What are the implications if Juno finds that Jupiter has a solid core?

Question

Juno has arrived at Jupiter, and will begin taking measurements to determine if the gas giant has a solid core. But what I cannot seem to find is the implications such a discovery would have. This paper says that there are essentially two models - the Core Accretion model and the Disk Instability model.

Core Accretion follows the idea that gas giants start off as rocky bodies which quickly accrete mass and gas, eventually leading to runaway growth and forming gas giants. This model may take from one to a few Myr, and requires a fair amount of rocky material in the protoplanetary disk.

The Disk Instability model says that gas giants form in a similar manner to stars; collapsing in from clouds of gas. In this instance, no central core is needed to begin accretion. This happens at a much faster rate, and these gas giants can still produce cores via sedimentation.

My questions are thus:

• If Juno discovers a solid core on Jupiter, will that allow us to pick one of the two models, since both could evolve a solid core?
• If we discover that Jupiter does or does not have a solid core, what does that mean for the development of Earth and life?

I've looked around, but haven't been able to find a source that links the two very neatly.

Answer 1

If Juno discovers a solid core on Jupiter, will that allow us to pick one of the two models, since both could evolve a solid core?

A solid core itself won't be a smoking gun because as you said, both models predict that a solid core is possible. If Jupiter does not have a solid core however, the disk instability model begins to look a bit better.

Something else interesting here is the size of the core. Most core accretion models for gas giants predict very large cores (on the order of 10 times the mass of Earth). They also tend to be very dense because they form as a solid body that eventually becomes the core of a much larger planet. Disk instability models do allow for a solid core, but the cores tend to be smaller and less dense because they don't develop around an already solid body.

So the data from Juno won't tell us for certain which model is more accurate, but the lack of a solid core, or a relatively small and less dense core will definitely make the disk instability model look better.

If we discover that Jupiter does or does not have a solid core, what does that mean for the development of Earth and life?

I have to say that this is more of a big picture question that I'm not really qualified to answer, especially when it comes to the connection to life.

But to keep it very short, determining which of these models is more accurate will allow us to get a better idea of how long it took Jupiter to form. If core accretion is more accurate, Jupiter likely took millions of years to form, and the protoplanetary disk was around for a long time compared to our estimates of how long they usually last. Earth was also developing within this disk, so anything we can learn about the solar system while Jupiter was forming can likely be applied to the environment of Earth as it was forming.