Martian Map Quest
Winds of Time
Mars Global Surveyor has been orbiting the red planet since Sept. 12, 1997. The mission has examined the entire Mars surface and provided a wealth of information about the planet’s atmosphere and interior. A new batch of high resolution photos, taken between February and July 2002, were added online this month and they bring the total number of images in the online gallery to more than 123,800. The images are available from the Mars Orbiter Camera Gallery.
|This composite of MOC daily global images, acquired in early May 2002, shows what the planet looked like in early northern spring. Click for global animation . Credit: NASA/JPL/Malin Space Science Systems, Caption by: K. S. Edgett and M. C. Malin, MSSS|
The martian map quest offers not only a close view but also has guided the selection of optimal sites for a slew of landing rovers planned to launch in the next few months. Although Mars’s diameter is only about half that of our home planet, it has as much surface land mass as Earth – because it’s all land mass. This poses a mapping challenge not unlike mapping all the Earth from orbit, in hopes of finding a safe harbor.
Evaluation of landing sites for two Mars Exploration Rover (MER) missions, due to launch around early summer, has relied heavily on these orbital camera views for mineral mapping, detailed imagery and topographic measurements. Scientists and engineers have whittled down an initial list of dozens of candidate landing sites to four finalists. Of these four, two are clear favorites among the scientists: Meridiani Planum and Gusev Crater. The final decision, which will be made by Ed Weiler, NASA’s associate administrator for space science, is expected this month, just weeks before the first of the two MER spacecraft is scheduled for launch. Both rovers will touch down on Mars in January 2004.
"The extraordinary wealth of information contained in this unprecedented release of new views of Mars attests to the ongoing scientific value of the reconnaissance of Mars that has been provided by Mars Global Surveyor for the past five years," said Dr. James B. Garvin, NASA’s lead scientist for Mars exploration at NASA Headquarters, Washington, D.C.
Windy and White Capped
In many of the 11,664 new pictures being posted on the Internet this month by the camera team for NASA’s Mars Global Surveyor mission, the winds of Mars leave their marks. To verify what the camera shows, computer models have tried to predict possible wind patterns on Mars. In preparation for final landing selections over the course of the next month, these computer-simulated landing scenarios will be run repeatedly. If these simulations turn up an unexpectedly high risk of failure – for example, if the terrain at one of the sites is deemed too rough to land safely, or if models of Mars’s air circulation indicate that high winds might cause the spacecraft to crash – Meridiani or Gusev could be replaced by one of the two alternate sites, most likely the site at Elysium Planitia .
As one example of how alien weather looks to mission planners, many orbital images show the sculpting effects of martian winds and a consequently modified landscape. The pattern of sand dunes on a patch of southern-hemisphere desert resembles scales on a fish (image lower right).
On a larger scale, full-globe Mars images show wispy water ice clouds shaped by winds as the seasons change.
Other new images reveal details of features such as gullies, landslides and seasonal frost. Because the ultimate goal of Mars exploration is to look for signs of life, one priority would be to find areas where water flowed over long periods of time, either continuously or episodically; or where water ponded for long periods of time, such as in a lake.
Frosty North Pole
The retreating north polar seasonal carbon dioxide frost cap (image upper right) is seen at the top of Mars. Other white features in the image are clouds of water ice crystals in the martian atmosphere. The Martian atmosphere is about 1% of Earth’s total (sea level) pressure and presently is 95% carbon dioxide.
The left half of the global picture shows the Tharsis region, which includes several very large volcanoes. Olympus Mons, the largest martian volcano, is as wide as the Hawaiian Island chain is long; it is the dark, somewhat circular feature at the far left. As the largest volcano in the solar system, Olympus Mons, is 16 miles high, or 100 times larger than Mauna Loa in Hawaii. Toward the lower right, the system of deep Valles Marineris chasms can be seen. The Valles Marineris canyon covers one-fifth of Mars circumference, 9 times longer than the Grand Canyon in Arizona.
Limb to Limb
The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) red and blue wide angle cameras provide daily coverage of the planet "from limb to limb." The "limbs" are the edges of the planet as seen to the west and east of the spacecraft. Depending on weather conditions, clouds or haze can sometimes be seen above the limb. This picture (upper left image) was taken by the blue camera in December 2002. It is an oblique view looking westward across heavily cratered terrain at high southern latitudes. A thin line of haze, high in the martian atmosphere, can be seen above the planet’s surface. The view of craters in the foreground is enhanced by the presence of bright, winter-time carbon dioxide frost. The darkness above the limb is outer space.
"Indeed, there remain new discoveries to be made about the history of water, climate variability, and character of future landing sites from the continuing flow of images, spectra, and related information from the Global Surveyor," Garvin continued. "Without the new perspectives provided by Mars Global Surveyor, the critical scientific and engineering assessment of potential landing sites for the Mars Exploration Rovers would not have been possible."
The Mars Orbital Camera experiment on the Global Surveyor is in excellent health and continues to return a wealth of new information every day. The Global Surveyor will support the planned landing missions by observing the sites and monitoring the weather on Mars.
The Jet Propulsion Laboratory, Pasadena, Calif., manages the mission for NASA’s Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena. JPL’s industrial partner is Lockheed Martin Astronautics, Denver, which developed and operates the spacecraft. The Mars Orbiter Camera is operated by Malin Space Science Systems, San Diego.