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Sperm Stored In Space Produces Healthy Baby Mice On Earth (theguardian.com)
An anonymous reader quotes a report from The Guardian: Reproduction may be possible in space, Japanese researchers have said, after freeze-dried sperm stored on the International Space Station for nine months produced healthy offspring. The scientists said their findings could have significant ramifications for human settlements in space, which they consider "likely." The average daily radiation dose on the ISS is about 100 times stronger than that on Earth, posing a threat of serious reproductive problems for any space-dwelling organism. But mouse sperm stored on the ISS for 288 days from August 2013 to May 2014, then returned to Earth, fertilized in vitro and transferred into female mice, produced healthy offspring. The space-preserved samples showed evidence of slightly increased DNA damage compared with control samples preserved on Earth, but this was found to be largely repaired in embryos following fertilization. The birth rate and sex ratio of pups derived from the sperm stored in space was comparable to those of pups derived from the control samples. Subsequent whole genome analysis revealed only minor differences, and the pups developed into adults with normal fertility. The study was published in the proceedings of the U.S. National Academy of Sciences on Monday.
Ok, before we talk about colonizing Mars or any other planet with gravity not equal to earth's (and that includes zero gee), we need to see if mice, at least, can become pregnant, bring their pups to term and have them live a full healthy life on the space station. Preferably for two or more generations.
Why? Well this would be the best indication that it will be possible for humans to do the same and, IF (and this is a big if) humans respond similarly AND if partial gravity (like Mars' 1/3 G or the Moon's 1/6 G) is less harmful than the zero gee (okay "micro-gravity") in the space station, then that would be an important first step to determining whether or not humans are capable (without modification) of colonizing other worlds or space itself.
If the mice cannot conceive or do not develop normally through their entire life cycle, then a long process of finding the cut-off point from 0 to 1 G may have to begin. Then, because humans are not mice, this program may have to be repeated (someday) with (very brave) volunteer couples. So let's hope that this first test is passed successfully; it would alleviate "some" concern that these human trials may not end in tragedy.
There are plenty of other concerns about raising humans in outer space (radiation, isolation, etc.) but some of these other problems can be overcome with technology we already possess (like lots of shielding). Too low gravity? Well unless we want the colonists to be spending a large amount of time during pregnancy and potentially child rearing in big centrifuges, there is no currently known way to artificially create it (or lessen it).
Then again, there's the possibility of Humans 2.0. That's why I'm studying genetic engineering! :)