In 1995, NASA sent 30 fertilised Japanese quail eggs to the Mir space station for 16 days; what scientists found after they returned raised new questions about life without gravity

In 1995, NASA sent a batch of fertilised Japanese quail eggs from Earth to the Mir space station as part of an experiment built around a deceptively simple question: can embryos develop normally without the pull of gravity?

The eggs spent 16 days inside an incubator aboard Mir before their developing embryos were preserved and brought back to Earth for examination.

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At first glance, it may have seemed like a small biological experiment. But researchers were investigating whether the earliest stages of life could unfold normally in an environment where one of the most familiar forces on Earth was almost completely absent. And when scientists examined what had happened to the embryos, the results were not quite what they expected.

Why did NASA send fertilised quail eggs into space?

The experiment was part of NASA’s broader effort to understand how living organisms respond to microgravity.

As astronauts began spending longer periods in orbit, researchers needed to investigate more than the effects of spaceflight on adults. They also wanted to understand what happened to biological processes that normally developed under Earth’s gravity.

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Bird embryos provided a useful way to study the question. The fertilised Japanese quail eggs travelled to Mir aboard the same Space Shuttle mission that carried NASA astronaut Shannon Lucid to the space station. Once there, they were placed inside an onboard incubator.

For the next 16 days, the developing embryos grew in an environment dramatically different from the one they would have experienced on Earth.

The experiment was harder than it sounds

Keeping the eggs inside an incubator was only part of the challenge. Lucid eventually had to remove the eggs individually and preserve the developing embryos so they could be examined after returning to Earth.

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Doing this in microgravity created an unusual safety problem. The embryos had to be fixed using a chemical solution. On Earth, a spilled drop would fall onto a surface. Inside a spacecraft, however, a liquid droplet could float through the cabin.

NASA therefore had to develop a specialised system that would allow the astronaut to work with the eggs without releasing potentially dangerous chemicals into the station.

Engineers at NASA’s Ames Research Center designed a system using interlocking bags and attached gloves, giving Lucid a controlled way to handle the eggs and preserve the embryos.

The embryos were growing in a completely different environment

Inside Mir, the eggs were exposed to microgravity rather than the constant gravitational pull experienced by embryos developing on Earth. But gravity wasn't the only difference.

The space station also exposed the experiment to other conditions that could influence biological development, including increased radiation and differences in temperature.

If something unusual appeared in the embryos, scientists would have to determine whether gravity was responsible or whether another aspect of the space environment had played a role. The researchers therefore compared the space-flown embryos with control groups on Earth.

Then scientists examined the embryos

After the embryos were preserved and returned to Earth, researchers could finally examine them in detail. NASA’s records documented the developmental stages reached by the embryos and compared them with the control groups.

What they discovered provided one of the most intriguing clues yet about how the space environment could affect developing life.

The results did not suggest that development simply stopped in microgravity. Instead, the researchers observed a more complicated picture, one that included developmental differences and an unexpected finding that stood out when the space embryos were compared with their Earth-based counterparts.

What did NASA discover?

According to Lucid’s NASA-published account of the mission, 13% of the embryos incubated aboard Mir showed abnormalities, a rate she reported as more than four times higher than that of the Earth-based control embryos.

Later scientific records added more detail to the picture.

Many of the embryos had reached broadly expected stages of development, but some showed abnormalities involving the eyes, limbs and beaks. Researchers also recorded slight differences in growth when the space-flown embryos were compared with laboratory and synchronous control groups.

The findings, however, did not establish that microgravity itself was solely responsible.

Lucid noted that researchers also considered the higher temperature inside the Mir incubator and the greater radiation exposure aboard the space station as possible contributing factors.