Ever dream of being an astronaut as a kid?

Chances are, once you looked past the really cool stuff – after all, who wouldn't want to see space firsthand, or take a step on the moon? – you probably learned that, well, space travel can be pretty tough on your body.

Take your bones. Since the pull of gravity constantly challenges your skeleton – since your bones need to resist gravity to keep you upright – living in a low- or no-gravity environment can affect your skeleton. Months or years in space lowers your bone mass, which is why astronauts need to take special care to keep their bones healthy.

But there are other effects, too. All that calcium leaching from your bones can travel to your kidneys, upping the risk of painful kidney stones. And living low-gravity in space affects your muscle memory, so your balance can feel off when you get back to Earth.

Now, scientists have discovered that your heart goes through major changes in space – at least temporarily. Here's how that astronaut dream job might affect your ticker, and what would happen when you get back home.

Scientists have known for a while that going into space is tough on your heart. Space tends to reduce blood pressure, while dehydration leads to lower blood volume. It also increases the amount of blood pumped through your vessels with each heartbeat, which translates to extra work for your heart muscles.

On top of that, the radiation astronauts are exposed to during some missions can affect heart health. The radiation causes high blood pressure – also called hypertension – because it prevents your blood vessels from "relaxing."

So, overall, it's not a huge surprise that astronauts are much more likely to die from heart disease than the general population.

The first step to solving astronauts' cardiovascular problems is understanding them in the first place. And that's exactly what a team of researchers at Stanford University set out to do.

First, they took blood from healthy test subjects, who have no history of cardiovascular disease. Then, they manipulated some of the blood cells to develop into heart cells. Finally, they sent half the heart cells into space for about six weeks, and kept the rest of the cells on Earth to serve as a control group.

Perhaps not surprisingly, they found that time in space significantly changed the heart cells. All in all, they found that space travel changed the activity of more than 3,000 genes within the heart cells. And while many of those changes were reversed once the cells returned to Earth, the researchers found that 1,000 genes were still abnormally active (or inactive) after 10 days on Earth.

This study could be the first step to better understanding how space travel affects your heart. But there's still a long way to go. While we now know that many genes become more or less active in space, researchers still aren't sure which of those genes are most important – or exactly how those gene changes affect your heart on a molecular level.

But it's still a promising step toward protecting astronauts' hearts. As researchers learn more about the genetic changes that occur in space, scientists can work on developing drugs or other treatments to minimize the changes and – hopefully – keep space travelers' hearts healthier.