Soils, Highlands and Lowlands, Tectonics, Volcanism, 11 October!There is dirt not only on Earth, but also on the Moon, Mars, Venus, and other 1.places in the solar system.!The dirt on the Moon: !A.Through a microscope, you can discern tiny spheres of glass in the dirt a.of the Moon. !These spheres are particles of moon dust melted by the heat of a 1.collision, pulled into a sphere by surface tension, and frozen in this shape. !These spheres are perfect mirrors when they are formed, but they 2.become less spherical and reflective after getting hit by dust from the solar system and high energy particles over a millennia.!You will only find highly reflective sphere around fresh craters A.(around a few hundred million years old). !Pieces of dust/soil on the Moon are dark grey and jagged. !b.This jaggedness and the fact that there is no air on the moon cause a 1.lot of friction between these particles of dust. This causes the dust on the moon to be as clingy as wet beach sand, although it is itself bone dry. !On Earth, particles of dust do not touch each other as they are A.surrounded by a surface film of air. This makes them less sticky. !This dust is so clingy that footprints made by astronauts on the B.Moon will stay visible for a million years. !Astronauts on the Moon brought back a lot of moon rocks, which are c.now curated in Houston. !The bulk of these rocks have not been thoroughly examined. !1.A few were researched in depth, and the rest were roughly A.examined so they could be retrieved if they proved interesting later. !The reason for this is lack of funding. !B.After the space program proved that the US could land on the a.moon before the USSR, politicians saw no further reason to continue funding it. !To save money, they fired scientists who would analyze the b.results of the mission.!The Genesis rock: oldest rock on moon that could be brought back 2.to earth.!Scientist figured out where this rock would be, and astronauts A.found one that met their description. !The rock they retrieved was well over 4 billion years old.!B.The dirt on Mars.!B.Our information on the dirt of Mars comes from landers sent to Mars a.since 1970.!These spacecraft provide images show that Mars looks like a red 1.desert.!There may have been water on mars at one point, but not any A.more. !There are lots of rocks in various stages of decomposition. !b.Most are jagged, but all are of different shapes and sizes. !1.The surface soil of Mars is clingy like the soil on the Moon, but unlike c.the Moon, Mars does have an atmosphere.!To find this out, one of the Mars landers drilled into Mar's soil. !1.The soil must be clingy for a different reason, but as of yet there is 2.none. !The surface of Mars is also covered by dust/sand that blows in the wind. !d.Though the air of mars is thin (1/120th as thick as the earth's air), it 1.moves fast. !On mars, there are many whirlwinds, dust devils, and vast storms A.that can cover the whole globe of mars. !This dust piles up into sand dunes that have the same five basic 2.shapes of sand dunes on earth. !The sand of Martian sand dunes is finer than Earth sand dunes, A.because earth has thicker air which can blow around larger particles. The air of Mars is only strong enough to lift the smallest dust particles. !Sidenote: Most sand in Earth's deserts is actually brought form a.beaches by huge storms. !The net wind is inbound, so this sand piles up in deserts. !1.Some sand might blow away (ex. West Africa), but most stays 2.where it was deposited by the wind.!The Dirt on Venus:!C.The first several spacecraft to land on Venus and send back images were a.from the Soviet Union. !Venus is hazy, so astronomers were surprised that the bottom layer of 1.air on Venus was clear enough for the spacecraft to take good picture of its surface. !The rocks of Venus are mostly volcanic, which was expected from a b.surface that has solidified from lava in geologically recent times. !Highlands and Lowlands: !2.Some parts of a planet's crust are higher or lower than other parts: !A.Highland rock is lighter in density, so it is higher than lowland rock. It is a.also lighter in color. !Lowland rock is heavier in density, so it is lower than highland rock. It is b.also darker in color. !This is a feature of most rocky objects in the inner solar system.!c.Earth:!B.The highlands rise above the water as continents. In general, these a.highlands are made of granite type rocks. !The lowlands are filled with oceans. In general, these lowlands are made b.of basalt type rocks. !These are loose, general descriptions, but they will suffice for an c.Astronomy course.!Side note: The continent of Africa is a plateau of highlands with a very d.sharp drop into the ocean (lowlands).There is little continental shelf around Africa. !Moon:!C.The highlands are a light, granite type rock. They are generally 4.2-4.4 a.billion years old.!The high lands are saturated with craters which have helped 1.astronomers figure out the geological history of the moon. !For example, astronomers could surmise that most impacts on the A.moon occurred in the earliest part of the moon's career when the highlands were already at the surface. By the time the maria filled up, there were much less impacts. !We now know that this was a period around 3.8 billion years a.ago called the late bombardment. !Cratering has been sparse since the late bombardment and for a b.lot of time before then.!The lowlands are dark, basalt type rock. They are generally 3.2-4.2 b.billion years old. !Some lowlands are much newer than highlands.!1.The round lowlands are gigantic craters which filled in with lava 2.hundreds of millions of years after the crater was formed. !These lowlands were called "maria" by Galileo because he thought 3.they were seas. We still use that name although we know they are solidified basalt. !Because the stark different between the Moon's highlands and lowlands c.can be seen with the naked eye, humans have been trying to find patterns in these formations for many centuries. For example, the man in the moon, the crab on the moon, donkey on the moon, woman in the moon, etc. None of these are actually on the moon.!Venus: !D.Venus has two continent sized highlands, and the rest of it is lowlands. !a.If you filled the lowlands with water, the boundaries between 1.highlands and lowlands would look like shorelines.!There are also some small high areas throughout Venus. !2.Plate tectonics. !3.This topic is represented by a small
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