'Beyond day and night': How alien worlds without cycles could inspire new forms of life
Produced by: Tarun Mishra Designed by: Manoj Kumar
Alien Life Without Day-Night Cycles
Research suggests that life on many potentially habitable exoplanets may not experience traditional day and night cycles due to their tidal locking. These planets orbit stars such as red dwarfs, leading to one hemisphere constantly facing the star while the other remains in perpetual darkness.
Billions of Potentially Habitable Planets
The Milky Way contains between 100 billion and 400 billion stars, with approximately 70% being red dwarfs. A 2013 study estimated that 41% of these stars have planets in the habitable zone, where conditions could support liquid water. This suggests there are around 28.7 billion such planets orbiting red dwarfs alone.
Characteristics of M-Earths
Planets orbiting red dwarfs, known as M-Earths, are often tidally locked. This means their rotation period matches their orbital period, causing one side to always face the star and the other to remain dark. This lack of a day-night cycle poses unique challenges for any potential life forms.
Impact of Tidal Locking
Tidal locking creates a significant difference between the day and night sides of these planets, potentially leading to extreme temperature variations. This could affect how life evolves, with organisms possibly developing new biological rhythms to adapt to these conditions.
Earth Analogues for Study
On Earth, organisms living in dark environments, such as deep-sea creatures and cave-dwellers, provide insights into how life might adapt to constant darkness. For instance, naked mole rats and deep-sea mussels have circadian rhythms synchronized to environmental cues other than light.
Potential for Alternative Cycles
Research models suggest that even without a day-night cycle, M-Earths might experience other periodic environmental changes. Factors like atmospheric dynamics, cloud formation, and weather patterns could create regular cycles in temperature and humidity, potentially influencing biological rhythms.
Adaptations to Environmental Cycles
If such cycles exist, life on M-Earths might evolve to synchronize with these environmental changes rather than traditional light-dark cycles. This could lead to unique biological processes and behaviours adapted to the planet's specific conditions.
Implications for Alien Life
The study of potential life on M-Earths challenges our assumptions about how life evolves. The absence of a day-night cycle on these planets could lead to unexpected adaptations and evolutionary strategies, highlighting the diverse possibilities for life beyond Earth.