Baby planets may be doing something sneaky with their water to protect it from unruly stars: ScienceAlert

Creating rocky planets is a messy, dangerous, and hot business. Planetesimals accumulate, creating heat and pressure on the newborn world.

The teenage star nearby bombards them with intense radiation. This probably “cooks” all surface oceans, lakes, or rivers, which is a disaster if you’re looking for places where life could arise or exist.

Indeed, life needs water and the planets around these stars are among the most likely to harbor life. But that doesn’t look too encouraging if the radiation washes the water away.

Scientists at the University of Cambridge in the UK have created a complex model that describes a world in which most of the water is locked away 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 Earth oceans.

Cambridge PhD student Clare Guimond, along with two other researchers, came up with the model, which describes newborns around M-type worlds orbiting red dwarf stars.

“We wanted to study whether these planets, after such a tumultuous upbringing, could rehabilitate themselves and continue to host surface water,” she said.

His team’s work shows that these planets could be a very good way to replace the liquid surface water driven out at the start of the host star’s 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 absorb water into their structure.”

Sequestering water on a world in formation

M-type red dwarfs are the most common stars in the Galaxy. This makes them good subjects for studying planetary formation variables. They form like other stars.

Once past infancy, they also tend to be explosive and temperamental, just like other stars. However, they remain colic much longer than other stars. This does not bode well for the surfaces of nearby planets (or protoplanets).

If it is not cooked, the water migrates underground. But would that happen with all the rocky planets? How big of a world does it take to do this?

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

Most are found in the upper mantle. This rocky layer is directly below the crust. It is generally rich in so-called “anhydrous minerals”.

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

The new research has shown that larger planets – around two to three times larger than Earth – generally have drier rocky mantles. This is 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 when Earth was born, but also the water-rich objects that accumulate to form planets. However, it’s really more aimed at the environment of forming larger rocky planets around M-type red dwarfs.

Thanks to their star’s stormy adolescence, these worlds likely experienced chaotic weather conditions for long periods of time. These could have functioned to send liquid water deep underground. Once their stars had settled, water could emerge in various ways.

The model could also explain how Venus could have changed from a barren hellscape to an aquatic world. The question of water from Venus is still much debated, of course.

However, if there were liquid pools and oceans four billion years ago, how did they come about?

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

“It’s possible he tapped into his inner water to do this.”

Implications for exoplanet research

Finally, ongoing research could give new directions in the search for habitable exoplanets in the rest of the Galaxy. “That might help narrow down our sorting of which planets to study first,” Shorttle said.

“When we’re looking for the planets that can best hold water, you probably don’t want one much more massive or wildly smaller than Earth.”

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

Future research will likely focus on the habitability and climates of rocky and surface water-rich worlds.

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

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