Rovers would be a bad choice for the lava tube, obviously, since the floor of the tube is likely just a pile of rubble from a few billion years of rock-falls.

I would kill to know the extent of contiguous open area in those tubes- on the moon and Mars.

“One interesting concept comes from a proposed mission to study lunar lava caves. Mark Robinson, the Principal Investigator for the Lunar Reconnaissance Orbiter Camera, has proposed a mission he calls “Arne” (named after the fictional character Arne Saknussemm, in Jules Verne’s novel Journey to the Center of the Earth, who discovered a passage to the Earth’s interior through Iceland’s Snæfellsjökull volcano crater). Arne consists of a soft landing spacecraft and three small “pit-bots,” spherical flying robots about 30 cm in diameter. The lander would touch down inside one of the newly discovered lava pits found on the Moon; from the bottom of one of the pits, there is a direct line-of-sight to Earth for communications. Once landed, the small flying pit-bots would traverse into the side chambers of this opening into the Moon’s interior, survey the walls and determine if these pits are surface expressions of a cave system created by flowing lava.

The flying pit-bots of Arne could use a lithium hydride and peroxide propulsion system that levitates the vehicle for short, one-to-two-minute hops. Images, magnetic and thermal information, and obstacle avoidance data are taken for the cave walls during flight. Two flying pit-bots can mutually support each other, relaying their data back to the lander at the tube opening, which can then be sent directly back to Earth. By using alternate hops of each pit-bot, they can move into and survey several hundred meters of an existing cave system.

These drone-like vehicles could be a relatively inexpensive way to explore lunar lava tubes. We might also apply this technique to the exploration of above-ground features on the lunar surface. Landforms like sinuous rilles (such as the Rima Hadley—a winding valley briefly investigated during the 1971 Apollo 15 mission) exposes hundreds of kilometers of mare crust in its walls. Flying drones could travel the length of the rille, examining wall outcrops in many wavelengths, looking for compositional variations to decipher the history of the exposed lavas. Flights through and into craters with very steep walls are also possible, so that shock melt deposits (which tend to be found on the floors of craters) can be accessed and studied. Spectacular, 360-degree views from high-flying drones could obtain geologic information at scales in between those obtained from orbit and those made by traversing the ground, allowing us to understand the geology of large areas. Such capability would be particularly valuable in prospecting and mapping the polar regions, where ice deposits are irregularly and heterogeneously distributed deep within permanently shadowed craters.”

The LIDAR-on-a-chip is in development- somewhat demonstrated in the lab (The big profit motivation would be for self-driving cars) I was interested in having it perfected for the lava-tube application. The technology will be there quite soon, I have no doubt whatsoever. While such a LIDAR would have countless applications for various space missions, there is a huge profit motive to make such a device for terrestrial applications- so I suspect corporations are investing far more in it than NASA could.

I think that integrated photonics will be every bit as revolutionary as integrated electronics has been… devices we can’t even imagine will become consumer items. I don’t work on the nuts-and-bolts of the technology, but I follow it very closely as part of my job. It will revolutionize the field I work in.

However a lot of study is needed before placing any humans in one- clearly they are not perfectly stable, otherwise these skylights would not exist. A 10-ton slab falling on a habitat would be disastrous even if the gravity is low there. Moon-quakes do happen often- with a cycle frequency of ~27 days.

The tubes certainly can capture people’s imagination, and they certainly captured mine- I personally feel they should be made a high priority for study. So I have thought about how to study them.

Like integrated electronics, the field of integrated photonics promises to be revolutionary. The ability to package lasers and complex optical devices on a chip integrated with electronics opens up the possibility of extremely compact lightweight powerful instruments. One such possibility is a LIDAR on a chip.

You can make an optical phased array where emitters and receivers are arrayed on a chip with spacing on the order of the wavelength, allowing you to transmit a directed beam from the flat surface of the chip by controlling the phase of the individual emitters- combined with detectors and processing electronics this can be engineered into a LIDAR that is EXTREMELY compact.

It could be lowered on a tether into a Lunar lava tube, or- even more exciting- FLOWN into a Mars lava tube on a drone to map the interior. Sensors for long term monitoring of lava tubes should be left in place to determine stability…

Unlike ER, I do think we should establish a presence on, and around, the moon as a stepping stone to Mars, and Lava tubes are a promising location to consider.

This shows how Americans are lapping it up:

https://www.google.com/url?q=https://tv.parrotanalytics.com/US/for-all-mankind-apple-tv-plus&sa=U&ved=2ahUKEwjp85qYoKf5AhUEKH0KHeiWAO4QFnoECAIQAg&usg=AOvVaw2BS3Y_Y7izvCOOCrGKIfzv