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A montage made from images culled from my "Mars Image Gallery" of the Great 2003 Apparition. These images were taken between April 5 and August 27, 2003 and are made to the same image scale. Mars came closer to Earth than it has been in over 50,000 years. From Albuquerque, Mars never became higher than about 40 degrees altitude. However, I was still able to obtain some good images when seeing allowed. Note the shrinking South Polar Cap as Mars' southern hemisphere Approached mid-Summer. Mars is a fascinating planet to observe. Besides the Earth, it is the most hospitable planet that we know of. Unfortunately, Mars is usually distant and difficult to observe because of its small apparent size. It makes closer approaches to Earth every two years and even during the most favorable apparitions, it rarely exceeds about 25 arcseconds in diameter. Even so, during these close approaches, a wonder of features can be observed including aspects of Mars' unique geology and weather. The ice caps change size as they respond to the seasons. MARTIAN GEOLOGY Mars is a rocky planet with a complex geology. The surface is a ligh orange color and marked by darker splotches. The light areas usually correspond to a thin blanket of bright dust. Dark areas are thought to represent areas of exposed bedrock. The red color of Mars is due to the abundance of iron oxide, or rust, on the surface. This color itself may owe itself to the abundance of water in the primordeal Mars or may be oxidized meteoric dust. The Martian surface can be divided into two parts: the Southern Hemisphere is dominated by an ancient, heavily cratered highlands and the Northern Hemisphere is covered by a younger, relatively smooth and crater-free lowland plain. In addition, there are two volcano-tectonic complexes. The largest of these is the Tharsis Plateau. Tharsis contains several huge volcanoes including Olympus Mons, the largest volcano in the Solar System. The smaller volcano-tectonic complex is developed in the Elysium region. Olympus Mons is a shield volcano about 550 km (330 miles) across and over 20 km (12 miles) in height. Three other of the giant volcanos of Tharsis form a line and are, from south to north, Arsia Mons, Pavonis Mons, and Ascraeus Mons. To the east of the Tharsis Plateau is
the huge canyon complex Valles Marinaris. Huge outflow channels originate in the
canyons and empty into the southern
The highland areas are heavily cratered
and preserve two large impact structures:
Ice Caps Mars has a thin atmosphere, composed largely of carbon dioxide. About 20% of this CO2 freezes out at the poles. As the ice at the summer pole sublimates, a significant portion of the atmosphere migrates to the opposite pole to freeze at the winter pole.
Orographic Clouds Bluish white condensation clouds made of ice particles often form over elevated regions in the Tharsis region. These often occur in the mornings or evenings as moist are from low regions blow up and over the high peaks.
Morning Clouds and Polar Hood Ice particles condense in the evenings and continue to linger for a short time after sunrise. This gives rise to thin, whitish or bluish clouds near the morning terminator. Ice particles also condense over the winter poles creating a polar hood.
Dust Storms
Making Observations of Mars Mars has a high surface brightness and is bright in infrared. Red and infrared (IR) light penetrates the thin atmosphere and reveals the most of surface detail. Dust storms are opaque to red and IR and appear bright in red light images In blue light, the Martian atmosphere is less transparent. Water clouds, probably composed largely of ice crystals, appear bright in blue light. The polar regions are often shrouded by bright polar hoods. Orographic clouds over high topographic features are also often apparent near the sunrise or sunset terminator. Mars has a small apparent size, even during its closest approaches. In order to capture the maximum amount of detail, many imagers use high focal ratios of f/30 - f/80 to capture the most detail through oversampling. An IR blocker is required to prevent infrared light from leaking through the red and blue filters of the standard color webcam and registering on the CCD.
Martian Satellites - Deimos and Phobos The small moons of Mars are difficult to observe visually because of their proximity to the overwhelming brilliance of Mars. They can be detected more easily with a CCD camera.
Links Association of Lunar and Planetary Observers (ALPO), Mars Section British Astronomical Association (BAA), Mars Section Communications in Mars Observations (CMO) Books "The Smithsonian Book of Mars" by Joseph M. Boyce, Smithsonian Institution Press, Washington, 321 pp. 2002. "The New Solar System" edited by J. Kelly Beatty, Carolyn Petersen, and Andrew Chaikin, 421 pp. 1999. |
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All images are copyrighted by Thomas Williamson. No images may be used
without permission.
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Mars had an apparent diameter of only 9.5 arcseconds when this
image was obtained on December 17, 2003 (01:31 UT). It shows a large dust storm
first observed on December 13, 2003. The storm was easily visible through the
eyepiece. 8" f/7
newtonian and Philips ToUcam webcam.
Mars three days after the one above (December 20, 2003, 00:49 UT) reveals the
continuing but subsiding dust storm.
