NASA launched the Galileo spacecraft, which comprises the Galileo Orbiter and Space Probe, atop a Space Shuttle in 1989, using a 38-month orbit of Venus and the Earth’s gravitational pull to gain the necessary speed to reach Jupiter.
While the Galileo Orbiter was designed to orbit and study Jupiter and its moons, the Galileo Probe was released near Jupiter and was sent into the gas giant itself on 7 December 1995. It entered the atmosphere of Jupiter at 30 miles per second (46km per second), the highest impact speed ever achieved by a man-made object. Amazingly, Jupiter’s dense atmosphere slowed the craft to 0.07 miles per second (0.12km per second) in just four minutes.
The probe’s heat shield, made of carbon phenolic, was able to withstand the 15,500°C ball of plasma caused by this sudden deceleration, producing light brighter than the Sun’s surface. It remained active for about 78 minutes as it passed through Jupiter’s atmosphere, losing more than half of its mass in the process before being crushed by the huge pressure.
Wrapped in black and gold blankets to provide insulation and protect against micrometeorites, the probe conducted nine experiments that measured Jupiter’s atmospheric structure. It discovered the presence of a large amount of argon, krypton and xenon. For these to form Jupiter would need to be at a temperature of -240°C, suggesting it once orbited much further from the Sun earlier in its lifetime.
The only other man-made object to enter Jupiter’s atmosphere was the accompanying Galileo Orbiter, which was set on an intentional fatal collision course with Jupiter in 2003 so that it did not accidentally contaminate any nearby moons by crashing on them.
Image courtesy of NASA