题型：阅读理解 题类：常考题 难易度：普通
四川省雅安市2018-2019学年高二上期英语期末考试试卷
Are you a morning person? You might not like the findings in this new research.
From a lack of air and drinking water to solar radiation, theoretical Mars pioneers face any number of potential obstacles to settling on 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. A team of European scientists recently demonstrated why that could be a problem.
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 interrupted by things like jet lag（时差）and night shift work.
For the study, the researchers compared mice with healthy, 24-hour circadian clocks to mice with a genetic change that caused them to have shorter, 20-hour circadian clocks. 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.
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.
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.
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