Prof. Jayant K. Tripathi

Earth has an unique position among all other planets in respect of its habitability and presence of life. Unlike its neighbor planets on both sides, it lies at a position where carbon dioxide and water remain in its atmosphere and hydrosphere affecting the Earth's climate. Although, these molecules in the atmosphere are the global warming gases, they react with rocks on the Earth surface by the process of weathering to take hold of carbon dioxide and cool Earth’s surface temperature in geological time scales. In the geological past, the Earth has entered into many warm and cold periods, either externally influenced by Sun and Earth relation cycles, or internally by the process of weathering regulated through plate tectonics. We came out of the last cold condition, influenced by Himalayan mountain building and related weathering, recently (geologically speaking) around ten thousands years ago. If the Earth’s habitability has been controlled by the Earth’s position with the Sun, the process of weathering on the surface has been responsible for drawing down the continuous outflow of carbon dioxide from the Earth’s interior through volcanism. Otherwise, accumulated carbon dioxide would have been havoc for the life system, even for the present habitable position of the Earth in the solar system. Rock weathering sequesters carbon dioxide by chemical reactions to deposit limestones on the ocean floor, provides nutrients to the life system, produces a huge amount of sediments, which buries in large basins a huge amount of organic matter produced by the life system. As a result, carbon dioxide gets locked and becomes unavailable to the atmosphere, bringing colder climate in the long-term geological time scales. The Earth has been using this self-regulation with its own material and resources for its habitability to the life system.