Water could be a natural byproduct of rocky planets forming — so it could be almost everywhere

Water might be a byproduct of the formation of all rocky planets, a new study proposes.

The Curiosity rover on Mars. Image credits NASA / JPL-CALTECH.

From all we know of life today, water seems to be a key ingredient. Life on our planet spawned and lived its early years in water. So our efforts to find extraterrestrial life focused heavily on identifying planets with liquid water. However, a new study suggests that water may be much more bountiful in the universe than we’d expect. In fact, it may be a byproduct of the formation of any rocky planet.


“There are two hypotheses about the emergence of water. One is that it arrives on planets by accident, when asteroids containing water collide with the planet in question,” says Professor Martin Bizzarro from the Centre for Star and Planet Formation at the Faculty of Health and Medical Sciences, University of Copenhagen.

“The other hypothesis is that water emerges in connection with the formation of the planet. Our study suggests that this hypothesis is correct, and if that is true, it is extremely exciting, because it means that the presence of water is a byproduct of the planet formation process”.

Together with Assistant Professor Zhengbin Deng, Bizzarro performed an analysis of a black meteorite known as “Black Beauty”. This meteorite is 4.45 billion years old and found its way to Earth from the original crust of Mars. As such, it contains unique insight into the ancient history of the solar system. They explain that the findings showcase that water may be much more common in the universe than we’ve assumed up to now.

The duo found that Mars harbored water for the first 90 million years of its existence. This would be long before the planets in the inner Solar System (like Earth and Mars) were bombarded by water-rich asteroids, as per our previous hypothesis. In other words, it couldn’t have been asteroids seeding water onto planets (or, at least onto Mars).

Black Beauty was first discovered in the Moroccan desert, and soon found its way to the market — for around USD 10,000 dollars per gram. The team gathered the funds to buy some 50 grams of the meteorite back in 2017 and started working on it in the lab. They crushed and dissolved some 15 grams of the meteorite and processed them with a new technique they developed.

“We have developed a new technique that tells us that Mars in its infancy suffered one or more severe asteroid impacts. The impact, Black Beauty reveals, created kinetic energy that released a lot of oxygen. And the only mechanism that could likely have caused the release of such large amounts of oxygen is the presence of water,” Zhengbin Deng says.

“It suggests that water emerged with the formation of Mars. And it tells us that water may be naturally occurring on planets and does not require an external source like water-rich asteroids,” Bizzaro adds.

The dry river and lake beds visible on Mars today are undeniable proof that the planet once harbored liquid water. However, its surface is quite cold — so the authors wanted to understand how this could be. Their analysis suggests that asteroid impacts likely released a lot of greenhouse gases into its atmosphere. Their warming effect on the planet’s climate led to the conditions that allow for liquid water to exist on its surface.

Going forward, the team plans to examine microscopic water-bearing minerals in the asteroid, which have remained unchanged since they first formed.

The paper “Early oxidation of the martian crust triggered by impacts” has been published in the journal Science Advances.

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