It's too weird to make up: NASA fed some of its precious Apollo 11 lunar samples to cockroaches. And dumped it in fishbowls. And injected mice with it. No, really.

NASA still has most of the moon rocks the Apollo 11 crew brought home, but a small fraction of the astronauts' bounty was used up in a little-known but vitally important set of experiments that ensured lunar samples were safe to keep here on Earth.

Scientists were pretty sure that there weren't any potentially dangerous germs living on the moon , but they couldn't be absolutely sure. And while the retrieval of moon rocks was an incredible gift to science, it could have been quite a curse on Earth if those rocks had turned out to be a risk to terrestrial life. So as part of the agency's preparations for the mission, NASA had to put together a program of tests.

"We had to prove that we weren't going to contaminate not only human beings, but we weren't going to contaminate fish and birds and animals and plants and you name it," Charles Berry, who was in charge of medical operations during Apollo, said in a 1999 oral history . "Any of the Earth's biosphere, we had to prove we weren't going to affect it. So we had to develop an amazing program that was carried off really for three flights' worth. A lot of trouble."

Related: Apollo 11 at 50: A Complete Guide to the Historic Moon Landing

The astronauts themselves were shuffled into quarantine after their return to Earth, where they remained isolated from all but 20 humans for three weeks, from the moment Neil Armstrong and Buzz Aldrin left the moon. A collection of mice also shot to fame while the astronauts were in quarantine: They were injected with lunar material and were monitored just as closely as the crew, who also joined in the watch.

"They always wanted to know how the rodents were doing," Judith Hayes, chief of NASA's Biomedical Research and Environmental Sciences Division, who used to work in the building that once housed the quarantine facility and who has talked with scientists who accompanied the astronauts during that time, told Space.com. "If the rodents did well, then they would likely be released on time, if the rodents weren't well, they would likely be examined much more carefully and longer."

But confirming humans and mice would survive a chance lunar encounter wasn't enough, and keeping all other terrestrial life safe was a little more complicated than watching for coughs or rashes. One NASA document refers to trying to establish procedures as navigating a "sea of ignorance" and emphasized that the authors couldn't predict how much moon rock the tests they outlined would consume.

A lab technician studies a Japanese quail that was exposed to lunar samples collected by the Apollo 11 mission. (Image credit: NASA)

First, NASA chose the species it would use. In addition to the mice, the agency and its partners also selected other representative species: Japanese quail to represent birds, a couple of nondescript fish, brown shrimp and oysters for shellfish, German cockroaches and houseflies for creepy-crawlies, and more. (Sadly, while we found images of the mice, birds and plants, the moon rock-eating roaches eluded us.)

Then, the agency tapped into its precious cache of 49 lbs. ( 22 kilograms ) of newly delivered lunar material. Scientists ground everything to dust, half of which they baked to sterilize and half of which they left as it was. The prescription varied a little with animal type: mice and quail got the lunar sample as an injection, insects had the sample mixed into their food and aquatic animals had the moon dust added to the water they lived in.

NASA watched the menagerie for a month in case anything seemed to suffer from the lunar exposure. The German cockroaches that were fed moon dust — true to the insects' reputation — thrived despite the exotic diet. And all the animals did well, with one glaring exception: Whether in lunar water or not, many of the oysters died, which the scientists chalked up to having tested animals during their mating season.

"The results of these tests provided no information that would indicate that the lunar samples returned by the Apollo 11 mission contained replicating agents hazardous to life on earth," concluded the authors of a paper recounting the tests on "lower animals" published in the journal Science a year after Apollo 11.

NASA grew a range of terrestrial plants, including liverwort, in lunar soil (above). (Image credit: NASA)

In addition to testing animals, NASA also worked with the U.S. Department of Agriculture (USDA) to test plants for any adverse reactions to lunar material, just in case. (As a USDA employee newsletter published in August 1969 recounted, "What will a little moon dust do to your tomato plants? Probably nothing.") These experiments included growing seeds in lunar soil and tested not just tomatoes, but also tobacco, cabbage, onion and fern. Some of these plants actually grew better in the regolith than in the sand scientists used as a comparison.

Similar experiments were conducted after Apollo 12 and 14 as well and tested a total of 15 different animal species, according to a NASA document . While the animal and plant tests were ongoing, NASA also cultured samples on petri dishes to search for any microorganisms that flourished.

Other plants exposed to lunar samples included sorghum and tobacco plants. (Image credit: NASA)

"They didn't find any microbial growth on the lunar samples, and they didn't have any microorganisms that they at least initially attributed to any extraterrestrial source or lunar source. And the crew didn't have any signs of an infectious disease, and all the rodents survived the exams, so everybody did well," Hayes said.

Finally, NASA was confident that lunar regolith was harmless. After Apollo 14, in 1971, the agency stopped testing animals and ended the strict quarantine procedures for astronauts returning from the moon. It also stopped quarantining lab technicians working with lunar samples who might have come in contact with the moon rocks.

NASA had good reason to eliminate the animal tests, of course. "Planetary scientists were unhappy about the amount of material which they viewed as wasted on these experiments and the extent to which quarantine diminished the focus on planetary research," according to a NASA report .

But for a brief few years, cockroaches ate the moon.