On February 3, 1966, an inflatable ball bounced across the surface of the Moon. Inside was Luna 9, the first spacecraft to land softly on another world. After coming to rest, the Soviet Union’s lander unfolded four protective “petals” to reveal a camera and took the first picture from the lunar surface.

Luna 9 extended the USSR’s existing lead in the Space Race propaganda campaign, as the focus of the race shifted toward a crewed landing. The image made the cover of The Science News-Letter. “The photographs show that the moonscape is covered seemingly with a somewhat porous material,” the cover story reads, “pockmarked with small pits and scattered with oddly shaped rocks.” These lunar images had the potential to settle a scientific debate about the potential of sending astronauts to the Moon.

Knowledge about the lunar surface was still limited, and at least one scientist was skeptical about landing a large spacecraft. Thomas Gold of Cornell University believed that a layer of dust coated the Moon’s surface, making it too unstable for a heavy lander.

But other scientists like Gerard Kuiper thought Gold was misguided, based on the data from the United States’ Ranger impact probes. After Luna 9, Kuiper and his collaborators quickly published their interpretation of the images. Using the texture and structure of craters, they argued that the surface was “solid, cohesive, though highly vesicular, material.” They compared the craters to those on a volcano in Hawai‘i and speculated that surface material might be made of volcanic rock with a highly pitted surface.

A few months later, Gold published his own interpretations. In his paper, co-authored with B. W. Hapke, he argued that solid volcanic rock wasn’t consistent with other data. Gold argued that radar and other observations indicated a much more intricate surface texture than could be seen in the Luna 9 images.

“An unresolved, more complex structure is clearly necessary,” he wrote, “such as would be provided by fine cohesive powder.” Gold then described lab experiments using cement powder, which produced images similar to the Luna 9 pictures.

Luna 9 also shifted while sitting on the surface. While this enabled stereoscopic pictures, Gold thought it might also be a sign of collapsing dust structures. Neither Gold nor Kuiper had changed their minds.

Later in 1966, America’s first lunar lander, Surveyor, provided more information from the lunar surface. Other scientists published interpretations of Luna 9 images and compared them to pictures from Surveyor. The scientific understanding of the lunar surface evolved, and it quickly became clear that Gold was wrong, and a crewed landing would be possible.

“Gold’s dust” may not have been as deep or treacherous as he initially believed, but the Surveyor robots and Apollo astronauts did see their feet sink slightly into a layer of lunar soil. The astronauts also contended with harmful dust sticking to equipment, which future missions to the Moon are taking into consideration. More robots are heading to the Moon this year, equipped to help us better understand the lunar environment—including lunar dust.

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