14 DAY TRIAL // There are many strange formations on Mars whose images sparked the imaginations of many people around the world and many have come with theories until the official scientific explanations. Among them is an image of a spooky anomaly, first observed in 1976 by Viking, called the Mars Face, or pictures of "dust-devils" mini tornadoes that spin on the Martian surface with no obvious tornado clouds to generate them.
New photographs are showing yet another bizarre apparition: the black hole. The latest images sent from NASA's Mars Reconnaissance Orbiter HiRISE shows a dull lava plain, apparently not much different from other similar volcanic plains on Mars. There's one problem: a black spot in the center.
The black spot is actually a window onto an underground world. The team of astronomers spotted one of seven possible entrances to subterranean caves on Mars. In a paper presented at the Lunar and Planetary Science Conference, Glen Cushing, Tim Titus, J. Judson Wynne and Phil Christensen have even baptised the seven caves with female names: Dena, Chloe, Wendy, Annie, Abbey, Nikki, and Jeanne.
Mars Reconnaissance Orbiter has a high resolution camera on board, reaching a little better than 20 meters per pixel, which created these excellent images. The HiRISE camera can see the detailed shape of the slightly scalloped edge of a hole on the flank of Mars' Arsia Mons, but no amount of image enhancement can bring out any further details inside the hole.
This could only mean one thing: the cave is shaped like a bubble and each entrance is in fact a tiny round crack in the ceiling. The cave is larger below the ground than the entrance we can see at the surface and it's very deep.
How deep? No one knows exactly, but scientists have begun extensive calculations considering the illumination conditions and the sensitivity of the camera to put a lower limit on how deep that cave must be for HiRISE to be able to see nothing at all inside it from the outer space.