The Mars we know today is a dead world. We have yet to find a trace of life on it. Everything we have found, except for dust storms and some freezing and thawing cycles, has been lifeless, but shows that once there was more activity than there is now. And while I use Burroughs name for the planet in the title of this post, perhaps evoking thoughts of the alien species he envisioned, the use is more poetic. I don't think they was every life on Mars. Calling it Barsoom before the event I am about to describe is more about the chance of life cut short.
Mars features many of the Sol System's most extreme cases: the largest crater, the largest volcanoes, and the largest canyon. These features do not fall at random locations and are interconnected to the same ancient event roughly 4 billion years ago.
The crater is called the Hellas Crater. It is 8 km deep and ringed by highlands. It is 2100 km in diameter and it has been estimated that the asteroid that created the crater was over 200 km in diameter. It is larger than anything known to have hit Earth since the Moon was formed.
Which brings me to Olympus Mons and Valles Marineris. I keep hearing them cited for their size, but their size brings into question of how and why they formed. There is no good answer for that. Between them lies the Tharsis Plateau, an area as elevated as the Hallas Crater is deep. And there is the link. The impact that caused the Hellas Crater also caused the Tharsis Plateau. The force of such an impact was almost enough to break the planet. For practical considerations, it did. We will never know what the planet might have looked like had the impact not occurred. Much of what we take for granted on Mars may not be the case. Many theories exist on why Mars has so little atmosphere and water and such an enormous impact provides a much more likely reason that most others.
The impact not only raised the Tharsis Plateau, but led to the extreme vulcanism that dominates that region. The Valles Marineris is the remains of a crack that did not spew forth lava and it probably much filled in from what it once was. Time and erosion have turned a deep crack into a wide valley. The force of the impact would have sent material flying off, possibly at sufficient velocity to escape Mars orbit. What might have once been on it's way to becoming a cold but almost habitable world is now dead and lifeless.
These are just my observations and suppositions, but I have found I am not alone in my analysis. Others have come to the same conclusion that these features are all related. What erases any doubt in my mind are how extreme and unusual for the Martian surface they are. Some may point out a smaller grouping of volcanoes north of the Hellas Crater, but I would also point out that directly opposite on the surface of Mars is another sizable crater. Proportionally, they match the Hellas Crater and the Tharsis Plateau with its volcanoes. Both incidents indicate that the early Mars (or euphemistically, Barsoom) had a crust and molten mantle just like Earth still does. It accounts for the traces of running water that now seems to be absent and the lack of a viable atmosphere. It's a plausible explanation that fits the pieces of the puzzle.
Burroughs dreamed of a Mars that might have been before we fully understood it. His Barsoom is closer to what Mars might have been without the impact that produced the Hellas Crater. Barsoom was broken and leaves us with a challenge; can we bring it back?
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