The last time we saw Jupiter up close, it was 16 years ago, when a probe from NASA’s Galileo spacecraft took a death plunge through the cloud tops and radioed back tantalizing data that all but screamed, “To be continued...”

Now NASA is headed back to the big planet, looking for the clues to help answer pressing questions about the early days of the solar system. Because whatever was in Jupiter at the beginning — more than 4.5 billion years ago, when the solar system was formed — is still there, scientists say, hiding in a mysterious gas giant made up of dust and gas left over by the Sun.

A spacecraft named Juno (after Jupiter’s wife in Roman mythology) is scheduled to lift off Friday morning from the Cape Canaveral Air Force Station in Florida, embarking on a five-year trip. On July 4, 2016, as determined by planetary mechanics, not American patriotism, Juno will pull into orbit around Jupiter and spend a year there, making scientific observations of gravity, magnetic fields and the wetness of the Jovian atmosphere.

And then scientists may learn more of the secrets of Jupiter, which has twice as much mass as the rest of the planets in the solar system combined.