Goldilocks Planets “With a Tilt” Can Develop Extra Advanced Life – Watts Up With That?
PICTURE: IMPRESSION OF THE ARTIST OF EXOPLANET, WITH INCLINED ROTATION AXIS (ADAPTED FROM THE ORIGINAL IMAGE OF NASA) Show more CREDIT: NASA JPL
Planets that are tilted around their axes like the earth are more capable of developing complex life. This finding will help scientists refine the search for more advanced life on exoplanets. This NASA funded research will be presented at the Goldschmidt Geochemistry Conference.
Since the first discovery of exoplanets (planets orbiting distant stars) in 1992, scientists have been looking for worlds that could support life. It is believed that in order to sustain even basic life, exoplanets must be just the correct distance from their stars for liquid water to exist; the so-called ‘Goldilocks Zone’. However, other factors are also important for a more advanced life, especially the oxygen in the air.
Oxygen plays a crucial role in breathing, the chemical process that drives the metabolism of the most complex living things. Some basic life forms produce oxygen in small amounts, but for more complex life forms such as plants and animals, oxygen is critical. The early earth was poor in oxygen, although there were basic forms of life.
The scientists created an elaborate model of the conditions under which life on earth can produce oxygen. The model allowed them to enter various parameters to show how changing conditions on a planet could alter the amount of oxygen produced by photosynthetic life.
Lead researcher Stephanie Olson (Purdue University) said, “The model allows us to change things like the length of the day, the amount of atmosphere or the distribution of land to see how the marine environment and oxygen-producing life in the oceans react.”
The researchers found that increasing day length, higher surface pressure, and the formation of continents affect ocean circulation patterns and associated nutrient transport in ways that can increase oxygen production. They believe these relationships may have contributed to the Earth’s oxygen supply by promoting oxygen transfer into the atmosphere as the Earth’s rotation slowed, its continents grew, and surface pressures increased over time.
“The most interesting result came when we modeled the ‘orbital obliquity’ – how the planet tilts when it orbits its star,” explains Megan Barnett, a PhD student at the University of Chicago who was involved in the study. She continued, “A higher tilt in our model increased photosynthetic oxygen production in the ocean, in part by increasing the efficiency with which biological ingredients are recycled. The effect was comparable to doubling the amount of life-sustaining nutrients. “
The globe tilts around its axis at an angle of 23.5 degrees. This gives us our seasons, with parts of the earth receiving more direct sunlight in summer than in winter. However, not all planets in our solar system are inclined as the Earth is: Uranus is inclined at 98 degrees, while Mercury is not inclined at all. “For comparison, the Leaning Tower of Pisa is tilted about 4 degrees, so the planetary inclinations can be quite large,” said Barnett.
Dr. Olson continued, “There are several factors to consider when looking for life on another planet. The planet has to be the correct distance from its star to allow liquid water to flow in and to have the chemical ingredients for the creation of life. But not all oceans will be great hosts for life as we know it, and an even smaller subset will have suitable habitats for life to approach the complexities of animals. Small inclinations or extreme seasonality on planets with Uranus-like inclinations can limit the spread of life, but a modest inclination of a planet about its axis can increase the likelihood that it will develop oxygen-rich atmospheres that act as beacons for microbial life and metabolism . could power large organisms. The bottom line is that worlds that are modestly tilted about their axes are more likely to develop complex lives. This helps us to narrow down the search for complex, perhaps even intelligent, life in the universe. “
Timothy Lyons, Distinguished Professor of Biogeochemistry in the Department of Earth and Planetary Sciences at the University of California, Riverside, commented:
“The first biological production of oxygen on earth and its first significant enrichment in the atmosphere and oceans are milestones in the history of life on earth. Studies of the earth teach us that oxygen could be one of our most important biosignatures in finding life on distant exoplanets. Building on knowledge gained from Earth through numerical simulations, Olson and colleagues have explored a critical area of planetary possibilities that is greater than those observed in Earth’s history. Importantly, this work shows how key factors, including a planet’s seasonality, could increase or decrease the possibility of finding oxygen from life outside of our solar system. These results will certainly help us in our search for this life. “
Professor Lyons was not involved in this work, this is an independent comment