(from Controversies in Science)
Did life on Earth arise from Panspermia?
- 1 Points For
- 1.1 Complexity in the dirt
- 1.2 Life's building blocks found in a COMET
- 1.3 NASA scientist: Evidence of alien life on meteorite
- 1.4 Go Panspermia!
- 1.5 Comets Bring Microbial Life
- 1.6 Humans are made from stars
- 1.7 Microorganisms Potentially formed from Hot and Cold Stardust
- 1.8 Space-traveling bacteria wears a protective coat
- 2 Points Against
- 3 References
Complexity in the dirt
The 1976 Viking's Mission to Mars conducted a labelled release experiment and found that in Mars, microbial life was present. .
Life's building blocks found in a COMET
NASA scientists discover glycine in a comet. Glycine is the fundamental building block for life. It is used to make proteins in living organisms. Since it was found in a comet, it supports the theory that the life's ingredients were formed in space and then delivered to earth by meteorites.
NASA scientist: Evidence of alien life on meteorite
In what seems to be the greatest discovery in recent history, NASA's Richard B. Hoover discovered clear proof of bacteria fossil evidence in meteorites that are rarely spotted entering the Earth's atmosphere. This discovery makes life on comets possible. He also had found that Mars can sustain life because liquid water is present. This supports the fact that before entering the Earth, forms of life on the meteors existed.
Panspermia or abiogenesis? Did life migrate here through space or begin on Earth? Spores were found to be able to withstand high pressure and high temperature, so it is possible for microbes to have come down to the earth from outer space through meteorites.
Comets Bring Microbial Life
The Hoyle-Wickramasinghe panspermia theory proposes that life on earth was originated approximately 4 billion years ago by comets containing microbial life. Some of the microorganisms continue to be found. Nowadays, Panspermia is considered as a serious alternative to life being originated solely on earth. There are many places on Earth where microbial life is present such as, Antarctic soil and ocean floors. Thus, it is evident that it was transferred from the cosmic life cycle to the Earth. During the cosmic life cycle, comets expanded microbial life.
Humans are made from stars
20 different atoms make up all living material which include atoms that are found in steller nucleosynthesis. Steller nucleosynthesis is a nuclear reaction that takes place in the stars, therefore we can make the conclusion that we are made up of atoms from the stars.
Microorganisms are able to survive/thrive in ultraviolet light.
Various planets including Mars and Venus are showing signs of life in water and clouds on the planets surface. .
Stratospheric air shows signs of bacteria which is above the atmosphere free from aerosoles from the earth.
Microorganisms Potentially formed from Hot and Cold Stardust
If a microorganism is successful in going through extreme 'mixing', in which dust from both the coldest and hottest regions of the solar nebula is gathered and lands on Earth, then life was already present in the material that it has collected from the celestial bodies.
Space-traveling bacteria wears a protective coat
Scientists believe that Space-traveling bacteria would be susceptible to damage from the ultraviolet (UV) light of stars; however,a thin layer of carbonized material would protect them and block the UV light.
Panspermia is not reproducible
Scientists Wickramasighe and Bhargava conducted a cryosampler experiment to prove or dismay the theory of Panspermia. Sixteen samples were collected from the cryosampler at various altitudes and split between the two scientists to prove the proposed theory. Wickramasighe stated to have detected microorganisms present from the cryosampler samples. However, Bhargava was unable to produce the same results. This is possibly a fluke that Wickramasighe found any living microorganisms. When asked to reproduce the same results, he declined.
Lichens Die After Re-Entry
After attaching the bacteria and lichens wrapped in rock casings to the space shuttle, their growth rate, ability to germinate and their activity were analyzed. The bacteria could not survive the harsh conditions in space while the lichens lived. Upon re-entering the earth's atmosphere, the lichens died and the rock casings had turned to glass. .
Unreliable Information on Interstellar Medium
When scientists searched for organic material in the interstellar medium, they scanned an absorbance range of 3.0 to 3.5 micrometers because that is the range most biological substances absorb at. However, a false result could have occurred because that range of wavelength is not exclusive to organic materials. In fact, water and ammonia also absorb wavelengths of 3.0 to 3.5 micrometers. Another problem with the concept of life in the interstellar medium is that the ratios of certain elements in space are not suitable for compounds like DNA, RNA and bacterial cytoplasm. For example, 100 times more phosphorus than what can be found in the medium is required to form such compounds. Unfortunately, we do not know enough about the interstellar medium right now to make accurate statements about its composition and its nature. For instance, how can we be certain that life on Earth came from space when we are unfamiliar with the conditions these foreign bacteria originated in?
For the theory of panspermia to be true, the organisms must first leap from their hosting planets onto a carrier with a similar environment as the planet of origin. The cells must then reach the earth before the harmful cosmic rays can kill them, which would take approximately two days. Then the cell must survive entering the Earth's atmosphere and the impact of landing. No host that is capable of fitting the above requirements is in existence therefore panspermia is not possible. 
Extreme Environments Disprove Panspermia
Regardless of the appropriate conditions, such as water and nutrients and the fact that the dormant spores will grow, creating a potential for panspermia, the environments (threats of vacuums and radition) in which the spores are growing in are too harsh for further development. Therefore, panspermia can not exist. 
Panspermia: Progenote or Prokaryotes (Group 6)
Based on the current theory of genetic code progenotes were the ancestors of prokaryotes. Therefore, if panspermia was true progenotes would have come to earth from other planets. Based on scientific analysis progenotes would have not survived the journey to earth as they are not fully evolved complex micro-organism. 
Panspermia doesn't account for similar biology
If there were organisms here on earth from outer space they would be simple, standout, and have characteristics easily recognizable. Panspermia was used to view that life on Earth had originated from outer space. There has been a hypothesis formed that space continues to provide the Earth with life. Any microorganism that had come from outer space to Earth would have had to survive extreme weather conditions in space. 
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