9.3-Geology of Moon and Mercury, 9.4-Geology of Mars

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9.3 Geology of the Moon and Mercury
Geology of the Moon
-maria is dark and smoother, lunar highlands are brighter and heavily cratered
-maria is the only noticeable volcanic features on the Moon
-flat surfaces of maria Æ lunar lava spread easily and far Æ traced back to Moon·s formation
-no water or other gases are a part of the Moon because the giant impact released it and Moon was
formed from the giant impact debris
-few tectonic features found on the maria
-surface wrinkles Æ small-scale tectonic stresses
-the side we don·t see has higher altitude than the near side
-allowed lava to well up and fill crater basins only on the near side
-has very few marias on this side
Moon today
-desolate and nearly unchanging
-geologically dead since maria formed more than 3 billion years ago
-tiny particles burn up and rain directly onto the surface of Moon
-the micrometeorites gradually pulverize the surface rock Æ why the lunar surface is covered by a
thin layer of powdery soil
Geology of Mercury
-impact craters visible everywhere on Mercury
-less crowded together Æ molten lava covered some up during the heavy bombardment)
-these lava flows probably occurred when heat from radioactive decay accumulated to melt part of
the mantle
-Caloris Basin Æ largest single surface feature, huge impact crater Æ more than 1/2 of radius
-has tremendous cliffs Æ past tectonics quite different from other terrestrials
-tectonic forces compressed the crust Æ surface crumple
= did not stay the same size, SHRANK
-shrinking of mercury?
-heat swelled up Mercury Æ cooled Æ contracted by perhaps as much as 20 km in radius
-mantle and lithosphere contracted along with the core Æ tectonic stress Æ great cliffs
-probably closed off remaining volcanic vents, ending Mercury·s volcanisms
9.4 Geology of Mars
-southern hemisphere: Æ high elevation Æ numerous large impact craters (Hellas Basin)
-northern hemisphere: Æ below the average surface level Æfew impact craters
-volcanism was most important in erasing Mars, erosion and tectonics also played a part
-tallest volcano in the solar system (Olympus Mons, large enough to cover Arizona)
-most of the volcanoes are near the Tharsis Bulge
-volcanoes can still be active in Mars
-radiometric dating of meteorites shows some of them to be made of volcanic rock as little as 180
million years ago (very recent)
-Valles Marineris Æ long, deep system of valleys (tectonic feature)
-may have formed tectonic stress accompanying the uplift of material that created the Tharsis Bulge,
cracking the surface and leaving the tall cliff walls of the valleys
-no liquid water exists today Æ unstable on Mars Æ too cold
-mars probably once had very different surface conditions
-warmer temperature, greater air pressure Æ water to flow and rain to fall
-had lots of water at one point
-proved by two twin robotic rovers Spirit and Opportunity
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Document Summary

Maria is dark and smoother, lunar highlands are brighter and heavily cratered. Maria is the only noticeable volcanic features on the moon. Flat surfaces of maria lunar lava spread easily and far traced back to moons formation. No water or other gases are a part of the moon because the giant impact released it and moon was formed from the giant impact debris. The side we dont see has higher altitude than the near side. Allowed lava to well up and fill crater basins only on the near side. Geologically dead since maria formed more than 3 billion years ago. Tiny particles burn up and rain directly onto the surface of moon. The micrometeorites gradually pulverize the surface rock why the lunar surface is covered by a thin layer of powdery soil. Less crowded together molten lava covered some up during the heavy bombardment)

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