- 4328 - COMETS - support life? By incorporate physics, biology, and chemistry into studying panspermia as the origin of life is rare to have such a diverse range of topics in one research area. Future astrobiology studies may use these findings to build on our research on panspermia.
------------------------- 4328 - COMETS - support life?
- 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”,
stimulated significant scientific debate and is still controversial today.
-
- One thing that all could agree on was that
the detection of this object indicated that ISOs regularly enter our Solar
System. Subsequent research has revealed
that, on occasion, some of these objects come to Earth as meteorites and impact
the surface.
-
- If “ISOs” have been coming to Earth for
billions of years, could it be that they brought the ingredients for life. “Panspermia” is the theory that the seeds of
life exist throughout the Universe and are distributed by asteroids, comets,
and other celestial objects. ISOs can potentially seed hundreds of thousands of
Earth-like planets throughout the Milky Way.
-
- “Panspermia” is the theory that life was
introduced to Earth by objects from the interstellar medium (ISM). This life took the form of “extremophile”
bacteria capable of surviving the harsh conditions of space. Through this
process, life is distributed throughout the cosmos as objects pass through the
ISM until they reach and impact potentially habitable planets.
-
- This makes panspermia substantially
different from competing theories of how life on Earth began (abiogenesis), the most widely accepted of
which is the “RNA World Hypothesis”.
-
- This hypothesis states that RNA preceded
DNA and proteins in evolution, eventually leading to the first life on
Earth. We must consider the physics
behind panspermia (how many objects collided with Earth prior to the earliest
fossilized evidence for life?), biological factors (can extremophiles endure
supernova gamma radiation?).
-
- The detection of ‘Oumuamua” in 2017
constituted a major turning point for astronomy, as it was the first time an
ISO was observed. The fact that it was detected at all indicated that such
objects were statistically significant in the Universe and that ISOs likely
passed through the Solar System regularly.
-
- Two years later, a second ISO was detected
entering the Solar System (2I/Borisov), except there was no mystery about its
nature this time. As it neared our Sun, 2I/Borisov formed a tail, indicating it
was a comet.
-
- Some of these objects become meteorites that
impact on Earth’s surface, and a few have even been identified. This includes
“CNEOS 2014-01-08”, a meteor that crashed into the Pacific Ocean in 2014.
-
- “Oumuamua” serves as a novel data point for
panspermia models, as we can use its physical properties, particularly its
mass, size (spherical radius), and implied 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 in the interstellar medium and, with these
models, we can approximate the total number of objects that impacted Earth over
0.8 billion years which is the hypothesized period of time between Earth’s
formation and the earliest evidence for life.
-
- Knowing the total number of collision
events on Earth over that 0.8 billion-year period is vital for panspermia, as a
greater number of collision events with interstellar objects over that period
would imply a higher probability for panspermia. The physical properties of the interstellar
Oumuamua allow for the creation of mathematical models that determine the
plausibility of panspermia.
-
- These considerations ultimately affect the
number of objects that will impact Earth (that were not sterilized by
astrophysical sources) and the plausibility of panspermia. Based on their combined physical and
biological models, the astronomers derived estimates for the number of ejecta
that struck Earth before life emerged. According to the oldest fossilized
evidence found in western Australia (from rocks dating to the Archaean Eon),
the earliest life forms emerged ca. 3.5 billion years ago.
-
- We conclude that the maximum probability
that panspermia sparked life on Earth is on the order of magnitude of 10-5, or
0.001%. Although this probability appears low, under the most optimistic
conditions, potentially 4×10^9 total habitable zone exoplanets exist in our
Galaxy, which could indicate a total of 10^4 habitable worlds, 10,000 harboring
life.
-
- A final result of about 100,000 habitable
planets that could harbor life in our galaxy with estimates based on the most
optimistic projections regarding planetary habitability. It assumes that all
Earth-sized rocky planets orbiting within habitable zones are capable of
supporting life, meaning they have thick atmospheres, magnetic fields, liquid
water on their surfaces, and all life-bearing ejecta that survive entering our
atmosphere are capable of depositing microbes on the surface.
-
-
January 25, 2023 COMETS -
support life? 4328
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--------------------- --- Saturday, January 27,
2024
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