Geography of Mars

Lecture Notes for the Midterm

• Introduction
  • See Viewgraphs: Introduction
  • What have you gotten yourself into this time?
    • How have you imagined Mars?
    • How did that affect your decision to take this class?
  • Mars powerfully affects the human imagination at all levels:
    • It's long been understood to be the "next planet out" and proximity raises curiosity
    • It is, furthermore, the most terrestrial of the other terrestrial planets and, so, people can imagine our species living (or attempting to live ...) on Mars
    • Early scientific discoveries, many of them mistaken, fed into this perception of Mars being in some sense habitable
      • Telescopy and the mapping work by visually exhausted astronomers led to the perception of lineations that made some people think these were possibly water bodies or canals
      • This came at a time when science had grasped the fact of extreme environmental change in Earth history, including ice ages, desertification, and civilization collapses due in part to desertification or to irrigation-related salinization, so the canals idea fell on fertile ground and led to all kinds of romantic speculation about a martian civilization struggling heroically to move water around on a desiccating planet
      • Maybe such beings might look at Earth with hostile eye....
      • And so was born a very persistent science fiction trope.
  • Science can, indeed, be wrong but, alone among human systems of knowledge acquisition, it is peculiarly able to self-correct by collecting more data, developing better theories, better argumentation linking data and theory, and endless testing of hypotheses
    • The scientific community quickly got over canals, using spectroscopy, better telescopes, and the findings of psychological experiments
    • Ultimately, missions were launched to Mars by the USA and USSR and what came back was one dead planet, little distinguishable from the moon or Mercury, at least at first, due to quirks of flyby paths (e.g., Mariner 4 in 1965 and Mariner 6 and 7 in 1969) and crash-landings (e.g., USSR Mars 2 lander in 1971 and Mars 6 lander in 1974)
    • That was quickly remedied by some stunningly successful early US missions, such as Mariner 9 and Viking 1 and 2, but the Viking landers were disappointing when their life-seeking experiments came a cropper
    • The late 1990s and the 21st century, however, have created a detailed view of this planet, which is utterly fascinating in its own right and which led to this class
    • Mars may have enjoyed a time of warm and thick atmosphere that supported surface water, with stream drainages of several types and, increasingly plausibly, an ocean and other large water bodies. It may well have evolved life. Unfortunately, that clement period came to a brutal end about 3-3.8 billion years ago, leaving a very cold and very arid planet. Humans may be able to settle there, but it will be a very harsh existence that would make Antarctican research stations seem like Easy Street. I served on an engineer's dissertation committee in an Australian university in 2019, in which the conditions of life in permanent small settlements on Earth (Negev Desert in Israel and the peri-Arctic in Sweden) were being described via participant-observation to help Mars second-stage settlement planners anticipate and prepare for them.
  • As I've said, Mars is an utterly fascinating planet in its own terms, totally separate from any kind of human exploration there. It is a planet of extremes:
    • It has the tallest volcano by far in the entire solar system, Olympus Mons. This dwarfs Mount Everest's 8,848 m (which would hardly peek above the great rampart at the base of Olympus, which is 8 to 10 km tall. The volcano itself is >21 km above Mars' geoid ("sea level" datum) and some 26 km higher than the floor of Amazonis Planitia to the west.
    • It has the longest and deepest canyon in the solar system, making our own Grand Canyon look like a scratch in the sidewalk
    • It features an extremely deep and wide impact crater, Hellas Planitia, which is pretty stunning in hypsometrically tinted elevation maps based on the MOLA sensor
    • The dead, crater battered impression given by the early Mariner flyby missions have a regional base in reality: There are some spectacularly cratered surfaces that have changed little over as many as 4.1 billion years. Mars is geologically active, but not as much as Earth is, so it does preserve wide swaths of truly ancient terrain that was long since tectonically recycled on Earth. A deeper understanding of Earth's ancient history awaits human exploration of these cratered highlands.
    • Mars has a really nasty atmosphere. Density averages about 0.6% of Earth's at sea level, but it is quite variable due to pressure pulses created by the summer polar ice cap sublimating carbon dioxide ice. No matter how much that pressure pulse is, however, Mars' air pressure is so insanely low and has been for over 3 billion years that water can only exist as ice or vapor, almost never as liquid: Mars is below the triple-point of water (the phase diagram for the solid, liquid, and vapor states of water as a function of temperature and pressure).
    • Even with that low, low air pressure, oddly enough, wind is a major erosional and depositional agent on Mars! There are wind-etched features everywhere and dunes, too. Mars gets these freak dust storms, especially in the Southern Hemisphere spring and summer, some of which just snowball into planet covering shrouds. One of these killed the Opportunity rover in 2018 after more than 14 years of surface work (it was designed to last a bit over 90 Earth days!).
    • Mars is just savagely cold. This map, showing a couple of weeks work by the Thermal Emission Spectromer on the Mars Global Surveyor orbiter, is color-coded to show the temperature extremes on Mars, but you have to look close. The "warm" reds and oranges depict temperatures around -65° C (-85° F), while the purples are -125° C (or -193° F). This sequence was taken during a massive dust storm back in 2001, and you see the planet warm up like crazy as the dust traps heat, but that "heat" isn't going to feel warm to you!
    • All of these extremes are found on this quite small planet
  • Nature of Geography: What's a nice geographer like you doing on a planet like Mars? Geographers themselves are not agreed on what geography itself is and fights about it erupt every several years. The definitions of geography can be grouped into four main camps:
    • Human-environment tradition focussing on topics showing the human impact on the natural environment or the natural environment's impact on human society
    • Regional geography tradition dedicated to the synthesis of natural and social information about a region and differentiating one region from another
    • Spatial tradition focussing on the production and testing of specialized knowledge about the distribution of particular phenomena and the processes behind their distributions
    • Physical geography tradition holds to the analysis of physical and biological processes on Planet Earth as an integrated system and was a little dismayed when some geographers started venturing into social science questions over a century ago
  • Geography and Mars
    • How the four traditions apply to the study of Mars: the latter three clearly fit, while the human-environment tradition awaits sustained human presence on Mars (though there are several human geographers taking up martian topics!)
    • The contribution of geography's regional tradition to exploration of a different planet: "Areography," including the orders of relief scheme I'll use to organize martian landscapes
    • The hundred or so geographers I've identified doing research on Mars are dominated by geomorphologists (æolian, fluvial, and glacial geomorphologists) with a substantial minority of GIScientists (GIS, remote sensing, and spatial statisticians), though I have also found a few human geographers doing work on the history of Mars research and on space policy.