It's one small step for science, and potentially one giant leap for mankind's ability to populate space.

Spanish scientists have found that frozen sperm samples are still viable after exposure to simulated space flight, opening up the possibility of an space-based sperm bank.

The small preliminary study, presented at the European Society of Human Reproduction and Embryology in Vienna which began Sunday, exposed human sperm samples to microgravity.

In microgravity, which is sometimes misleadingly referred to as zero gravity, there are limited effects of gravity and objects appear to be weightless.

The samples were then analyzed for concentration, motility, vitality, morphology and DNA fragmentation. Researchers found there was almost no difference between the control sperm on Earth, and the sperm which had been exposed to microgravity.

The scientists exposed the sperm to microgravity for a few seconds at a time by transporting the samples on a small aerobatic training aircraft. Scientists chose to use frozen sperm because radiation can affect the quality and viability of fresh sperm.

Dr. Montserrat Boada from Dexeus Women's Health in Barcelona, who presented the results, stressed the study was only preliminary and would require further work.

The team will now move on to larger sperm samples, longer periods of microgravity, and using fresh rather than frozen sperm, she said.

"If the number of space missions increases in the coming years, and are of longer duration, it is important to study the effects of long-term human exposure to space in order to face them," Boada said in a statement.

"It's not unreasonable to start thinking about the possibility of reproduction beyond the Earth."

But there are other issues to contend with if humans are traveling -- and potentially reproducing -- in space. Over time, astronauts experience loss of bone, atrophying muscles and blood volume loss. Space travel could also increase the likelihood of cancer.

Previous studies have shown that radiation from galactic cosmic rays could have long-lasting effects on the brain, affecting learning, memory, multitasking and mental health. A study earlier this year found that the longer astronauts are in space, the more likely they are to have herpes, chickenpox and shingles reactivate.

In recent years, private companies have begun discussing the possibility of human colonies in space, taking the idea from being the stuff of science fiction, to being something that could really happen.

SpaceX founder Elon Musk has spoken of his ambitions to colonize Mars, and in 2017, he announced plans to land two cargo ships on the Red Planet in 2022. On Sunday, Musk tweeted a picture with the words "Occupy Mars."

In 2013, Dutch company Mars One began selecting crew members from thousands of applicants for its Mars colony. The company went bankrupt earlier this year.

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