By: Jeff Beish, Former A.L.P.O. Mars Recorder
What may be the first Martian topographic relief features ever identified from Earth, or from near Earth, has been found by Leonard Martin at Lowell Observatory's Planetary Research Center and Jeff Beish, Former A.L.P.O, Mars Recorder. These may be the first topographic features identified since the Viking Orbiter stopped sending data back to Earth in November 1982. Now, the Hubble Space Telescope has imaged the Red Planet near opposition in February 1995 containing an identifiable topographic feature on Mars (see Figures 1 and 2).
Figure 1. A CCD image of Mars with exploded view inset
reveals a topographic relief in the exact position of Elysium Mons. The
arrow points to a bright feature of the sunlit slope of the volcano with
a shadow to the terminator side of Marsí limb. Image taken from the left-hand
image of PR95-17 ST Scl OPO HST labeled Tharsis Region 160°
Longitude. Bottom inset is an image of Elysium Mons taken by the Viking
Orbiter- I spacecraft during the Viking Space Mission to Marts during the
period from July 1976 throughout November 1982. Image by NASA.
To illustrate that the HST image of the apparent volcano Elysium Mons Figure 1, bottom inset, reveals the volcano as seen from the U.S. Viking Space Mission to Mars during the period from July 1976 throughout November 1982. Notice the bright escarpment and following shadow towards the terminator of Mars.
To identify a topographic relief on another Solar System body, such as the Moon or Mars, one must be able to see sunlit wall, cliff, slope, escarpment, and/or a corresponding shadow. For instance, a Lunar crater with the right lighting conditions may show a bright Sunlit wall or rim and a shadow on the opposite side of the wall or rim and the reverse on the other side of the crater.
A Martian volcano would appear as a triangular slope with a corresponding shadow on the opposite side from the Sun. This would appear similar to a Lunar dome or a steep Lunar mountain, except domes are usually rounder in shape.
The 500-km wide Elysium Mons is located at 213.° 5W, 25° N and stands 9-km high over the Elysium Planitia. This volcano has steeper slopes than the other large volcanoes, such as those found in the Tharsis region of Mars. The very large volcanoes Olympus Mons and Arcia Mons are very flat, appearing like giant cow patties and would not cause much of a shadow or sunlit slope. Ascraeus Mons and Pavonis Mons have steeper slopes and may be revealed in HST images in the next apparitions of Mars.
The 23-km high volcano Ascraeus Mons, located at 104.° 3W, 11° N, is 400-km wide and is one of he largest volcanoes in the Tharsis region of Mars. The phase terminator appeared to be just right to identify these two volcanoes described above. During the next apparitions of Mars, the planet will be larger and we hope topographic relief of the Red Planet will be identified.
The author feels that observing these features on Mars
from ground-based telescope is impossible and will not be practical in
our life times. The Hubble Space Telescope is the finest astronomical observing
instrument ever constructed.
Figure 2. A CCD image of Mars with exploded view inset reveals a topographic relief in the exact position of Ascraeus Mons. The arrow points to a bright feature of the sunlit slope of the volcano with a shadow to the terminator side of Marsí limb. Image taken from the center image of PR95-17 ST Scl OPO HST labeled labeled Valles Marineris Region 60° Longitude.