Much of the valleys on Mars, typical of the planet’s landscapes, were created by catastrophic short-lived floods, with large amounts of water rushing to the surface. This is about a quarter of the total volume of all the valleys that formed on the young planet. Which calculated US researchers use satellite images from NASA’s Mars Exploration Orbiter. They published the results in the journal on Wednesday temper nature. With this research, planetary scientists are trying to understand the early climate on Mars.
Mars is the immediate neighboring small planet Earth. If we look from the Sun, Earth is the third planet and Mars is the fourth. Mars is about four and a half billion years old. The average temperature of -55 ° C makes Mars a cold desert and sandstorms sometimes blow larger than Russia.
The surface of Mars is now dry. There is water in the form of ice and steam, but liquid water is intolerable. Because of the low air pressure (less than a hundredth of the air pressure here on Earth), water on Mars evaporates or freezes instantly.
Over the course of days to weeks, the water scattered outside the lake at lightning speed
It used to be different. Dry rivers, water-dotted valleys, and empty lakes the size of Earth’s small seas betray the abundance of water on Mars billions of years ago. The young planet at that time was much warmer than it is now and the air pressure is higher.
Although it was already known that some valleys were formed from lakes that overflowed their banks, according to ancient ideas, the valley network on Mars in general formed gradually and slowly. For example, due to groundwater or prolonged precipitation.
Mars may have had a long climate with a water cycle as here on Earth: water evaporates into the atmosphere and returns to the surface via rain or snow. The prolonged and continuous rain that fell on the ground paved a path through the surface, and thus a valley network is said to have formed.
But American researchers have now calculated that at least a quarter of the valley network on Mars was created not gradually, but rather rapidly due to overflowing lakes. The lakes, temporarily due to rain or groundwater, filled up and erupted on the sides. Over the course of several days to weeks, the water rushed out of the lake at lightning speed and made its way across the landscape, carving out chunks of land.
To do the calculation, the researchers studied satellite images taken by the Mars Exploration Vehicle. This is a NASA satellite that has been orbiting Mars for about sixteen years. Satellite images of the valleys’ topography show whether they are forming very slowly, for example due to rainfall, or due to a large amount of water that has rushed rapidly over the landscape as a result of a lake overflowing. “When a lake empties due to a flood, a hole is created in the banks,” says Martin Kleinhans, a physical geographer at Utrecht University who was not involved in the study. “This looks like a breach, like that created during dam holes in Zeeland, for example. From the hole in the lake comes a long valley that stretches far across the landscape. If the river does not start from a lake, but consists of several branches like The Rhine, it is likely that it originated from slow erosion.”
The researchers only looked at traces of flowing water that formed on the young planet Mars and filtered out the most recent. Using an algorithm, they then calculated the total size of the two types of valleys on the satellite imagery. The slowly accumulating valleys have a size of about 4.3 x 1013 Cubic meters. The size of the valleys caused by the flood is about 1.4 x 1013 Cubic meters. So a quarter of it was due to floods.
Planetary scientists study valleys on Mars because they help them reconstruct what the planet’s climate should have looked like billions of years ago. “The only way to do this far back in time is to study the footprint you leave on the terrain,” says Tjalling de Haas, who is also a physical geographer at Utrecht University and not involved in the research. The study indicates that the formation of valleys did not necessarily require a prolonged rainy climate on Mars. Only, just as on Earth, it also applies to Mars that what you see in one place should not apply to another. The prolonged elongated climate can still explain the remaining three quarters of the valley network.”
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