MGS has been an astonishing, overwhelming success. It has dramatically altered our conception of what Mars is all about. Yet it has not received anything like the acclaim and renown that was heaped upon Pathfinder. Why not? Is it because there was a long delay between the arrival of MGS at Mars and the beginning of its true scientific mission? Perhaps. Is it because the "cutesy coefficient" of MGS is not considered to be high, and there is a perception that the public cannot fully appreciate the beauty and majesty of fundamental scientific discoveries? Whatever the reason, the outstanding accomplishments of MGS have not generated the ballyhoo that accompanied Pathfinder. That’s a shame. MGS is a valiant, unsung hero that will forever remain a key linchpin in the history of the exploration of Mars. The amazing treasure-trove of data acquired by MGS, including over 50,000 images already taken by the Mars Orbital Camera (MOC), will stimulate new and original insights into the nature of the Red Planet for years and years to come.

There was considerable doubt, shortly after MGS entered orbit around Mars in 1997, that the mission would ever meet even a small percentage of its scientific objectives. The original mission profile contained a four-month period of extensive aerobraking following Mars Orbit Insertion (MOI), after which the main scientific mapping mission would begin in early 1998. This aerobraking, a comparatively new technology that essentially uses repeated dips into the upper atmosphere of Mars to remove energy from the orbit, would change the highly elliptical orbit achieved after MOI into a near circular orbit optimized for scientific observation. After the first month of aerobraking, however, the mission engineers discovered that one of the two MGS solar panels, the same panel that had been slightly damaged shortly after launch, had bent dangerously backward during its initial passes through the atmosphere. Aerobraking was discontinued temporarily by lifting the low point, or periapsis, of the orbit out of the Martian atmosphere. The MGS team then spent several weeks both analyzing the health of the ailing solar panel and restructuring the entire aerobraking activity.

To minimize the stress on the damaged solar panel, the new MGS mission plan limited the depth to which the spacecraft would dip into the atmosphere during each of its aerobraking passes. This change reduced the amount of energy that would be removed from the orbit with each pass, thereby considerably extending the total length of the aerobraking activity and making it impossible to achieve the proper orbit for scientific observations on the original mission schedule. The new mission plan that was developed divided the remaining aerobraking into two long, distinct phases, approximately a year in combined duration. These two aerobraking phases were separated by a six month period during which the MGS spacecraft acquired some science data, from a decidedly non-optimum orbit, while celestial mechanics governed the drift of the spacecraft orbit into a proper position with respect to the Sun. Finally, in late March of 1999, the spacecraft reached the science observation orbit for which it had been originally designed.

Since April 1, 1999 the Mars Global Surveyor has acquired valuable scientific data on nearly all of its over 7.000 orbits around Mars. The harvest of data is a veritable feast for planetary scientists. With the entire suite of instruments working together, MGS is able to treat Mars as a system, drawing broad inferences from the simultaneous measurements. Imaging acquired by the three MOC cameras can be compared with same site topographic data obtained from the Mars Orbiter Laser Altimeter (MOLA), as well as mineralogical information deduced from the observations of the Thermal Emission Spectrometer (TES). The combination of data creates a scientific synergy that immeasurably enhances the quality of the scientific conclusions that can be made about any particular site and therefore, by extrapolation, about Mars as a whole. Dozens of outstanding technical papers about the MGS results have already been published, and probably hundreds more will follow in the years ahead.

Several astonishing new discoveries about Mars have resulted directly from the millions of individual data points acquired by the MOLA, an all solid-state, sub-meter precision laser altimeter. Based on this MOLA data, a topographic map of the entire Martian surface has been created with a worst-case elevation accuracy of less than 43 feet (13 meters). This is phenomenal accuracy, especially when it is recognized that there are still sections of the Earth where the elevation uncertainty is as high as a hundred meters.

The Martian topographic map suggests a dramatic landscape of extremes. The total range in elevation from the highest point on Mars to the lowest, for example, is roughly 20 miles (32 kilometers), compared to a 12-mile (19.3-kilometer) variation on Earth. The data confirm that the Martian south pole is much higher in elevation than the north pole. How much higher? About 4 miles (6.4 kilometers), or 20,000 feet (6,096 meters)! In fact, on Mars, downhill is north, and if flowing water still existed on Mars, it would all head into the vast watershed that is the northern lowlands. Based on the detailed topographic data, it appears virtually certain that at some epoch in the distant geologic past, one or more ancient oceans existed in that northern lowland area.

Precise MOLA measurements have also revealed the size and scope of an enormous asteroid impact on Mars some billions of years ago. That impact created the Hellas Basin, a gigantic feature in the Martian southern hemisphere. The asteroid carved out a hole roughly half the size of the United States. The elevation of the bottom of the mammoth basin averages a staggering 20,000 feet below the elevation of its rim. The material thrown out by the impact created widespread highlands that dominates the geology of a large portion of the southern hemisphere of Mars.

Tens of thousands of TES spectra have led to the preliminary conclusion that at a scale of a few miles (kilometers), the mineralogical composition of Mars is remarkably homogeneous. In other words, most of Mars looks similar in terms of its mineral content. This is a very surprising discovery. Is global dust mantling the mechanism that is producing this homogeneity? Or is some other unknown process at work? Would there be substantially more mineralogical variation at smaller scales? Like all pioneering spacecraft, MGS has raised as many questions as it has answered.

Last year’s twin failures at Mars have perhaps suppressed public recognition of the outstanding accomplishments of MGS. That’s unfortunate. Now would be an excellent time to finally recognize, with sustained and widespread applause, an unsung hero among the family of planetary spacecraft. Congratulations to the Mars Global Surveyor and the hundreds of engineers and scientists responsible for its success. Your contributions have created an invaluable treasure for all of mankind.