IT CAME FROM MARS

The first optical storage techniques--which would later create the compact disc--were developed in 1965, but data transfer was still agonizingly slow: Mariner 4 radioed these pictures over 134 million miles with a puny 10-watt radio transmitter at the rate of 81/3 bits per second. Each grainy image took 8 hours to receive, but the payoff was huge: surprising evidence of deep impact craters.