On Monday, the Indian Space Research Organization (ISRO) announced the Chandrayaan-2 mission, which will send a rover to the south-side of the moon later this year. It will be India’s second lunar mission and the first time any country has visited the moon’s south side. The ISRO’s six-wheeled rover will analyze the lunar crust for traces of water and helium-3, an isotope that is integral to developing fusion energy on Earth.

The running joke among nuclear physicists is that fusion energy is always 30 years away, but when it gets here, India wants to be the one providing the fuel.

“The countries which have the capacity to bring that source from the moon to Earth will dictate the process,’’ Kailasavadivoo Sivan, chairman of the ISRO, told Bloomberg. “I don’t want to be just a part of them, I want to lead them.’’

Nuclear fusion is the same process that powers the sun and involves smashing hydrogen atoms together to produce helium, which releases a ton of energy in the process. If this fusion energy can be captured, it would effectively be a source of unlimited energy on Earth. Unfortunately, building a nuclear fusion reactor, aka a “star in a jar,” has proven to be incredibly difficult.

Today, most fusion reactors use a mix of hydrogen isotopes called deuterium and tritium as nuclear fuel. Although the techniques for instigating fusion differ, one of the more successful approaches involves a deuterium/tritium fuel cell that is hit with a high dose of concentrated energy. This causes the fuel cell to turn into a plasma that is compressed with magnetic fields (or liquid metal) to cause nuclei to fuse and release a bunch of energy. So far, no lab has been able to extract more energy from this reaction than it took to make it happen in the first place, which is required to create a scalable fusion energy power plant.

A related problem has to do with the byproduct of deuterium and tritium fusion: High energy neutrons that rocket out of the nuclei of these isotopes during the fusion process. These so-called “fast” neutrons are the source of energy that needs to be harvested in a fusion reactor, but they are remarkably tough to contain. Neutrons react with the walls of nuclear reactors more than protons, which causes them to have to be replaced more often. Moreover, they aren’t charged particles, so they are harder to manipulate with electric and magnetic fields.

This is where helium-3 comes in. By taking tritium out of the equation and using a mixture of deuterium and helium-3, the fusion process produces a proton, rather than a neutron. This results in less energy waste and easier containment since protons are charged particles , which makes it easier to directly harvest energy from the fusion reaction by manipulating the protons with electric and magnetic fields. In short, adding helium-3 into the mix would make fusion reactors non-radioactive and incredibly more efficient.

Work on helium-3 fusion has been slow going because its so rare on Earth, but initial results have been incredibly promising. Last year, for example, researchers at MIT increased the efficiency of a fusion reaction by an order of magnitude after adding small amounts of helium-3 to a fuel cell containing hydrogen and deuterium. Other research that uses two helium-3 isotopes instead of a deuterium-helium-3 mix has also proven to be remarkably efficient in small reactors.

Among the many triumphs of NASA’s Apollo missions in the 60s and 70s was confirming that the lunar surface contained an abundance of helium-3 because the moon doesn’t have an atmosphere to repel the stuff. In fact, the amount of energy that could be created using all the helium-3 stored on the moon is more than 10 times the amount of energy stored in all the fossil fuels on Earth. As the prospect of fusion energy seems increasingly realistic, this has launched an international race to the moon to be the first to extract this valuable resource from the lunar surface.

Moon Express, which became the first private company to receive permission from the US government to launch an object beyond Earth orbit last year, has set its sights on the moon for helium-3 mining. In 2016, China also announced its intention to put a rover on the moon to scout for helium-3 mining locations. Now, India has announced its intention to join the race to harvest what may turn out to be one of the most valuable energy sources ever discovered.