'Pits' On Moon Are Thermally Stable Regions For Lunar Exploration, NASA's LRO Finds

The authors noted in the study that lunar caves would provide a temperate, stable, and safe thermal environment for long term exploration and habitation of the Moon.

Lunar 'Pits' have shaded locations that always harbour a comfortable temperature of around 17 degrees Celsius, NASA-funded scientists have found. They made this discovery using data from NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft and computer modelling.

These shaded regions may lead to pits and caves. The study describing the findings was recently published in the journal Geophysical Research Letters.

Pits Are Thermally Stable Sites For Lunar Exploration

According to the study, the pits are thermally stable sites for lunar exploration, compared to other regions on the surface of the Moon.

The temperatures at other places on the lunar surface may reach as high as 127 degrees Celsius during the day, and may plummet to minus 173 degrees Celsius at night. These temperatures are unsuitable for astronauts visiting the Moon. One of the most important missions of NASA is lunar exploration, because this will help scientists understand the unknown in space. 

NASA's LRO Camera has imaged the Marius Hills pit three times. Each time, the camera imaged the pit with very different lighting. The image at the centre was taken when the Sun was high above, giving scientists an awesome view of the Marius Hills pit floor. The depth of the Marius Pit is about 34 metres. 

In 2009, pits were discovered for the first time on the Moon. The Japanese Aerospace Exploration Agency's (JAXA's) SELENE spacecraft had discovered pits on the Moon. 

Why These Pits Will Serve As Ideal Shelters For Lunar Exploration

Scientists have always wondered if these pits led to caves that could be explored or serve as shelters. If these pits are used as shelters, they may offer protection from solar radiation, cosmic rays, and micrometeorites. 

In a statement released by NASA, Tyler Horvath, who led the research, said about 16 of the more than 200 pits are probably collapsed lava tubes. 

LRO Project Scientist Noah Petro of NASA's Goddard Space Flight Center said lunar pits are a fascinating feature on the lunar surface, and create a stable thermal environment. One day, these pits can be explored. 

How Are Lunar Pits Formed?

When molten lava flows beneath a field of cooled lava or a crust forms over a river of lava, lava tubes are formed. These tubes are also found on Earth. Lava tubes are long, hollow tunnels. When the ceiling of a solidified lava tube collapses, a pit is opened. This pit leads into the rest of the cave-like tube.

The study found that two of the most prominent pits on the Moon have visible overhangs that lead to caves or voids. 

David Paige, a co-author on the paper, said humans evolved living in caves, and to caves humans might return when they live on the Moon. 

In order to find out whether the temperature within the pits diverged from those on the surface, Horvath processed data from a thermal camera called Diviner. This is an instrument aboard the LRO, which has been continuously measuring the temperature of the lunar surface for over 11 years. 

The team focused on a roughly cylindrical 100-metre-deep depression about the length and width of a football field in an area of the Moon known as the Mare Tranquillitatis. After this, the researchers used computer modelling to analyse the thermal properties of the rock and lunar dust. This helped them chart the pit's temperatures over time.

Which Pit Is The Most Habitable?

The thermal environment of the pit located in Mare Tranquillitatis is more hospitable compared to anywhere else on the Moon, the study said. The temperatures vary minimally around a comfortable 17 degrees Celsius, wherever the Sun does not shine directly. 

Important Findings Of The Study

According to the study, the temperatures within the permanently shadowed reaches of the pit fluctuate only slightly throughout the lunar day. The temperatures remain at around 17 degrees Celsius. Images taken by LRO's Lunar Reconnaissance Orbiter Camera suggest that a cave extends from the bottom of the pit. The cave is also likely to have this relatively comfortable temperature.

According to the researchers, the shadowing overhang is responsible for the steady temperature, and limits how hot things become during the day. The overhang also prevents heat from radiating away at night.

A lunar day is equal to about 15 Earth days. During a lunar day, the surface is constantly bombarded by sunlight and is frequently hot enough to boil water. According to NASA, brutally cold nights also last about 15 Earth days. 

Therefore, the researchers concluded that lunar pits stay warmer than the surface during the night, with the floor maintaining temperatures greater than 230 K or minus 43.15 degrees Celsius, according to the computational models. 

The study also found that the caves stemming from the lunar pits would behave like blackbody cavities at around 290 K or 17 degrees Celsius. If a black body at a certain temperature is surrounded by other objects in equilibrium at the same temperature, the body will emit exactly as much heat as it absorbs. The caves have nearly invariable temperatures far from the opening.

The authors noted in the study that lunar caves would provide a temperate, stable, and safe thermal environment for long term exploration and habitation of the Moon.