October 19thth2017, astronomers Pan-STARRS survey We detected the first interstellar object (ISO) passing through our solar system. 1I/2017 U1 This object, known as ‘Oumuamua, has stimulated significant scientific debate and remains controversial. One thing everyone could agree on was that the detection of this object indicates that ISOs are regularly intruding into our solar system. Furthermore, subsequent research revealed that some of these objects sometimes come to Earth as meteorites and impact the surface.
This raises a very important question. If ISOs have been coming to Earth billions of years ago, could they have brought the ingredients of life with them? recent papersA team of researchers considered the effects of ISO in causing panspermia, the theory that the seeds of life exist throughout the universe and are distributed by asteroids, comets, and other celestial bodies. According to the results, ISO could seed hundreds of thousands (or perhaps billions) of Earth-like planets throughout the Milky Way.
The team was led by University senior David Kao. Thomas Jefferson High School of Science and Technology (TJSST). He was joined by Peter Pravchanis an associate professor of physics and astronomy at George Mason University (GMU) and director of the Mason Observatory. michael summers, professor of astrophysics and planetary science at GMU. Their paper, “Impact of ‘Oumuamua on panspermia” was recently posted online and is being reviewed for publication. American Astronomical Society (AAS).
To briefly summarize, panspermia is the theory that life was brought to Earth by objects from the interstellar medium (ISM). According to this theory, this life took the form of extremophile bacteria that could survive in the harsh conditions of space. Through this process, life is distributed throughout the universe until objects pass through her ISM and reach and impact potentially habitable planets. For this reason, panspermia is very different from competing theories about how life on Earth began (also known as abiogenesis). The most widely accepted theory is RNA world hypothesis.
This hypothesis states that RNA preceded DNA and proteins in evolution and ultimately led to the first life (i.e., indigenously originating life) on Earth. But as Cao told Universe Today in his email, panspermia is difficult to assess.
“Panspermia requires incorporating so many different factors, many of which are open-ended and unknown, that it is difficult to assess. For example, the physics behind panspermia (life’s earliest fossilized We need to consider factors such as (how many objects have collided with the Earth) and biological factors (can extremophiles survive supernova gamma rays?).
“In addition to each of these factors, there are questions that we still don’t have answers to or can’t model effectively, such as whether an object containing life would actually reach Earth if it were to collide with Earth.” such as the number of extremophiles and their probability. Life could actually start from foreign extremophiles. These factors, along with changes in the rate of star formation and some recent rogue floating Many factors, such as planet detection, come together to make panspermia difficult to assess, and therefore our understanding of the validity of panspermia is constantly changing.”
The detection of ‘Oumuamua in 2017 was a major turning point for astronomy, as it was the first time that ISO had been observed. The fact that it was detected indicates that such objects are statistically significant in the universe, and that ISOs are likely to have periodically passed through our solar system (some of which are still here). may exist). Two years later, a second ISO was detected entering the solar system (2I/Borisov), but this time there was no mystery about its nature. As it approached the Sun, 2I/Borisov formed a tail, indicating it was a comet.
Subsequent research has shown that some of these objects hit the Earth’s surface as meteorites, and some have been identified.This too CNEOS 2014-01-08a meteorite that crashed into the Pacific Ocean in 2014 (and galileo project). As Cao explained, the detection of these interstellar visitors also has implications for panspermia and the ongoing debate about the origins of life on Earth.
“Oumuamua serves as a new data point for the panspermia model because its physical properties, particularly its mass, size (sphere radius), and implied ISM number density, can be used to determine the number density and mass of interstellar objects. Because it allows you to model density.” Medium. These models allow us to estimate the magnetic flux density and mass flux of objects within the interstellar medium, allowing us to approximate the total number of objects that have impacted the Earth over 800 million years, which is , a hypothetical period up to the formation of the Earth) and the earliest evidence of life).
“Knowing the total number of impact events on Earth during that 800-million-year period is critical for panspermia. The higher the number of impact events with interstellar objects during that period, the more likely panspermia is. That is, the physical properties of the interstellar ‘Oumuamua allow the creation of a mathematical model that determines the authenticity of panspermia. ”
In addition to a mathematical model that takes into account the physics behind panspermia: number density, mass density, total impact events, etc., Cao and his colleagues biological model This represents the minimum object size necessary to protect extremophiles from astrophysical phenomena (supernovae, gamma-ray bursts, large asteroid impacts, passing stars, etc.). As discussed in a previous article, recent studies have shown that cosmic rays erode all but the largest ISOs before reaching another star system.
These additional considerations ultimately influence the number of celestial bodies (those not sterilized by astrophysical sources) that impact Earth and the plausibility of panspermia. “To derive the minimum object size, we applied a variety of models, including the sphere-packing method, which roughly estimates the distance from the ejecta to the nearest supernova progenitor. (using Orion A), the gamma rays that reach that ejecta, and the attenuation coefficient (the amount of radiation that the ejecta absorbs) based on the most likely chemical composition of the ejecta (water ice),” Cao said. Ta.
Using a combination of physical and biological models, the researchers came up with an estimate of the number of ejecta that hit Earth before life arose. According to the earliest fossil evidence (from Archean rocks) found in western Australia, the earliest forms of life appeared around 1950. 3.5 billion years ago. Cao Cao said:
“We conclude that the maximum probability that panspermia spawned life on Earth is on the order of 10.-Five, or 0.001%. Although this probability seems low, under the most optimistic conditions, potentially 4×109 There are a total of 10 possible habitable zone exoplanets in our galaxy.Four A habitable world with life.
“Furthermore, although we limited our analysis to the first 800 million years of Earth’s history, before the earliest fossilized evidence of life, life could seed at any point in a planet’s life. , because the habitable lifespan of planets is quite long (up to 5 years – 10 billion years), we increased our estimate of the total number of habitable worlds with life in the galaxy by an order of magnitude. ”
From this, Cao et al. ultimately obtained about 10 results.Five Habitable planets in our galaxy that may harbor life. However, these estimates are based on the most optimistic predictions of the planet’s habitability. In other words, it assumes that all Earth-sized rocky planets orbiting within the habitable zone are capable of supporting life. That means they have thick atmospheres, magnetic fields, liquid water on their surfaces, and all life-bearing ejecta that survives entry into the atmosphere. Microorganisms may adhere to the surface.
As Cao summarized, their results neither prove panspermia nor settle the debate about the origin of life on Earth. Nevertheless, they provide valuable insights and constraints on the possibility that life came here via objects like ‘Oumuamua. Either way, these discoveries could have significant implications for astrobiology, an increasingly diverse field.
“We incorporate physics, biology, and chemistry to study panspermia as the origin of life, but it is rare to have such a diverse range of topics in one research field. Astrobiology is more interdisciplinary. We believe this is a positive trend because it allows experts from all backgrounds to advance astrobiology. Our research contributes to this trend. Possible. Regarding our findings regarding panspermia, it is unlikely that panspermia gave rise to life on Earth, but the number of habitable zone planets in our galaxy with life is quite large.
“Future astrobiology research could use these findings to build on our work on panspermia, but do so by incorporating all factors that may influence the plausibility of panspermia.” Our findings open new lines of inquiry for future panspermia research by updating models and incorporating additional factors. We believe that one potential area of research should we find evidence of life on other worlds in the future, whether in our solar system or through biosignatures in exoplanet atmospheres, is the possibility of life being reached by the panspermia mechanism. It is to consider experimental and observational tests to distinguish life from life that has evolved and arose on its own.”
References: arXiv
