WASHINGTON — Are aliens really out there on some distant planet? If they are, a new study finds they probably “lean” the same way we do. Researchers believe, if they exist, alien life would most likely be found on planets with an Earth-like tilt.
Such planets could have twice as much of the nutrients capable of evolving complex organisms. The new findings narrow down the search for extra-terrestrials that could one day contact us. The report also identifies worlds outside the solar system (exoplanets) where there could be intelligence.
Scientists explain that when Earth rotates, its spin axis – an imaginary line that passes through the North and South Poles – slopes. Seasons arise as a result, with parts receiving more direct sunlight in summer than in winter.
Now, sophisticated simulations of the conditions needed for plants and animals to evolve discovered the tilt increases atmospheric oxygen. The chemical is one of the most vital ingredients for advanced life, as we know it, to develop.
“The most interesting result came when we modelled ‘orbital obliquity’ – in other words how the planet tilts as it circles around its star,” says co-author Megan Barnett, a graduate student at the University of Chicago, in a media release.
“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.”
Finding oxygen is also key to finding life
Computer simulations reveal changing environments alter the amount of oxygen from photosynthesis, converting light into chemical energy. An exoplanet needs to be just the right distance from its star to sustain even primitive life – orbiting inside the so-called “Goldilocks” or habitable zone. The NASA-funded study concludes that looking for planets that also tilt holds the key to finding E.T.
Earth and Uranus tilt at an angle of 23.5 and 98 degrees, respectively. Meanwhile, Mercury has no tilt at all.
“For comparison, the Leaning Tower of Pisa tilts at around 4 degrees, so planetary tilts can be quite substantial,” Barnett adds.
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, it is critical. Early Earth had little oxygen even though basic life forms still existed.
“The model allows us to change things such as day length, the amount of atmosphere, or the distribution of land to see how marine environments and the oxygen-producing life in the oceans respond,” explains lead author Dr. Stephanie Olson of Purdue University.
There’s something in the water too
Increasing day length, higher surface pressure, and the emergence of continents all influenced ocean circulation and nutrient transport in ways that may increase oxygen production. These relationships may have contributed to Earth’s oxygenation by favoring its transfer to the atmosphere as the rotation of the planet slowed, continents grew, and surface pressure rose.
“There are several factors to consider in looking for life on another planet,” Dr. Olson says. “The planet needs to be the right distance from its star to allow liquid water and have the chemical ingredients for the origin 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 progress towards animal-grade complexity,” Olson continues. “Small tilts or extreme seasonality on planets with Uranus-like tilts may limit the proliferation of life, but modest tilt of a planet on its axis may increase the likelihood that it develops oxygenated atmospheres that could serve as beacons of microbial life and fuel the metabolisms of large organisms. The bottom line is that worlds that are modestly tilted on their axes may be more likely to evolve complex life. This helps us narrow the search for complex, perhaps even intelligent life in the universe.”
Alien life needs a planet that hits all of Earth’s milestones
Professor Timothy Lyons, a planetary scientist at the University of California-Riverside who did not take part in the study, adds the study is “certain to help guide our searches for that 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,” Prof. Lyons concludes.
“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.”
The team presented their findings at the virtual Goldschmidt Geochemistry Conference.
SWNS writer Mark Waghorn contributed to this report.