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In Search of Valles Marineris

by Richard Orr, a customer of C-7 who owns an Astro-Physics 155mm EDF.

Used by permission of the author, this appeared in Oct. 1998 "Mason-Dixon Astronomer"
Vol 16, Issue 7, July 1999 - the newsletter of the Westminster Astronomical Society of Maryland. It has to do with finding Valles Marineris (largest canyon complex in the solar system) on Mars using the 155mm and an 8mm Radian -- a real challenge.

In 1969, I saw Yosemite Valley for the first time. The great U-shaped, glacial-cut valley with its glistening two to three thousand foot white walls and free falling waterfalls made quite an impression on this young teenager. Many following spring vacations were spent climbing the great granite walls of Yosemite Valley.

In 1973, I saw the Grand Canyon for the first time. Nothing had prepared me for the view from the North Rim. Stretched in front of me was a 217 mile long canyon carved by the mighty Colorado River. The river was a mile below and the South Rim nine miles away as the crow flies. It was incomprehensible. Even after numerous hiking trips into the canyon, rafting the full length of the canyon, and even mapping some of its largest caves, I still am overwhelmed when I return to the Grand Canyon.

In 1979, I stood at the edge of a 1,000 mile long section of the Great Rift Valley in East Africa. Where I stood, the tearing of two continental plates way from each other had created an eerie surrealistic moon-like landscape, unlike any other on Earth. I could almost feel the continent ripping itself apart.

But the biggest prize was, I thought, forever beyond my reach. When I was young I dreamed of visiting Mars, but as time passed so did the hope that I would ever physically leave Earth. And it is on Mars that the largest canyon complex in the Solar System resides. To stand on the north rim of Valles Marineris, a canyon complex so large that you would not be able to see the south rim due to its great expanse and the curvature of the planet, would forever remain only in my dreams.

As all amateur astronomers know, you do not need a spaceship to travel the heavens. However, the question remained was it possible to see Valles Marineris in a moderate-sized telescope?

Mars boasts the largest volcanoes in the Solar System. Olympus Mons, the largest, covers an area the size of Arizona. The great Martian canyon and the giant volcanoes (Olympus, Ascraeus, Pavonis, and Arsia Mons) of the Tharsis dome are linked in origin. When the up welling of magma from the Martian interior raised the Tharsis dome (which in turn provided the fuel for the great volcanoes which sit on top of it) the surface area surrounding the dome was stretched. The pull from the raising dome proved too much for the Martian crust at its eastern end causing a series of large faults which collapsed to form a canyon complex unmatched anywhere else in the Solar System. The final touches to the great canyon system was sculptured by landslides, wind, and running water.

This great east-west complex of canyons known collectively as Valles Marineris runs from the tortured landscape of Noctis Labyrinthus near the summit of the Tharsis bulge and ends at the western edge of Margaritifer Sinus. In doing so, the 2,480 mile length canyon, with an average depth of nearly 4 miles, spans a fifth of the planet,s circumference.

The Viking Orbiter Spacecraft was the first to identify Valles Marineris for what it is, but it was not NASA scientists which first saw it. For on the classical maps of Schiaparelli (1877) and Antoniadi (1896) the exact location of Valles Marineris, at least in part, was drawn as a thick canal located just north of Solis Lacus (the eye-of-Mars) and labeled as Agathadaemon. [Agathadaemon is a minor mythological Greek deity of good fortune that had the form of a serpent. From what I can find out, back then pet snakes were believed to be reincarnations of the family,s ancestors and were considered lucky.]

A thick nodule in Agathadaemon called Tithonius Lacus was also included on their maps which closely matches the widest and deepest section of Valles Marineris. Viking showed that Tithonius Lacus was really three huge parallel canyons named Ophir Chasma, Candor Chasma, and Melas Chasma. If I could observe through my telescope the classical albedo markings of Tithonius Lacus and/or Agathadaemon, I too will have seen the great canyon system -- the search was on.

Mars and I are old friends. When Mars comes into view all other celestial objects seem to become secondary. By the time this years Mason-Dixon Star Party had arrived, Mars was already well passed opposition and was noticeably shrinking in size from week to week. Although, I had accumulated a dozen or so 1999 drawings of Mars previous to the Mason-Dixon Star Party, Tithonius Lacus and Agathadaemon had yet to be seen.

On the first evening of the star party, I had planned on going to the scheduled evening talks. But Mars was holding enticingly steady in the evening sky. Since atmospheric stability often decreases as evening progresses, I decided to forego the talks and focus on Mars. In my 155mm refractor, using a 2.5x Barlow, and an 8mm Radian, the planet,s disk was holding surprisingly still at 341x. I observed (and drew) Mars from about 9:15 to 10:15 EDT. After which the planet quickly became orange mush as the stability of the sky decreased.

Solis Lacus was obvious. In fact, people asking to look through the refractor at the star party had little problem seeing the eye-of-Mars, the North Polar Cap surrounded by a gray band, and the bright South Polar Hood -- even without any filter. Less easy, but not really difficult, using a red #25 filter, was my prize Tithonius Lacus. In addition, during brief periods of clarity at the eyepiece I could make out Agathadaemon running from the east end of Tithonius Lacus and connecting to the west end of Aurorae Sinus. I was seeing nearly a quarter of the total length of the great Martian canyon system. Success.

My daughter (3 years old), or my son (11 months), or possibly a descendant of theirs, may someday stand at the edge of Valles Marineris and view the Martian canyons as I would have liked to have see them. All I can do is seed their interest. I can tell them about my visits to Yosemite Valley, the Grand Canyon, and the Great Rift Valley. I will also show them an old drawing that I did back in June of 1999, at the Mason-Dixon Star Party, and point out that that small insignificant looking smudge line under the eye-of-Mars represents the largest, most impressive canyon, known to man.

If I'm lucky, they might throw a rock into the canyon for me.

Richard L. Orr


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