Study Demonstrates LIBS Plasma Behavior for Space Exploration

A recent study published in Icarus studied the performance of laser-induced breakdown spectroscopy (LIBS) under extraterrestrial conditions. This study, which was led by Fabian Seel and his team, comprised of researchers from the Institute of Optical Sensor Systems, German Aerospace Center (DLR), and Humboldt-Universität zu Berlin, investigated atmospheric conditions, laser irradiance, and sample lithology affect laser-induced plasmas (1). The goal by learning this information was to discover how to better optimize LIBS instruments for planetary exploration.

LIBS is an atomic spectroscopy technique that has been used for the elemental analysis of rocks and samples from other planetary bodies (2,3). One of the benefits of using LIBS for planetary analysis is that it does not require sample preparation beforehand for analysis. Over the past decade or so, LIBS has grown in popularity in space exploration (2). The technique first emerged as a popular method for space exploration applications when it was successfully utilized on NASA’s Curiosity rover in 2012 (1). Since then, interest in LIBS as a tool for planetary surface analysis has surged, leading to its incorporation in multiple missions exploring Mars and beyond (1). However, designing LIBS instruments for specific extraterrestrial environments remains a challenge because of how environmental factors influence laser-induced plasma behavior.

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To address these challenges, the research team conducted high-speed plasma imaging with a temporal resolution of just 2 nanoseconds, capturing the plasma's evolution from ignition to decay. In their study, the researchers compared LIBS plasma formation under three distinct atmospheric conditions. These conditions were the terrestrial atmosphere, which was used as a reference baseline; the Martian atmosphere, which was meant to replicate Mars’ environment; and airless conditions, which simulated planetary bodies such as the Moon (1).

As part of the study, the team also tested LIBS performance across three different laser energies—11.86 mJ, 8.75 mJ, and 6.56 mJ—and on four geological materials, including basalt, soapstone, and lunar regolith simulants (LHS-1 and LMS-1) (1).

The results indicate that atmospheric conditions do influence plasma size and emission intensity. For Earth-like conditions, the research team observed plasma expansion to a size of 1.1 mm to 1.6 mm within 1 to 3 microseconds (1). For Martian-like conditions, the researchers noted that plasma expansion occurred much more rapidly, reaching a size of 2.6 mm to 3.6 mm in just 500 to 700 nanoseconds, but with an emission intensity reduced to 30% of Earth-based levels (1). Finally, for airless conditions, the plasma was significantly weaker, reaching its maximum extent of 2.0 mm in just 40 nanoseconds, with emission intensity dropping to less than 20% of terrestrial conditions (1).

Numerous conclusions can be drawn from these results. First, LIBS plasma behaves differently based on the environmental conditions, especially under low-pressure environments. While atmospheric conditions played a dominant role, the influence of sample lithology (rock type) was surprisingly minor—except in the case of soapstone under airless conditions (1).

In contrast, laser irradiance had a minimal effect on plasma size within the studied range, though higher laser energy did enhance emission intensity. This suggests that future LIBS instruments may have flexibility in laser power settings without significantly affecting plasma expansion (1).

By demonstrating that LIBS systems optimized for specific atmospheric conditions can still function across a range of sample types and laser settings, the researchers help provide some information that can potentially contribute toward developing improved instruments for future space missions.

To improve the accuracy of spectral readings, scientists must understand how plasma emission decays over time (1). As space agencies continue to explore new space missions to explore nearby planetary bodies, LIBS is expected to remain a popular technique that will play a key role in some of these missions, particularly when geochemical analysis is needed. The research by Seel and his colleagues marks a significant step toward optimizing LIBS technology, ensuring that future missions will be equipped with the best possible tools for unraveling the mysteries of the solar system (1).

References

1. Seel, F.; Schroder, S.; Clave, E.; et al. Lifetime, Size, and Emission of Laser-induced Plasmas for In-Situ Laser-induced Breakdown Spectroscopy on Earth, Mars, and Moon. Icarus 2025, 427, 116376. DOI: 10.1016/j.icarus.2024.116376
2. Wetzel, W. The Impact of LIBS on Space Exploration: Lunar and Asteroid Exploration. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/the-impact-of-libs-on-space-exploration-lunar-and-asteroid-exploration (accessed 2025-03-25).
3. Wetzel, W. LIBS Proves its Versatility for Moon Missions in New Study. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/libs-proves-its-versatility-for-moon-missions-in-new-study (accessed 2025-03-25).