MOLA: Background Persons using this investigation will need to understand topography. Mapping skills such as the latitude/longitude grid system used on Earth, will transfer to this Mars based activity. The math concept of ratios will be utilized. You will need to know about water erosional processes, faulting , volcanism and some tectonic surface events. In the following sections we will go over specific topics pertaining to our exploration of Mars. Note: On Earth we refer to geological processes, or geomorphology. "Geo" of course is the prefix referring to Earth. Naturally, "geo" should not be used to reference Mars. It will be a hard habit to break. "Ares-" should be used, producing terms like areography- the study of the surface features of Mars, which is our task in this investigation. The Mystery The planet Mars is one half the size of Earth with only one quarter of Earth's surface area. The gravitational force on Mars is one third of Earth's. By contrast the areological features are gigantic. Olympus Mons, the largest volcano known in the solar system, stands 26 km, or almost 3 times the height of Mt. Everest. Canyons, valleys, craters, out-wash flows, any surface feature is larger on average on Mars than Earth. The mystery science seeks to solve is why? How did these structures form? The forces and events must have been tumultuous. But where are the dynamics than shaped Mars's surface, now? Today Mars shows no sign of tectonic plate motion, no volcanism, and no running surface water to produce erosional features. The dynamic Earth continues to exhibit these forces. If we are to compare Earth and Mars, we must learn much more about the historical "geology" which took place on both planets . Our satellites and landed robotic probes, now and in the future, collect information which may lead to answering this exciting mystery. New understandings of Martian history are being written today, as a steady stream of information pours back to us. A new view of Mars is forming. Is this view of Mars we now see, a picture of Earth's past, two billion years ago, or is it Earth's future? Here Mars Global Surveyor is being lifted from a shipping container at the Space Simulation Lab. Note the round structure. This is the telescope of the MOLA instrument. Mars Global Surveyor Homepage Tutorial Topics: MGS - Mars Global Surveyor Launched in November 1996, the space craft traveled for 10 months to reach Mars followed by a year of positioning. In March 1999 its mission will officially begin. The Mars Orbiting Camera - MOC, will produce a photographic record and MOLA, the Mars Orbiter Laser Altimeter, will map the Martian topography. MGS will fly around Mars in a near circular orbit at an altitude range of 375 km to 445 km above the surface. The orbital period will be 117 minutes, repeating approximately every 7 Martian days. MOLA - Mars Orbiter Laser Altimeter An altimeter measures altitude, the height a plane or satellite is above a planet's surface. A laser altimeter uses focused light pulses to do the same. MOLA's solid state laser fires short pulses of infrared light 10 times per second at the surface of Mars and measures the time for the reflections to return. Upon return to the satellite, a telescope focuses the light scattered by the terrain and possibly clouds, onto a series of detectors. By knowing the speed of light, the satellite's position and its height above the planet, one can map the surface based on the return time of the pulse. The heights of mountains and the depths of valley's will be revealed to a precision of 40 centimeters. Laser altimeters have a small footprint on the planet's surface. MOLA's beam is only 130 meters wide. Each track along the planet's surface measures elevation continuously. See a diagram of MOLA First MOLA pass provided improved accuracy of Martian topography. Profiles of first 18 MOLA passes. Viking Missions to Mars In 1976 two space craft were sent to map Mars and then land to take surface pictures and conduct tests. These were Viking I and II. Prior to these missions the Mariner 9 craft was sent to the planet on a mapping mission. Mariner images where used to select Viking landing sites. Viking images became the basis for determining the landing site of the Mars Pathfinder in 1997. They were made by way of radar altimetry. While there are many forms of radar altimeters, they differ from laser altimeters in two ways; their footprint is large - tens of kilometers across images are overlapped and the results averaged Another distinguishing factor between radar and laser refers to the electromagnetic spectrum. Recall that wavelengths shorten toward the gamma ray end and length on the radiowave side. Radar altimeters most often operate in the high microwave bands and laser altimeters in infrared wavelengths. Greater detail can result by use of a shorter wavelength. Vertical Exaggeration In our investigation we will be working with topographic data returned from the MOLA instrument. Data sets are often compressed horizontally so they take less space and graph more easily. We will need to keep this in mind. The graph, (right - click for detail) serves as an example. Note the V.E. 100:1. This ratio means that the vertical is exaggerated 100 times for each unit on the horizontal. For example track 24 has a huge spike structure. This is actually the profile of Olympus Mons. This broad based shield volcano returns to its true shape when you add 100 units to the horizontal for each 1 on the vertical scale. Scale of Profiles Another item to remember when working with graphs is to watch the scale on the y-axis. As one decompresses the data, each zoom in, changes the scale. On the graph above, each y-axis tick mark represents 1,000 meters. On the graph above, each mark stands for 100 meters. Note on both profiles that latitude is represented on the bottom. While not labeled, the longitude is displayed at the top. Note the zero on the first profile's y-axis. This represents the "areoid." On Earth the "geoid" is the hypothetical mean elevation of Earth's surface, which coincides most of the time with mean sea level. For a planetary reference point on Mars, science calculates the areoid. To express it simply, it's an average of the highest and lowest elevations. Negative values on this axis is below the areoid It is a lowland, but does not mean below sea level. It does not correspond to "what the sea level was when Mars had an ocean." Basics of Mars Erosional and Tectonic Features Our point of reference for the study of Mars will be Earth features. Alluvial Fan (side view) Normal Fault (side view) Escarpment (side view) Slumping: This excellent image from the camera on the Mars Global Surveyor show just how powerful erosional forces are. the cliff face you are seeing is a little over a mile in height. Considering that north is at the top of the page, the trend of the cliff slope runs NW to SE, while the cliff (escarpmant) itself faces SW. The recessed area of the escarpment was the result of slope faliure or “slump”. Look closely at the bottom of the escarpment at the material that once made up the actual slope. Another interesting aspect of this image is the difference in appearance between the SE portion of the slope and the NW area. What do you think some reasons for this are? Sheild Volcano: Olympus Mons is the largest volcano on Mars. This shield volcano, similar to volcanoes in Hawaii, measures 624 km (374 mi) in diameter by 25 km (16 mi) high. It is 100 times larger than Mauna Loa on Earth. Located on the Tharsis Plateau near the equator, Olympus Mons is bordered by an escarpment. The caldera in the center is 80 km (50 mi) wide and contains multiple circular, overlapping collapse craters created by different volcanic events. The radial features on the slopes of the volcano were formed by overflowing lava and debris. Valles Marineris is Mars' largest canyon system The entire system extends over 4000 km (2490 mi), covering about one fifth the circumference of Mars. Some parts of the canyon run as deep as 7 km (4 mi) and as wide as 200 km (125 mi). Compared to Valles Marineris, the Grand Canyon on Earth seems quite small at 446 km (277 mi) long, 30 km (18 mi) wide and 1.6 km (1 mi) deep. If Valles Marineris was placed on the surface of Earth, it would stretch from Los Angeles to the Atlantic coast. Channels are among the more puzzling and intriguing features of the Martian surface. The most controversial aspect of the channels is whether they were formed by running water. Present climatic conditions on Mars prevent the existence of liquid water at the surface, so a water worn origin implies that very different climatic conditions prevailed in the past. A denser atmosphere and higher temperature are both required. Because of the difficulty in explaining how climatic conditions could have changed so drastically, alternative methods of erosion, such as by wind and lava, have been suggested. Three main types of channels have been recognized: (1) runoff channels appear as dendritic networks, or arrays of relatively small channels or valleys located mainly in the old, densely cratered terrain; (2) outflow channels ap pear as large scale tributaries; and (3) fretted channels appear as long, rela tively wide, flat floored valleys that possess tributaries and increase in size downstream. Return to the MOLA Index

The Caves of Mars Project is funded by a NIAC Phase II Grant from the NASA Institute for Advanced Concepts.
Copyright © 2002-04 - Complex Systems Research; Inc.