Unnatural Anomaly Discovered On Mercury?

On the Internet appeared the video, on which shows, according to the author of the video, as in the photos, which were taken by U.S. space probe MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging), American automatic interplanetary station (AWS) for the study of Mercury, on the surface of Mercury has been found an unusual object. (Photo by NASA)

This image is a portion of the MDIS global mosaic basemap that was acquired during MESSENGER's first year in orbit. The scene, with north to the right, shows a geological feature termed Victoria Rupes – a long cliff or scarp that formed when Mercury shrank slightly as its core cooled.

To the right (Victoria Rupes Cliffs) we can cleary see an un-natural anomaly, as nature never creates straight lines, ever!

The scale is 5.6km long or 3.4 miles, that is gigantic. Could this be an entrance/exit or the black rectangular area has been placed by NASA onto the image to hide a structures up there?

Date Created: February 10, 2012
Instrument: Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS)
Latitude Rang: 47° N to 59° N
Longitude Range: 321° E to 331° E
Resolution: 250 meters/pixel
Scale: The crater just left of center is approximately 42 km (26 mi.) in diameter
Projection: Azimuthal equidistant