Color or Grayscale
Grayscale — 8-bit grayscale image that can be used with your own palette. Note: Blue Marble and MODIS True- and False-color images are not available for downloading as grayscale.

File Types
In addition to the standard file formats—JPEG, PNG, GeoTIFF, or GoogleEarth (KMZ)—many (not all) datasets support these "data value" formats. (Note: These data values are only approximations based upon the scaled range of the imagery. These values should not be used as scientific absolutes but only for simple analysis. Read more about these formats on our blog.)

CSV: Comma-separated values. Suitable for Excel (2007 and later) and other tools.

CSV for Excel: Modified CSV. In Excel versions prior to 2007 worksheets could not support more than 256 columns. To remedy this, this option will resize the image to 250x125. The first row contains the longitude values for the center of the cell; the first column contains the latitudes, also at the center.

Floating point GeoTIFF: returns a GeoTIFF file containing the float data values for the image.