Solar Energy Tracker Powers Down After 17 Years (image) NASA/Goddard Space Flight Center Share Print E-Mail Caption Banner Image: The Sun is Earth's primary power source. Energy from the Sun, called solar irradiance, drives Earth's climate, temperature, weather, atmospheric chemistry, ocean cycles, energy balance and more. Credit Credit: NASA / Scott Wiessinger Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.