The Earth and Mars are two planets which evolved very differently. By studying locations on Earth whose environment might be similar with that of Mars, scientists are able to theorize about 'the red planet' as well. Meteor Crater is one such study site in the Colorado Plateau, 73 km east of Flagstaff, Arizona. This terrestrial impact crater, 1.2 km in diameter and 185 m deep, is clearly visible in satellite imagery.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 126.96.36.199.0