Surprise! Venus Might Have Oceans of Water Trapped Inside Its Crust
Venus is a violent, inhospitable planet.
With its thick and toxic atmosphere brimming with carbon dioxide, it's permanently encased in dirty-yellow clouds of sulfuric acid, trapping all heat beneath, where the pressures and temperatures rise to instant-death levels. But there might be a glimmer of hope deep below the hellscape on the surface.
The second planet from the sun might have oceans of water trapped in the layer of mantle below its crust, which could pour out as piping hot water vapor (steam) if we could crack it open, according to a recent study shared on a preprint server.
Obviously, this doesn't mean Venus could be terraformed, and it probably never will be. But if we ever found a way to tap a water "reservoir" beneath its crust, our understanding of Venus, and other terrestrial planets beyond our solar system, could be changed forever.
Young worlds covered in an ocean of hot magma
In the past, scientists have proposed that colossal steam and CO2 atmospheres could be outgassed by magma oceans on Earth and other terrestrial (rocky, Earth-like) planets. When rocky, Earth-like planets form, the distribution of volatile elements like carbon (C), hydrogen (H), and oxygen (O) in the primary planetary components, which include the core, the hot mantle, and outer atmosphere, determine and regulate the way a terrestrial planet's atmosphere first forms, and evolves over time. As the planet is pummeled by more and more resource-rich meteors and other bodies, the iron-core forms, and a worldwide ocean of hot magma forms. Think of simulations of the Earth being struck by a giant asteroid, and how the result is a colossal magma ocean that pours out through the ripped crust, like blood from a wound.
By very loose analogy, this is how Earth-like planets begin. But a significant portion of the C and H would undergo short- and long-term geochemical cycling. "The shock degassing of substantial H2O (water vapor) from hydrated minerals to simulate impacts during planetary accretion motivated investigation of the blanketing effect of a steam atmosphere above the molten early Earth," wrote the study authors. But the creation of atmospheres in this way would be contingent upon intense exchanges with the molten interior of a rocky planet. The researchers examined the evolution of magma ocean-atmosphere systems across a range of conditions, and determined that complex reactions that happen when a planet's magma is exposed prevent roughly 75% of the water contained within it from escaping into the atmosphere, which can slow or prevent the formation of oceans on a planet's surface.
Oceans of water may be trapped in the mantle of Earth-like planets
However, if natural conditions or some other mechanism allowed for a molten surface to persist in the "open air" of a rocky planet's surface, this could enable the transition of its atmosphere from a CO-rich atmosphere to one rich in water. According to the research, a large portion of the water deposited on terrestrial planets like Venus (or Earth) throughout their early and formative years could remain trapped inside their interiors during the "magma ocean phase." This would mean the water contained within could only escape over very gradual, geological timescales.
"Ultimately, the high solubility of H2O in magma oceans may enable its safe storage during the tumultuous phase of planet formation," concluded the authors in their study. While this doesn't imply that water oceans will form on Venus, it still means terrestrial planets — including Earth and other rocky planets beyond our solar system — might retain water beneath the crust, trapped in the mantle below. Even if the surface conditions could kill any human being in an instant.