Revisiting the Soviet Lunar Sample Return Missions

China’s Chang’e 5 lunar sample return mission launched on November 23, 2020, and landed on the Moon a little over a week later. On December 16, the spacecraft successfully brought back pristine Moon samples to Earth—a feat that had not been accomplished since the Soviet Union’s Luna 24 mission in 1976.

The Soviets successfully executed three robotic sample return missions as part of the Cold War Moon Race with the United States. Even though the USSR failed to ever launch cosmonauts to the Moon to overtake the American Apollo program, it continued with its robotic exploration of Earth’s only satellite during the early and mid-1970s.

The Soviet sample missions were closely clustered on the surface of the Moon. The first mission, Luna 16, returned 101 grams from Mare Fecunditatis in September 1970, between the U.S.’s Apollo 12 and Apollo 14 landings. The following year, the USSR launched an automated lunar rover, or Lunakhod, along with the Luna 17 spacecraft. A year following that (February 1972), Luna 20 returned 55 grams of soil from the Apollonius highlands region. Luna 16 and Luna 20 were very similar in design and sampling method. A drill at the end of the sampling arm collected soil from a few tens of centimeters (about a foot) below the surface. The arm then placed the sample into the return capsule on top of the vehicle. The spherical, ablative return sample container then launched directly to Earth to land inside the USSR.

In 1973, Soviet engineers pulled off the second successful Soviet Lunakhod mission, Luna 21. Three years later, the USSR launched Luna 24 after the failed landing of Luna 23. Luna 24’s objective was to return lunar samples from Mare Crisium from as deep as two meters below the Moon’s surface, 6-7 times deeper than its predecessors. It returned its sample to Earth on August 22, 1976, totaling 170.1 grams (6.00 oz). Until the launch of Chang’e 5, Luna 24 was the most recent lunar sample return. It was the last lunar spacecraft that the Soviet Union or Russia has ever launched.

The instrument mission and design for all of the Soviet lunar sample return missions were the product of the planetary scientists and geologists of Babakin Science Research Center, which took over robotic solar system exploration from Sergei Korolev’s Design Bureau in the early 1960s. The Lavochkin Production Organization, famous during World War II for its Soviet fighter aircraft, built the hardware that carried the instruments. A Proton launch vehicle from the Khrunichev Factory launched each mission. 

Although there were three successful sample return missions, the Soviet lunar program was not without its failures. Luna 15 was an attempt at a sample return mission to preempt the Apollo 11 mission by landing on the Moon on July 21, 1969. Unfortunately, it crashed instead of landing softly. In October 1974, Luna 23 set down on Mare Crisium (the Sea of Crises), but technical difficulties prevented its drilling arm from working correctly. The Soviets ran the same mission again in Luna 24, and were successful.

In the spirit of international cooperation, in December 1976, the USSR and NASA agreed to swap a gram of lunar sample. Apollo astronauts had brought 382 kilograms (842 pounds) of lunar samples to Earth and the Soviet sample missions returned 226.1 grams (0.5 pounds). In 1978, Soviet scientists from the Vernadsky Institute of Geochemistry and Analytic Chemistry of the USSR Academy of Sciences published a scientific paper that concluded that the samples from Luna 24 had evidence of water in them. 

For those who doubted the veracity of the Soviet lunar program, the Lunar Reconnaissance Orbiter Camera (LROC) has imaged the landing sites and spacecraft of Luna 16, 20, and 24). Their locations and activities are beyond a doubt. Identifying their precise locations beyond the capability of 1970s technology had both historic and geologic importance. We now know the precise geographical origins of the Soviet lunar samples, and that knowledge adds meaning to the scientific studies of the samples.

The successful Soviet Luna sample return missions returned small, but important, samples from three close locations on the Moon. In this new era of lunar exploration, several countries plan to soft land on the Moon over a much broader expanse of the lunar surface. China’s Chang'e 3 was the first robotic soft landing since Luna 24 and Chang’e 5 has brought back new extractions for the first time since 1976. India, Japan, and Russia plan to launch robotic missions in the coming years as well. And, of course, NASA is preparing to return humans to the Moon in the Artemis program.