NASA's Juno spacecraft is going closer to the massive and mysterious planet Jupiter than any spacecraft has ever gone.
The ship has flown more than 1.7 billion miles over five years, and on Thursday Juno began executing the sequence of commands that will take it right to Jupiter's clouds.
On July 4th, the engines will switch modes again, and the ship will begin burning fuel to slow it down enough so that Juno can be swept into Jupiter's orbit. If it succeeds, the $1.1 billion mission will give scientists the most complete data set so far of a planet little understood.
"Juno is very special because it is one of those rare missions where it is entirely focused on looking inside Jupiter," said Curt Niebur, lead program scientist for New Frontiers, which oversees the Juno mission, in an interview with CNBC. Being covered with, and largely composed of gaseous elements, Jupiter does not have the kind of same kind of rocky surface a planet like Mars or Earth has.
"With the instruments and techniques we are using, we can unzip the planet and really peer inside it and understand what its deepest internal structure is," he said.