Baby planets can do something insidious with their water to protect it from unruly stars: ScienceAlert

Creating rocky planets is dirty, dangerous, and hot business. Planetesimals coalesce, putting heat and pressure on the newborn world.

The nearby growing star bombards them with intense radiation. That’s likely “baking” any surface oceans, lakes, or rivers, which is a disaster if you’re looking for places where life might arise or exist.

That’s because life needs water, and the planets around these stars are among the planets most likely to harbor life. But that doesn’t look too hopeful with the radiation evaporating the water.

Scientists at the University of Cambridge in the UK have created a complex model that describes a world where most of the water is trapped deep below the surface, not in pools or oceans but in rocks.

Technically, it’s trapped in minerals deep below the surface. If conditions are right on the worlds around these most common stars in the galaxy, there could be enough water to equal several of Earth’s oceans.

Clare Guimond, a PhD student at Cambridge, along with two other researchers, developed the model describing newborns around M-type worlds orbiting red dwarf stars.

“We wanted to investigate whether these planets can rehabilitate themselves and host surface water after such a turbulent upbringing,” she said.

Her team’s work shows that these planets could be a very good way to replace liquid surface water that was displaced during the host star’s early life.

“The model gives us an upper bound on how much water a planet could carry at depth based on these minerals and their ability to incorporate water into their structure.”

Sequestration of water on a forming world

M-type red dwarfs are the most common stars in the galaxy. This makes them good objects to study the variables of planet formation. They form just like other stars.

Once past infancy, they also tend to be outburst and temperamental just like other stars. However, they remain colicky much longer than other stars. That doesn’t bode well for the surfaces of nearby planets (or protoplanets).

If it is not baked away, the water will migrate underground. But would it happen with any rocky planet? What world size do you need for this?

The team found that a planet’s size and amount of water-bearing minerals determine how much water it can “hide”.

Most end up in the upper mantle. This layer of rock lies just below the crust. It is usually rich in what are called “anhydrous minerals”.

Volcanoes feed on this layer, and their eruptions can eventually bring steam and haze back to the surface through eruptions.

The new research showed that larger planets — about two to three times larger than Earth — typically have drier rocky mantles. That’s because the water-rich upper mantle makes up a smaller proportion of its total mass.

Hidden water and planetary science

This new model helps planetary scientists understand not only the conditions at Earth’s birth, but also the water-rich objects that gather to form planets. However, it is more aimed at the formation environment of larger rocky planets around M-type red dwarfs.

Thanks to their star’s tumultuous youth, these worlds likely experienced chaotic climate conditions for long periods of time. These could have worked to send liquid water deep underground. Once their stars settled, the water could exit in a variety of ways.

The model could also explain how early Venus might have transitioned from a barren hellscape to a water world. The question of the water of Venus is of course still hotly debated.

However, if pools of liquid and oceans existed four billion years ago, how did they happen?

“If that [happened] Venus must have found a way to cool down and regain surface water after being born around a fiery sun,” said Oliver Shorttle, Guimond’s research partner.

“It may have tapped water from within to do this.”

Implications for finding exoplanets

Finally, current research could provide new guidelines for searching for habitable exoplanets in the rest of the galaxy. “This could help refine our sighting of the planets we’re asked to study first,” Shorttle said.

“When we’re looking for the planets that are best at holding water, you probably don’t want one that’s significantly more massive or wildly smaller than Earth.”

The factors in Guimond’s model also have implications for the formation and mineralogy of rocky planets. More specifically, it can explain what’s stored inside a planet, particularly between the surface and the mantle.

Future research will likely address the habitability and climate of both rocky and surface water-rich worlds.

This article was originally published by Universe Today. Read the original article.


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