The largest ocean in the Solar System exists in an unexpected place. It is unlike any ocean on Earth, or even like those on a promising lunar world like Europa. This ocean resides somewhere beneath the soft bitten-peach atmosphere of Jupiter, vaporous and crystal-coloured, made not of water but of liquid hydrogen. The hydrogen becomes a liquid as both temperatures and pressures mount beneath Jupiter’s atmosphere. Like the sun, Jupiter is made mostly of hydrogen and helium.
This composition is what sets the four Jovian planets Jupiter, Saturn, Uranus, and Neptune apart from the four inner rocky planets. Enormous, billowing layers of gas surround small but dense cores. As dreamy as it would be to visit a planet like Saturn, any traveller would find that there is no surface on which to land their craft. Neither can they fly through the atmospheres of gas giants since the intense environment would lead to fatal malfunctions? Spacecraft entering would be melted and crushed, then inevitably vaporized before much time had passed. They are beautiful worlds indeed, but they echo like pieces of art in a shadowy museum: look but do not touch.
For this reason, and for the breadth of their distance from Earth, we haven’t yet been able to discern much of the inner life of planets like Saturn and Jupiter. It may be the case that when approaching Jupiter’s core electrons are forced off hydrogen atoms, causing the liquid ocean to become electrically conducting. The planet’s core may be either solid or perhaps more like a dense, thick collection of gas. It’s undoubtedly hot up to 90,032 degrees Fahrenheit (50,000 degrees Celsius). Measurements by spacecraft reveal a diffuse core, something which may have resulted from a planet 10 times more massive than Earth colliding with Jupiter over 4.5 billion years in the past. This impact disrupted the core, spreading the heavy elements which should have been concentrated there. Jupiter’s powerful gravity increases the chances that an incoming body will result in a collision rather than a simple grazing event. As Jupiter is more massive than all other planets combined, it has a stronger gravitational attraction.
Jupiter is already larger than some stars at 140,000 km versus 121,000 km for some of the smallest stars. With the added mass and material from Saturn, is it possible that the new cosmic body would become massive enough to sustain fusion and become a new star? Images from the simulation are shown below. The two planets first approached one another, the looming Jupiter bending Saturn’s rings with its gravitational pull, arching them, both planets heating up as they touched and then merged two swirling, sultry atmospheres into one.
It wouldn’t be the first time a planet in our Solar System goes missing. Some research suggests that a fifth Jovian planet existed between Jupiter and Neptune at some early point in our system’s formation. It was later ejected and erased from our night sky, just as the ancient world that collided with Earth and created our moon was also erased, preserved now only by the stony, cool orb of moonlight in the late dark. Together Jupiter and Saturn played an important part in the creation of life on Earth. Their gravity kept our planet safe from many of the disasters which could have wiped out the very first organisms, or otherwise made conditions unfavourable for us to emerge at all. Losing them and creating a new world would not only change the landscape of our Solar System but would also destroy intimate artefacts from the story of mankind.
