Assessing Water Dynamics at Lunar Gravity

 Karl H. Hasenstein · John Z. Kiss · Christopher P. McKay

Microgravity Science and Technology (2026) 38:63;  https://doi.org/10.1007/s12217-026-10277-w

 For colonies on the Moon, plants can provide food, oxygen, water purification, and waste recycling, making them a critical component of long-term human habitation beyond Earth. While scientists have learned a great deal about how plants grow in space, much less is known about how water behaves around plant roots under lunar gravity.

On Earth, gravity helps water move through soil and distribute evenly around roots. The Moon's gravity is only about one-sixth as strong, which could significantly alter how water flows, spreads, and is retained in growing systems. Understanding these differences is essential for designing future lunar greenhouses and agricultural systems.

In this study, we investigated how water behaves under lunar gravity, an important question for future human settlements on the Moon. The research was conducted during the Blue Origin New Shepard 29 (NS-29) flight, which briefly simulated the Moon's gravity during a suborbital mission.

How the Experiment Was Performed.

We built a small device containing chambers filled with three different liquids: pure water, a 30% glycerol solution, and a dilute salt solution. These chambers were photographed throughout the flight using an onboard camera. During the mission, the spacecraft first experienced near-weightlessness and then rotated, creating an acceleration close to lunar gravity for about 2.3 minutes. During this period, the experiment recorded images that captured how the liquids responded to the reduced gravitational environment.

We focused on the shape of the liquids' surfaces, known as the meniscus. The meniscus is the curved surface visible when a liquid contacts the walls of a container. Its shape reflects the balance between gravity and surface tension, making it a useful indicator of how fluids behave under different gravitational conditions.

Major Findings.

The results showed clear differences between Earth gravity and lunar gravity conditions. Under Earth's gravity, the liquid surfaces were flatter because gravity exerted a stronger downward force. Under lunar gravity, the liquid surfaces became more rounded and curved. The liquids also formed thicker films along the chamber walls.

 These observations indicate that when gravity is weaker, surface tension plays a much larger role in determining where water moves and how it is distributed. In other words, water behaves less like a freely flowing liquid and more like a fluid strongly influenced by the surfaces it touches.

One particularly interesting result involved the glycerol solution. Compared with pure water and saltwater, the glycerol mixture appeared to improve wetting, allowing the liquid to spread more effectively across surfaces. This suggests that additives such as glycerol might help manage water distribution in future lunar growing systems.

Implications for Lunar Agriculture.

Our experiments have important implications for growing plants and crops on the Moon. Lunar soil, known as regolith, consists largely of fine dust and fragmented rock. It is generally poor at absorbing water and may even repel it under some conditions. Combined with reduced gravity, these properties could make irrigation much more difficult than on Earth.

Uneven water distribution may create overly wet zones and dry zones within the root environment. Excess water can limit oxygen availability and lead to root hypoxia, a condition that can impair plant growth. Thus, our findings suggest that future lunar agriculture may require specialized additives, different soil particle sizes, or engineered watering systems to ensure healthy root development.

Limitations and Future Work.

We acknowledge several limitations. Conducting experiments during spaceflight is challenging, and factors such as leaks, storage conditions, temperature changes, and surface roughness of the test chambers likely influenced the results. Nevertheless, the experiment successfully demonstrated that fluid behavior changes significantly under lunar gravity. We conclude that future studies should focus on how water moves directly through lunar regolith and regolith-like materials. Such work will help scientists develop practical systems for growing plants and producing food during future lunar missions.