Planets with low density are inferred to be composed mainly of hydrogen and helium, whereas planets of intermediate density are inferred to have water as a major constituent.
As the system falls toward the surface of the planet, helium gas is transferred into the balloon, forming a partially inflated system very similar to an ascending zero pressure balloon.
By analogy with the other giant planets, helium was also expected to be present.
The rock-ice cores that emerge can then pull in large amounts of hydrogen and helium gas, forming gas planets like those in our outer solar system.
Now planetary scientists Hugh Wilson and Burkhard Militzer of the University of California, Berkeley, have performed quantum mechanical calculations to see what happens when magnesium oxide (MgO)—a key ingredient in the rock of Jupiter's core is submerged in a hydrogen-helium fluid at the planet's heart.
The two largest, the gas giants Jupiter and Saturn, are composed mainly of hydrogen and helium; the two outermost planets, the ice giants Uranus and Neptune, are composed largely of substances with relatively high melting points compared with hydrogen and helium, called ices, such as water, ammonia and methane.
If so, he explains, the planet may contain substantial quantities of water, and perhaps hydrogen and helium.
The outer clouds are about 90% hydrogen and 10% helium, but further in the planet becomes richer in helium and the heavier elements.
As the droplets descend through the lower-density hydrogen, the process releases heat by friction and leaves the outer layers of the planet depleted of helium.
It may get to the point that more helium is needed from off-planet, which would be a feasible option as long as manufacturing and space travel were unaffected, which they wouldn't be.
