Was multicellular life on Earth dependent on plate tectonics?

How did complex life arise and evolve on Earth and what does this mean for finding life outside Earth? This is what a recent study published Nature hopes to address while a few researchers explored how plate tectonics, oceans and continents are responsible for the emergence and evolution of complex life on our planet and how this could address the Fermi paradox, while trying to improve the Drake equation on why we haven’t found life in the universe and the parameters for finding life respectively. This study has the potential to help researchers better understand the criterion for finding life beyond Earth, especially with regard to the geological processes exhibited on Earth.

Here, Universe today discusses this study with Dr. Taras Gerya, professor of earth sciences at the Swiss Federal Institute of Technology (ETH-Zurich) and co-author of the study, on the motivation behind the study, significant results, follow-up studies, what this means for the Drake equation, and the implications of the study of finding life beyond Earth. What was the motivation behind this research?

Dr. Gerya tells Universe today“It was motivated by the Fermi paradox (“Where is everyone?”), which points out that the Drake equation typically predicts that there are between 1,000 and 100,000,000 actively communicating civilizations in our Galaxy, which is an overly optimistic estimate is. We tried to figure out what needs to be corrected in this equation to make the Drake equation prediction more realistic.”

For the study, the research duo compared two types of planetary tectonic processes: a single lid (also called a stationary lid) and plate tectonics. Single lid refers to a planetary body that does not exhibit plate tectonics and cannot be broken down into individual plates that exhibit motion by sliding toward each other (convergent), sliding past each other (transform), or sliding away from each other (divergent). This lack of plate tectonics is often attributed to the lid of a planetary body being too strong and dense to break apart. Ultimately, the researchers estimate that 75 percent of planetary bodies that exhibit active convection in their interiors do not exhibit plate tectonics and do possess single lid tectonics, with Earth being the only planet to exhibit plate tectonics. Therefore, they concluded that single-lid tectonics are “likely to dominate the tectonic styles of active silicate bodies in our Milky Way,” the study said.

In addition, the researchers investigated how planetary continents and oceans contribute to the evolution of intelligent life and technological civilizations. They noted the importance of life that first developed in the oceans because it was protected from damaging space weather for the first few billion years of Earth’s history, while single-celled life thrived in the oceans. However, the researchers also highlight how dry land provides numerous advantages for the evolution of intelligent life, including adaptations to different terrains, such as eyes and new senses, which helped animals evolve to hunt quickly, among other biological resources that sustain life made possible. to adapt to the different terrestrial environments across the planet.

Ultimately, the researchers concluded that dry land contributed to the evolution of intelligent life across the planet, including abstract thinking, technology and science. Therefore, what were the most important results of this study, and what follow-up studies are currently in progress or planned?

Dr. Gerya tells Universe today, “That very special condition (>500 million years of coexistence of continents, oceans and plate tectonics) is necessary on a planet with primitive life to develop intelligent technological communicative life. This condition is very rarely realized: only <0.003-0.2% of planets with any life can meet this condition.”

Dr. Gerya continues: “We plan to study the water evolution in the interior of the planet to understand how the stability of the ocean volume at the surface (which implies the stability of the coexistence of oceans and continents) over billions of years can be maintained (as on Earth). We also plan to investigate the survival time of technological civilizations based on societal collapse models. We have also started a project on the evolution of the oxygen state of the interiors and atmospheres of planets to understand how oxygen-rich atmospheres (particularly essential for the development of technological civilizations) can be formed on planets with oceans, continents and plate tectonics. Progress in these three directions is essential, but will depend heavily on the availability of research funding.”

As noted, this research was motivated and attempts to improve on the Drake equation, which represents a multivariable equation that attempts to estimate the number of active, communicative civilizations (ACCs) that exist in the Milky Way Galaxy. In 1961, Dr. Frank Drake proposed to postulate several views that he encouraged the scientific community to consider when discussing both how and why we haven’t heard of ACCs and states:

N=R* xfP xne xfl xfi xfc x L

N = the number of technological civilizations in the Milky Way Galaxy that can potentially communicate with other worlds

R* = the average star formation rate in the Milky Way Galaxy

FP = the fraction of those stars with planets

Ne = the average number of planets that can potentially support life per star with planets

Fl = the fraction of planets that can support and develop life at some point in their history

Fi = the part of the planets that develops life and evolves into intelligent life

Fc = the part of civilizations that develop technology that can send detectable signals into space

L = the length of time that technological civilizations send signals into space

According to the study, the Drake equation estimates that the number of ACCs varies widely, between 200 and 50,000,000. As part of the study, the researchers proposed adding two additional variables to the Drake equation, based on their findings that plate tectonics, oceans and continents have played a crucial role in the development and evolution of complex life on Earth, namely :

FOK = the proportion of habitable exoplanets with notable continents and oceans

Fpt = the fraction of habitable exoplanets that possess notable continents and oceans that also exhibit plate tectonics that have been functioning for at least 500 million years

Using these two new variables, the study produced new estimates for fi (opportunities for planets to develop life and evolve into intelligent life). So, what is the significance of adding two new variables to the Drake equation?

Dr. Gerya tells Universe today“This allowed us to redefine the key term of the Drake equation f and estimate it more correctlyi – probability that a planet with primitive life will develop intelligent technological communicative life. Originally fi was (wrongly) estimated as very high (100%). Our estimate is many orders of magnitude lower (<0.003-0.2%), which likely explains why other civilizations are not contacting us.”

Furthermore, when introducing these two new variables into the entire Drake equation, the study estimates a much smaller number of ACCs at <0.006 to 100,000, which is in stark contrast to the original Drake equation estimates of 200 to 50,000,000. What implications could this study therefore have for the search for life beyond Earth?

Dr. Gerya tells Universe today“It has three major consequences: (1) we shouldn’t have much hope of being contacted (the chance of this is very low, partly because the lifespan of technological civilizations may be shorter than previously expected), (2) we should use remote sensing to search for planets with oceans, continents, and plate tectonics (COPT planets) in our Milky Way based on their likely different (low-CO2) atmospheres and surface reflectivity signatures (due to the presence of oceans and continents), (3) we must take care of our own planet and civilization, both of which are extremely rare and must be preserved.”

This study comes as the search for life beyond Earth continues to gain traction, with NASA having confirmed the existence of 5,630 exoplanets at the time of writing, with nearly 1,700 classified as Super-Earths and 200 as rocky exoplanets . Despite these incredible numbers, especially since the discovery of exoplanets in the 1990s, humanity has yet to detect any signal from an alien technological civilization, which in this study is called ACCs.

Probably the closest we’ve come to receiving a signal from space was the Wow! signal, a 72-second radio burst, received by Ohio State University’s Big Ear radio telescope on August 15, 1977. However, this signal has yet to be received since then, along with a complete lack of signals. With this study, scientists may be able to use these two new variables added to the Drake equation to help narrow the scope of finding intelligent life beyond Earth.

Dr. Gerya concludes by telling Universe today, “This research is part of an emerging new science – Biogeodynamics, which we are trying to support and develop. Biogeodynamics aims to understand and quantify the relationships between the long-term evolution of the planetary interior, surface, atmosphere and life.”

How will these two new variables added to the Drake equation help scientists find life beyond Earth in the coming years and decades? Only time will tell, and this is why we are science!

As always, keep doing science and keep looking up!

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