When we observe the Moon with a telescope, our attention is drawn to the enormous number of impact craters that mark its surface. They come in many sizes and are easy to distinguish because they are usually delimited by a mountainous circumference that rises above the surrounding terrain, formed by the material ejected at the moment of impact. These craters are the most common, but in 2009, when scientists examined an image of the region known as Marius Hills, taken by the Japanese spacecraft Kaguya, they discovered a small circle on the ground that caught their attention. The opening lacked the raised ring at the edges, it was more of a hole, a deep pit that opened into the flat surface of the Moon. At the time of the photograph, the sun’s rays fell on the place from above and that allowed us to see the vertical walls that penetrated the ground to the bottom, located more than 80 meters deep. This type of formation has its counterpart on Earth, including on Mars and Venus, and is known by names such as subsidence crater, pit crater, or, as English-speakers call it, a “pit crater.”
Although the Marius Hills pit crater was the first to be discovered, images taken by spacecraft that have orbited the Moon since, notably the Lunar Reconnaissance Orbiter of the NASA ( LRO), have allowed us to discover many more, as our guests commented in Talking with Scientists Gabriel López Martínez and Laura Parro.
Gabriel López Martínez is an aeronautical engineer and is doing a master’s degree in Astronomy and Astrophysics at the International University of Valencia, supervised from a distance by Laura M. Parro, PhD in planetary geology and researcher at the Lunar and Planetary Laboratory of the University of Arizona. Both have carried out a study of the subsidence craters identified on the Moon, the number of which, at this moment, is close to 300.
Gabriel comments that lunar pit craters have a volcanic origin. When the Moon was formed, after the collision of a body the size of Mars with the Earth, the surface of our satellite was incandescent and gradually cooled down. In some places, under the crust, subterranean rivers of lava flowed, which, when the flow ended, emptied, leaving behind cavities of many different sizes. When the flow took place near the surface, the roofs of these underground cavities were weaker and collapsed, creating a subsidence pit or pit crater.
The pit craters that have been identified so far on the lunar surface are irregularly distributed, says Laura Parro, there are places of greater concentration than others, some are aligned revealing the existence of lava tunnels under the surface. In general, all these data provide information on lunar geology and make it possible to determine which areas are the most interesting for further study.
Gabriel’s work consists of developing a code that allows analyzing the 278 lunar pit craters known to date, to determine which are the most interesting to be used as shelters for future lunar bases. Astronauts carrying out long-duration activities on the lunar surface are exposed to extreme conditions caused by excessive radiation, micrometeorites and tremendous changes in temperature. A pit crater can be the gateway to an underground cavity where the rock walls and ceilings become shields that protect from radiation or micrometeorites and, in addition, offer much more stable temperature conditions. On the other hand, the study tries to determine which of the known well craters may be the best considering the proximity to sources of resources, such as the water accumulated in the form of ice in certain craters whose shadow never falls on sunlight. .
As lunar exploration enters a new phase with the program ARTEMIS that intends to send human beings to the Moon again with the aim of establishing a continuous presence there, both on the surface and in orbit, studies such as those carried out by Gabriel López and Marta Parro are of vital importance to select the best places for future bases moons and provide information on lunar geology.
Gabriel López and Laura Parro present the results of their research at the XV Scientific Meeting of the Spanish Astronomical Society (SEA).
Gabriel López Martínez is an aeronautical engineer and is doing a master’s degree in Astronomy and Astrophysics at the International University of Valencia.
Laura M. Parro is a PhD in planetary geology and a Margarita Salas Postdoctoral Researcher at the Lunar and Planetary Laboratory at the University of Arizona.