Worlds with a permanent day and night side aren’t obvious places to look in the search for extraterrestrial life. Apart from having extremes of temperature, such planets would make it hard for a biological clock to get going.
But now it seems that if these worlds also have oceans, then tides could drive a biological clock just like a rising and setting sun would, according to a simulation by Avi Loeb and Manasvi Lingam at Harvard University.
We used to think that not having a day-night cycle would make it harder for life to emerge, because of the lack of a circadian clock. On Earth, these built-in timekeepers play an important role in several biological contexts, including reproduction.
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Abigail Beall 