"Natural geology: rock fractures often happen in straight lines," McDowell said on Friday. "I understand it's about 30 cm, and it's the intersection between two linear rock fractures."
NASA published on its website photos made by Curiosity at the site of the rectangular hole.
The attention of space lovers was attracted by the image, which was obtained using the Mastcam camera installed on the rover in the Greenheugh Pediment area on May 7. NASA released it later that week.
The image shows a rectangular recess that resembles an entrance to catacombs, which some Internet users have already dubbed an "alien door."
Shortly afterwards, multiple colorized versions of the original black-and-white image have been created, including a panorama created by stitching together several of Curiosity's photographs, as shown on Gigapan.com, a panoramic photography company's website.
However, according to some reports, several clues indicate that the image's subject is indeed not a door. According to a LiveScience report, it is just around 1 meter tall. Moreover, it likely was formed when a massive boulder fell out under its weight.
The interviewed researcher pointed to a boulder on the surface close to the right of the "door," which has a smooth vertical edge - presumably because it dropped out recently and has not been exposed to the Martian winds for long.