Cosmic Samples and the Origin of the Solar System (Astronomy)

Recall cards on the cosmic samples that reach Earth and what they reveal about how the solar system formed. Meteors, the shooting stars produced when tiny particles burn up in the atmosphere, and the meteor showers Earth meets when it crosses a comet's debris stream, from the Perseids to the Leonids. Meteorites, the fragments that survive to the ground: the iron, stony, and stony-iron classes, primitive versus differentiated bodies, and the amino acids in the Murchison meteorite that date the solar system to about 4.56 billion years. The solar nebula model of formation: a collapsing spinning disk, the condensation sequence that split the rocky inner planets from the icy giants, planetesimal accretion, and differentiation. What other planetary systems teach us, found by the Doppler and transit methods and by Kepler: super-Earths, hot Jupiters, and planetary migration. And the long-term evolution of worlds, where size governs how long a planet stays geologically alive, from the dead Moon to plate-tectonic Earth and Olympus Mons on Mars.