Scientists are exploring the potential of the Moon’s permanently shadowed regions (PSRs) to host an incredibly stable laser system, a development that could revolutionize precision measurements in space and underpin a new generation of space-based technologies. The research, led by teams at JILA, the National Institute of Standards and Technology, and the University of Colorado Boulder, alongside NASA’s Jet Propulsion Laboratory and the Physikalisch-Technische Bundesanstalt in Germany, focuses on leveraging the extreme cold and isolation of these lunar regions to create a cryogenic silicon cavity with unprecedented stability.
The core concept centers around utilizing silicon cavities – essentially highly refined structures designed to contain and manipulate light – within the PSRs. These regions, found near the lunar poles, are perpetually shielded from sunlight, resulting in some of the coldest temperatures known in the solar system. This extreme cold, combined with the natural vacuum and minimal seismic activity, creates an ideal environment for minimizing thermal noise, a major limiting factor in the performance of lasers on Earth.
According to the research, a silicon cavity within a PSR could achieve a coherence time exceeding one minute – more than ten times better than the most advanced terrestrial systems. Coherence time refers to how long a laser maintains a consistent phase, a critical factor for precision measurements. A longer coherence time translates directly to greater accuracy and stability.
“Such a stable laser establishes a foundational technology for a range of advanced space-based applications,” researchers stated. These applications include establishing a precise lunar time standard, enabling long-baseline optical interferometry (a technique for combining light from multiple telescopes to achieve higher resolution), and distributing stable optical signals between satellites. The technology also has implications for fundamental physics research, such as more accurate tests of general relativity and the development of space-based quantum networks.
The team’s work involves detailed modeling of the thermal behavior of silicon cavities within PSRs, considering factors like radiative heat transfer and conduction. Their analysis predicts that 10cm diameter silicon cavities could reach temperatures below 100 millikelvin (mK), a fraction of a degree above absolute zero. This level of cooling is crucial for minimizing thermal expansion and contraction within the silicon, which can disrupt the laser’s stability.
The benefits extend beyond simply creating a more stable laser. The researchers highlight the potential for a “lunar time standard,” a highly accurate clock based on the lunar cavity. This standard could serve as a critical component of a future positioning, navigation, and timing (PNT) infrastructure on the Moon, addressing the challenges of precision landing and navigation in the shadowed regions. Currently, landing near PSRs is difficult due to limited optical and terrain-relative navigation capabilities caused by the low sun angles and long shadows.
The proposed system relies on a passive cooling strategy, utilizing radiative cooling from deep space and the natural cryogenic environment of the PSRs. This approach minimizes the need for complex and potentially unreliable cooling mechanisms. Engineers plan to leverage existing technologies, such as those used in the James Webb Space Telescope and far-side seismic suites, to achieve the necessary cooling performance.
The lunar environment also offers advantages in terms of vacuum and seismic stability. The Moon’s lack of a substantial atmosphere provides a naturally ultra-high vacuum, simplifying the construction of the cavity chamber. The Moon’s minimal tectonic activity results in significantly lower seismic noise compared to Earth-based laboratories, enhancing the performance of longer cavity lengths.
Once the silicon cavity material is transported to the Moon, the system engineering is expected to be relatively straightforward. The resulting laser could then serve as a master optical oscillator, distributing its phase stability to a network of satellites via optical links. This would simplify frequency control systems for satellite constellations used for communications, navigation, and other applications.
The development of a stable lunar laser also has significant implications for the advancement of space-borne quantum technologies. Ultrastable lasers are essential for driving and interconnecting optically active quantum systems, and a lunar-based laser could provide a crucial foundation for building space-based quantum networks. The Earth-Moon distance, at just one light-second, is short enough to allow for the transmission of a highly accurate time scale back to Earth, synchronizing metrology labs globally.
The PSRs are already attracting attention as potential landing sites for upcoming missions, including NASA’s Artemis program and other international efforts, due to their potential resources – including water ice, carbon dioxide, and helium-3 – and proximity to areas with continuous solar power. The research underscores the multifaceted benefits of these regions, positioning them as key locations for future scientific and technological exploration.
Researchers acknowledge that deploying and maintaining such a system presents engineering challenges. Future work will focus on refining the design of the cryogenic silicon cavity and developing robust methods for its deployment and long-term operation. However, the potential rewards – a new era of precision measurement and advanced technologies in space – are substantial, marking a potential historic milestone in humanity’s capability to build quantum infrastructure beyond Earth.
