According to a new study, about 3 to 3.5 billion years ago a massive volcanic system caused the outer layers of Mars (its crust and mantle) to rotate around its core, re-shaping the planets geology.
The so-called great shift had been predicted theoretically but never demonstrated. The phenomena was caused by the huge Tharsis volcanic system (the largest volcano in the solar system) which first started to form about 3.7 billion years ago on Mars. The findings were published in the journal Nature. [Photon Propulsion Could Launch Spacecraft To Mars In Days]
Here’s how the shift happened. The formation of the Tharsis volcanic system on Mars was accompanied by several hundred million years of volcanic activity. During this period, a buildup of molten rock formed and eventually grew to a mass of a billion billion tons or about 1/70th the mass of the Moon. The mass was so huge that its gravity caused Mars’ crust and mantle to swivel around. Subsequently, the volcanic system shifted to an equilibrium position on the equator bringing Mars’ crust and mantel along for the ride. The current position of the Tharsis volcanic system is about 20 to 25 degrees from its original position, pre-shift.
The results have big implications for understanding the evolutionary path of Mars. The study proves that, before the shift, the poles of Mars were not in the same place as they are today. This clarifies observations of traces of glacier melting and retreat in the former polar regions that had been previously unexplained by scientists.
In addition, scientists modeled Mars’ climate before the shift and found that large amounts of ice would have accumulated in areas that now correspond to dry river beds. It’s likely that the ice melted, carving out the channels and rivers we see today, as the shift slowly brought the ancient polar regions closer to the equator.
The study radically alters the evolutionary time-line of Mars and changes our perception of Mars as it was 4 billion years ago. According to the new chronology, the period of liquid water stability on Mars was most likely a direct result of the Tharsis volcano and the subsequent shifting poles. This explanation seems to challenge the idea that Mars was once a natural water world similar to Earth.