Magma ocean — Safekipedia Adventurer

Magma oceans are huge areas of melted rock that cover the surface of a planet or moon when it is just forming. These oceans of magma happen when a celestial body is coming together, either by collecting smaller pieces or being hit by other large objects in space.

Full volcanic planet, magma ocean in surface

In the early days of our Solar System, magma oceans formed when small pieces of rock melted from heat. This heat came from radioactive decay, especially from a type of aluminium called aluminium-26. As planets grew, big impacts provided more heat to melt the surface. These magma oceans help shape the planet by separating heavier metals to form a core and releasing gases to create an atmosphere.

Both the Earth and the Moon likely had magma oceans when they were young. These oceans of molten rock could last for millions of years before cooling down and letting the planet develop a more stable surface.

Magma ocean heat sources

The early solar system had several sources of energy that helped form magma oceans. One important source was the radioactive decay of aluminium-26. This produced heat and melted small rocky bodies called planetesimals. The heat moved outward through convection.

Another source of heat came from impacts as planets grew. When a planet’s core formed, heavy metals sank and released heat. This melted the planet from the inside. A famous example is the Moon-forming impact on Earth. It may have created a very deep magma ocean.

Lunar magma ocean

The formation of the lunar magma ocean which was a layer of molten rock believed to measure hundreds of kilometers in depth.

The Apollo missions showed that the Moon once had a big ocean of melted rock. They found rocks made of a mineral called anorthite. This mineral is lighter than melted rock. It suggested these rocks floated up when the Moon was very young.

The lunar magma ocean was thought to be very thick and very hot. As the Moon cooled, this ocean hardened, leaving clues on the Moon’s surface.

Earth's magma ocean

During its formation, Earth likely had large areas of molten rock, called magma oceans. These were caused by huge impacts, including the one that formed the Moon. Scientists believe these magma oceans were very deep, about 1,000 kilometers.

Today, Earth has a liquid outer core made mostly of molten iron and nickel. This layer surrounds Earth's solid inner core and lies below the mantle.