Meteorites Reveal That Martian Water Came from Different Sources

Scientists have been struggling to solve one of Mars' biggest mysteries: is or was there water on it, and where did its water originate? Researchers may have discovered a clue in the tiny slices of meteorites that plunged down to Earth from Mars. A new study recently published in the Nature Geoscience journal elaborates on this idea.

Mars seems to have been wet and warm eons ago. Then its atmosphere slowly got stripped off, and Mars was left with its present thin atmosphere and deserts. How did Mars originally get its water? Researchers looked at Mars' many layers to find the answer. Just like every other planet, Mars has an atmosphere, a crust, a mantle, and a core. The meteorites from Mars serve as samples of its crust. It is the layer where Mars harbors its largest water reservoir, estimated to have 35% of its total underground water.

The most well-known Mars meteorites are Allan Hills and Black Beauty. Thin slices of these meteorites have been studied by researchers to understand better Mars' distant past, which includes the origin of its formation and when it accumulated water.

In their findings, scientists estimated Black Beauty's age at two million years, and it was formed and separated from the planet when Mars was hit by a massive impact, laminating pieces of its crust together. The event effectively captured various materials from the different historical points in Mars' timeline.

According to the University of Arizona Lunar and Planetary Laboratory planetary sciences assistant professor and author of the study Jessica Barnes, Black Beauty enabled them to form a picture of what the crust of Mars was like billions of years ago.

The atoms that compose chemical elements are known as isotopes. The study team looked into the chemical composition of the two meteorites in search of two kinds of hydrogen isotopes, particularly those known as heavy hydrogen and light hydrogen. The ratio of the two hydrogen isotopes is useful in understanding the origins of the water traces in the rocks.

According to Barnes, the two isotopes in the two meteorites suggested that the water on Mars came from two sources. Researchers speculate that two planetesimals, or building blocks of planets, may have collided with each other but never wholly mixed. It is a new theory that is incongruent with a previous one that suggested that Mars was formed much as Earth did.

Earth's magma ocean helped in creating its atmosphere, core, and the plate tectonics and crust. With the new data from the two meteorites and other past data, which included those collected by Curiosity, scientists now believe that Mars did not form in the same way.

According to Barnes, these data revealed that the crust was more or less the same throughout time, and the atmospheric changes happened with time. The crust was very different from Mars' mantle, but upon analysis of Martian volcanic rocks, the researchers found them some to be enriched, while others are depleted; they had water that bears the differing hydrogen isotopes.