This phenomenon is suggested by the variation in composition of igneous rocks. Ancient
ultramafic rocks are generally composed of lighter elements than those found in more
recently formed basalts. Some of the oldest rocks are high in Lithium but their distribution
is extremely limited.
The suites of ions diffusing into younger gaseous planets are therefore likely to
comprise mainly of low energy hydrogen, helium, carbon, nitrogen and oxygen. Compounds
form from these - producing more gases such as carbon dioxide and ammonia and heat
is given off in the process.
A gaseous planet will have its beginnings in the outer edge of the Solar System -
perhaps in the Kuiper Belt - a gas cloud ring some 50 AU from the Sun (1 AU is the
distance of the Earth from the Sun). It is at this distance that some of the hydrogen
atoms from the solar wind, having lost much of their energy, exist as cold binary
molecules. These low energy molecules can become attracted to each other by gravitational
pull and start to clump together as ‘knots’ in the cloud. As these knots get bigger
they begin to migrate inwards on their orbit around the Sun. As they do this they
sweep up more hydrogen and helium molecules, and gradually become gas planetesimals
of significant mass.
By the time the migration inwards has reached a radius of 30 AU from the Sun, the
planetesimal will have increased its diameter to something in the region of 50,000
km. A diffusion mechanism of higher energy ions will have manifested itself by now
and light ions would be adding mass to a planet which would resemble Neptune.
At 19 AU from the Sun, the gaseous planet would look like Uranus (a diameter of around
50,000 km). At 9.5 AU it would look like Saturn and have a diameter of around 120,000
At theses orbital distances the planet would likely be pulling in cosmic dust particles
which would consist of slightly heavier elements like lithium, beryllium and carbon
and would be held at a distance in ring formations. Subsequent ionising of these
particles would allow their diffusion into the gaseous body of the planet by the
effect of its magnetic field. Ions of the elements, nitrogen and oxygen would begin
to diffuse into the gaseous planet, also, and it would be at this stage that all
the main elements responsible for the formation of life would be in abundance. These
are carbon, hydrogen, nitrogen and oxygen and it is likely that the ambient temperatures
and pressures would be ideal for the spontaneous formation of many different types
of complex organic molecules. So we may be able to envisage the ‘primordial soup’,
not so much as a soup, but more like a suspension of organic coated particles in
a moist atmosphere.
At 5 AU from the Sun, the planet would now have enormous proportions and its diameter
would be of the order of 150,000 km - much like Jupiter in form. Ions of heavier
elements up to calcium will likely be diffusing into a planet like Jupiter creating
the first ultramafic magma materials at a small core.
Much nearer to the Sun than this, (possibly at around 4- 3 AU) the Jupiter-like planet
will start to lose its hydrogen and helium gas envelope to the solar wind as these
molecules absorb energy. The tiny compressed core, possible less than a 1000 km diameter,
will all be that remains of such a massive structure.
Ceres is a small rocky planetesimal at the distance of 2.8 AU, and its diameter is
only 950 km. It could be an example of the core of a gaseous planet.
The Planetary Metamorphosis sequence described so far suggests the evolutionary scenario
of our planet Earth since its formation in the outer reaches of the Solar system.
Let us now have a look at what is in store for the future?
Soon this planet will enter a different phase and begin a process of decay and final
destruction. In about a hundred million years, Earth will be at an orbital position,
(0.86 AU) which is halfway towards Venus’ present position. Equatorial temperatures
(from my graph) will then reach around 70 degrees C. The lighter gases in the atmosphere,
such as oxygen and water vapour, will have started to drift away from the planet.
Only the polar regions will remain at a habitable temperature but by then the whole
surface of the Earth will probably be covered by deep water - if methanogens are
in fact creating millions of tons of water each year, as I believe they are. All
land animals will be extinct by then except those associated with mankind and living
under artificial conditions with them. The same would apply to sea-life. Only those
fish held in temperature controlled waters such as in large aquaria would still exist.
Perhaps, only the heat resistant microbes such as methanogens would survive in these
warm conditions and some of these would reside deep in the crust below the oceans.