National Geographic : 2013 Jul
Solar System 47 have hurled them into the outer solar system. “We were dumbfounded,” says Donald Brown- lee, head of the Stardust team and Joswiak’s boss. “It was astounding to find these highest- temperature materials in the solar system’s coldest bodies. The solar system was literally turning itself inside out.” When most of us were growing up, the solar system seemed reliable and well behaved. “There were nine planets orbiting in well-determined orbits like clockwork, forever,” says Renu Mal- hotra of the University of Arizona. “Forever in the past, and forever in the future.” Planetarium displays and the lovely mechanical devices called orreries embodied this idea, which went back to Isaac Newton. In the late 17th century Newton showed that a planet’s orbit could be calculated from its gravitational interaction with the sun. Soon clockmakers were building increasingly elaborate orreries, with brass planets that circled the sun on unchanging pathways. Newton himself knew that reality was messier. The planets, he recognized, must also interact with one another. Their gravitational tuggings are far weaker than those of the sun, but over meteorite Long ago, somewhere between Mars and jupiter, two asteroids collided. This two-pound meteorite was probably blasted off the larger one, called vesta. jupiter’s gravity later slung it to Earth, where it landed on the Antarctic snow.