Mars had oceans and rivers. What happened to them?

The fact that Mars was a watery world is argued by geologists and planetary scientists from the universities of Paris and Copenhagen in the scientific journal “Science Advances”. They have done an analysis of meteorites that were ejected from Mars billions of years ago due to an asteroid hitting and then falling to Earth. Planetary scientists can determine which celestial body a particular meteorite comes from. There are 294 Martian meteorites on Earth today. Some of them come from the primitive stage of the planet’s existence, when both Mars and Earth experienced unusually frequent collisions with rocks from space. According to the theory prevailing today, it was these meteorites falling on both planets that provided them with a large amount of water. “With them, not only a huge amount of melted ice fell on the planet, but also organic molecules, amino acids, and this is all that life needs to arise,” – says the prof. Martin Pizarro of the Center for Star and Planet Formation at the University of Copenhagen.

If the ice caps alone melted, water would cover the entire surface of Mars to a depth of 20 metres

His team examined exactly how much water fell on Mars at that time. To do this, they measured the levels of chromium isotopes in primordial Martian rocks and compared them with this parameter in meteorites, which are called carbonaceous chondrites. These calculations show that there was a lot of water – at first the entire planet was probably covered by an ocean 300 meters deep, and in some places it could be up to a kilometer deep!

“The results of this study are roughly consistent with what we already know about Mars’ past,” says Dr. Anna Kuciak, a planetary geologist from the Institute of Geosciences of the Polish Academy of Sciences in Warsaw. Not only chemical analyzes, but also geological traces on Mars indicate that there is a lot of water on the planet. – For example, the topography indicates that river valleys once existed like those on Earth. We can observe the places where the water began to collect and form the river bed, its course, and finally the classic deltas at river mouths – says Dr. Susiak.

Scientists are also observing a different type of waterway remnant. “These are drainage channels through which water flows very violently. These types of gaps are formed as a result of the sudden accumulation of water and the breaking of the barrier that prevents it – says Dr. Susiak. This barrier may be, for example, the melting of a glacier or a break in the continuity of the shores of a lake. Then Water can fall to the ground with great force, carving a deep channel, completely different from river channels.” In the geological future on Earth, such an event may occur after the ocean penetrates Africa after the eastern part of the continent separates from it along a valley The Great Rift” – says Dr. Susiak. On Mars, they could also be violent outflows of water emerging from underground melting ice as a result of being heated from the inside, for example by volcanoes.

The last major argument that scientists confirm for their belief that Mars was once not red, but a blue planet, is the composition of today’s very thin and very thin atmosphere. “It definitely contains an isotope heavier than hydrogen – deuterium, for example, on Earth,” says Dr. Suciak. How did this happen? This is mainly due to two factors – the first is the small size of Mars, so the air molecules are not held so tightly by gravity as they are on Earth.

In addition, Mars does not have a magnetic field and may never have. Therefore, cosmic radiation is much stronger than radiation on Earth, and it is protected by strong magnetism. – When the heavy, energetic particles of cosmic rays and the solar wind reached molecules of water vapor floating on Mars, they split them into oxygen and hydrogen atoms. Oxygen combines with iron almost instantly to form iron oxides, which are responsible for the red color of Martian soil, while lighter hydrogen isotopes tend to escape into space because they were less well preserved due to the Red Planet’s weaker gravity. Thus the Martian atmosphere was enriched with heavier hydrogen isotopes, which we are detecting today in the Martian atmosphere – says Dr. Susiak.

For millions of years, water from the seas and lakes of Mars evaporated, creating clouds from which rain or snow fell, but also bombarded with cosmic radiation from above. The atmosphere, initially thick and thick with fumes from erupting volcanoes, became thinner and thinner as volcanic activity ceased. About 3.8 billion years ago, the rivers and oceans of Mars began to disappear. From time to time, there have been periodic floods or floods associated with volcanic eruptions and the release of large amounts of groundwater. But it quickly evaporated. Not that it was too cold. At one point, the atmospheric pressure on the planet became so low that, just after passing the 0°C temperature, the water began to boil and evaporate – says Dr. Susiak.

About 3 billion years ago, liquid water ceased to exist on Mars. However, there was still a lot of water ice. This comes after studying the 2.1 billion-year-old Martian meteorite NWA7034 found in 2011, which contains 30 times more water than meteorites, which are about 1.5 billion years old, and 10 times more than similar meteorites from the same period. . It is therefore possible that the meteorite NWA7034, which has been given a fictional name by planetary geologists, formed during the period when there was water on Mars.

It seems that there is no water on Mars today. But only apparently, because in fact there is a lot of things left. “Mars still has a lot of water, but in the form of ice. If the ice caps alone melted, the water would cover the entire surface of Mars to a depth of 20 meters – says Dr. Susiak. We know today that there is much more ice underground on Mars than Surface “This ice sometimes appears after a collision with an asteroid several meters high, which removes the top layer of Martian soil,” says Dr. Susiak.

Sometimes, some of that ice will also melt. This is what happens on the slopes of Martian craters that are exposed to sunlight during the summer months. As it was possible to observe thanks to data from the Mars Reconnaissance Orbiter, distinct streaks appear on the slopes of the Gale and Newton craters. It is most likely brine, i.e. water mixed with salt and calcium perchlorate. Traces of these watercourses are visible throughout Mars’ equatorial belt, where the weather is warmer. Although the air temperature on the Red Planet usually does not exceed 0 ° C (the air temperature in warmer places can reach 20 ° C, but can even drop to minus 120 ° C), thanks to the perchlorate and salt content , Mars’ brine melts in the cold at minus 23 degrees Celsius, however, it also boils and evaporates very quickly, leaving only streaks that the orbiter notices.

Of course, water is not the same as on our planet, because the perchlorate contained in it is very toxic. Perhaps the water that lies deep in the ice is less toxic. According to new research, it may still be in a liquid state! Based on measurements from the MARSIS probe, which uses radar to study the icy terrain of Mars, scientists from the University of Southern Queensland in Australia have concluded that it may be warm enough under the ice caps at the planet’s poles for liquid water. They are there, and at the same time the ice protects them from evaporation. This subglacial lake, similar to the one on Earth in Antarctica, is located up to 3 km below the surface of the Martian ice. If it really existed, because opinions among scientists are still divided.

If such a lake exists, and if we gain access to its waters, perhaps we will finally find traces of life there, which scientists studying Mars have been looking for for many years. Also a.d. Bizarro is very interested in this. He believes that 4.5 billion years ago, when a large ocean rippled on Mars, conditions for the emergence of life on the Red Planet were more favorable than on Earth. “At that time, a catastrophic event occurred on our planet, which was the impact of another planet,” explains the professor. Bizarro. – tore off a significant part of the matter from the Earth, which formed the Moon along with the remnants of the second planet. According to prof. Bizzarro, this event must have evaporated most of the water and was fatal to potential life.

However, Mars has experienced such disasters, evidence of one of which is the asteroid impact crater into which Oceanus Borealis then spilled. – To this day, you can see that on the northern side of Mars there is a flattening 6 km deep. Therefore, the beginning of the existence of both planets was equally turbulent, says Dr. Kuciak. In her opinion, both planets were twins with equally good conditions for the emergence of life, but it appeared long after both planets collided with huge objects from space. On Earth, it was the meteorites and smaller comets striking its surface that brought the organic material from which the first living things may have arisen. According to current knowledge, this happened more than 4 billion years ago, and life on Mars could also have appeared in a similar period.

“Finding traces of it, for example by the Perseverance rover, which is now combing Mars from this angle, will prove that life appears in space wherever the right conditions are,” says Dr. Susiak. Perhaps Earth is no exception in this regard.