A potentially habitable moon cave

For decades, scientists have searched for lunar caves deep and protected enough to serve as safe habitats for long-term manned missions. Recently, an Italian research team reported preliminary evidence of a horizontal cave located at the base of a shaft in the “Sea of ​​Tranquility” that may meet these criteria.

Discovered through radar scans, the cave’s existence still needs confirmation through physical inspection to determine its accessibility and habitability. If proven to be such a cave, this discovery would not only validate the research method used, but also pave the way for finding additional caves.

The lunar surface, however, presents numerous hazards, including extreme temperatures, micro-meteorite impacts, and intense radiation. A practical solution is to use subterranean habitats, which provide considerable protection, and minimize exposure to the harsh airless lunar environment, venturing outside only when conditions are relatively safer.

Experts estimate that the optimal way to achieve this is by using the existing lunar caves. This approach would eliminate the need to transport heavy drilling and dredging equipment to the Moon, thus shortening the timeline for creating an underground base and significantly reducing mission costs. Currently, the cost of landing one kilogram of equipment on the Moon is estimated at about one million dollars.

The lunar surface is dotted with numerous vents that, according to satellite images, appear to constitute vertical shafts that extend tens of meters deep or more. Researchers believe that there are also many “lava tubes” on the Moon – horizontal caves that form the remains of volcanic activity, which could be very suitable for housing a manned base.

Some of these tubes are visible in satellite images as slightly raised formations resembling plant roots near the surface. In other cases, surface features suggest collapsed ceilings of such horizontal caves. However, these observations provide only indirect evidence of the existence of such caves.

Vertical axis apertures have also only been studied remotely, using satellites orbiting the Moon. In-depth analysis of optical images and measurements from other instruments allows researchers to estimate the geometry and depth of these vents, assess the continuity of underground cavities, and even study temperature fluctuations within the shafts.

However, researchers have yet to find evidence of the most sought-after site: a horizontal cave accessible from the surface via one of these shafts. The discovery of such a cave would provide a tangible site for exploration, first by robotic vehicles and eventually by human missions.

A team of researchers led by scientists from the University of Trento in Italy reported such a discovery in the journal Nature Astronomy, using advanced radar measurement analysis techniques. They examined data from NASA’s Lunar Reconnaissance Orbiter (LRO), which has been orbiting the Moon since 2009. The team focused on measurements from the mini-RF radar instrument, analyzing data collected during the first years of the satellite’s operation, until 2011.

They focused on radar signals transmitted at oblique angles rather than directly overhead. Their objective was to find out if the signals penetrated a possible horizontal cave extending from the bottom of the shaft – rather than being reflected directly up – and thus confirm the existence of such caves through radar scans.

Analysis of the measurements revealed signs of a cave at the bottom of a known shaft located in the “Sea of ​​Tranquility”—the area where Apollo 11, the first spacecraft to reach the moon, landed in July 1969. This shaft, known as MTP, has been extensively studied through satellite imagery.

It features a pit with a funnel-shaped upper section and sloping walls that descend to a depth of approximately 135 meters below the lunar surface at its deepest point. The diameter of the shaft varies between 80 and 100 meters.

Based on the analysis of measurements and comparison with computer simulations, the researchers believe that there is a cave at the bottom of the MTP with a width of about 45 meters. According to them, the findings match two possible models: one of a nearly horizontal cave with a slope of only about three degrees and a length of 25 meters; the other of a steeper cave with a slope of about 45 degrees and a length of 77 meters.

The horizontal cave was “probably an empty lava tube,” the head of the research team, Lorenzo Bruzzone, told The Guardian, adding that such features could serve as human habitats for future explorers as they were “a natural shelter against the moon.” harsh environment.”

Satellite images of the Moon’s surface have revealed over a hundred shaft openings, but the MTP is currently the only one where a possible horizontal cave has been discovered at its base. Researchers hope that more such caves will be found, which may require a new satellite equipped with suitable instruments.

The radar aboard NASA’s Lunar Reconnaissance Orbiter (LRO) was not specifically designed for this purpose and is generally limited to surveying shafts that are 80 meters in diameter or larger.

“There are possible shafts that constitute lava tube vents on both the Moon and Mars. What is new here is the apparent confirmation of the existence of a horizontal cave at the end of a shaft,” explained Prof. Oded Aharonson of the Department of Earth and Planetary Sciences at the Weizmann Institute of Science, who was not involved in the current research.

“The researchers developed a model of the subsurface topography using the extraordinary radar data, and their findings appear plausible.”

“If a lunar colony becomes a reality, it will need to protect people and equipment, and lava tubes are ideal for this purpose, not only on the Moon but also on Mars,” added Aharonson, who conducts research in such caves. “They can provide protection from strong solar storms, similar to those experienced in recent months. While Earth’s magnetic field protects us from these storms, the Moon and Mars lack a global magnetic field, making radiation levels during such potentially dangerous events.

In addition to providing protection, such caves may also have important scientific potential, Aharonson says. “Subterranean areas in caves are likely more insulated from temperature changes than the surface. If there was microbial life on Mars, it can be speculated that it survived in warmer places, such as inside caves, making it a great place to look for them.”