Other Planets in Milky Way Could Have Oceans and Continents Like Earth’s

A study published in Science Advances on Feb. 17 found that water could have been part of Earth’s early formation, increasing the likelihood that this would be the case for other planets, too.

“All our data suggest that water was part of Earth’s building blocks, right from the beginning. And because the water molecule is frequently occurring, there is a reasonable probability that it applies to all planets in the Milky Way,” study lead author professor Anders Johansen from the Centre for Star and Planet Formation at the GLOBE Institute at the University of Copenhagen said in a press release.

Scientists previously theorized that water arrived on planets like Earth after they formed through collisions with ice asteroids. This would make the presence of water on any planet in the galaxy a matter of chance. But, in recent years, new theories have emerged. Another paper published in August 2020 found that water may have been part of Earth’s original building blocks.

That paper, led by the French-based Centre de Recherches Pétrographiques et Géochimiques, drew its conclusions by looking at the composition of a type of meteorite that has a similar composition to early Earth.

The new study, on the other hand, was based on computer models. The researchers modeled planet formation to see how long it would take using which building blocks. They calculated that Earth, Venus and Mars were all made through a process called “pebble accretion,” in which millimeter-sized particles of dust and ice gather together into planets.

“Up to the point where Earth had grown to one percent of its current mass, our planet grew by capturing masses of pebbles filled with ice and carbon. Earth then grew faster and faster until, after five million years, it became as large as we know it today,” Johansen said in the press release.

This theory does not require water to be brought to a planet from outside. Instead, what determines the presence of liquid water on the planet is how far it is from its sun. It also increases the likelihood that liquid water would form on other planets in our galaxy, since they could have formed in the same way from the same materials.

This, in turn, increases the chance that these planets would host extraterrestrial life.

‘With our model, all planets get the same amount of water, and this suggests that other planets may have not just the same amount of water and oceans, but also the same amount of continents as here on Earth. It provides good opportunities for the emergence of life,” study co-author professor Martin Bizzarro, also at the University of Copenhagen, said in the press release.

This is not the first study to suggest that other planets in our galaxy were likely to have oceans. A NASA-led study published in June of 2020 looked at the likelihood that other planets in the Milky Way would have ice-covered oceans similar to those on Saturn’s moon Enceladus and Jupiter’s moon Europa. They calculated that 14 of the 53 planets they studied could be ocean worlds.