Tracing the moon’s geological history with LUGO

Some parts of the moon are more interesting than others, especially when searching for future places for humans to land and work. There are also some parts of the moon about which we know less than others, such as the Irregular Mare Patches (IMPs) that dot the landscape. We know very little about how they were formed, and what that might mean for the history of the moon itself.

A new mission, called the LUnar Geology Orbiter (LUGO), aims to collect more data on the IMPs and search for lava tubes that might serve as future homes to humanity.

IMPs are a set of “enigmatic volcanic landforms,” according to a new paper by Petr Brož of the Czech Academy of Sciences and his co-authors, published in Acta Astronautica. Ninety-one of these features have been found so far, and they are typically characterized by a topographical depression that can range from a few hundred meters to a few kilometers in width. They have two main features—a relatively smooth mound surrounded by a “hummocky and block floor.”

Interestingly, they have significantly fewer impact craters than the surrounding area, suggesting they are either really old or really young, depending on the processes that created them. Understanding those processes is one of LUGO’s primary mission objectives.

The other primary mission objective is to gather more data about lunar lava tubes. These features of the lunar landscape are also hotly debated, but they could potentially be critical to the future human settlement of the moon. Estimates of their features, such as size and depth, vary widely and could dramatically differ on whether they will be helpful to lunar colonists or not.

Enter LUGO—the proposed orbiter that will collect more data than ever before on these features. In its current suggested form, it has four instruments, each of which will contribute unique data to its scientific mission.

According to the paper, the first and most important instrument is a ground-penetrating radar. This instrument will look through the lunar surface to map out the subsurface domain of both the IMPs and lava tubes.

For IMPs, it can detail the interface between bedrock and regolith and show the subsurface structure of the feature. Similarly, it can detect differences in dielectric properties between open cavities underground and the surrounding rock in lava tubes, creating a subterranean picture unlike anything ever captured on the moon.

A hyperspectral camera will help collect age-related data on the regolith surrounding lava tubes and inside IMPs. It can also perform some basic spectroscopy, allowing scientists to estimate the composition of the regolith in the areas of interest.

The last two instruments, a narrow-angle camera (NAC) and a LiDAR sensor, will combine to create an accurate topographical map of the features of interest. The NAC, in particular, can provide extremely high-resolution images of the features, helping to determine their age and potentially their formation mechanisms.

The mission plan calls for multiple passes over the six largest IMPs, all of which are more than 1,000 m in diameter. Other, smaller IMPs and lava tubes are considered secondary targets, as are other interesting lunar geological features such as lunar domes and “floor-fractured craters.”

LUGO won’t be acting alone, though—three other missions are slated for the next few years that would complement its scientific objectives.

NASA’s DIMPLE lander is planned to take radioisotopic measurements of the age of regolith at its landing site. LunarLeaper, scheduled for launch by ESA around 2030, would also carry a ground-penetrating radar, but would be based on the surface rather than in orbit, and therefore would have a relatively limited range. Trailblazer, another orbital mission, could also help fine-tune the spectra and signals analysis required by LUGO’s operators.

Ultimately, LUGO has yet to be funded, and therefore, it has a long way to go until launch. But if it is funded, it seems well-placed to provide lots of additional insight into the geological formation process and features of the moon at a level of detail we’ve never had before. If we do end up using some of that data to plan the location of future lunar bases, the people living in them will surely be thankful.