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- Water data: new model of the young Solar system will help in the search for life on Mars
Water data: new model of the young Solar system will help in the search for life on Mars
Scientists have calculated the probability of migration of various bodies in the early Solar system. The constructed model shows that the bulk of the water on the terrestrial planets was delivered by icy objects from the area beyond the orbit of Jupiter. Mars, located closer to the source of this stream, received more water than Earth, and in the period 3.5–2.5 billion years ago, it probably had an ocean. At the same time, microbial life forms could have originated on the Red Planet. The results of the study make it possible to narrow the search area for its traces to certain geological layers, which increases the chances of research success. However, experts note that the presence of water in itself does not mean the existence of life. For more information, see the Izvestia article.
How ice from the vicinity of Jupiter created oceans on Earth
Scientists from the Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences have developed a new model of the early Solar System dating back to the epoch of planet formation. As part of the work, experts reconstructed the gravitational "corridors" along which various celestial bodies moved in the vicinity of our star.
One of the key conclusions was the assumption that the bulk of the water on the Earth's surface was delivered by icy bodies from the region beyond the orbit of Jupiter and the outer asteroid belt. Mars, which was in the path of this flow, received more such objects per unit of its mass than Earth. As a result, in the period 3.5–2.5 billion years ago, the surface of the Red Planet was probably covered by the ocean.
These data indirectly confirm the hypothesis that if there was life on Mars, then the conditions for its origin could have existed during this period. Clarifying the time frame of the proposed Martian biosphere makes it possible to focus the search for traces of it on rocks of the appropriate geological age, increasing the chances of finding traces of life on Mars.
— Planetesimals formed at an early stage of the Solar system. These are the objects that later formed planets. Inside the "snow line" (at a distance three times further from the Sun than the Earth), they were "dry", and behind it they contained ice, since the star's energy was no longer enough to evaporate it," Sergei Ipatov, a leading researcher at GEOHI RAS, told Izvestia.
Sergey Ipatov, a leading researcher at GEOHI RAS
According to him, the terrestrial planets Mercury, Venus, Earth and Mars were originally formed from local dry planetesimals. Later, when young Jupiter gained significant mass, its gravity began to direct icy bodies into the region of these planets. Their influx was provided by the outer giants Saturn, Uranus and Neptune. By this time, the planets of the terrestrial group had already become massive enough to hold the water coming from outside.
Why did Mars get more water?
Calculations have shown that the total mass of H2O on Earth, delivered from the region beyond the orbit of Jupiter and the outer asteroid belt zone, could exceed the mass of all modern oceans, said Sergey Ipatov.
— It is possible that the water that was formed during chemical reactions inside the Earth had a total mass several times greater than that introduced from the outside. However, only a small part of it could get out of the depths to the surface. At the same time, bodies falling from the Jupiter region delivered water directly to the earth's oceans," he explained.
The scientist noted that in such collisions, part of the substance of the impacting body was not retained by the gravity of the Earth and was ejected back into space. Therefore, the total mass of icy objects that reached the planet was greater than the volume of water that eventually remained on its surface.
At the same time, according to him, the amount of moisture received on Venus was comparable to that on Earth. However, due to the extremely high temperature and pronounced greenhouse effect, the water on this planet evaporated and was lost relatively quickly.
Unlike Earth, Mars, located closer to the asteroid belt and Jupiter, could capture even more icy planetesimals in terms of its mass. However, due to the weak gravity — with a mass about ten times less than that of Earth — the Red Planet was unable to hold significant amounts of water, and over time it gradually dispersed into outer space.
Nevertheless, calculations of the probabilities of collisions of migrated bodies with Mars show that stable oceans may have existed on Mars for a certain period, the expert said. It was during that era that conditions could have been favorable for the appearance of life on the Red Planet.
Channels on Mars
— It is believed that 3.5–2.5 billion years ago Mars had a permanent hydrosphere, and then a biosphere could exist on it. It is possible that the level of organisms on the Red Planet was comparable to those that inhabited the Earth at the same time — the simplest single—celled organisms," added Sergey Ipatov.
In his opinion, the modeling data helps to reduce the time and geographical scope of the search for possible traces of ancient microbial life on Mars and to focus research on rocks that formed during this "wet" period. Also, the role of giant planets like Jupiter may become a significant criterion for searching for exoplanets — objects suitable for life — in other star systems.
Could there be life on Mars?
— The Earth was formed as an element of a dynamic system. According to modern concepts, some of the water was captured by the planet directly from the protoplanetary disk, while the other came later along with asteroids and comets. In the future, water was repeatedly redistributed between the mantle, crust and ocean," Oleg Korablev, head of the Planetary Physics Department and Deputy director of the Space Research Institute of the Russian Academy of Sciences, told Izvestia.
As for Mars, there is a lot of observational evidence of the existence of liquid water on it, but there is no direct connection with the developed biosphere. Besides water, climate stability, protection from radiation and an active geochemical cycle are also necessary for the emergence of life, he added.
The ocean on Mars probably existed for hundreds of millions, but not billions of years, the expert noted. After that, the planet's magnetic field disappeared, and the atmosphere turned into a degenerate state. If life on the Red Planet did arise, then, apparently, it was simple — microbial and local. It could only be preserved in subsurface niches.
— In cosmogony, there has long been a question of where there is so much water on Earth. In the region near the Sun, where our planet was formed, there was practically no H2O: gas molecules, including water vapor, were displaced by the intense solar wind. At the same time, beyond the "snow line", in cold areas, water molecules condensed on dust particles, significantly increasing their mass. Giant planets and their moons were subsequently formed from this substance," said Sergey Yazev, senior researcher at the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences, director of the Astronomical Observatory of Irkutsk State University.
According to him, the calculations made clarified the ideas of how the planets of the terrestrial group were formed from small bodies, including those coming from behind the "ice line" and therefore containing a lot of water.
A snapshot of glaciers on Mars
Speaking of Mars, there is really a lot of water on the planet, but today it is mostly in a frozen state, the expert noted. According to him, the Great Northern Plain in the past was a huge, albeit relatively shallow ocean. Now a dry, frosty desert stretches in its place. At the same time, the expert emphasized, the presence of water in itself does not mean the existence of life. H2O is found almost everywhere in the Solar system, but convincing signs of biological activity have been found only on Earth.
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