light northern area to be a weathered desert continental region.  We now know that the dark central areas are mostly highlands, and the apparent continent is actually the lowland, the site of our hypothetical ocean.

Now, the timing is critical here.   Obviously, the Ocean, if it existed at all, must have existed after the meteor bombardments that made the southern hemisphere so moonlike.   If it was gone by then, then obviously, the northern hemisphere would have ended up looking just like the south’s moonscapes.   So, it either developed afterwards, or was there before and after.   Either way, the period of the Ocean must be much closer to us than the period of the bombardment.

Where did this Ocean come from?   That’s not clear.  It may have always been present, and Mars could have been a very wet world before Argyre and Hellas.   Considering how immense those impacts were, then Mars must have been literally buried beneath waters, for an ocean to actually survive and reform. 

North Pole Shorelines

Or it may be that the Ocean may have actually been formed by cometary water, so that its period of development may have been during the bombardment.   In which case, the early age of Mars, some three billion years ago must have been a very exciting place indeed.   Impacting comets and meteors blasting huge craters, water vapours from the impacts filling the atmospheres, melting or melted balls of comet ice flowing in rivers across the surfaces, forming the southern seas and the northern ocean even as Volcanoes sputtered and belched.    If, in fact, the water, or part of the water was cometary, then we should see channels and flow areas in the highlands, marking the pathways of water as it made its way to the Ocean and the southern Seas.    If this is how it happened, it must have been a savage, exciting, world, full of possibilities, including even the possibilities of life.

Of course the huge question is how much water there was, and how long it lasted.   Here, opinions are split.   The consensus is now that Mars must have had surface water at one point.  The evidence of rivers pathways, of sediment deposits, of water erosion is unmistakeable.   Water is clearly present at the poles in the ice caps.

But what was it like?   Were the rivers of Mars fast flowing affairs, sudden floods, boiling away in a too thin atmosphere even as they ran.   Was Mars water only a brief affair, perhaps a matter of years or millenia.   In this view, the wet period of Mars was frenzied and brief, evaporating away almost immediately.

At the other end of the debate, are those who argue for and speculate upon a Martian Ocean, an immense body of water that may have endured for hundreds of millions or even billions of years.   Existing, perhaps two billion years ago or less.  It is one of those debates that cannot be conclusively answered without someday going there and poking around in person.

Mars Oceans (NASA Art)

But over time, the indications seem to be inclining steadily towards the ‘long wet’ proponents.   The evidence for water, and particularly, the evidence for lots of water just keeps getting better and better.   Analysis of the atmosphere, spectrographic readings of the surface and evaluation of the soil and surface by probes seems to provide mounting evidence for a lot of water, and for water lasting a lot longer than we previously believed.   Among the remarkable discoveries are calculations based on the atmosphere composition that the planet may have had enough water to, at a minimum, cover its entire surface fifty feet deep.   There is evidence of a frozen sea buried beneath the surface of thousands of square miles area.   There is a quick observation of something that might have been a geyser.   There is evidence of a lot of water at the poles, and not just frozen carbon dioxide, and evidence of frozen water under the surface in permafrost.

Some researchers estimate that Mars at one time may have had enough water to cover the entire planet to a depth of a mile.  Even now, some researchers estimate that there may still be enough water at the poles and buried under the surface to cover the planet to a depth of 20 meters or more.

So, was there an ocean?   Seas?   The debate rages on.   Nevertheless, it is a romantic thought, and we can’t really know for sure, but the evidence allows us to at least entertain the possibility.   For the record, I can admit to stretching things for the romantic side, to opt for a warm ocean world.

But there is more.   The presence of surface water for any length of time, or the presence of an Ocean for a protracted period of time, suggests that the atmosphere must have been denser.   As dense as Earth’s atmosphere currently, as much as 100 or 150 times denser than it is on Mars now.  (The Martian atmosphere is currently seven tenths of one per cent of the thickness of terrestrial atmosphere at sea level).

A dense atmosphere, if it existed, would have produced a greenhouse effect, leaving Mars a far warmer world than it is now.   Of course, warm is a relative concept, and does not necessarily give us a tropical Mars.   Today’s Mars gets very very cold, the mean temperature is minus 63 celsius, with highs of twenty degrees and lows go down to minus 130 degrees.   Living in northern Manitoba where we occasionally approach minus 40 or 50 below, that’s spectacularly appalling.   A warm Mars may have merely had polar or sub-polar temperatures.

Whatever Happened to Young Mars

So what happened to the warm Mars?   Where did all that water and atmosphere go.   Undoubtedly, some of it boiled off into space over millions and billions of years.  Mars gravity is only 38% of Earth’s, and Earth continually loses bits and pieces of its atmosphere.   So if Earth’s atmosphere is normal for its gravity, then Mars would have real problems hanging onto what it had.

But is Earth’s atmosphere normal for its gravity.   Venus is slightly smaller than Earth, with perhaps 85 to 90% of terrestrial gravity, and yet, its atmospheric envelope is far denser than Earth’s.   At its surface, air pressure is ninety times Earth’s.   And Venus is far closer to the sun and far hotter than our world, so its losses from heating and solar wind must be greater.   So, the bottom line is that with only three planets to work with, we have too much range and few too samples to really know what is or isn’t typical, or whether a thick atmosphere on Mars really is or isn’t sustainable.   So, while Mars lower gravity may be a culprit, we really can’t know.   It is entirely possible that gravity isn’t the story at all, or its not the beginning or end of the story.   Likely, it is part of the story, but equally likely, not the whole.

Mars magnetic field is now dead, although there are weak ‘fossil’ magnetic fields all over the planet, leftovers of the days when the planet’s core was turning like a dynamo.   Some of these ‘fossil’ magnetic fields extend well beyond the planet’s atmosphere.   Earth’s magnetic field protects us from the charged particles, the higher radiations of the sun.  These charged particles would otherwise sterilize life and split the molecules of the atmosphere, liberating the hydrogen and oxygen of water.  Hydrogen would quickly escape in the lighter gravity.

Was this the fate of Mars?   Its oceans stolen, its atmosphere thinned, not just by gravity, but by uninterrupted solar radiation?   Possibly, though its worth noting that Venus, as super hot and baked dry as it is, still has a massive atmosphere, despite it too lacking a magnetic field.   On the other hand, Venus has little or no apparent water or hydrogen at all.   Once again, we’ve got too much range and too few samples to really come to a conclusion.  At best, we can speculate that the dead magnetic field and solar radiation was a part of it.

One thing which definitely appears to have happened, is that a lot of atmosphere seems to have gotten locked up in the planet’s surface simply through geological processes.   The Viking Probe discovered astonishing quantities of carbon dioxide and very strange chemistries in Martian soil.  The red colour of the world comes in large part from massive quantities of oxygen trapped in the rocks, along with carbon and other elements.   Oxygen, Carbon and even Hydrogen atoms are inherently unstable, they bond easily with each other and other substances to form complex molecules.   So simple chemistry, particularly ocean and water chemistry, might well have conspired to lock away a large part of the Martian atmosphere.

And of course, it is known that at least some of that atmosphere simply froze out at the poles, becoming frozen carbon dioxide.   How much is locked away up there, we do not know. 

Some enterprising science writers have suggested that Mars might live again.   Simply drop a few nuclear weapons at the poles, and liberate all that frozen carbon dioxide and water.   The atmosphere becomes thicker and moister, and the greenhouse effect kicks in, warming the planet up.   The hotter temperatures liberate gases in the soil, and or makes it easier to liberate, and voila, a nice habitable planet in only a few decades or centuries.   Of course, I suspect that if terraforming Mars is possible, it would take more than a few hydrogen bombs lobbed at the poles.  But it makes a nice fantasy.

One quite interesting theory notes that Mars particular mixture of atmospheric gases seems to be chemically stable at very low pressures, that is, approximately the pressure of Mars current atmosphere.    At higher pressures, the atmosphere isn’t stable and tends to chemical reactions and reduction.   So, it appears almost that Mars current atmosphere sits in a plateau or island of stability.

The implications of this are simultaneously encouraging and depressing.   What this seems to suggest, is that planetary atmospheres may have ‘islands of stability’, densities at which a particular mix of atmosphere works best, and which seem to be self perpetuating.   So, an atmosphere in an island of stability may actually be stable for a very long time, but once it falls out of that island of stability, it becomes very unstable, rapidly deteriorating until the next island of stability at a lower pressure.

If this is correct, and frankly, I’m just pissing in the wind here, then its possible that Mars thick air/wet surface period might have been very stable and might well have lasted a very very long time.   Which suggests that the dessication and thinning of the world, once some threshold point, was very rapid.   Mars went into free fall, or free falls,  until reaching the current plateau.

The bad news here is that if this is correct, then it is going to be very very very hard to find a way to push the Martian atmosphere back up to something Earthlike.   There will be very little opportunity for gradually building the atmosphere will have an innate tendency to return to its ‘island of stability’.   Of course, we have no idea what the time frames are, so if this process of stabilization takes millenia, and we can rebuild the Martian atmosphere in centuries, we might get away with it.

Mars still holds surprises.   The most recent news is that geologists are finding signs of different kinds of rock on Mars.   The theory was that it was all volcanic basalts from a single formation.  Earth’s diversity of rocks from basalts to granites comes from plate tectonics, the fact that our rocks are continually being subsumed, remelted, and spit up, refining them.   The idea was that Mars, lacking plate tectonics would not continually subsume and refine its rocks, so all you’d bet would be basalts, like Venus.   Now they’re finding pockets of granite and other materials.  Where does this come from?   Perhaps the volcanism is a little freakier than we’ve thought.  Perhaps the Hellas and Argyre impacts or smaller meteor impacts took the place of tectonic subduction, producing limited quantities of higher ‘refried’ rocks.

On to Barsoom!

So, having pored over the Mars that Burroughs knew, and the Mars we know now, are we prepared to investigate Barsoom.

Join me in the other Matching Mars discussions, wherein we locate the vanished seas of Torquas and Throxeus, chart the Artolian hills, pinpoint Gathol, explain Omean, reveal the Carrion Caves, map the Toonolian marshes, identify the lost sea of Korus, discover the mountains of Torquas and find the forests of Kaol and Onvak, matching these regions to the actual geography of Mars. And from there, once we’ve got the geography linked, we can then locate the cities and states of John Carter’s Barsoom on the template of the real Mars, making

Burroughs Crater on Mars ~ 72.5S  243.1W 

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First Step in Terraforming Mars
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