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The ten most significant science achievements of MGS during its first year of mapping, ordered from the interior of the planet outward.

1. Evidence for significant remnant magnetization of the Martian crust consistent with an early, vigorous molten interior core dynamo. These remnant anomalies in the ancient Martian crust indicate that in its early evolution Mars did have a global magnetic field. It has been conclusively established that Mars currently has no global magnetic field (MAG). 

2. The first reliable global models of the structure of the Martian crust and lithosphere, showing two distinct interior provinces that do not correlate globally with the hemispheric dichotomy, as well as evidence for buried basins and possibly channels beneath the northern plains (Radio Science and MOLA).

3. The highest integrity global topographic model produced for any planet including Earth, that reveals the 30-km dynamic range of topography, the pole-to-pole slope that controlled the transport of water in early Martian history, and the flat northern hemisphere, that may represent the location of a large ancient ocean. After removal of the gravitational signature of the topography, the rough elevated southern hemisphere has a relatively smooth gravitational signature indicating a state of near isostatic compensation, while the low, flat northern plains display a wider range of uncompensated gravity anomalies that indicate a thinner, but stronger crustal layer than in the south (Radio Science and MOLA).

4. Identification of two different surface compositions that point to globally distinctive zones of crustal evolution. Thermal emission spectra of low albedo regions indicate volcanic rocks of basaltic composition in the south and andesitic composition in the north. The widespread occurrence of plagioclase and pyroxene signatures and the lack of weathered hydrated materials attest to the absence of pervasive weathering. No areas of carbonate, sulfate, or quartz have been found. The high albedo areas are characterized by a non-diagnostic spectrum, much like the atmospheric dust (TES).

5. Thick layered sequences of strata in the Valles Marineris, possibly volcanic in origin, that would indicate a greater role than previously thought of surface and intrusive volcanism during early to mid-martian history. Layering is widespread on Mars. These thick layered sequences of layered rocks were found in numerous places within the Valles Marineris. Friable layered sequences are widespread and exhibit complex histories of deposition and removal(MOC).

6. Detection of several coarse-grained hematite deposits, possibly indicative of deposition in a surface hydrothermal environment , and evidence for recent volcanism (TES, MOC and MOLA).

7. Evidence for a complex depositional and erosional history that elucidates the central importance of dust transport on the global and local scale in influencing Mars' current and past climate. Widespread, continuing aeolian activity is evidenced by the abundance of dunes, sand sheets, dust cover, and dust devils (MOC).

8. The first reliable estimate of the present-day surface water inventory from the volumes of the polar caps, and evidence for distinctive evolution of the north and south polar caps (MOLA and MOC). 

9. Clear evidence for of a sapping origin of many channels from probable melting of ground ice, and possible evidence for recent liquid water in many spatially isolated regions (MOC).

10. Significantly improved understanding of atmospheric dynamics, from seasonal monitoring of temperature, pressure and opacity, and measurement of cloud heights (TES, Radio Science, MOLA, Accelerometer, MOC). Extensive atmospheric profiles, accurate topography, stable wave detection and records of the seasonal distribution of water ice and carbon dioxide ice clouds and dust provide new boundary conditions and dynamics for testing and evolution of global circulation models. Systematic global observations of thermal structure and distributions of water ice clouds, carbon dioxide ice clouds, and dust are revealing the dynamical and seasonal variations of the atmosphere in unprecedented detail. The utility of the data is greatly enhanced through computer simulations using general circulation models (GCMs). These new data on Martian meteorology include observations of baroclinic waves, Rossby waves, thermal tides, and a resonantly-enhanced diurnal Kelvin wave.

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