Group's Impact Database (formerly Suspected Earth Impact Sites, SEIS) list rates this as improbable for an impact origin. This catalog notes that the observed circular area was visible in Google Earth as having a flat top in the center. They suggest that the flat tops indicates that the strata within the center of this feature is flat-lying and undisturbed. If this is an impact structure, the strata within the center of it would not be flat lying. Instead, the strata within it center would be complexly and distinctly folded, tilted, and faulted as a result of an extraterrestrial impact. After the existence of a possible impact structure was announced, in early March 2006 an expedition traveled through the site and informally published their findings: "[C]ontinued north . . towards a large circular feature that was recently announced to be an 'impact crater' . . We drove past the 'central uplift' along its western edge, then drove into the central part. It is evident, that what is considered the 'central uplift' is in fact nothing more than an eroded outlier of the Gilf, the undisturbed horizontal bedding being clearly visible at all times. The circular shape appears to be pure coincidence, the whole feature is the result of drainage patterns and subsequent eolian erosion, there is nothing to suggest its impact origin." And "We were now in the crater area, looking at the western edge of the central uplift area of the 'crater'. What we saw were uniform horizontal layers of sedimentary rocks, undisturbed except by the processes of natural erosion. The jumbled, chaotic rock formation that we would expect to see in the central uplift area of a crater was not evident at all." A study published in Meteoritics & Planetary Science reported a field investigation of another "crater field" East of the Gilf Kebir, also reported based on remote sensing data. After analyzing the presence/absence of several geologic features associated with impact craters, such as target rocks, breccias, pseudo-shatter cones, and circular morphology, the authors concluded: "[T]here are [sic] no clear and unequivocal evidence supporting the impact origin of the circular structures in Glif Kebir region; until substantial evidence is produced, it's necessary to identify the origin of the craters in others [sic] endogenic geological processes." They proposed the most likely alternative source of the crater to be a hydrothermal vent, although they went on to say: "However, even