
These textures are extracted from 
Visible Earth: A catalog of NASA images and animations of our home planet
http://visibleearth.nasa.gov
The terms of use can be found here:
http://visibleearth.nasa.gov/useterms.php

snow.ppm
is a detail from "Alaska"
Alaska.A2002063.2155.500m.jpg
Credit:
Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

rocks.ppm
is a detail from "Turkish Glaciers"
uludoruk_ali_2012253_lrg.jpg
Credit:
NASA Earth Observatory image by Robert Simmon, using EO-1 ALI data from the NASA EO-1 team. Caption by Adam Voiland. Congratulations to Britton, Dakota Steve, Alev Akyildiz, and Eric Jeffrey for being some of our first readers to solve the puzzler.

fields.ppm 
is a detail from "Mississippi River Well Below Normal"
mississippi_tm5_2011226_lrg.jpg
Credit:
NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using Landsat data provided by the United States Geological Survey. Caption by Holli Riebeek

shore.ppm
is a detail from "Laguna Ojo de Liebre, Mexico"
lagunaojodeliebre_ali_2009261_lrg.jpg
Credit:
NASA image created by Jesse Allen, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Michon Scott

shallow_water.ppm
is a detail from "Crater Lake, Oregon"
ISS013-E-54243_lrg.jpg
Credit:
Astronaut photograph ISS013-E-54243 was acquired July 19, 2006, with a Kodak 760C digital camera using a 400 mm lens, and is provided by the ISS Crew Earth Observations experiment and the Image Science & Analysis Group, Johnson Space Center.

deep_water.ppm
is a detail from "Wildfire Smoke over the Atlantic Ocean"
atlantic_amo_2012263_lrg.jpg
Credit:
NASA image courtesy Jeff Schmaltz, LANCE MODIS Rapid Response Team at NASA GSFC. Caption by Michon Scott.