Theoretically, such a structure cannot exist.
Planetary scientists at Caltech have uncovered the mystery of the formation of layers of ice at the South pole of Mars, whose existence has long been considered inexplicable. They developed a model that showed that the main role played by several factors, including fluctuations in the planet’s axis. About it reported in a press release on phys.org (translation — lenta.ru).
Mysterious structure consists of alternating layers of frozen carbon dioxide and water, extending to a depth of one kilometer. Theoretically, such a structure cannot exist, since “dry ice” is less thermally stable than water. A new model suggests that this pattern has arisen by a combination of three factors: the change in the angle of the axis of the planet, the reflectivity of ice to sunlight and an increase in atmospheric pressure during the melting of “dry ice”.
Scientists have developed a theoretical model that matches observations of the satellites. It suggests that in the last 500 thousand years, the axis of rotation of Mars hesitated, causing the South pole of the planet receive different amount of sunlight. “Dry ice” was accumulated when light was scarce, and freeze-dried, when it was the peak of the solar radiation. However, together with frozen carbon dioxide accumulated a small amount of water ice, which served as protection to the underlying layer of carbon dioxide.
The oldest and deepest layer of ice formed 510 million years ago after a period of extreme insolation, when the carbon dioxide was in the atmosphere.
Such a mechanism was predicted in 1966 by Robert Leighton (Robert Leighton) and Bruce Murray (Bruce C. Murray) of the California Institute of technology. They suggested that Mars with a thin atmosphere of carbon dioxide can have long-term stable polar deposits of CO2 ice, which in turn will control the global atmospheric pressure.