Artist rendering of Juno spacecraft in orbit around Jupiter. NASA
The last NASA mission to orbit Jupiter, the Galileo, was designed, flown and its data analyzed as if it was circling the only Jupiter in the sky.
This is hardly surprising since the spacecraft launched in 1989, before the exoplanet era had arrived. Ironically, Galileo entered its Jupiter orbit in late 1995, just a few months after the first exoplanet was detected.
That planet, 51 Pegasi b, was a Jupiter-sized planet shockingly close to its host star, and its location and white-hot temperatures turned upside down many then-current theories about gas giant planets and their roles in the formation of solar system. Scientists are still struggling to make sense of what 51 Pegasi b, and the 250 or so Jupiters found after it, are telling us.
So the Juno mission, which is scheduled to begin orbiting Jupiter on July 4, will arrive at a planet understood quite differently than when Galileo made its appearance. Juno was built first and foremost to unravel some of the enduring mysteries of the planet: When and where was it formed? Does it have rocky core? Is there water deep in the atmosphere?
But the ...