The prevailing theory for gas giant formation, known as the core accretion model, says planets like Jupiter start out as small, rocky worlds that accumulate enough material to accrete a gaseous envelope. This suggests Jupiter’s chemical composition should closely mirror the Sun’s.

But it’s not clear how the smallest particles stick together, other than the fact that our universe is full of fully-formed planets. Other theories have been proposed, like the disk instability theory, which suggests that gravitational forces bind settling nebula particles together like a collapsing balloon. However, this implies that Jupiter doesn’t have a core, which scientists find unlikely.

In short, if we find that Jupiter is wetter than expected, we’ll have cast doubt on aspects of the core accretion model. From Juno’s first science pass, JIRAM, the probe’s infrared mapper, couldn’t comment on the profound implications of this, but did find low relative humidity inside one of the planet’s hotspots. That was expected—the Galileo mission found the same thing—but the information can still be useful in that it gives scientists a lower limit to how dry Jupiter is.

Seeing the data is exciting, but there are big questions left to be answered. What is Jupiter’s core made of? Are we right about solar system formation models? These are tough questions, and the answers will require lots more data, modeling, and interpretation, or in short, science.

NASA recently said peer-reviewed papers from Juno’s first flybys are coming soon. So stay tuned—Juno has a lot more to reveal about Jupiter.

Additional reading:

Juno’s Science—What do we hope to learn?

Measuring Jupiter’s water abundance by Juno: the link between interior and formation models, Helled & Lunine (2014)

Earth Proton Whistlers