9781422283714

  Jupiter and Saturn   lie far beyond our   neighbor Mars. Distant Wor lds

At their brightest, Mars and Jupiter appear about as bright as each other in the night sky. So we might be tempted to think that they are about the same distance away. But nothing could be further from the truth. On a space shuttle trip to the planets, a trip to Mars when it was closest to us would take about three months. Mars is one of our planetary neighbors, sometimes coming as close as 34.8 million miles (56 million km). A trip to Jupiter when it was closest would take more than two years . The planet never comes closer to the Earth than about 372 million miles (600 million km). To continue on to Saturn would extend our journey time to nearly six years. Even at its closest to Earth, Saturn lies over 746 million miles (1.25 billion km).

∆ Only the planets out to Saturn are shown in this orrery of 1733.

∆ Saturn from a Voyager space probe .

6

6