I'll talk today about three main topics:
- How the CSULB Geography of Mars class developed
- The development of Mars cartography from Earth-based observation to
orbiter-derived remote sensing
- And, if we have time, my "orders of relief" scheme for regionalizing the
physiographic surface of Mars to organize my students' mental maps of Mars
From the Geography of Hazards to the Geography of Mars
My involvement with Mars and the creation of the Mars class were accidental.
Much of my research is in the area of hazards, both natural hazards and
technological hazards. Back in the late 1990s, I did a project on the
controversy that had erupted around the plutonium dioxide carried on the
Cassini-Huygens spacecraft being readied for launch to Saturn. A large
movement had sprung up, much of it online, to stop its launch and, later, its
gravity-assist swing by Earth to gain velocity for the long voyage to Saturn.
The mission did launch in 1997 and made its fly-by of Earth in 1999, but NASA
wanted to learn ways of better managing risk communication. They'd gotten
wind of my project
and asked me to present it to a teleconference to five NASA centers.
discussion, they expressed concern about another mission they suspected would
become even more controversial: the Mars Sample Return Mission (MSR). This
was intended to collect samples of martian soil and rock and then launch them
off the surface of Mars, send them to Earth, and recover them, perhaps with
the "crash landing in the Utah desert" method. The mission would be
controversial because the rovers or landers that collected the samples would
probably be powered by plutonium dioxide radioisotope thermal generators and
also because of the vanishingly small probability of martian life, should it
exist or still exist, back-contaminating the earth ("the Andromeda Strain").
Though extremely unlikely, back-contamination could be very consequential if
it did happen. So, NASA expected this to be a very controversial, if
critically important mission.
They asked me if I would consider following this controversy as it developed
and amplified towards launch, which they expected in 2008. I said I would and
began learning as much as I could about a planet that had been little more
than a pinkish dot in the sky to me before. This proved quite challenging.
Meanwhile, President Bush announced his "Vision for Space Exploration" in
January 2004. It would re-orient NASA around the goals of human-crewed
missions to the Moon and to Mars. The Mars endeavor would entail a piloted
spacecraft going out to Mars and entering orbit and then safely returning to
Earth, followed by another mission that would send astronauts back to Mars and
then have a team land and collect samples, returning during the same launch
window (up to 30 days optimistically). "Just like Apollo." This would be
extremely expensive, not least because of the risk to human life, but there
was no commensurate augmentation of the NASA budget to accommodate this costly
new direction (shutting down the Shuttle was supposed to defray some of the
costs). NASA has to follow presidential directives, so money started being
sucked out of other programs, including the MSR. The mission was delayed,
first to 2008, then 2011, 2014, 2016, and then just dropped off the radar
(though it remains one of the space community's highest scientific
priorities). So, there I was, stranded with all this hard-won knowledge about
Mars with no project. Rather than forget it all, I decided to make it
available to our students, first as a special topics course in 2007 and then
as a regular catalogue offering (GEOG 441/541) in 2012, 2014,
and again in 2015. GEOG 441 is for juniors and seniors; GEOG 541 is for
GEOG 441/541: The Geography of Mars Class
Student Learning Objectives for GEOG 441/541
- Familiarity with Mars as a richly realized place
- Grasp of deep time in the martian landscapes, most of which date back
more than 3 billion years
- Deeper appreciation of Earth through contrast with Mars
- Understanding of how geographers (I've found at least 100) can and do
contribute to the study of Mars through their work in physical geography,
remote sensing, GIS, and even a few human geography projects
- Ability to reason and formulate testable hypotheses
- Understanding of the power and limitations of remote sensing data
- Practice in mapping Mars, visualizing martian data, and writing
- Some fun looking at how Mars affects human imagination (e.g., the
canals of Mars, radio contact with Mars, the Face on Mars)
Topics in the Geography of Mars Syllabus
- Introduction: science, geography, and Mars
- History of Mars exploration
- Remote sensing basics
- Sources of data on Mars available today
- Mars in space: Mars as a terrestrial planet
- Physiographic regionalization
- Orders of relief
- Processes behind the patterns
- Climatic regionalization
- Human-environment interactions: imagining Mars
History of Earth-Based Mars Exploration: Telescope Era
The telescope era was launched by Galileo in 1609 (though others have a good
claim on the invention of the telescope). Early telescopists were fascinated
by Jupiter and Saturn and there was less exploration of Mars. Francisco
Fontana in Italy (one of those claiming to have created a telescope in
1608) turned his telescope onto Mars in 1636 and made a sketch map of what he
saw: A bright disk with a line paralleling its limb and a "black pill" in the
center. In 1638, he was pleased to report seeing Mars in gibbous phase. The
astronomical community had figured out that a planet beyond Earth, visible
through reflected light, should show gibbous phases because of the angle
between it, the sun illuminating it, and the Earth observer. He drew Mars in
gibbous phase, again with the black pill in the center. The identity of the
black pill has been argued, on the one hand, to be the dark "Blue Scorpion" of
Syrtis Major or, on the other, more likely hand, a defect in his telescope
lens (Fontana saw a similar black pill on Venus).
Huygens turned a telescope on Mars in 1656 and reported seeing nothing but
a blank disk. I wonder if he happened to be looking at Mars during one of its
great planetary dust storms that can obscure the surface entirely. In 1659,
however, he saw and made a sketch of a dark mass, which was almost certainly
the Blue Scorpion of Syrtis Major. The sketch shows a messy triangle, its
point directed downward, to the north in the reversed view of telescopy.
Huygens reported seeing this dark mass move over the course of the night and
inferred that the planet was rotating and its day length was close to that of
the earth. He left another sketch map in 1672, which shows, not only the
familiar dark (Syrtis) mass but an ellipse outlined at the top of the sketch,
possibly the South Polar ice cap.
many sketches of his observations of Mars in 1666.
These sketches show changing dark masses, sometimes linked together with a
dark line or separated by a light line. They also often show as many as four
bright areas, perhaps the polar ice caps and possibly other light albedo
spots, such as Hellas Planitia. He noted that Mars rotated around its own
axis, estimating its daylength at 24 hours and 40 minutes, very close to the
modern figure of 24 hours and 37 minutes.
Herschel built very large reflecting telescopes that were much simplified
in design from the Newtonian reflecting telescopes. In 1783, he was able to
observe Mars with such detail that he could estimate Mars' axial tilt from the
rotation of light and dark areas on the surface (~30°, vs the
modern figure of 25°). Noticing the consistent presence of light spots at
either end of the axis of rotation and their growth and shrinkage, he
explicitly surmised they might be polar ice caps.
In 1831, Wilhelm
Beer and Johann Mädler collaborated to map regularly observed
features on Mars, figuring they were probably fixed geological features. They
transferred these features to a geographic grid they fashioned for the planet,
with a prime meridian in the Meridiani Planum area (hence the name for this
feature). The contemporary areographic grid is based on Beer's
and Mädler's work, the prime meridian passing through the middle of a
small crater, Airy-0, inside Airy Crater. Airy-0 was first spotted in Mariner
6 and 7 images and agreed upon in 1969 as the embodiment of Beer's and
Mädler's prime meridian for Mars.
By 1867, so many details had been seen so regularly that Richard
Proctor decided to assign names to them. He transferred astronomical
drawings by William Dawes onto a stereographic projection and named features
to honor famous Mars explorers of the past, such as, well, Dawes Continent and
Dawes Ocean, Mädler Continent, Beer Sea, Herschel Continent, and Keppler
Land. This idea was appealing to other cartographers, such as Camille
Flammarion, who added more details in the spirit of Proctor, such as
Huygens Land, Fontana Land, Cassini Land, and, er, Flammarion Sea.
This tradition was superseded by Giovanni Schiaparelli, an Italian astronomer
who created several Mercator maps based on observations of the spectacular
1877 opposition. A Mars opposition occurs when Mars and the Earth are on the
same side of the sun, in a direct line with one another. In this particular
one, both planets were at the perihelion side of their orbits, which brought
them within 56 million kilometers of one another. Schiaparelli did a large
number of drawings and, when he transferred the markings to the Mercator grid,
he assigned names for mythical and historical places on Earth, such as
Elysium, Utopia, Arcadia, Hesperia, Arabia, Thaumasia, and Tharsis. He called
the thinner dark streaks seen on Mars by then canali, which can be
translated as "channels" or ... "canals." Guess which translation stuck? And
we were off and running with the first great martian craze: canals on Mars,
which could only imply canal-builders. Schiaparelli bequeathed not only the
first craze through a gain in translation, but his idea for toponymy stuck.
We use a version of his names for various albedo features to the present.
When names for features are proposed to the International Astronomical Union,
they are checked for consistency with the system based on Sciaparelli.
Before I show a couple of the Schiaparelli maps, I'd like to show an
impression of what he and others may have been seeing with the well-developed
telescopes of the time. There remains an amateur astonomer tradition of
observing planets, stars, and other celestial objects and recording one's
observations photographically or graphically. One person who does a lot of
this and transfers his images to the areographic grid is Damian Peach.
Here is one of his maps from 2007, showing south on the top and north to the
bottom, as was normal for 19th century Mars cartographers.
Here is the 1877
Sciaparelli map, done fresh after the great opposition. We see the dark
areas of the 2007 map and the many bright areas. These are, however, bounded
by dark areas and streaks in between them. The modern names are recognizable,
such as Hellas, Elysium, Chryse, Thaumasia, and Tharis. Schiaparelli's
1884 map shows most of the streaks as thinner and fainter than in 1877 and
also more linear.
Schiaparelli's maps just enchanted Percival
Lowell, as did Flammarion's book, La planète Mars et ses
conditions d'habitabilité (1892). Lowell was a wealthy Bostonian,
who'd spent a lot of his youth travelling, kind of a natural geographer. He
came across Schiaparelli's maps and was struck by the concept of
"canali." He secured a site in the American Southwest near Flagstaff,
Arizona, where the air was stable, to build a major astronomical observatory
and equip it with the best instruments money could buy. He spent a lot of his
time there observing Mars and making detailed drawings of his observations.
He drew great swathes of shaded areas and then lots of long, nearly straight,
thin lines criss-crossing Mars in an elaborate spider's web of lineations,
with nodes darkened in at many but not all their crossings. He became
convinced that the lineations he, Sciaparelli, and many others reported were,
in fact, constant features of the martian surface consistent with a canals
interpretation, they showed seasonal changes in width and color (perhaps
riparian vegetation), and they seemed to go from dark areas near the poles
(seas?) to the drier seeming bright albedo areas along the equator.
At the time he was writing, the scientific community had become
increasingly aware of profound environmental changes in Earth's past, such as
ice ages and desertification. Archæology was framing the collapse of
some ancient civilizations to great droughts and the propinquity theory
(concentration of plants, animals, and people on oases in a desiccating Middle
East) for the establishment of farming and pastoralism. Intelligent life on
other planets was a topic of serious conversation. So, Lowell thought that
his observations of lineations looked like the kinds of heroic engineering
that an intelligent species might try in the face of a desiccating planet
seemingly so like our own ancient Middle East. So, at first (1885), he was
within the norms of discourse in the scientific community of his time.
Indeed, he contributed, not only to advanced telescopic observation and
recording of Mars but to the early application of spectroscopy to Mars.
The canals hypothesis began to run into a wall of criticism. Alfred Russell
Wallace pointed out that spectroscopy indicated Mars was stunningly cold,
about -35° F, which would rule out canals of liquid water. Other
scientists reported having trouble seeing canals or any kind of lineations.
As peer criticism mounted, Lowell began to shy away from peer review and went
directly to the public to press his case in books with such titles as Mars
and Its Canals (1906) and Mars, the Abode of Life (1908). He began
to drift into pseudoscience, leaving behind an enduring legacy of science
fiction and a tradition of popular culture crazes about Mars.
The canals or at least lineations Powell discussed endured in cartography as
well. In 1962, Earl C.
Slipher prepared a map of Mars at the behest of the U.S. Air Force, which
was used to plan the Mariner flyby missions of 1965 and 1969. This beautiful
map is replete with faint, narrow, straight shadows.
Contemporary Orbiter-Based Maps of Mars
There now exist several global-scale maps of Mars, based on imagery from Mars
orbiters since Mariner 9 (1971-1972). A great contribution came from the
Viking mission's two orbiters, which carried the Visual Imaging System, which
consisted of a pair of television cameras. These produced overlapping images
40 km by 44 km in surface coverage from 1,500 km up. They yielded nearly
50,000 images with pixel resolution between 150 and 300 m (and some areas were
imaged at 8 m resolution). The results included a digital terrain model and
the Mars Digital Image Model.
Mars Global Surveyor was the first successful mission to Mars after Viking,
operating from 1997 to 2006. Among its instrumentation were three standouts
for the cartography of Mars:
- Mars Orbiter Camera (MOC), which had one narrow-angle high-resolution
camera (1.5-12 m resolution) and two wide-angle lower-resolution (230 m to 7.5
km) regional context cameras, one blue and one red. A
global map of Mars was produced as an interactive portal to access
detailed images of Mars, projected onto a Mercator projection or, as here,
divided into the standard thirty "quadrangles" for Mars, the sixteen
equatorial quadrangles shown in Mercator, the twelve mid-latitude quadrangles
shown on a Lambert-Conformal Conic projection, and the two poles on a Polar
Stereographic projection. By clicking on any of the quadrangles shown here (or here for the Mercator version), you
are taken to a MOC mosaic of that particular region.
Emissions Spectrometer (TES) infrared albedo map. The absorption of
infrared radiation by the basalts that also absorb much of the visible light
spectrum and the strong reflectance of dust that also appears bright in
visible light makes for a gorgeously detailed map of albedo differences.
- Mars Orbiter Laser Altimeter (MOLA), which captured laser pulses emitted
from the MOLA instrument as they reflected back up to MGS. The delay in time
from emission to captured reflection was multiplied by the speed of light to
gauge the distance from the spacecraft to the surface. The result was an
extremely detailed digital elevation model of Mars. During its lifetime
(until June 2001), MOLA took 671,121,600 individual laser pulse
measurements, yielding the most detailed elevation model for ANY planet in the
solar system, including our own! MOLA was the basis of a number of maps.
- The most common representation of the MOLA digital elevation map shows
the extreme elevational contrast of Mars (from 8.2 km below martian "sea
level," or the gravitationally equipotential surface, in Hellas Planitia to
21.2 km above the equipotential datum on top of Olympus Mons) as a hypsometrically
tinted map. The color ramp ranges from black through purple, blue, green,
yellow, orange, red, brown, and beige to white. Dr. Tyner, on seeing this,
commented that it's a "propaganda map" or, more kindly, an example of
"persuasive cartography." No doubt innocently applied, this color ramp feeds
into the discussion of whether Mars ever had oceans. Looking at this color
ramp, the Northern Lowlands and Hellas Planitia fairly scream oceans!
- Another ramp was used in a rendering of the MOLA DEM by Kevin
M. Gill on his Apoapsys
blog. It shows the lowlands in green and the uplands in brown, much like the
hypsometrically tinted elevation maps of Earth. This creates an oddly
Macháček has produced another rendering of the MOLA DEM in
hypometric tints, this time ranging from aqua to brown, muted like the Gill
rendering but still visually persuasive of oceans on Mars.
- Gill did another rendering of the MOLA model, this time in greyscale,
ranging from black to white. This is a lovely rendering, echoing the
appearance of the greyscale in which the MGS MOC and Viking VIS captured
panchromatic images of Mars or images confined to particular bands and yet
clearly indicating the elevational contrasts of Mars.
Hargitai is a prolific planetary cartographer in Hungary, and he has
produced exquisite maps of Mars based on the MOLA DEM and shaded along a color
ramp running from light yellow through an ochre brown. The map conveys the
topographic information provided by MOLA but in tints reminiscent of the
colors on the Mars surface.
- The MOLA DEM has also been represented, not as a contour map
hypsometrically tinted, but as a shaded
relief map, again a stunning visual representation of the planet. The
image is less likely to evoke thoughts of martian oceans.
Geographic produced a stunning map in 2001, which combined the MOLA DEM
with a true-color MGS MOC image mosaic. Here is a link to a version of the National Geographic map with place names.
The U.S. Geological Survey has done geological maps of moons and planets on
behalf of NASA since 1963. Here are geological maps of Mars, the first based
on analysis of Viking
Orbiter images and the most
recent an update including data from NASA's Mars Global Surveyor (1997-
2006), NASA's Mars Odyssey (2001-), ESA's Mars Express Orbiter (2003-), and
Mars Reconnaissance Orbiter (2006-).
The Orders of Relief Scheme
One of my main student learning objectives in the Geography of Mars class is
construction of a vivid mental map of Mars. To develop a sense of Mars as a
place, I decided to present its regions in a (mostly) nested hierarchical
scheme. This is modelled roughly on the Nevin Fenneman "Physiographic
subdivision of the United States" model presented in the Annals of the
Association of American Geographers back in 1916. This idea of nesting
progressively finer areal units in coarser scaled ones has taken on a life of
its own in many introductory geography courses to the present day. On Earth,
the orders of relief scheme might represent the first order as the division
between continents and oceans. The second might be great physiographic
divisions, such as the Atlantic Plain or the Pacific Mountain System. The
third would be geomorphic provinces, such as the Pacific Border Province,
nested in the Pacific Mountain System. The fourth might be Fenneman's
sections, such as the California Coastal Ranges, nested in the Pacific
For Mars, the first order would include the great crustal dichotomy between
the smooth Northern Lowlands and the intensely cratered Southern Highlands.
Another would be the great Tharsis volcanic rise, which occupies about a
quarter of Mars' surface area. The second order is made up of the large,
visually distinctive features that can be used as the framework for a mental
map by allowing easy positioning of other features by reference to one or
another of these features (e.g., "Promethei Terra lies to the southeast
of Hellas Planitia"). Because of their function in framing the rest of
martian geography, they often do not nest tidily within the first order
features. The third order would be large regions, some of them bigger than the
second order features but less obviously distinct. I used the third order to
introduce the martian geological periods and how they are determined by
relative density and sizing of craters. These nest within the first order
features. The fourth order would be smaller features nested within third
order features, comprising landscape scale features. Fifth order features
would be small features at the scale of the landers' and rovers' activities or
the fine-scale imagery from orbiters. These would nest within the fourth
Hoping to improve my presentation of this scheme in the Spring 2015 offering
of the Geography of Mars class, I've been working on maps delineating these
features' boundaries, using broad, fuzzy lines to express the statistical and
geological uncertainty in defining their boundaries. To do this, I used the
MOLA white-brown-red ... blue-black hypsometrically tinted MOLA map as the
base, importing it into an open-source graphics program called GIMP (GNU Image Manipulation Program; I used GIMP
2.6, but 2.8 is now available). GIMP allows line and polygon delineation as
"paths," which can be "stroked" with various brushes, and the stroked lines
saved as separate layers above the background image. These can be hidden or
shown as wanted. Various layers can be made visible, togehter with the
background image, and the visible layers can be output as JPEG or PNG image
files. I eventually used more than 30 paths to define each of the regions at
the first, second, and third orders of relief and displayed them as over 30
stroked line layers. Each path and each layer is named for the feature in
question. If you would like to open this image, first download GIMP, then the
image file, and then open the image file in GIMP. The default mode should
show the Layers, Channels, and Paths toolbox beside the image, and you can use
the layers button (looks like a stack of papers) to open and close various
layers to see the scheme. The image file is at https://home.csulb.edu/~rodrigue/mars/regions/mercatorMOLApaths.xcf.
A Few Online Interactive Map Resources
The Internet has enabled interactive
mapping of Mars. This allows the reader to learn the locations of place
names on Mars and the topography and geology of Mars at adjustable scales.
Here are a few to get you started on your own explorations of Mars: