Panspermia: Not a Porno

Biology 103
2005 Second Paper
On Serendip

Panspermia: Not a Porno

Brom Snyder

The current debate on the origin of life on Earth usually pits those who believe life emerged out of a primordial soup of molecules and evolved into life as we know it and those who believe that God created life as we know it. A third explanation of the origin of life on Earth is gaining more credence within the scientific community, this theory is called panspermia. The panspermia hypothesis states that life on Earth is a result of living cells from space crashing into the earth and evolving into life as we know it. (1) (2)

The panspermian explanation for life on Earth is not a new one. An ancient Greek philosopher, Anaxagoras, asserted that the all life was the product of "tiny seeds pervading the cosmos." (1) In the latter half of the 19th Lord Kelvin and other prominent scientists promoted the panspermia hypothesis. Kelvin, in 1881, argued:

"when two great masses come into collision in space, it is certain that a large part of each is melted , but it also seems quite certain that in many cases a large quantity of debris must be shot forth and in all directions...should...the earth [come]into collision with another body, comparable in dimensions to itself...many great and small fragments carrying seeds of living plants and animals would undoubtedly be spread through space...we must regard it as probable in the highest degree that there are countless seed bearing meteoric stones moving through space." (3)

Although it seems unlikely that highly organized and improbable life forms like animals and plants would survive spinning through space without protection, the strain caused by extreme temperatures and radiation would kill most complex organisms; scientists now believe that some bacteria can survive in these extreme conditions. In 1908 the panspermia theory gained more credibility when Svante Arrhenius proved that seeds retained their viability when exposed to temperatures near absolute zero and then carefully reheated. (3) Arrhenius' discovery laid the foundation for modern theories of panspermia where dormant bacteria and other organic molecules from space are the origin of the life on Earth.

There are a number of factors that support panspermia as the answer to the origin of life on Earth. The first is the short time span between the formation of the Earth and the appearance of life. Most scientists agree that the Earth formed 4.55 billion years ago and there is evidence of photosynthetic organisms existing as early as 3.85 millions years ago. Photosynthetic bacteria are complex organisms and the likelihood that they are the first living organisms is small due to their complexity. (2) Panspermia explains the earliest living organism known to date being complex photosynthetic bacteria by stating that bacteria may have arrived from somewhere else, where life had a longer time to evolve than it did on Earth. Panspermia expands the timeframe in which life could emerge on Earth, allowing for its development on other planets or even other solar systems and then arriving on Earth via asteroid or comet.

Scientists seeking to discredit the panspermia hypothesis point to the extreme conditions of a voyage through space. They argue that during the entry into the atmosphere, almost all meteorites would get too hot for organic material to survive. They also assert that exposure to ultraviolet light during spaceflight would kill all organic material. (2) (4) Proponents of panspermia point to bacteria's ability to survive in extreme conditions on Earth ( bacteria thrive in thermal vents along the ocean floor and some even live in nuclear reactors) as evidence that they could survive journeys in space. Studies of meteorites reveal that although meteorites experience tremendous amount of friction upon entry into the Earth's atmosphere the heat generated only extends several millimeters deep into the meteor. The interior of the meteorite of would not experience a dramatic temperature rise. Rocks from Mars jettisoned from the surface by the impact of meteorites or comets, called nakhlites, also provide a vessel for the safe transport of organic material as the temperature of the interior of these rocks does not rise above 100 degrees Celsius during their exiting the Martian atmosphere and descent to Earth. (1)

Radiation presents a problem for panspermia advocates. Organic material in meteorites is protected from ultraviolet light if there is thin layer, measuring several microns, between the radiation and the organic material. However, a meteorite traveling through space would be bombarded by different types of radiation. Much of this radiation, like gamma rays, would not be stopped by a layer of rock, rather the rock would cause "showers of secondary radiation within the meteorite" killing organic material. (1) Although some bacteria are very resistant to radiation, the likelihood of their survival would depend on the length of the journey; scientists assert that they live for as long as several decades. (1) The longer the journey of the meteorite the more likely the radiation would kill all organic material.

The panspermia hypothesis offers a different perspective on the origin of life on Earth. The hypothesis is not without its problems, the most prescient being the survival of bacteria in deep space for decades, if not hundreds of years. This concern is not without merit but as scientists develop a greater understanding of the hardiness of living organisms and organic material it seems like there is a possibility that such material can survive in space for extended periods of time. If panspermia is indeed how life was started on Earth it means that we are not alone, across space at one time there existed at least some form of life beyond that of just the Earth. Although panspermia describes where life on Earth comes from, it leaves the larger question of how life started unanswered.

1)"Did Life Come From Another World" by David Warmflash and Benjamin Weiss in Scientific American October 24, 2005.

2) "Panspermia"

3)"Evolution of Life: A Cosmic Perspective" by N. Chandra Wickramasinghe and Fred Hoyle May 2001

4) "Problems with Panspermia or Extraterrestrial Origin of Life Scenarios" from the Intelligent Design and Evolution Awareness Center