In 1967, Biosatellite II irradiated parasitic wasps for 2 days in orbit; females later laid as many eggs as controls, and hatchability remained excellent

In September 1967, NASA launched a small satellite called Biosatellite II into orbit. Inside was an unusual cargo: insects, frog eggs, microorganisms, and plants, spread across 13 biology experiments, according to NASA's mission archive. Scientists exposed some of the wasps aboard to gamma radiation as they orbited Earth. The female wasps that were irradiated in orbit laid the same number of eggs as those that stayed on the ground, and the eggs hatched at excellent rates, according to NASA's technical report on the mission. That was surprising, because radiation typically damages egg production. More than 50 years later, this small experiment still raises questions about the effects of spaceflight on living cells.

What actually happened in orbit

For this mission, the team used a species of parasitic wasp known as Habrobracon, chosen for its short, roughly ten-day generation time and the relative ease of handling its eggs in the lab. The wasps launched from Cape Kennedy, Florida (the site's official name from 1963 to 1973, before it reverted to Cape Canaveral) and reached an orbit some hundreds of kilometers above Earth. The initial plan was for the experiment to run for three days, but, according to Smithsonian's National Air and Space Museum, the threat of storms in the recovery area and communication problems with the spacecraft caused NASA to end the flight after 45 hours.


During that time, groups of female wasps inside the capsule received doses of gamma radiation from a strontium-85 source built into the spacecraft, in amounts reaching up to 4,000 roentgens. For comparison, an equal number of females stayed on the ground and received matching radiation doses as controls. After the capsule was recovered in Hawaii, researchers counted the number of eggs laid by each female wasp and measured hatchability.

Why the egg-laying dip disappeared

When insects are irradiated, the result is usually predictable. Within about a week, the production of eggs falls off dramatically. This is due to the damage done by the radiation to the dividing cells, which ultimately become eggs. This phenomenon is known as the "second week trough." However, the wasps irradiated in orbit around the Earth didn't act this way. During the second week, these females laid as many eggs as the unirradiated ground-based wasps, per the mission findings. By day ten, they were laying more eggs than the control group. Perhaps more significantly, the eggs the wasps laid hatched at high rates and showed little evidence of genetic damage.

Scientists tried to reproduce the result on the ground, but failed

It was natural that researchers wanted to know why space travel appeared to protect the wasps from the usual radiation damage. So they tried to duplicate the conditions of launch, flight, and landing here on Earth. The wasps were spun on rotating devices to simulate weightlessness, shaken to mimic the vibrations of a rocket launch, and spun in centrifuges to mimic the heavy forces of liftoff and reentry, all while being subjected to similar doses of radiation.

None of these ground experiments reproduced the protection observed in orbit. A follow-up NASA-funded study found stark contrasts between the actual flight results and those from wasps subjected on the ground to simulated launch and recovery forces, though it stopped short of pinning the difference on rotation specifically. They knew that weightlessness was a factor, but they could not yet tell how or why it appeared to protect the developing eggs. That mystery was never quite resolved in this report.

Why this old experiment still matters

Biosatellite II was part of a small NASA program built specifically to study the effects of spaceflight on biology, decades before astronauts on the International Space Station had access to modern laboratories. A mission summary published in the Life Sciences and Space Research journal explains that the satellite carried more than a dozen separate biology experiments, all to test how living things respond to radiation and weightlessness together.

The wasp results were just one piece of that puzzle, but they brought up a question scientists still are trying to answer: does traveling through space change the way radiation affects living cells, and if so, how? Today this information is more relevant than ever. Space agencies are planning longer trips to the Moon and Mars, exposing astronauts to much more cosmic radiation than anyone experienced on a 45-hour trip in 1967. A humble wasp experiment more than half a century ago reminds us that scientists have much to learn about safely keeping living things, including humans, on long journeys away from Earth.