Curium is a synthetic radioactive element used primarily as a power source for space missions and medical devices, as a tool for analyzing rock and soil chemistry on Mars, and as a target material for creating new superheavy elements in particle accelerators. It has no everyday commercial uses. Nearly all curium applications take advantage of the intense energy released when its atoms decay.
Powering Devices in Space and Medicine
Curium’s most practical application is as a compact energy source. Two isotopes, curium-242 and curium-244, generate significant heat as they undergo radioactive decay. That heat can be converted into electricity using thermoelectric generators, making curium useful for powering batteries in environments where solar panels or conventional batteries aren’t reliable. Space missions that travel far from the Sun or operate in darkness for extended periods benefit from this kind of power. The same principle applies to certain implantable medical devices that need a long-lasting, miniaturized power supply.
Curium-244 is particularly well suited for these roles. It has a half-life of about 18 years, meaning it produces steady energy output over a useful timeframe without decaying too quickly or too slowly. Curium-242, with a half-life of only 163 days, generates more intense heat per gram but burns out much faster, limiting it to shorter missions or applications.
Analyzing Rocks and Soil on Mars
One of curium’s highest-profile roles is aboard NASA’s Mars rovers. The Curiosity rover carries an Alpha Particle X-ray Spectrometer (APXS) that uses curium-244 as its radiation source. The instrument works by bombarding rocks and soil with alpha particles and X-rays emitted by the curium. When those particles hit a sample, the atoms in the rock emit characteristic X-rays back, and the spectrometer reads those signals to identify which elements are present.
This technique can detect elements ranging from sodium to bromine and beyond, including trace amounts. It’s especially sensitive to salt-forming elements like sulfur, chlorine, and bromine, which are important clues about whether water once flowed through Martian rock. A newer method even allows the instrument to detect compounds that are normally invisible to X-ray analysis, such as bound water and carbonates, when they make up more than about 5% of a sample’s weight. The elemental data helps scientists reconstruct the geological history of a site, understand how rocks and soils formed, and choose the most scientifically interesting samples for closer analysis by other instruments on the rover.
Creating New Superheavy Elements
Curium-248, the longest-lived isotope that can be produced in useful quantities, serves as a target material in particle accelerators. Researchers prepare thin curium metal targets on substrates made of metals like beryllium, tantalum, or molybdenum, then slam high-energy ions into them. When a heavy ion collides with a curium-248 nucleus and the two fuse, the result can be an atom of a superheavy element that doesn’t exist in nature.
This approach has been used in attempts to synthesize elements at the far edge of the periodic table. In one well-known experiment, uranium-238 ions were fired at curium-248 targets to search for superheavy elements produced in the collision. These experiments are extraordinarily difficult. The fusion events are rare, the resulting atoms often survive for only fractions of a second, and the curium targets themselves can be damaged by the intense particle beams. Still, curium remains one of the heaviest and most neutron-rich target materials available, giving it a unique role in pushing the boundaries of known chemistry.
How Curium Is Produced
Curium doesn’t exist in nature. It was first created in 1944 by Glenn Seaborg, Ralph James, and Albert Ghiorso using the cyclotron at the University of California, Berkeley. They produced curium-242 by bombarding plutonium-239 with alpha particles. The element was named after Marie and Pierre Curie.
Today, curium is produced as a byproduct inside nuclear reactors. When uranium fuel absorbs neutrons over time, it gradually transforms through a chain of reactions: uranium captures neutrons and undergoes beta decay to become plutonium, which captures more neutrons to become heavier plutonium isotopes, and eventually curium. Extracting it from spent reactor fuel is a complex, multi-step chemical process. First, uranium, plutonium, and neptunium are separated out using solvent extraction. Then a fraction containing curium along with lanthanide elements is isolated. Finally, curium is purified from that mixture using high-pressure ion exchange chromatography. The difficulty and expense of this process is one reason curium remains available only in small quantities for specialized research.
Why Curium Has So Few Uses
Several properties limit curium to niche applications. Its most stable isotope, curium-247, has a half-life of about 15.6 million years, but it’s extremely difficult to produce in meaningful amounts. The isotopes that are available in larger quantities, like curium-244, decay relatively quickly and emit intense radiation. Curium-242 decays into plutonium-238, and curium-244 undergoes both alpha decay and spontaneous fission, making handling hazardous and requiring heavy shielding.
If inhaled or ingested, curium concentrates primarily in the skeleton. Research on an accidental human exposure found that about 90% of inhaled curium-244 ended up in bone, with smaller amounts in muscle tissue (3.4%) and the liver (2.2%). The highest concentrations per unit of tissue weight were found in the respiratory tract, followed by bone and liver. This tendency to accumulate in bone makes it a long-term internal radiation hazard, similar to other heavy radioactive elements like plutonium. These safety challenges, combined with the cost and difficulty of production, mean curium will likely remain a specialized material used only where no practical alternative exists.