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A hunt for fossils on Mars

Where to look for the remains of ancient forms of life existed on Mars? A new theory for the formation of the oceans suggests areas to explore the red planet in search of fossils.

The research, conducted by J. Alexis Palmero Rodriguez of the Planetary Science Institute in Arizona, examines the geology of the northern plains of the planet to explain how billions of years ago, Martian oceans were formed: it was the water from the groundwater to flow to the surface through cracks in the crust Mars. This process would result in the formation of seas and lakes in a short time - a few years - but also their survival for millennia.

Mars, however, even at that time, had thin atmosphere pier. Water liquid - and any living creatures that used to house - they were constantly exposed to extreme temperature changes and the damage caused by ultraviolet radiation from the Sun If Mars evolved life forms, "we should find them there, where the water would remain permanently in liquid form: that is underground, "said Rodriguez Palmero.


bad news for fossil hunters, because they dig beneath the surface of the planet would take time and equipment not yet available for the rover, the remote-controlled robots that have so far been sent to explore the Martian surface. You give hope to the new study: in the northern part of Mars, says Rodriguez, "to rise to the surface water was very old, trapped in underground aquifers for billions of years: a very stable environment for the birth and evolution of living organisms. "The sediments left behind by the planet's surface that water could be accessible deposits of fossil rover.
Emergence
slow
The mineral analysis shows that in some periods in the past the surface of Mars has been under water. And on the plains north of the planet, many scientists point out deposits of sediment on the bottom of Earth's oceans.

In the past, some theories have suggested that the oceans of Mars were formed as a result of sudden and massive leakage of water from underground. But there is a open question: "It is thought that these 'empty' sudden water on the Martian surface have carved out a particular type of channels, but they are rare and only released in a few regions of the planet," says Rodriguez.

addition, "there is a vast system of canals linking the highlands of Mars to large basins, it is believed, at one time contained the oceans," said the scholar. "But if these channels do not exist, as did the water to accumulate to form lakes and seas?"

The authors of the new study, published this month in the journal Icarus, they examined a region of northern Mars that lies south of a grading Scopuli called Gemini. Here a deposit sediment lies on top of a basin heavily affected by impact craters and cracks due to earthquakes. By analyzing the spectroscopic data obtained by the orbiters, scientists examined the rocks and minerals, and concluded that the water has flowed from the ground for about two billion years.

The overall landscape also suggests that there was no question of sudden spurts, but the water has slowly emerged through the long and fractures in the crust. Scientists believe that the water came from a vast underground aquifer that extended from the plains up to higher areas. In the plains, due to rise of the water, the water was not absorbed by the soil, but forming stagnant seas shallow lakes or chains of small, similar to those formed in the northern regions of Alaska in the spring melting of snow.

The new theory suggests that Martian lakes and oceans have remained stable for thousands of years, subject to seasonal cycles of freezing and melting. "They should be kept stable until the emergence of water from underground," says Rodriguez. "The lakes are highly saline fluids even if the temperature drops below zero, we have found on Earth that can accommodate living organisms. The stagnant water, then, becomes more stable if it is covered by ice." Stable in the lakes, the creatures of the underground water would have emerged with had more chance of surviving the impact with the new environment, bombarded by ultraviolet rays.

"We know that life forms evolve and adapt better to new environments if they are provided a long period of time in geological terms," \u200b\u200bcontinued the scholar. "If the surfacing of the water was slow and gradual, successive adjustments to life on the surface were more likely to succeed."

Bones on Mars? Hard
According to this theory, the next robots sent to Mars should be able to find fossils on the walls of craters or cracks that open onto the northern plains, basins that once housed the Martian oceans.

The landing site for the Mars Science Laboratory, NASA's next mission to Mars, has not yet been chosen, but one of the candidates, the Mawrth Vallis, good meets the parameters outlined by the new research.

According to Victor Baker, a planetary scientist at the University of Arizona who was not involved in the study, "Rodriguez and his colleagues have put together a theory that ties together many different phenomena that otherwise seem anomalous. It is an idea that will undoubtedly be taken into account. "

For Baker the water in the subsurface of Mars had the potential to sustain life. "Even today, just below the Martian surface, there are environments in terms of chemical, pressure and temperature, are not very different from terrestrial subsurface environments where there is life, "he says.

But, warns the scientist does not expect to find fossils on Mars that resemble those we know." A fossil can be any sign of life forms existed in the past. Not necessarily have to be a bone. It may be a trace, evidence of a chemical reaction that can be tied to a biological process. To think that Mars may have experienced something like the Cambrian explosion - the most intense period of evolution of life on Earth - would be to go too far. It would be too risky, however, expect to find traces of organisms similar to those experienced on Earth early in its history ".

Source: http://www.nationalgeographic.it