As astronaut Scott Kelly gets used to living life on Earth again--he spent a full year on the International Space Station--Elon Musk continues to plow through SpaceX successes. Musk's long-term goal of eventually supporting human migration to other planets hasn't changed, but something else has.

That'd be Scott's DNA.

What happened to Scott's genes.

The big goal of Scott spending a year in space was for NASA to learn more about how extended time off Earth influences people physically and psychologically. Since Scott has a twin, Mark, who incidentally is also an astronaut, NASA had a perfect opportunity to do some comparative study.

As Katherine Hignett reports in her article for Newsweek, NASA researchers took a close look at Scott and Mark's DNA once Scott got back from ISS. They found the extended time in space resulted not only in issues like increased inflammation, but also nutrient changes that altered gene expression.

Most of the changes researchers noted were only temporary. For example, the telomeres on Scott's chromosome had lengthened on his mission, but they shortened right back up in just two days once Scott was earthbound again. But a full 7 percent of Scott's genes still showed signs of alteration after six months. That has the researchers questioning whether the changes are much more long-term.

Different DNA, new questions.

NASA's results throw a big ethical problem at Musk and SpaceX: What if the effects on DNA are even more pronounced with long-term space colonization? Even if the changes aren't more drastic, what are the implications for the ability of human beings to survive, especially given that changes were noted in genes connected to DNA repair? (Think mutations here, for better or worse.) What do those changes mean over many generations, and could they eventually threaten what it means to be human in the most basic sense? Should we continue to reach for planets simply because the technology is extending our arms, even if we don't know what's in store for our health and species? After all, 7 percent isn't a small number when you understand that, comparatively, we're genetically separated from chimps by only 4 percent. And roughly 10 percent of our genes regulate the expression of our other genes, so influencing one gene can affect others.

I find the whole thing a little unsettling.

Then again, sometimes you simply won't get an answer unless you take a really big risk. Just ask scientists like Marie Curie, whose Nobel prize-winning radium work essentially poisoned her to death. Modern researchers take as many precautions as they can, but they can only protect themselves based on the current information they have. Even now, we don't always know whether much of what we do in science is a threat.