Rick Robinson

Jul 14th 2021

Crushed Space Rocks Hint at Water-Rich Exoplanets


What do you get when you bake crushed space rocks in a laboratory oven?

Two research teams at separate universities have recently performed independent variations on just that experiment. And what they got was evidence of water — enough of it to suggest that rocky, Earth-like exoplanets rich in water may be common in the universe.

This matters because such planets, like Earth, bring together the key ingredients of life: water, which accounts for most of the mass of living cells and organisms, and the vital mineral substances needed for the biochemical processes that support life.

In a nutshell, if Earth-like exoplanets are common in the universe, chances are that extraterrestrial life is also common.

Water’s “Origin Story”

Water, or H2O, combines the most common element in the universe, hydrogen, with the third most common, oxygen. So, it is not a rare substance. But liquid water, the building block of life, is trickier to come by. In most of the universe, it either freezes into ice or boils away as water vapor.

Martin Bizzarro of the University of Copenhagen in Denmark, a member of one of the research teams working with crushed space rocks, tells Futurity about a prevailing theory of the origin of water on Earth and Earth-like exoplanets. Simply put, it may just be an accident — as a result of planets colliding with ice-rich asteroids or comets.

But there’s a second theory, too — that it’s no accident at all. The Copenhagen team’s study of a meteorite called “Black Beauty” suggests that water on rocky planets may have actually been there all along, delivered as part of their natural formation process.

“Water may be naturally occurring on planets and does not require an external source like water-rich asteroids,” Bizzarro told Futurity.

Black Beauty’s Eventful Journey

The meteorite studied by the Copenhagen team, called “Black Beauty,” was found in Morocco, but scientists believe that it originated from Mars. About 4.45 billion years ago — and some 90 million years after Mars itself was formed — the meteorite was smacked off Mars by an asteroid impact.

It ultimately ended up on Earth, where it was found and sold for $10,000 per gram. The University of Copenhagen was able to buy 50 grams of the meteorite. (Its much less vivid official name, per the initial research report in Science Advances, is NWA 7533.) When 15 grams of it were crushed and baked in a special laboratory oven, the crushed space rocks released an impressive amount of oxygen gas.

“The only mechanism that could likely have caused the release of such large amounts of oxygen is the presence of water,” co-experimenter Zhengbin Deng told Futurity. The enormous energy of the asteroid impact that knocked Black Beauty off Mars must have also vaporized a large body of water, breaking it down to hydrogen and oxygen.

The hydrogen dissipated into space, but some of the oxygen was left trapped in the rock until it was released by crushing and baking the rock in a Copenhagen lab.

Further Adventures With Crushed Space Rocks

Meanwhile, according to Science News, another research team at the University of California at Santa Cruz, headed by astrophysicist Maggie Thompson, was also baking crushed meteorite fragments and measuring the gas that escaped.

Unlike Black Beauty, the meteorites the Santa Cruz team studied are a type called carbonaceous chondrites. These are not believed to be fragments knocked off a planet but rather primordial material that never became part of a planet but still resembles the dust grains that formed the planet originally.

But when UCSC’s research team heated these primordial crushed space rocks, they got similar results to the Copenhagen team: 62% of the gas released by the carbonaceous chondrites was water vapor, Science News reports. The water in these meteorites was never broken down into hydrogen and oxygen because they were never subjected to the extreme conditions of being knocked into space by an asteroid impact.

Watery Worlds Beyond

Mars is not an exoplanet — it is a fellow member of our own solar system. And the carbonaceous chondrites, never part of any planet, probably also originated in our solar system rather than from interstellar space. But the same basic processes at work in our solar system are also likely to operate in planetary systems of other stars.

“Measuring the outgassing composition from meteorites can provide a range of atmospheric compositions for rocky exoplanets,” Thompson told Science News. And the results suggest that steamy atmospheres of water vapor may be common for newly formed rocky planets.

All these research findings come at the same time that NASA reports that the James Webb Space Telescope should be able to detect oxygen in the atmospheres of exoplanets. Because the presence of water and the presence of oxygen are so closely tied together — and both are associated with life — the recent discoveries involving crushed space rocks bring us that much closer to the ability to detect life beyond the solar system.

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