Early Saturday morning in Florida, a bit after 3:30 a.m., a massive rocket carrying a 1,500 pound probe bound for the Sun stood ready on the launchpad. With four minutes left in the countdown, a few engineers called a 'No go'—part of the system wasn't 100 percent ready for launch. The countdown stopped. No one was taking any chances with this mission. Around an hour after the original launch time of 3:31 a.m., the launch was scrubbed.