Today Mars is a desiccated desert. Conditions on the planet's surface exclude the possibility of stable existence of liquid water. But it was not always so. At the dawn of the solar system, Mars had a full-fledged hydrosphere. This is indicated by the characteristic details of the relief of the red planet, carved by the once flowing water flows along its surface, as well as the results of chemical analysis of sedimentary deposits. According to most scientists, in the distant past, Mars possessed a much denser atmosphere, which made possible the existence of liquid water.
There is another important aspect directly related to the climate of ancient Mars. It is associated with the so-called. the paradox of the faint young sun. The fact is that 4 billion years ago, our star emitted about 30% less energy than it is now. Usually, to explain the paradox, the global greenhouse effect is used, which significantly raised the average temperature of the planet.
But not all planetary scientists agree that Mars had such a dense atmosphere that it was able to compensate for the lack of solar radiation. According to the alternative opinion, the average temperature of ancient Mars was much lower than it was believed and it was almost completely covered with ice. Large streams of water, traces of which can be seen on images of space stations, were formed only during asteroid bombardments and periods of volcanic activity.
Researchers Cole Brown and Darren Williams of Pennsylvania State University have offered their own explanation for the paradox. According to their study, the results of which were announced at the 232nd Annual Meeting of the American Astronomical Society, Mars may have formed much closer to the Sun than is commonly believed.
The researchers investigated the possibility that Mars and Venus originally formed together and were originally a double planet. Both bodies revolved around a common center of mass and, like Pluto and Charon, were constantly facing each other by the same side. Calculations made by scientists showed that the planets could be in this position for about 100 million years, which is quite enough for the formation of the Martian hydrosphere.
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But in the long run, the configuration turned out to be unstable. The accumulated gravitational perturbations led to the fact that Mars set off on a "free voyage" in the solar system, eventually moving to its current orbit. Venus, on the other hand, approached the Sun. The effects caused by this transition could explain the current anomalous rotation of the planet and its lack of satellites.
Brown and Williams admit that the likelihood of the scenario described is not very high. Researchers have performed thousands of simulations in which Mars formed along with Venus. In most of them, the red planet would eventually collide with Earth or Venus. In another 20% of cases, Mars was thrown out of the solar system. 10% of simulations ended up falling into the Sun. And only 13% of the time, Mars safely entered its current orbit.
Of course, 13% is clearly not enough for this hypothesis to seriously affect the prevailing ideas about the evolution of the solar system. But at the same time, the figure is large enough to take it into account and conduct additional research on such a possibility.
