After examining radar images taken by the Lunar Reconnaissance Orbiter in 2010, Leonardo Carrer and his team found that a deep pit discovered 15 years ago in the Sea of Tranquility — the same region of the Moon where the Apollo 11 astronauts landed — appears to lead to a subsurface cave conduit tens of meters long. The researchers believe the site could prove a promising location for a future lunar base.
Although we typically imagine such bases on the Moon’s surface, the high-radiation environment and huge temperature swings might force astronauts to live several meters underground. A natural cave with a large entrance could save a lot of digging. Many of the world’s space agencies do, in fact, have long-term plans for lunar bases, and while the Sea of Tranquility doesn’t offer the same advantages as other lunar destinations like the Aitken Basin, it does have historical significance as the site of the first Moon landing.
As for its scientific appeal, basalt layers in the region could retain evidence from when volcanic activity on the Moon peaked three and a half billion years ago. The outgassing during this period could have been so extensive that a temporary atmosphere about 1% as substantial as Earth’s could have built up. If so, it would have created a short-term habitability window that might have allowed microbial life to exist for an extremely limited time. Finding evidence in the basalt to support that hypothesis would be difficult, for sure. However, exploring a lunar cave would still provide a valuable record of the Moon’s geological, meteorological, and environmental history.
Even more exciting would be exploring caves on Mars, which may still be a habitat for life today. Thousands of possible cave entrances have been identified on the planet — everything from “skylights” to deep fractures, pit craters, and other void spaces. It’s difficult to say from orbital images how deep these caves go, but a large number of them should reach far down into the subsurface. Many of these are lava tube caves, which are also common on Earth.
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