Picture of the Day: The Water Planet
THE WATER PLANET
Viewed from space, the most striking feature of our planet is the water. In both liquid and frozen form, it covers 75% of the Earth’s surface. It fills the sky with clouds and is practically everywhere on Earth; from inside the rocky crust to inside our cells.
This detailed, photo-like view of Earth is based largely on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. In all, the Earth’s water content is about 1.39 billion cubic kilometers (331 million cubic miles), with the bulk of it, about 96.5%, being in the global oceans. As for the rest, approximately 1.7% is stored in the polar icecaps, glaciers, and permanent snow, and another 1.7% is stored in groundwater, lakes, rivers, streams, and soil.
Only a thousandth of 1% of the water on Earth exists as water vapour in the atmosphere. Despite its small amount, this water vapour has a huge influence on the planet. Water vapour is a powerful greenhouse gas, and it is a major driver of the Earth’s weather and climate as it travels around the globe, transporting heat with it.
For human needs, the amount of freshwater for drinking and agriculture is particularly important. Freshwater exists in lakes, rivers, groundwater, and frozen as snow and ice. Estimates of groundwater are particularly difficult to make, and they vary widely. Groundwater may constitute anywhere from approximately 22 to 30% of fresh water, with ice accounting for most of the remaining 78 to 70%. [Source: NASA]