A longstanding mystery that has puzzled scientists for years might finally have a solution: how Mars managed to sustain rivers and seas long after the planet began to cool and its atmosphere thinned. As per the new study, published in the 'Journal of Geophysical Research: Planets', it's all thanks to a cycle of water and carbon dioxide.
Around four billion years ago, Mars was warm and wet, with extensive rivers, lakes, and a large northern sea. This period spans the Noachian era (4.1–3.7 billion years ago), known for its warmer climate, and the Hesperian era (3.7–3 billion years ago), when the planet began losing its atmosphere and cooling. Despite the colder climate of the late Noachian and early Hesperian, traces of river channels and seas remained, indicative of liquid water. Researcher Peter Buhler of the Planetary Science Institute in Arizona postulates that this could be the result of carbon dioxide ice settling onto the south polar cap.
According to Buhler, the origins of Mars' major landscape features—such as its largest lake, valleys, and the extensive esker system (remnants of rivers once flowing beneath an ice sheet)—are explained by this model in a self-consistent manner. The model relies solely on a process already observed today: carbon dioxide collapsing from the atmosphere and settling on the planet’s surface.
Buhler further explains that some 3.6 billion years ago, carbon dioxide from Mars’ atmosphere froze and settled on a layer of water sheet at the poles. This layer served as an insulating blanket, trapping heat from Mars' interior and increasing pressure on the underlying ice. Consequently, without the need for a warm climate, nearly half of Mars' water melted and began moving toward the surface. The water thus trapped was only allowed to flow along the boundary between the ice sheet and the rock beneath it.
The meltwater from the ice sheets form rivers beneath the ice that leave behind impressions called eskers. Scientists have found many eskers near Mars’ south pole, with size the same as suggested by Buhler's model.
Around four billion years ago, Mars was warm and wet, with extensive rivers, lakes, and a large northern sea. This period spans the Noachian era (4.1–3.7 billion years ago), known for its warmer climate, and the Hesperian era (3.7–3 billion years ago), when the planet began losing its atmosphere and cooling. Despite the colder climate of the late Noachian and early Hesperian, traces of river channels and seas remained, indicative of liquid water. Researcher Peter Buhler of the Planetary Science Institute in Arizona postulates that this could be the result of carbon dioxide ice settling onto the south polar cap.
According to Buhler, the origins of Mars' major landscape features—such as its largest lake, valleys, and the extensive esker system (remnants of rivers once flowing beneath an ice sheet)—are explained by this model in a self-consistent manner. The model relies solely on a process already observed today: carbon dioxide collapsing from the atmosphere and settling on the planet’s surface.
Buhler further explains that some 3.6 billion years ago, carbon dioxide from Mars’ atmosphere froze and settled on a layer of water sheet at the poles. This layer served as an insulating blanket, trapping heat from Mars' interior and increasing pressure on the underlying ice. Consequently, without the need for a warm climate, nearly half of Mars' water melted and began moving toward the surface. The water thus trapped was only allowed to flow along the boundary between the ice sheet and the rock beneath it.
The meltwater from the ice sheets form rivers beneath the ice that leave behind impressions called eskers. Scientists have found many eskers near Mars’ south pole, with size the same as suggested by Buhler's model.
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