Copyright © 2008 by Jim Secosky. Published by the Mars Society with permission A GOOD WAY TO LEARN ABOUT MARS: USE MARS SATELLITES Jim Secosky email: [email protected] Website: Red Planet Trek: http://paws.flcc.edu/~secoskjj ABSTRACT NASA has allowed amateurs to suggest areas to be imaged with Mars satellites. From 2003, until contact was lost in the fall of 2006, amateurs picked sites to be photographed with the Mars Global Surveyor (MGS) under the public target program. In 2007, elementary, high school, and college students from around the world started to direct NASA to places to focus on with the powerful HiRISE on the Mars Reconnaissance Orbiter. Jim Secosky, a retired science teacher and amateur user of HST, suggested thousands of places to explore with MGS's Mars Orbiter Camera (MOC). From the over 500 Jim received, he has put together a series of images that illustrate many geological features. Key Words: Mars Global Surveyor, Arabia, layers, gullies INTRODUCTION The Mars Global Surveyor was launched in 1996 and finished its mission in 2001. In August 2003, after receiving 120,000 images (about 3% of the surface), NASA started to allow amateurs to suggest areas to be imaged with the Mars Orbiter Camera (MOC). By the time contact was lost with the spacecraft in November 2006, over 250,000 images had been taken, 4,000 suggestions were made by amateurs and about 1,000 images under the public target program were received. MOC took content images and high resolution images of three sizes. The image footprint was approximately 1 or 2 miles wide and about 6, 11, or 26 miles long. Amateurs suggested places to look at that showed most of the major features of Mars including dust devil tracks, layers, buttes, canyons, volcanoes, patterned ground, sand dunes, gullies, and possible glacial features. OBSERVATIONS Figure 1-MGS wide angle image showing ice cap and volcanoes. To give us some perspective, figure 1 shows some well-known major features. At the top is the northern ice cap. Olympus Mons, Alba Patera, Ascraeus Mons and Arsia Mons are the major 1 volcanoes on the Tharus Rise. Olympus Mons is three times higher than Earth's Mount Everest. Below Ascraeus Mons is a region of intersecting canyons knows as Noctis Labyrinthus or the labyrinth of the night. Just to its right or east the famous Valles Marineris begins. Figure 2-- MOLA elevation map This brightly colored map was done with a laser on the MGS. White represents the highest altitude, while dark blue the lowest. The high spots are volcanoes. Besides the volcanoes of the Tharus Rise, another smaller group of volcanoes are found with Elysium Mons. The deepest area, Hellas, represents a large impact. The Valles Marineris is a deep canyon, probably caused by tectonic forces from the great load of the Tharus Rise volcanoes. The highland/lowland dichotomy shows as a large difference in elevation between the northern plains and the southern highlands. Besides displaying a boundary in elevations, it is a boundary in surface ages. The southern highlands for the most part show a high density of impact craters. The older a surface is the more craters it will have. The northern plains are smooth with few craters so they are thought to be young--Amazonian in age. The south is an old surface called Noachian in age. In between the two great time periods is the Hesperian, named for the region to the northeast of Hellas. This display of Mars is often used; it has zero degrees longitude at the far left with the other lines of longitude being so many degrees east. HiRISE and the Mars Express both use this system of longitude. To the right of Olympus Mons are three large volcanoes in a line. Pavonis Mons, the middle one, sits right on the equator, thereby providing an easy reference to the location of the equator. Notice how Arabia has an old surface with many craters, yet has a lower elevation than the heavily cratered southern highlands. It is an interesting place. I suggested many areas for MGS to image in this region. It seems to have layered formations scattered throughout. Layers can be formed from volcanic processes, wind, or even under water. I was interested in tracing possible lakes and seas from the past, since life may once have thrived there. 2 Figure 3 --map made by Malin Space Sciences using MOC on MGS This map with visible colors has zero degrees in the center. Longitude is sometimes measured west of this line. Syrtis Major is a very dark feature easily visible with backyard telescopes. Notice Arabia is quite some distance from the bulge of Olympus Mons. Some have suggested that Arabia was an old impact that was subsequently uplifted as an isostatic adjustment to the mass of Olympus Mons. Others have suggested that it was formed from a great impact that struck the northern region on an angle. Just to the north of Arabia lies Ismenius Lacus, an area having vast reaches of so-called frettered terrain. Two bands located 30-40 degrees north and south of the equator are where most gullies have been discovered. Gullies that are found on steep slopes may be caused by recent flows of liquid water. 3 Figure 4--Lee, Bell, Wolff photo showing Arabia up close Throughout Arabia layers of rock have been found. The infamous "Face of Mars" is found at the upper western edge of Arabia in an area called Cydonia. Figure 5--The "Face" on Mars This feature looked just like a face in the Viking photos back in 1976. A more detailed view with the MGS showed it to be just an eroded plateau. 4 Figure 6--various views of image R19-01445 of the public target program. The image in the upper right was part of an image suggested by an amateur astronomer under the public target program. The R of the identification number denotes the mission phase. This image was number 01445 taken in month 19 of the R mission phase. The context image in the upper right contains a rectangle that shows the image footprint for the high resolution image. Other photos show parts of the high resolution blown up. Note the many layers. Some may be due to an ancient lake. The sequence for this formation would most likely be a large impact crater followed by the deposition of many layers in the crater and perhaps above it. Later erosion removed all but the small buttes in the center of the crater. In other words, these layers probably filled the entire crater. Recently, HiRISE imaged this general area and revealed many more layers (PSP_008520_2085). 5 Figure 7--images S21-00038 and S21-00037 from Malin Space Science Systems/NASA Inside a crater over 1,000 km away lays another butte that contains many layers similar to those of the previous picture. Again, these layers may have formed from lake or sea deposits. Since layers are seen so far away from each other the conditions for lakes may have been widespread in Arabia. Figure 8--image S07-00496 from Malin Space Science/NASA About 1,000 km from the previous two sets of layers, this group of layers does not lie inside of a crater; rather it is between craters, so there was something about Arabia that caused layered deposits to form. 6 Figure 9--map of Arabia produced by U.S. Geological Survey. This map made from Viking photos shows the locations of the three sets of layered terrain. Extensive layered areas also are found in Henry and in craters just to the left of this frame. Also, of interest is the report of the detection of methane just to the left or west of the bottom. Methane has been reported from three locations on Mars. Methane should not last on Mars, so if these reports are validated, microbes may be producing the methane. The small, colored rectangles on the map represent image footprints for MGS high resolution photos. They are one or two miles in width and 6, 11, or 26 miles long. In the public target program one had to carefully avoid areas that had been photographed already. One had to have a very good reason to reimage a location. When I choose suggestions for the program, I often viewed the Viking maps in pieces 5 degrees square, looking for interesting features or things that looked different. 7 Figure 10--S02-00191, fretted terrain north of Arabia Just north of Arabia lays a vast region of fretted terrain, named for elongated features that resemble wrinkles. Fretted terrain contains large cliffs with wide, flat canyons. It is thought that as ice in the subsurface disappears by sublimation the material just crumbles. At the low Martian atmospheric pressures and temperatures ice does not melt; it just goes directly into a gas. The image footprint shows an attempt to view the cliff edge at high resolution. Figure 11--cliff in S02-00190 This is a high resolution view of part of the cliff in the previous photo. Estimated at over one half mile high, this cliff would look amazing if you were standing at the base. Earth's Grand Canyon is just twice as tall this cliff. Maybe someday people will fly around cliffs like this on Mars, just as people fly over the Grand Canyon. 8 Figure 12--Phoenicis Lacus with Noctis Labyrinthus Just south of the equator sits a vast system of interlocking canyons called Noctis Labyrinthus. This view is on a Viking map. The high resolution view will be at the end of the arrow.