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> Issue reconfirmed:
> 
> https://phys.org/news/2021-07-goldilocks-planets-tilt-complex-life.html
> 
> "Planets which are tilted on their axis, like Earth, are more capable of evolving complex life.
> 
> ***
> 
> "Oxygen plays a critical role in respiration, the chemical process which drives the metabolisms of most complex living things. Some basic life forms produce oxygen in small quantities, but for more complex life forms, such as plants and animals, oxygen is critical. Early Earth had little oxygen even though basic life forms existed.
> 
> ***
> 
> "The researchers found that increasing day length, higher surface pressure, and the emergence of continents all influence ocean circulation patterns and associated nutrient transport in ways that may increase oxygen production. They believe that these relationships may have contributed to Earth's oxygenation by favoring oxygen transfer to the atmosphere as Earth's rotation has slowed, its continents have grown, and surface pressure has increased through time.
> 
> "'The most interesting result came when we modeled 'orbital obliquity—in other words, how the planet tilts as it circles around its star," explained Megan Barnett, a University of Chicago graduate student involved with the study. She continued, "Greater tilting increased photosynthetic oxygen production in the ocean in our model, in part by increasing the efficiency with which biological ingredients are recycled. The effect was similar to doubling the amount of nutrients that sustain life."
> 
> ***
> 
> "'The first biological production of oxygen on Earth and its first appreciable accumulation in the atmosphere and oceans are milestones in the history of life on Earth. Studies of Earth teach us that oxygen may be one of our most important biosignatures in the search for life on distant exoplanets. By building from the lessons learned from Earth via numerical simulations, Olson and colleagues have explored a critical range of planetary possibilities wider than those observed over Earth history. Importantly, this work reveals how key factors, including a planet's seasonality, could increase or decrease the possibility of finding oxygen derived from life outside our solar system. These results are certain to help guide our searches for that life.'"
> 
> Comment: These findings reinforce how special the Earth is, and it may well be only exact  copies will have life. Can our planet's specialness be the result of a series of natural accidents? Very doubtful.