What started as SpaceX founder Elon Musk’s effort to fix Los Angeles’s traffic problems could end up paving the way for an entire tunnel system on Mars, providing colonists with shelter and water.

Musk’s Boring Company is still in its infancy, having begun digging a small test trench on the grounds of SpaceX’s headquarters in February. At an appearance Wednesday at a conference on the International Space Station, Musk explained how such tunnel-building projects could become part of his real passion project: the settlement of Mars.

“I do think getting good at digging tunnels could be really helpful for Mars,” Musk said Wednesday . “You can build a tremendous amount underground with the right boring technology on Mars, so I do think there’s some overlap in that technology-development arena.”

Mars is home to profound quantities of frozen water, buried beneath red soil in massive glaciers between its equator and poles. A boring machine could provide access to bounties of ice, and other resources, too. “For sure there’s going to be a lot of ice mining on Mars, and mining in general to get raw materials,” said Musk.

Unlike Earth, the Martian surface is exposed to a constant bombardment of highly-energized particles from deep space, called galactic cosmic rays. These rays pose a serious health risk to any future Martian explorer.

On Earth, humans are protected by our planet’s formidable magnetosphere, formed in large part by its magnetic fields, which deflects these particles. But Mars has no global magnetic field, meaning any explorers would always be vulnerable to deadly, cancer-inducing radiation.

An underground habitat, however, could provide colonists shelter from the incessant radiation bombardment.

“And then, along the way, building underground habitats where you could get radiation shielding… you could build an entire city underground if you wanted to,” said Musk.

Boring beneath greater Los Angeles, where Musk ultimately hopes to connect disparate parts of the county, would certainly give SpaceX a considerable amount of tunneling experience. However, Musk notes that his boring machine, named Godot, is far too massive to take a trip into space.

“The Earth ones are really heavy — like, really heavy,” Musk said. “You’re not worried about weight for an Earth tunneling machine. Actually, you want one that’s nice and heavy. But a Mars one, you’d have to redesign it to be super light. That’s a tricky one — and then just take into account the different conditions on Mars and everything else.”

Here on Earth, Musk’s boring company already may be expanding beyond automobile traffic. On Thursday he tweeted that he had been given “verbal government approval” for The Boring Company to create a New York to Washingon DC Hyperloop, turning a seven-hour drive (or four-hour train ride) into a swift, 29-minute subterranean jaunt.