An 8,800-pound (4,000 kilograms) Falcon 9 rocket stage hit the moon last Wednesday (Aug. 5), stirring lunar regolith in a massive plume of dust observable all the way from Earth.
The rocket joined some 3,000 manmade objects scattered on the surface of our planet’s companion. Some experts think it’s about time we start treating the pristine lunar environment with a bit more respect.
Around 200 tons of Earth stuff have been either deliberately left on or crashed into the moon since the beginning of the space age. Some of this material has a prominent place in history books: The descent modules from all six Apollo landing missions, Soviet Lunakhod rovers from the 1970s and China’s 2010s Yutu 1 and 2 robots still sit where they had been left or ran out of power.
But there is also a lot of stuff on the moon that wasn’t really meant to end up there. Astronomer and space historian Jonathan McDowell says that many rocket stages and other objects left in orbit between Earth and the moon since the first lunar missions in the 1960s may have ended up on the gray dirt. Four years before the Falcon 9 upper stage crashed near Einstein Crater, for example, part of a Chinese Long March 3C rocket slammed into the moon’s far side. And experts think such incidents could become increasingly common in the coming years, as exploration of the moon intensifies.
“We’re in a transitional moment,” McDowell told Space.com. “From the era when there was rare lunar exploration mostly by the U.S. and the Soviet Union, we’ve seen over the past decade other nations landing on the moon and the beginning of commercial missions. But governance has not kept up with this. We don’t have an international set of agreements on how to operate near the moon, how to coordinate activities near the moon, and we’re really going to need it because, not only is the amount of activity at the moon increasing, but the number of different players is greatly increasing, too.”
Human activities on the moon are governed by the 1967 United Nations Outer Space Treaty, Marieta Valdivia Lefort, a policy officer at the Royal Astronomical Society in the U.K., told Space.com. Article IX of that treaty binds countries to “conduct the exploration of outer space in a way that avoids harmful contamination,” she said. But what exactly constitutes such contamination is unclear, she added.
“There are international legal frameworks that apply to activities on the moon and include obligations concerning harmful contamination, but there is no dedicated international ‘waste law’ or comprehensive ‘rubbish-management’ system for it,” Lefort wrote in an email. “The Outer Space Treaty does not define when contamination becomes ‘harmful.’ It does not set numerical waste limits, create approved disposal sites or require every object on the moon to be removed.”
The moon is big. Its surface area, around 14.7 million square miles (38 million square kilometers) rivals that of Asia, Earth’s largest continent, which covers 17 million square miles (44 million square km). But the moon’s low gravity — around 17% that of Earth — means the dust that an impact stirs up travels a long way and takes a long time to settle, McDowell said.
“It’s not just a local event,” he said. “It’s an equivalent to a continental-level event. In the future, when you have permanent human bases and scientific experiments on the moon, you don’t want rocket stages smashing into the moon on a regular basis, creating big plumes of dust that could contaminate instruments or disturb gravitational wave detectors.”
Moreover, the artificial material introduced and the craters that arise when heavy rocket stages smash into the lunar surface are altering the lunar environment, potentially erasing yet unexplored scientific material.
“The moon is naturally struck by meteoroids, and those impacts form part of the geological record that scientists are trying to understand,” Lefort wrote. “The main concern is the alteration of the moon’s physical and chemical environment, particularly where repeated disturbances could damage or obscure valuable scientific evidence.”
Gregory Radisic, a space law expert at Australia’s Bond University, told Space.com that the Falcon 9 crash was timely, as it can stir debate about responsible behavior in space before the moon gets too busy.
“It’s not by good planning that this didn’t hit something important,” he said. “It’s by pure luck that we’re only having a conversation about theoretical problems down the line and that this did not destroy a million-dollar experiment or an important site of scientific study.”
He added that spaceflight companies may start paying attention to the risks only after human lives are lost or expensive infrastructure suffers, resulting in tangible fines and consequences.
“When there is a loss of life or a loss of investment, the industry will start to care,” Radisic said. “As long as things are losing aesthetic or scientific value, the industry is not likely going to care.”
The Falcon 9 rocket stage that hit the moon was left in a high-altitude orbit around Earth in January 2025, after it propelled Firefly Aerospace’s Blue Ghost and ispace’s Resilience landers to the moon.
McDowell explained that, as the rocket stage was left relatively close to the moon, it got repeatedly influenced by lunar gravity, eventually spiralling into its surface.
“If you leave [an object] in an orbit that’s in this middle region that is far enough that the moon’s gravity is affecting it but not far enough out to go into orbit around the sun, then that orbit is very hard to predict,” McDowell said. “The orbital uncertainties multiply over many passes and, eventually, if you get unlucky, the moon tugs it into an orbit where it’s going to hit either the moon or Earth in a completely unpredictable way.”
McDowell said that, since the January 2025 launch, SpaceX has been pushing its moon-mission rockets farther out into orbit around the sun.
“I hope that we’re going to see a new norm evolve, and that what we have seen now is not how you dispose of your rocket stages in the future,” he said.
