One you left out: Because space-based remote sensing can tell us about Earth. See: http://science.nasa.gov/earth-science/focus-areas/ http://science.nasa.gov

One you left out: Because space-based remote sensing can tell us about Earth. See: http://science.nasa.gov/earth-science/focus-areas/ http://science.nasa.gov/earth-science/focus-areas/ (There are others.)