The fact that there is water on Mars is already a certainty, and we can definitely say that in the geological past of the planet, the water on Mars was liquid and formed a huge planetary ocean. But how did all this water get to Mars? According to a recent study, it appears that carbonate meteorites were responsible.

About 4 billion years ago, Mars had a much denser atmosphere than today, a magnetic field that protected the planet from the solar wind, and a planetary ocean. Under conditions of pressure and temperature similar to those existing on Earth today, water could exist in liquid form. We know this because of the traces left by liquid water on the now arid surface of a nearby planet: we see valleys carved by former rivers, long-dried deltas, and even the presence of compounds that could only have formed in the presence of liquid water.

But the planet’s core cooled faster than Earth’s core, so Mars lost its protective magnetic field, and the solar wind disrupted the atmosphere, and water on the surface either froze or evaporated directly. What is certain is that we no longer find water on the surface of Mars today, except as a temporary form of ice that sublimates rapidly due to the low pressure.

But where did all the water that existed on the surface of Mars in the past come from? A team of French, Danish and Swiss researchers puts forward an interesting hypothesis: bombardment with carbonate meteorites may explain the presence of a former Martian ocean at least 300 meters deep.

Generally speaking, meteorites are classified according to their composition, so we can have chondrites (or chondrites, stony meteorites, the most common meteorites found today), iron meteorites, iron-stone meteorites, or achondrites (a class that includes the rest of the meteorites, which do not fall into any of the above categories).

Chondrites also have several subclasses, and one of them is carbonate meteorites, which means that in addition to being high in iron and nickel (specific to meteorites), they also contain high levels of carbonates and…water. About 10% water or more. The researchers calculated that the bombardment of such meteorites in the early history of the solar system, and, accordingly, the planet Mars, could explain the amount of water that would have covered the entire planet with an ocean at least 300 meters deep.

How do we know that Mars was bombarded with meteorites? From the analysis of Martian rocks, a higher concentration of the isotope chromium-54 was found, which cannot be explained in any other way than meteorites; The Martian crust should not contain this isotope according to current theories of planetary evolution, so the only explanation is that this isotope was brought to Mars by a meteorite bombardment. Which, along with the chromium-54 isotope, also brought water.

It is very interesting to see how researchers gained access to Martian soil samples, as NASA and ESA are only now discussing a mission to deliver Martian rocks to Earth. Just like on Earth, meteorites fall on Mars from space, but they hit the planet’s ground at a much faster rate than on Earth because of the less dense Martian atmosphere.

This causes the Martian rocks produced by the impact to have such high velocities that some of them sometimes end up in space. Or even in the orbit of the Sun. And some of them, very rarely, cross the Earth’s orbit, usually after making millions of revolutions around the Sun. In this way, fragments of Martian soil can reach Earth in the form of meteorites, and we can learn data about the planet Mars without going there and telling robots to do it for us.

This is the new meaning of the phrase “if Mahomet does not go to the mountain, the mountain goes to Mahomet.” Do you remember how we said that there is a class of meteorites called achondrites, and all other meteorites do not fit into other categories? Well, Martian meteorites are achondric and extremely rare: of the more than 70,000 known, classified, and studied meteorites, only 343 are Martian. And that makes them extremely expensive: in 2011, the Natural History Museum in Vienna paid half a million dollars for a Martian meteorite weighing less than 1 kilogram.

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