In the second part of our two-part Earth Day episode, Water is More Important!?, we’re exploring the vital role that water plays in sustaining life on Earth and beyond. Our special guest is none other than Sandra Postel, director of the Global Water Policy Project. She will share her insights with us into the importance of this precious resource.[[So. I’m sitting here on my bachelor pad, and you have me wondering. How did it all get here? The water, I mean. It seems Earth has an awful lot of it. I mean, blue planet, and all that rot.]]Sandra Postel appears on The Cosmic Companion for Earth Day, 22 April 2023. Creative Commons 4.0 Attribution 2023 The Cosmic Companion.It turns out that no one is quite sure how or why water formed in such great quantities on Earth. Certainly, being at the right distance from the Sun, and having a thick atmosphere, allowing water to pool on its surface helps. But, how did water first arise on our world?Researchers have been puzzling over this question for years, and there are a few major ideas which have emerged.One theory is that water arrived on Earth through comets and asteroids. These space-borne clumps of rock and ice collided with our planet billions of years ago in large numbers, potentially bringing water with them. This theory is supported by the fact that the ratio of heavy to regular water on Earth is very similar to that found in comets, suggesting comets may have played a major role in forming the oceans of Earth.Another possibility is that water was present on Earth from the very beginning, during the formation of our planet. This theory suggests that water was present in the gas and dust cloud that eventually coalesced to form Earth. As the planet cooled and solidified, the water vapor condensed into liquid, forming oceans.[Cool water]A third theory is that water was created by the reactions that took place within the Earth’s mantle. This idea suggests that high pressures and temperatures within the mantle caused the formation of water molecules from the elements present in the layers of our nascent planet.And, it is also possible that each of these sources played a role in creating the aquatic environment of our water world. Today, water covers more than 70 percent of our planet, supporting millions of species of life. And, water around the planet, together with the life which depends on it, are threatened by global climate change, driven by human activity.Next up, we talk with Sandra Postel, director of the Global Water Policy Project.The Blue Marble on which we live is more than oceans, lakes, ponds and rivers. Water is also found in the atmosphere, aquifers, and life itself, including you and me.Heat from the Sun drives evaporation from oceans and other bodies of water, lifting water into the air. [wooooah!] Once in the atmosphere, this water vapor condenses into clouds, eventually releasing their moisture as precipitation, such as rain or snow, back onto the land and water.Moisture which falls onto land can either seep into the ground and become groundwater, or flow back into rivers, lakes, and oceans, restarting the cycle. The process is also influenced by factors like wind, temperature, and topography, which help determine the amount of precipitation that falls in different areas.This water cycle ensures that water is constantly moving and being redistributed throughout the planet, providing us with this essential resource that we all need to survive.[[Some desert plants only need water once every couple weeks under most conditions. Those ever-resilient tardigrades can last decades between drinks of water. And, some bacteria also use very little water, although their metabolism still depends on this vital liquid. The rest of us really need the stuff!]]There are several ways people can help conserve and protect this precious resource. Homeowners can seek out efficient appliances with the WaterSense label, and repair water leaks as soon as possible after they are discovered. R