Earth-like exoplanets may be much more common than previously thought
A new study led by UCLA scientists on how water forms on young exoplanets with hydrogen atmospheres and molten oceans of magma suggests that Earth-like planets may not be as uncommon as once thought and that the presence of water on such planets may be almost inevitable.
One of the historically annoying things about trying to figure out how many planets like Earth that there are in the galaxy is that we only have one real example of an Earth-like planet and we're standing on it.
Since a total sample size of exactly one is statistically meaningless, scientists are very keen to find Earth-like planets outside the Solar System or, at least, ones that can give us insights into the mechanisms that form such planets so meaningful conclusions can be drawn.
One key property that sets Earth apart is the presence of large amounts of liquid water on its surface – a necessary factor for the existence of life. Current hypotheses about how Earth got its water revolve mainly around it being carried to the primordial planet by comets, meteors, or space dust. This is a mechanism that requires very specific circumstances and suggests that watery Earth-like planets may be exceedingly rare.
The new UCLA study conducted in collaboration with the Carnegie Institution for Science indicates that watery exoplanets may not be as rare as previously thought. In fact, they could be a cosmic dime a dozen.
This conclusion is based on data about rocky super-Earths found orbiting red dwarf stars, which are very abundant. Taking this information, the team developed mathematical models of how young planets with hydrogen-rich atmospheres and magma oceans exchange materials in terms of specific compounds and reactions.
The team, led by UCLA professor Ed Young, found that the hydrogen dissolved in the liquid-hot magma, where it interacted with the oxygen there to produce water. Since these conditions are thought to be common in Earth-like exoplanets, that means water on them would also be common. The process also opens up the possibility that most of the water on Earth was homemade.
According to UCLA, the next phase of the study will be to make a more detailed examination of exoplanet atmospheres to refine their models.
"History shows that the more we learn about ourselves, the more typical Earth seems to be," said Young. "By changing our perspective about our place in the universe, we might change our approach to how we conduct future research and come to even more earth-shattering discoveries."
The research is published in Nature.