For decades, humanity has sent robotic explorers far beyond Earth’s comfort zone—into places where sunlight is weak, nights are brutally cold, and dust storms can last for months. The secret that keeps these machines alive isn’t futuristic magic or oversized batteries. It’s nuclear science. And at the heart of that science is a little-known element called neptunium, studied in extraordinary detail at Oak Ridge National Laboratory (ORNL).
Radiochemist Kathryn Lawson takes us behind the scenes of how deep-space missions like the Mars rovers Curiosity, Opportunity, Spirit, and Perseverance stay powered year after year. While solar panels work well near Earth, they’re unreliable in deep space or on planets like Mars, where sunlight is inconsistent and dust can smother equipment. Instead, NASA relies on radioisotope thermoelectric generators, or RTGs—compact nuclear-powered systems that convert heat from radioactive decay into steady, long-lasting electricity.
RTGs have been used by the United States since the 1960s, and they’re built around a specific material: plutonium-238. This isotope produces heat reliably for decades, making it ideal for long missions where maintenance is impossible. But plutonium-238 doesn’t exist naturally. It has to be made—and that’s where neptunium enters the story.
Neptunium, first discovered in 1940, is a radioactive element with 22 known isotopes. The most important one for space exploration is neptunium-237, a key ingredient in producing plutonium-238. At ORNL, neptunium targets are placed inside the High Flux Isotope Reactor, where they’re bombarded with neutrons. This process transforms neptunium atoms into plutonium-238 atoms, creating the fuel that powers spacecraft millions of miles from Earth.
ORNL is uniquely equipped for this work. Its facilities are the only ones in the world capable of producing these neptunium targets, making the lab a quiet but critical backbone of U.S. space exploration. Lawson’s research focuses on understanding neptunium at the smallest possible scale—sometimes examining particles smaller than a human hair using powerful digital and electron microscopes.
Because neptunium is both radioactive and relatively newly studied, much of its chemistry remains a mystery. Lawson’s microscopic images reveal how neptunium particles form, react, and change, providing clues that help scientists refine how targets are made. The goal is practical as well as scientific: more efficient production, lower costs, greater consistency, and a more secure supply of plutonium-238 for future missions.
What’s striking is how something so tiny can have such massive consequences. Lawson’s work on microscopic particles helps fuel spacecraft that roam alien landscapes, send back breathtaking images, and expand humanity’s understanding of the universe. Her research isn’t just about chemistry—it’s about keeping exploration alive in the harshest environments imaginable.
From a lab bench in Tennessee to the surface of Mars and beyond, neptunium chemistry plays an outsized role in humanity’s cosmic ambitions. Thanks to scientists like Lawson and the specialized work at ORNL, the engines of exploration keep running—quietly, steadily, and nuclear-powered—far from home.
Source: Oak Ridge National Laboratory on YouTube: “Nuclear at ORNL: Powering Space Exploration with Neptunium Research”
