From a lack of air and drinking water to solar radiation, theoretical Mars pioneers face any number of potential obstacles to colonizing the red planet.
Now, scientists have found something else to add to the list: seriously messed-up biological clocks.
One day on Mars -- which scientists refer to as the solar day, or "sol" -- is 37 minutes longer than a day on Earth. This means that our Earthling circadian rhythms don't match the red planet's rotational speed.
A team of European scientists recently demonstrated why that could be a problem. It's important to have a biological clock that is in sync with the planet's rotation, their research suggests.
"If we ever do get to the red planet, I suspect we will be faced with body clock problems," Dr. Andrew Loudon, a biologist at the University of Manchester and one of the study's authors, said in a statement. "Those people with abnormally slow body clocks would be best suited to living there.”
Circadian rhythms are the body's natural cycles of rest and waking, which tend to follow roughly 24-hour light-dark cycles. These natural rhythms -- which play a role in biological functions including brain wave activity and hormone production -- can be disrupted by things like jet lag and night shift work.
For the study, the researchers compared mice with healthy, 24-hour circadian clocks to mice with a genetic mutation that caused them to have shorter, 20-hour circadian clocks. They then released all the mice together into outdoor pens with freely available food, and studied how the population changed over the course of 14 months. Over several generations, the researchers found that the mouse population came to be dominated by mice with normal, 24-hour circadian rhythms.
In other words, the mice with healthy biological clocks were more likely to survive and reproduce, while the mice with shorter biological clocks were more likely to die off.
The finding is supported by previous research, which has found a link between night shift work and a heightened risk of fertility issues and diseases, including diabetes, cancer and cardiovascular disease.
"Our study is the first to look at long-term (one-year plus) consequences of abnormal circadian period in an outdoors environment in an animal," Loudon told The Huffington Post in an email. "People that work on rotational shifts are exposed to abnormal lighting regimes. This is known to be associated with health problems, including increased risk of Type 2 diabetes."
What does this all have to do with space travel? Since the Martian sol is longer than a day on Earth, people with shorter circadian clocks could suffer from health problems as they try to adapt to the rotational speed of the red planet.
“The rotation speed of Mars may be within the limits of some people’s internal clock, but people with short running clocks, such as extreme morning types, are likely to face serious intractable long-term problems, and would perhaps be excluded from any plans NASA has to send humans to Mars," Loudon said.
Unfortunately, the body is unlikely to adapt to the new conditions or "learn" to develop a longer clock. As Loudon explained, "Learning is not a likely option."
In other words: Sorry, super-early risers -- NASA might not want you for the next Mars mission.
What would it really be like to live on the red planet? Find out in the "Talk Nerdy To Me" episode below.