That means male gametes may safely travel in space.
Human colonization elsewhere is a long way off, of course, and will remain so if future U.S. presidents do what the last two have done and cancel programs of their predecessors to replace those with something bearing their own name. But the effects of microgravity on the cardiovascular, musculo-skeletal and central nervous systems are well known and tested in space flight while relatively little is known about the effects of different gravitational environments on human sperm and eggs.
Aeroclub Barcelona-Sabadell of Spain was responsible for the parabolic flights to create microgravity conditions. The study was performed using a small aerobatic training aircraft (CAP10), which can provide short-duration hypogravity exposure. The plane executed a series of 20 parabolic maneuvers, providing 8 seconds of microgravity for each parabola. Overall, ten sperm samples obtained from ten healthy donors were analyzed after exposure to the different microgravities found in space and ground gravity.
The sperm analysis comprised a full range of measurements currently performed for fertility testing - concentration, motility, vitality, morphology and DNA fragmentation - and results found no difference whatsoever in any of the parameters between the microgravity space samples and the control group samples from Earth. There was 100% concordance in DNA fragmentation rate and vitality, and 90% concordance in sperm concentration and motility. The minor differences were more probably related to heterogeneity of the sperm sample than to the effect of exposure to different gravity conditions.
This is a preliminary study and must be validated with larger sperm samples, longer periods of microgravity and fresh sperm. They used frozen because of the known effect of cosmic radiation on fresh sperm. Frozen samples are preserved in special cryostraws and transported in tanks.