The typical forecast for the Moon is far from cozy, with temperatures ranging from boiling during the day to 280 below zero at night. However, according to a new study, unique features known as moon pits can offer an oasis from the roller coaster temperatures.
To learn what might be inside these lunar craters, a team of UCLA planetary scientists used thermal imaging from NASA Lunar Reconnaissance Orbiter and fixed the temperature, at least in one of these pits, to be always a constant 63 degrees. The findings were recently published in the journal Geophysical Research Letters, and the UCLA editorial team is calling it the discovery of year-round “sweater weather.”
One of the authors of the study, Tyler Horvath, Ph.D. in planetary sciences. student at UCLA, said the pit could be the opening of a lava tube or cave and would be an ideal place for astronauts to live, offering perfect temperatures as well as protection from meteorites and radiation.
“Imagine a full day on the moon… you have 15 days of extreme heat that reaches the boiling point of water. And then you have 15 days of extreme cold, which is some of the coldest temperatures in the entire solar system,” Horvath said. “So being able to be in a place where you don’t have to spend energy to keep warm for those 15 days at night, it’s almost priceless because at night, if you’re trying to use solar energy as your primary form of energy, you can’t do that for 15 days.”
The UCLA research team focused on the gap in the Sea of Tranquility, or Mare Trenquillitatis region, which is about 220 miles from where Apollo 11 landed, and also the same distance to Apollo 17 landing site.
Cozy pixel on the moon
NASA’s LRO spacecraft has been continuously orbiting the moon, taking measurements with its suite of instruments, including the Diviner lunar radiometer, which has been continuously mapping the moon’s thermal emissions since 2009.
UCLA planetary scientist David Page is the principal investigator of the Diviner instrument and the lead author of the new lunar crater study.
Horvath was commissioned to create a 3D model of one of these interesting pits in the Mare Trenquillitatis area. During this process, the team noticed a single pixel in the infrared images that was warmer than most spots on the moon at night when temperatures dropped.
“We noticed that it was able to warm up really quickly and maintain a higher temperature than the surface normally does at night,” explained Horvath. “We’re like, ‘Oh, this might be more interesting than we thought.’
After rechecking the Diviner data and assessing how much sunlight the pit was receiving, the team determined the temperature of the pit floor during the day. Unfortunately, this does not confirm a cave opening, but it is still the working theory for these pits formed by ancient volcanic activity.
“It was still a great result that if there’s a cave there, it’s going to maintain temperatures that are 63 Fahrenheit all the time, 24 and seven every day forever, basically,” Horvath said.
How Trenquillitatis Pit and other caves on the Moon maintain their temperature comes down to a physical concept known as a blackbody cavity, which can self-regulate to maintain its temperature.
“Essentially, it’s a surface that’s a perfect radiation emitter and radiation absorber,” explains Horvath.
The temperature at the bottom of the pit also depends on its position relative to the Earth and the moon from the sun.
“If you’re closer to the sun, the temperature will be hotter,” Horvath said. “If you are farther from the sun, it will be colder.”
How did lava tubes form on the Moon?
Even from Earth, it’s obvious that the Moon has interesting features, including craters of all shapes and sizes. In 2009, Japan’s Kaguya spacecraft orbiting the moon discovered a new type of lunar feature in the form of deep chasms that researchers believe may contain man-made caves from collapsed lava tubes, similar to those found on Earth.
Horvath explains that billions of years ago there was very intense volcanic activity and lava flows created the dark spots we see today when we look up at the moon. The lava on the surface would have cooled first because it was exposed to the cold temperatures of space, where the caverns beneath the lava were still flowing.
“In some places, that lava will leave completely and leave a hollow tube, a tube of lava below the surface,” Horvath said. “These pits are kind of our way of seeing that they exist, that there’s a way to them, and they could be anywhere.”
NASA describes moon pits as “windows” where the roof of the lava tube collapsed.
On Earth, the UCLA research team behind the study even visited a lava tube in Hawaii Volcanoes National Park known as Devil’s Throat, which is similar in size to the Mare Trenquillitatis pit. The park is home to other lava tubes like the one pictured above that visitors can walk through.
Without physically walking to the moon and rock climbing into one of these pits, it will be difficult for researchers to learn if these huge caverns exist. After all, this may be possible because in the next four years, NASA plans to return humans to the moon and establish a permanent base.