Before Earth became the blue planet we know today, it was covered by a deep ocean of molten rock, or magma, that stretched hundreds or even thousands of kilometers deep.
As this magma ocean slowly cooled and hardened, different minerals formed at different rates, changing the chemical makeup of the remaining molten rock.
At the same time, gases were released from the magma into the atmosphere, affecting its composition.
Mars, as well as other rocky planets, went through a similar magma ocean phase during their early formation.
However, because these events happened billions of years ago, scientists have struggled to understand exactly how the process worked.
To learn more, researchers have been looking at clues from the atmospheres of these planets.
Noble gases, which do not react chemically, can provide information about the composition of ancient atmospheres.
In a recent study published in the Journal of Geophysical Research: Planets, a team of scientists, led by Schaefer, developed new models to simulate how the magma oceans on early Earth and Mars may have evolved over time.
Their models focused on how different types of iron—ferrous (reduced) and ferric (oxidized)—behave as magma crystallizes in the mantle, the layer of rock beneath the planet’s crust.
The researchers tested various starting conditions, including different magma ocean depths and chemical compositions, to see which scenarios best matched what we know about the atmospheres of early Earth and Mars.
For Earth, the results showed that models starting with a shallow magma ocean—either from a mantle that was only partially melted or one that began solidifying in the middle—were the most accurate.
This suggests that early Earth’s mantle may have had layers that remained molten longer, affecting both the planet’s atmosphere and its eventual solid structure.
On Mars, the results were more puzzling. None of the models matched previous research on Mars’s early atmosphere unless the initial magma had lower amounts of ferric iron than scientists currently believe.
These findings are helping scientists better understand how rocky planets like Earth and Mars formed, and why their atmospheres developed differently.
However, the study also highlights the need for more experiments to study the behavior of iron in molten rock, which could provide even clearer answers in the future.
Source: American Geophysical Union.
