As the Galileo spacecraft prepared to take up its orbit around Jupiter, a 746-pound probe released from the spacecraft in July slammed into the Jovian atmosphere. Dropping more than 125 miles through the clouds of the planet, the probe sent back the first-ever samples of the planet's dense air before being crushed by intense heat and pressure. "This will help clear up a lot of speculation about the composition of the Jovian atmosphere," says TIME's Leon Jaroff. "Scientists have been able to make a lot of inferences about the planet, but this would be the first time they've been able to sample the atmosphere. They expect to find a high water content, and some lightning, at the higher levels in the hour before the probe descends so far that Jupiter's extreme heat and pressure destroy it."