Human sperm has been sent to the International Space Station (ISS) for the first time, as Nasa tries to find out if humans could ever conceive in space.Carried aboard Elon Musk's SpaceX Falcon 9 rocket, the sperm will be the subject of a number of experiments to see how space and low gravity affect male sex cells.Astronauts onboard the ISS will thaw the frozen sperm to see if sex in space would lead to successful reproduction.The scientific study is being undertaken as part of Nasa's Micro-11 mission, which contains samples of frozen human and bull sperm.Once the Falcon 9's Dragon resupply capsule has completed the first stage of the journey and has docked, research will begin on the samples.Nasa hopes to understand how micro-gravity affects the swimming of sperm and how well they move in space.In a statement, it said: 'Little is currently known about the biology of reproduction in space, and this experiment will begin to address that gap by measuring, for the first time, how well bull and human sperm functions in space.'Successful fertilisation of a human egg depends on several factors and is broken down into two stages.The sperm cell must be activated and then change slightly as it swims toward an egg to fertilise it.In preparation for fusing with the egg, it must move faster and its cell membrane must become more fluid.In previous experiments with urchin and bull sperm, activation happens quicker in microgravity, but the steps that lead up to successful fusing are very delayed or simply do not happen at all.'Delays or problems at this stage could prevent fertilisation from happening in space,' Nasa warns.Nasa is sending up human sperm for the first time, but bull sperm is being sent up again for comparison.It will act as 'quality control' as the bovine cells are more regimented and uniform in their movements than their human equivalents.After thawing and activating the sperm samples, researchers will use video to assess how well the sperm move in the adverse conditions of space.Changes in the bull semen will allow researchers to detect subtle differences in sperm from both species.After being studied on the ISS, the samples will be mixed with preservatives and returned to Earth.Here, it will be determined if fusion occurred and whether the space sperm is any different to regular Earth sperm.Nasa added: 'We don't know yet how long-duration spaceflight affects human reproductive health, and this investigation would be the first step in understanding the potential viability of reproduction in reduced-gravity conditions.'The issue of successful conception poses problems for long duration space flight where humans will be on board spacecraft for several years.With sex a near-inevitability in future deep-space exploration, the ability to reproduce is essential as the missions may span several generations.Space is a hostile environment, with radiation a real concern for damaging living tissue.And while sperm is damaged by long-term solar radiation ex
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