Credit: ESA/A. Romeo

Researchers diving into lava tubes here on Earth believe that Martian and lunar tubes are one to three orders of magnitude more voluminous than on our home planet.

Credit: ESA/A. Romeo

The upshot of a new underground data base reveals Mars and Moon lava tubes are respectively 100 and 1,000 times wider than those on Earth, which typically have a diameter of 33 feet to nearly 100 feet (10 to 30 meters).

Credit: ESA/A. Romeo

Lower gravity on those celestial bodies, and its effect on volcanism, explain these dimensions (with total volumes exceeding 1 billion of cubic meters on the Moon).

These findings suggest a game changer for the future of space exploration, for those aiming at reaching the underground of both Mars and the Moon.

The work appears in the international journal Earth-Science Reviews titled “Lava tubes on Earth, Moon and Mars: A review on their size and morphology revealed by comparative planetology.”

This study involved the Universities of Bologna and Padua in Italy. The work was led by Francesco Sauro, a speleologist and head of the European Space Agency programs, CAVES (Cooperative Adventure for Valuing and Exercising human behavior and performance Skills) and Pangaea. He is also a professor at the Department of Biological, Geological, and Environmental Sciences at the University of Bologna.

Riccardo Pozzobon is a planetary geologist at the Department of Geosciences of the University of Padua.

Surface expression

Lead authors of the new paper, Sauro and Pozzobon, note that, “although it is still impossible to gather direct information on the interior of Martian and lunar lava tube candidates, scientists have the possibility to investigate their surface expression through the analysis of collapses and skylight morphology, morphometry and their arrangement, and compare these findings with terrestrial analogues.”

The Marius Hills Hole. Extensive lava tubes exist under Marius Hills and may be large enough to house cities.
Credit: NASA, Lunar Orbiter 2; Inset: Lunar Reconnaissance Orbiter

On Earth lava tubes are well known thanks to speleological exploration and mapping in several shield volcanoes. Speleologists have thoroughly studied lava tubes on Earth in Hawaii, the Canary Islands, Australia and Iceland, for example.

On the Moon subsurface cavities have been inferred from several skylights in Maria smooth plains and corroborated using gravimetry (the measurement of weight, a gravitational field, or density) and radar sounder data. On Mars, several deep skylights have been identified on lava flows with striking similarities with terrestrial cases, Sauro and Pozzobon explain.

Potential settlement

Their analysis shows that aside of collapses triggered by impacts/tectonics, most of the lunar tubes could be intact, making the Moon “an extraordinary target for subsurface exploration and potential settlement in the wide protected and stable environments of lava tubes.”

One prospect for intact lunar lava tubes is the collapse chains in Marius Hills, perhaps allowing future crews access to huge underground cavities.

For more information, go to “Lava tubes on Earth, Moon and Mars: A review on their size and morphology revealed by comparative planetology,” at:

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