Male astronauts could be replaced by sperm banks in space as all-woman crews conquer the galaxy armed with all they need to populate distant colonies, scientists say

Women could be sent in to space with a selection of sperm ready to populate other planets, researchers say, as they test the effects of zero-gravity on semen.

Frozen sperm could be transported in to space to 'open the possibility of creating a human sperm bank outside of Earth', say researchers at the Dexeus women's health centre in Barcelona.

This could mean male astronauts are replaced by all-women teams in order to reproduce while in space.

But further work is needed in order to fully understand the effect of space conditions and different levels of gravity. 

Frozen samples exposed to micro gravity conditions and those kept on the ground all seem to stay healthy, the researchers say. 

The study has been presented at the European Society of Human Reproduction and Embryology annual meeting in Vienna, Austria. 

It comes after NASA published a paper arguing single-sex crews are best for cohesion and women are more likely to be co-operative. 

Dr Montserrat Boada, from Dexeus Women's Health in Barcelona, said: 'Some studies suggest a significant decrease in the motility of human fresh sperm sample.

'But nothing has been reported on the possible effects of gravitational differences on frozen human gametes, in which state they could be transported from Earth to space.

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

The researchers used sperm from ten healthy donors, exposing some of the samples to microgravity by repeatedly flying in a steep arch in a small aerobatic aircraft.

The samples were then analysed for concentration, motility and DNA fragmentation – tests which are all performed to check for fertility.

No significant differences were found between the samples kept on the ground and those exposed to microgravity, according to the study.

'The lack of differences observed in the sperm characteristics between frozen samples exposed to microgravity and those maintained in ground conditions open the possibility of safely transporting male gametes to space and considering the possibility of creating a human sperm bank outside of Earth,' the researchers said.

However they added that this is a preliminary study, and they need to validate their findings with more samples and expose the sperm to space-like conditions for longer periods of time.

'Our best option will be to perform the experiment using real spaceflight but access is very limited,' Dr Boada said.