Large systems of underground caves on Mars and the Moon could prove to be safe havens for future human settlements, according to research presented at the European Planetary Science Congress in Riga.

The huge interconnected networks of caves – known as lava tubes – are formed as a result of volcanic activity and lava flows. Similar, smaller examples can be found on Earth in places like Lanzarote, Hawaii, Iceland, Sicily and the Galapagos Islands.

"The comparison of terrestrial, lunar and Martian examples shows that, as you might expect, gravity has a big effect on the size of lava tubes", said Riccardo Pozzobon, of the University of Padova.

"On Earth, they can be up to thirty metres across. In the lower gravity environment of Mars, we see evidence for lava tubes that are 250 metres in width. On the Moon, these tunnels could be a kilometre or more across and many hundreds of kilometres in length."

"These results have important implications for habitability and human exploration of the Moon but also for the search for extra-terrestrial life on Mars. Lava tubes are environments shielded from cosmic radiation and protected from micrometeorites, potentially providing safe habitats for future human missions. They are also, potentially, large enough for quite significant human settlements – you could fit most of the historic city centre of Riga into a lunar lava tube."

This new research is already being implemented in the European Space Agency's astronaut training programme. Pozzobon and his team lead a planetary geology training course which teaches astronauts how to carry out geological research in future missions to the Moon or Mars.

In a separate talk, Leonardo Carrer from the University of Trento demonstrated a concept for a radar system specifically designed to detect lava tubes on the moon from orbit. The system would use electromagnetic waves to probe beneath the lunar surface, determining the physical composition, shape and size of the caves, as well as their location.

"A mission carrying this instrument would enable a crucial step towards finding safe habitats on the Moon for human colonisation," Carrer said.