The experiment is designed to study sperm motility — that is, the ability to move and swim — in microgravity conditions, and how successful they are in triggering the physiological changes known as capacitation, which enables them to penetrate and fertilize eggs, according to this article from the NASA website. That information could help to answer the question of whether humans would be capable of reproducing if they settle in future colonies on the Moon or Mars, or if they venture on even longer journeys into the cosmos.
"If you don't have healthy sperm, you've got real risk to multi-generational survival in space," explains Joe Tash, an emeritus professor in the Department of Molecular and Integrative Physiology at the University of Kansas Medical Center. Tash was the lead scientist in developing the experiment, and continues to be involved as a consultant.
NASA has been conducting research on reproductive and developmental space biology since the 1990s, according to an email from researchers at NASA's Ames Research Center in California's Silicon Valley, who are involved in the Micro-11 research. In one study published in the March 14, 1995 issue of Proceedings of the National Academy of Sciences, for example, female frogs aboard a space shuttle were induced to ovulate so that their eggs could be fertilized. The study demonstrated that gravity-induced rotation of the zygote, the cell formed by the fusing of a sperm and egg, wasn't necessary to develop a free-swimming tadpole with a normal body.
Micro-11 marks the first time that human sperm — that is, aside from the ones inside male astronauts' bodies — have been launched into space, though there have been previous research efforts involving animal sperm. Back in the 1980s, German researchers launched bull semen into space on a suborbital rocket that briefly subjected them to a minute and a half of weightlessness, which was recorded on video, Tash says. Then, in 1997, Tash and colleagues sent samples of sea urchin sperm on two space shuttle missions. In those two experiments, it wasn't possible to shoot video under a microscope, so instead they looked at signal transduction, the molecular mechanism within the sperm cell that tells it when to start wriggling its tail.
The results of the German study and Tash's 1997 research both found that the sperm actually swam faster in microgravity than they do back on Earth. But in one of Tash's experiments, he detected what may be a big hindrance to procreating in space. When sea urchin sperm were exposed to chemical compounds called peptides that would be released by eggs, the signaling that triggers capacitation — an essential part of reproduction — occurred much more slowly.
The Micro-11 experiment will gather data on the effect of microgravity on swimming and capacitation in separate trials, according to Tash.
