What if life on Earth began when interstellar objects crashed here? Science alert
On October 19, 2017, astronomers with the Pan-STARRS survey detected an interstellar object (ISO) passing through our solar system for the first time. The object, known as 1I/2017 U1 Oumuamua, sparked significant scientific controversy and remains controversial today.
The one thing everyone can agree on is that the discovery of this object indicates that ISOs enter our solar system regularly. What’s more, subsequent research revealed that sometimes, some of these objects come to Earth in the form of meteorites and collide with the surface.
This raises a very important question: If microorganisms were coming to Earth billions of years ago, could they have brought the ingredients of life with them?
In a recent paper, a team of researchers looked at the implications of ISOs being responsible for panspermia – the theory that the seeds of life are present throughout the universe and are distributed by asteroids, comets and other celestial bodies.
According to their findings, ISOs could seed hundreds of thousands (or perhaps billions) of Earth-like planets throughout the Milky Way.
The team was led by David Kao, a senior at Thomas Jefferson High School for Science and Technology (TJSST). He was joined by Peter Plavchan, associate professor of physics and astronomy at George Mason University (GMU) and director of the Mason Observatories, and Michael Summers, professor of astrophysics and planetary science at GMU.
Their paper, “Oumuamua Effects on Panspermia,” recently appeared online and is being reviewed for publication by the American Astronomical Society (AAS).
To briefly summarize, panspermia is the theory that life arrived on Earth via objects from the interstellar medium (ISM). According to this theory, this life took the form of extremophile bacteria capable of surviving in the harsh conditions of space.
Through this process, life is distributed throughout the universe as objects pass through the ISM until they reach and impact potentially habitable planets. This makes panspermia significantly different from competing theories of how life began on Earth (also known as abiogenesis), which is the most widely accepted universal RNA hypothesis.
This hypothesis states that RNA preceded DNA and proteins in evolution, ultimately giving rise to the first (i.e. home-grown) life on Earth.
But as Cao told Universe Today via email, panspermia is difficult to assess:
“Panspermia is difficult to assess because it requires many different factors that need to be integrated, many of which are unconstrained and unknown. For example, we must take into account the physics behind panspermia (how many objects collided with the Earth before the oldest fossil evidence appears) “). For life?), biological factors (can extreme enthusiasts withstand supernova gamma radiation?), etc.
“In addition to each of these factors there are questions to which we do not yet have answers, or cannot effectively model, for example, the number of extremophiles that would actually reach Earth even if a life-carrying object collided with Earth, and the probability that life could It actually starts with alien organisms living in extreme conditions. The combination of these factors, along with many others, such as the variable rate of star formation and the recent detection of several free-floating rogue planets, makes it difficult to evaluate panspermia, and therefore, the understanding of the plausibility of panspermia is changing. continuously.”
The discovery of ‘Oumuamua in 2017 marked a major turning point in astronomy, as it was the first time an ISO observation had been made.
The fact that it was discovered at all suggests that such objects were statistically significant in the universe and that ISOs likely pass through the solar system regularly (it is possible that some of them are still here).
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 our sun, 2I/Borisov formed a tail, indicating that it was a comet.
Subsequent research has shown that some of these objects become meteorites that impact the Earth’s surface, and a few have been identified. This includes CNEOS 2014-01-08, a meteorite that struck the Pacific Ocean in 2014 (and was the subject of study by the Galileo project).
As Kao explained, the discovery of these interstellar visitors also has implications for the theory of panspermia and the ongoing debate about the origins of life on Earth:
“Oumuamua serves as a new data point for models of panspermia, as we can use its physical properties, especially its mass and size (spherical radius), and the implicit ISM number density, to model the number density and mass density of objects in the interstellar medium. These models allow us to estimate the flux density and mass flux of objects Existing in the interstellar medium, and through these models, we can approximate the total number of objects that collided with Earth over the course of 0.8 billion years (which is the assumed time period between the formation of the planet Earth and the oldest evidence of life).
“Knowing the total number of collision events on Earth over a period of 0.8 billion years is vital for mass seeding, as a higher number of collision events with interstellar objects during that period could mean a greater probability of mass seeding.
“In summary, the physical properties of interstellar ‘Oumuamua allow the creation of mathematical models that determine the plausibility of panspermia.”
In addition to mathematical models that take into account the physics behind panoplasia—for example, number density, mass density, total impact events, etc.—Cao and his colleagues applied a biological model that describes the minimum body size needed to protect extreme organisms from astrophysical events. (Supernovas, gamma ray bursts, large asteroid impacts, passing stars, etc.).
As covered in a previous article, recent research has shown that cosmic rays erode all but the largest ISOs before they reach another system.
These additional considerations ultimately affect the number of objects that will impact Earth (which are not sterilized by astrophysical sources) and the plausibility of mass seeding.
“In order to derive the minimum size of the object, we applied various models, for example, the spherical packing method to give a rough estimate of the ejecta’s distance to the nearest supernova (using Orion A, a dense star cluster, as our model) and the gamma rays that “It reaches those projectiles, and the attenuation coefficient (the amount of radiation absorbed by the projectile) depends on the most likely chemical composition of the projectile (water ice).”
Based on combined physical and biological models, the team derived estimates of the number of projectiles that struck Earth before life emerged. According to the oldest fossil evidence found in Western Australia (from rocks dating back to the Paleozoic), the oldest life forms appeared in California. 3.5 billion years ago. Cao said:
“We conclude that the maximum probability that panspermia sparked life on Earth is on the order of 10-5, or 0.001 percent. Although this probability seems low, under the most optimistic conditions, there are likely 4 x 109 exoplanets.” The habitable zone exists in our galaxy, which could refer to a total of 104 habitable worlds that harbor life.
“In addition, we limited our analysis to the first 0.8 billion years of Earth’s history before the first fossilized evidence of life, but because life can seed at any time in a planet’s lifetime, planets have much longer habitable lifetimes (up to 5 years).” -10 billion years), we have boosted our estimate of the total number of habitable worlds harboring life in our Galaxy by one order of magnitude.
Hence, Cao and his colleagues obtained a final result of about 105 habitable planets that could harbor life in our galaxy. However, these estimates are based on the most optimistic predictions regarding planetary habitability.
In other words, all rocky Earth-sized planets orbiting within habitable zones are assumed to be capable of supporting life, meaning they have thick atmospheres, magnetic fields, liquid water on their surfaces, and all the life-bearing projectiles that survive upon entering our atmosphere. It is capable of depositing microbes on the surface.
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As Kao summarized, their results do not prove panspermia or settle the debate about the origins of life here on Earth. However, they provide valuable information and constraints on whether life can get here via things like ‘Oumuamua.
Whatever the case, these findings are likely to have major implications for astrobiology, which is becoming an increasingly diverse field:
“We integrate physics, biology and chemistry in the study of panspermia as the origin of life, and it is rare to have such a diverse range of topics in one research area. I think astrobiology is moving towards becoming more interdisciplinary, which I think is a positive trend because It will allow experts from all backgrounds to advance the science of astrobiology.
“Our research may contribute in this direction. Regarding our findings on mass seeding, the possibility that mass seeding could have sparked life on Earth is unlikely, but the number of habitable zone planets harboring life in our galaxy is much greater.”
“Future astrobiology studies may use these results to build on our research on mass seeding. However, we do not incorporate or even know all the factors that might influence the plausibility of mass seeding.”
“I believe our findings open new lines of investigation for future panspermia studies to build on by updating our models or incorporating additional factors.
“One potential area of study if we find evidence of life on other worlds in the future, whether in our solar system or via biosignatures in the atmospheres of exoplanets, is to look at experimental and observational tests to distinguish between life that arrived via a mass scattering mechanism or life that arrived “By the mechanism of all-seeding or life that evolved and arose independently.”
This article was originally published by Universe Today. Read the original article.