A new way to discover Daisy World

The Daisy World model describes a hypothetical self-regulating planet that maintains a delicate balance involving biogeochemical cycles, climate, and feedback loops that maintain habitability. It is related to the Gaia hypothesis developed by James Lovelock. If these worlds exist, how can we detect them?

By looking at the information carefully.

Daisy World (DW) is home to two types of daisies: white and black. They have different albedo, with black people absorbing more sunlight and warming the earth, while white people reflect more sunlight and cooling the earth.

As the DW star becomes brighter, the temperature of the planet increases. At first, black daisies absorb more energy, so they grow. However, as the earth gets hotter, absorbing more energy becomes less desirable, and white daisies outnumber black daisies and begin to thrive. As they flourish, they reflect more sunlight and cool the Earth.

The result is a delicate homeostasis in which daisies regulate the Earth’s temperature and keep it within habitable ranges. It shouldn’t be too hot or too cold. The DW model shows how life can influence a planet’s climate and create conditions favorable to its own survival.

Earth isn’t exactly Daisy’s world, but life on Earth affects the climate. The DW model briefly illustrates the concept of basic climate feedback mechanisms.

In the new study, scientists from the University of Rochester’s Department of Physics and Astronomy and Department of Computer Science wanted to find a way to analyze how planetary systems such as the biosphere and geosphere are connected. If a self-regulating “daisy world” exists, how can we detect it?

The research topic is “Exo-Daisy World: Revisiting Gaia Theory through an Informational Architecture Perspective.” The lead author is Damien Sowinski, a research physicist and postdoctoral fellow in the Department of Physics and Astronomy at the University of Rochester. This study is awaiting publication and has not yet been peer-reviewed, but is available on the arXiv preprint server.

The idea is to find a way to detect agnostic biosignatures on exoplanets. A typical biosignature is a specific chemical that can be a byproduct of living things, such as oxygen or methane. Agnostic biosignatures indicate the presence of life, but do not rely on identifying what type of organism is producing it. Instead, they are like overarching planetary patterns produced by the living world.

For the authors, finding an agnostic biosignature starts with information and how it flows.

“In this study, we extend the classic Daisy World model through the lens of Semantic Information Theory (SIT) and explore the flow of information between the biosphere and the planetary environment, what we call the information architecture of the Daisy World System. ”, the authors say. explain.

Semantic information theory has been around since the mid-20th century. It attempts to define meaning in different contexts, how human subjective interpretation affects meaning, and related concepts in the same vein. With the proliferation of artificial intelligence and machine learning, there is a new focus.

There is a drive to understand the atmospheres and environments of exoplanets and how to distinguish between those that have the potential to support life and those that cannot. This is a complex issue that relies on agnostic biosignatures.

Agnostic biosignatures are complex patterns and structures that cannot be explained by non-biological processes. There are also imbalances, new energy transfers, abnormal levels of organization at different scales, and periodic or systematic changes that suggest biological causes.

Agnostic biosignature searches include complex molecules that require biological synthesis, chemical distributions that require metabolism, unexpected accumulations of specific molecules, and atmospheres and planets that require biological maintenance. May include surface features.

Examples of agnostic biosignatures on Earth include the coexistence of methane and oxygen in the atmosphere, the “red edge” of Earth’s vegetation spectrum, and daily or seasonal gas emission cycles.

“The search for life on exoplanets requires the identification of biosignatures that depend on the significant changes that life has made to the spectroscopic properties of the planet. The focus is on identifying the collective impact that life has on planetary systems, rather than detecting what we call the extraterrestrial biosphere,” the authors explain.

In other words, you cannot study biosignatures without studying the biosphere. In doing so, it is important to understand where and how the external biosphere reaches a “mature” state and strongly influences the atmosphere, hydrosphere, cryosphere, and lithosphere, collectively known as the geosphere. When they mature and exert a strong influence, it is consistent with the Daisy World hypothesis.

The authors’ aim is to study how information flows between the biosphere and planetary environments. To do this, they modeled the potential conditions for M-dwarf exoplanets and devised equations to describe the coevolution of these world daisies and their planetary environments. They have created what they call an “information story” for Exo Daisy World (eDW).

Homeostatic feedback of DW is usually based on physical quantities such as radiation flux, albedo, and percentage of plant growth range. That’s the physical story. However, the researchers used semantic information theory to derive complementary narratives based on the flow of information. In its research, SIT focuses on the interrelationships between agents (the biosphere) and the environment and how those interrelationships benefit the agents.

Their model showed that as the star’s brightness increases, the correlation between the biosphere and its environment strengthens. Correlation corresponds to different stages of information exchange between the two parties. This leads to the idea of ​​habenular control, which is the control exerted by flora through positive and negative differences in albedo compared to bare soil. In this way, the biosphere exerts a regulatory influence on the planet’s climate. In their informative narrative, the planet’s temperature is more constrained “at the cooler and warmer edges of the tolerable temperature range.”

Not all information flowing between the biosphere and the environment is relevant. The biosphere does not use all of it because some of it does not help maintain control of the biosphere. The authors say that by analyzing all this information according to information theory, it is possible to determine which information contributes to its viability, when and how.

Daisy’s world model is useful, but it is a toy model. For example, stochastic events such as volcanic eruptions are not included. But the big question is how does it relate to the extraterrestrial biosphere?

The authors say their study shows the potential of using approaches like SIT to understand how exoplanets and their biospheres coevolved, similar to those on Earth. are. More realistic models that include more of the complex network of interactions between living and non-living systems on exoplanets will be needed. Because the biosphere processes information in ways that abiotic systems do not, information-centric systems can cover agnostic biosignatures in ways that physical or chemical models cannot.

“As a result, the next steps in our research program will include applying SIT and other information-theoretic approaches to more complex models of coupled planetary systems,” the authors conclude. .