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other luminous matter.Terrestrials were too small to capture Hydrogen or helium-started w/o atmosphere- gravity=weakComposition- 98% helium and hydrogen, 2% other heavier elementsNebular Hypothesis- In 1755 Immanuel Kant put forth: the Solar System formed from the gravitational collapse of an interstellar cloud of gas.Nebular Theory- Solar Nebula is a giant cold cloud of gas-it has significant mass, and therefore begins to undergo gravitational collapse.Solar Nebula+time+gravity+collision=An orderly solar systemAccretion- accumulation of cosmic dust particles into a large object by gravitationally attracting more matterTypically gaseous matter in an accretion disk. Accelerates the growth of particles into boulder-sized planetesimals. Planetesimals- solid objects thought to exist in disks. Theorized that planet formation occurred.Late Heavy Bombardment- LHB- thought that billions of years ago asteroids hit terrestrial planets and the planets accreted them.Structure of Terrestrial Planets- Core-innermost layer, water and solids. Mantle- layer between crust and coreCrust- Outermost solid shell- rocky material. Differentiation- Separation of constituents into layers. Dense sank in, light objects came outMeteorite- piece of debris from either an asteroid or comet, survives its impact with earth’s surface.Lunar Maria- large dark spots on Earth’s moons that occurred from ancient volcanic eruptions. “seas”Lunar Highlands- Brighter parts of the moon that are easier to be seen, and are older than the marias. Parts are said to be younger than crateredOzone-gas that absorbs UV solar radiation about 15-50km above earth’s surface. In stratosphereGreenhouse Gas- gas that absorbs and emits radiation within the thermal infrared range.Greenhouse Effect- Radiation from greenhouse gases heat up a planets atmosphere to warmer than it shouldGreat Red Spot- persistent storm on the planet Jupiter, 22° south of the equator, which has lasted for at least 185 years and possibly as long as 350 years or moreGalilean Moons- 4 largest moons of Jupiter- lo-no impact craters lava, Europa, Ganymede, and Callisto. 1stgroup of objects found to orbit a planetPhotosphere- visible surface of the sun, underneath the opaque layer to which you can start to see visible lightGranules- on the photosphere, caused by convection currents of plasma within the suns convective zone.