Why Did the Climate of Mars Shift from Habitable to Inhabitable? Clues from Mapping Ancient Riverbeds | Planetary News – Planetary News

The changing distribution of riverbeds on Mars with respect to elevation and latitude. The top image shows the distribution of rivers in early martian history (>3.6 Ga) when the climate was warm and wet. The bottom image shows the distribution of rivers between 3.5 and 3 billion years ago as the atmosphere thinned, and conditions shifted to cold and dry. Credit: Kite et al., 2022.

Early in martian history, the climate was warm enough for potentially habitable lakes and rivers of water to exist. However, roughly 3.6 billion years ago, the climate shifted from being habitable to inhabitable when liquid water disappeared from the surface. Although the cause of this transition remains unknown, new findings suggest that the loss of an important greenhouse gas transformed Mars into a dry planet.

The past martian climate can be analyzed using patterns and shiftsin the spatial distribution of precipitation-fed rivers. A team of scientistsled by Edwin Kite at the University of Chicago searched for water-influencedlandforms using satellite images of the martian surface, including those fromthe 1972 Mariner 9 mission. By mapping overlapping riverbeds, the team reconstructeda timeline of paleo-river activity with respect to elevation and latitude overbillions of years. Complementary to their climate reconstruction, they used aglobal climate model to simulate various atmospheric conditions and observedhow these would affect rivers. They looked at several parameters in theirmodels that would cause Mars to be temporarily warm enough for liquid water toexist. The results suggest that changing the amount of CO2 (carbondioxide) in the atmosphere would not affect the stability of water. Instead, theloss of some important greenhouse gas must have caused the martian atmosphere tothin, forcing conditions to go from wet to dry.

Although the identity of this greenhouse gas remains unknown, these results show that non-CO2 gases played a dominant role in changing the water flow distribution on Mars. The team recommends that future sites explored by Perseverance include ancient riverbeds to better understand Mars climate change. Since Mars is the only planet whose climate is known to have changed from habitable to inhabitable, understanding what caused this shift could be crucial, given the current state of climate change on Earth. READ MORE

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Why Did the Climate of Mars Shift from Habitable to Inhabitable? Clues from Mapping Ancient Riverbeds | Planetary News - Planetary News