Mars: A New Look at the Old Hump
By J. Richard Jacobs
I WAS RECENTLY ASKED if we are still able to use things within our solar system for locale in science fiction. They cited all the studies being made, the probes, the rovers, and so on. While it is true that we are discovering more and more about the bodies within our solar system, my response to the question is, “Why not?”
I was raised on a Mars teeming with Fredric Brown’s pesky little green men who called everyone “Mac,” and Ray Bradbury’s ghosts staring soulfully back at me from deep, placid pools. It was a time when Percival Lowell’s canals, though largely discounted by then, were still being debated, quietly, in some responsible circles and the thoughts of H.G. Wells’ dying planet populated by a hungry, warlike race continued to bother a few imaginatively paranoid folk.
We can all agree that the Mars of today is somewhat different from what those earlier visionaries presented and now, armed with a wealth of information, speculations have become less imaginative and more scientific. It is, however, still speculation sprinkled with imaginings and will not be much more than that until such time as we are there with rock hammers, picks, and shovels in hand to test the Martian surface for real. Even Curiosity, as beautiful as she is, can’t give us all the information we need to “know.”
An idea about the origin of Mars was presented by Dr. Tom Van Flandern quite a while ago (The Exploded Planet Hypothesis) in which he suggested that Mars was at one time just a small satellite of a large, rocky planet in an orbit between Mars’ current location and the orbit of Jupiter, right smack in the middle of what is now the asteroid belt, and that this big rock exploded, altering the orbit of Mars and creating that belt of debris. Although the hypothesis is an interesting one (I do not argue against the possibility of planets exploding) and he supports it well, it does not wash with what we think we know of the basic mechanics of planets and their formation, although that, too, is changing daily; nor does it seem to fit with the presence of Jupiter, a mass great enough that it would have interfered with the accretion process, possibly enough to keep such a large planet from existing in the first place. One of the arguments cited in support of his position is the Titius-Bode Law which purports to predict the orbital distances of planets from their parent star. That law is now viewed more as a convenient mathematical construct and less as a law owing to our knowledge of extrasolar planets and their positions relative to their respective stars.
I have maintained an all-consuming fascination with the hump (the Tharsis Bulge) since its discovery, analyzing with intense interest all the images available of the area, and have come to a startling set of conclusions based upon what I see and, more importantly, what I do not see. The commonly held idea about the formation of the Tharsis Bulge is that it was the result of volcanic activity that forced the region to rise. But there are problems with this view, the amount of rise notwithstanding.
Inspection of the planet’s surface reveals to us that major volcanic activity occurred in isolated pockets, but the main “hot spot” is at the end of Valles Marineris near the top of the Tharsis Bulge. There are other volcanoes scattered about the surface, but none are a match for the three Tharsis montes: Ascraeus, Pavonis, Arsia and, the behemoth at the extreme end of the Tharsis region, Olympus Mons. Valles Marineris is a rift that would divide the entire United States of America into two distinct zones, north and south, if it were here instead of on Mars.
In the north, large areas of moderately smooth, low lying terrain dominate the scene. South of the Martian equator is a highland pockmarked with craters large and small, many of them very old indeed. On the opposite side of the planet but not antipodal to the hump is the Hellas crater and basin where a huge impactor left an indelible mark on poor little Mars. The Argyre crater/basin is likewise 
nowhere near being antipodal to the hump. Why is that important? Hellas nor Argyre can be accused of causing the hump. Conspicuously, although there are mountains, there are no significant mountain ranges to give us evidence of tectonic movement, with the possible exception of a fragmented chain that arcs away from about 10 percent of the valley’s length at the eastern end and terminates near the end of Noctis Labyrinthus.
The next thing we need to look at requires a change of venue, so we will move northward from the ecliptic a dozen or so astronomical units and peer downward on the system for an overview of orbital motion. Mercury and Pluto have the most eccentric orbits in the system, 0.21 and 0.25 respectively. Then comes Mars at a respectable 0.09. The next closest planet to that is Saturn at 0.06.
At this point we must make some assumptions upon which all the rest of this speculation is based. Mars does not have the volume of Earth, is farther from the sun, and the atmosphere was probably much thinner than ours at its best. So the first assumption made is that the lithosphere of Mars became rigid long before Earth’s did. The size of the Martian globe is so small that it is reasonable to conclude that it cooled much more quickly and much of its geologic activity came essentially to an end sooner. I subscribe to the idea that Mars had a respectable atmosphere and that there was considerable fluid water on its surface before the scenario I am about to outline occurred.
If the Tharsis Bulge is the result of the upward lift of magma filling the area, why are there no radial fractures in the region that would indicate a slow, volcanic expansion of the surface? No hot cross bun, no wrinkles around the eye. That there should be radial fracturing in the area, if what we are told happened actually did occur, is not cast in concrete, but close to it. The mountain ranges that do not exist present testimony to the fact that Mars became geologically sluggish (though not dormant) early in its life. There are no moons large enough (possessing adequate mass) to continually churn its viscera like the one we have that grinds our substrata into a plastic state, keeps the heat up, and aids in maintaining tectonic movement. On top of that, the moons that are there are most likely captured asteroids (both just large boulders) and we have no way of knowing when that took place.
When we look at the grand rift called Valles Marineris (Mariner’s Valley, named for the Mariner 9 orbiter that let us see it for the first time) it is immediately apparent that the valley was not formed by moving water, though there likely was water moving through it after its formation. We see no meandering canyon following the twists and turns that water does when it seeks out the path of least resistance to eventually spill into the sea. And the raised areas within the valley show no signs of having been carved to comply with water’s demands or varying soil densities. Noctis Labyrinthus at the western end gives a hint of fluid movement, but a close inspection brings that notion into question, though it doesn’t eliminate the possibility completely. The various chasms paralleling the valley indicate collapse of vast areas. We also see signs of sapping along the edges of Mariner’s Valley that clearly point to the movement of water but, I believe, after the rift was formed.
What was it, then, that created this 10 kilometer above the zero datum line bulge and gave rise (no pun intended) to the gargantuan volcanoes at the far end of it? It is here that I swallow deeply, hold my breath and present my wild speculation.
The orbit of Mars, let us say, was much more circular back when all I am about to describe took place, on the order of 0.04 to a maximum of 0.05 eccentricity—and its days were shorter, too. Then, out of the blackness arrived a massive body on its way in to the sun to be devoured there, ejected from the system, or become a close in planet. Because we have no record of these events we will invent the intruder. Give it a diameter of about 4,900 kilometers, and a mean density of around 5.4+ grams per cubic centimeter—yielding a heft just a little over half the mass of Mars.
When this dark gray specter passes Mars it is slightly behind but coming in fast. Structurally, it is stronger than Mars and will not be affected much by the close pass, just inside the Roche limit, it is about to make. As it approaches it begins to drag immense amounts of Martian material toward it in an easterly direction and this action generates a tremendous heat in the process, thus liquefying the Martian substrata into a molten mass. It then drags the whole thing west, allowing the area behind to collapse, but not totally. This results in a gentle slope upward to the west until the reduced gravitational struggle between the two bodies and increased drag induced by the harder, cooler material around it leaves a huge lump of what can only be referred to as a blob of magma.
Stress in the rigid lithosphere results in an incredible fracture over nearly the full length of this cataclysmic episode, leaving behind what we now know as Mariner’s Valley. The sheer weight and temperature of the mass at the western end pushes down on the planet below it, finds several subsurface channels, and much of the molten material vents off pressure suddenly and catastrophically at three points: Ascraeus, Pavonis, and Arsia Mons. Olympus Mons is a later addition and becomes the main vent over a much longer period. In the time immediately following this close encounter, the mound is considerably higher than its current 10 kilometers and it takes a very long time to cool, so it shifts slightly to the south at the western end and drags the valley with it. If this had not happened, Mariner’s Valley would be a completely straight gouge following a great circle path directly through Pavonis Mons and very close to the southern side Olympus Mons.
The near collision has other repercussions. The atmosphere of Mars is heated and that part of it that is not stripped off directly is burned and boiled off, reducing its density, oxygen level, and depth. Large quantities of carbon dioxide are then introduced directly by volcanic activity into the new, thinner atmosphere. The southerly shift of the main Tharsis mass causes a wrinkling of the surface in the south which is still visible in the form of low hills and rough terrain forming that arc I mentioned earlier. It also introduces a little southerly kink in the valley at its western end.
This rending and reforming of the substrata leaves great voids deep beneath the surface into which substantial quantities of water move. The pressure from the steam thus generated adds to the violence of the volcanic activity while speeding up the cooling process and leaving even more voids for water to fill. I suspect vast cisterns exist around and beneath all of the Tharsis montes, as well as around and in some of the great chasms, so deep that they are nearly impossible to locate by any means other than direct seismic testing and drilling.
Other consequences of this event are that the orbital velocity of the little planet is slowed, elongating its track into a more elliptical path closer to the sun and its rotational rate is reduced, making the days (sols) somewhat longer.
And what of the interloper? Having already put my head on the chopping block, let us just say that I cannot think of a more convenient way to explain the extreme eccentricity and obliquity in the orbit of Mercury, can you?
Now, consider the original question. The scenario I have laid out means there may be lakes, even seas beneath the surface. It also says there may be immense caverns waiting to be explored—colonized. NASA has spotted vertical shafts here and there. What are they? Martian wells? I ask you now, can we still use Mars as a locale for science fiction? For speculation? So, my friends, what if ...? 
J. Richard Jacobs is a country boy turned scientist turned author. He writes hard and soft science fiction, science fact, science fantasy and other things. He has written several novels, novellas and tons of short stories. He has been called the O’Henry of science fiction.
