Origin Of Life: The Panspermia Theory

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[Image credit: visibleearth.nasa.gov]

SiS is proud to feature the winners of the "2008 Integrated Graduate Program in the Life Sciences (IGP) Science and Society Class Distinction Award." Written as part of a course on science and society, these papers were chosen by IGP faculty to be published on SiS. This month, we present the following piece by PhD student Sonali Joshi.

How life originated on earth is a question that people have pondered for ages. Theories abound, from those based on religious doctrine, to the purely scientific, to others that border on science fiction. One possibility that hovers on this border is the panspermia theory, which suggests that life on Earth did not originate on our planet, but was transported here from somewhere else in the universe. While this idea may seem straight out of a science fiction novel, some evidence suggests that an extraterrestrial origin of life may not be such a far out idea.

One argument that supports the panspermia theory is the emergence of life soon after the heavy bombardment period of earth, between 4 and 3.8 billion years ago. During this period, researchers believe the Earth endured an extended and very powerful series of meteor showers. However, the earliest evidence for life on Earth suggests it was present some 3.83 billion years ago, overlapping with this bombardment phase. These observations suggest that living things during this period would have faced extinction, contributing to the idea that life did not originate on Earth.

However, in order for life to originate elsewhere in the universe, there would have to be an environment on another planet capable of supporting it. Our study of the universe suggests that life as we know it would have a hard time surviving outside of the Earth. But, it is important to note that life on Earth can withstand many extreme conditions. Some bacteria grow at temperatures as high as 113°C. At the other end, microbes can thrive at temperatures as low as -18°C; many can be preserved in liquid nitrogen at -196°C. They can also tolerate high doses of ionizing and UV radiation, extreme pressure, etc. These observations suggest that it is difficult to define the conditions that favor life, and make it harder for us to predict that life is unique to Earth.

The presence of water elsewhere in the universe reinforces this. Mars is believed to have contained water in the past. Much excitement for the presence of life on Europa, one of Jupiter’s moons, has been fueled by speculations that it may have underground oceans. However, while water is essential for life that we are familiar with, its presence does not necessarily indicate the presence of life.

The fact that organic matter is relatively common in space could also support the idea of extraterrestrial life. Organic matter refers to matter composed of compounds that contain carbon. All living things on Earth are carbon-based. A variety of organic compounds have been detected in meteorites that have landed on earth, including amino acids, which are the building blocks of proteins (and proteins are primary components all of living cells). The presence of carbon-based matter in meteorites supports the possibility that life on our planet could have come from outer space. But, even though life on earth is composed of organic matter, organic matter itself is not considered life.

Even if extraterrestrial life did exist, proponents of the panspermia theory must still determine how life arrived on Earth. The best candidates to act as “seeds of life” are bacterial spores, which allow bacteria to remain in a dormant state in the absence of nutrients. Bacteria constitute about one-third of Earth’s biomass and are characterized by their ability to survive under extreme conditions—those that we initially believed were unable to support life. In light of panspermia, the important question is if bacteria or bacterial spores could survive in space.

To address this question, scientists at the German Aerospace Centre in Cologne designed experiments using the Russian FOTON satellite. They mixed bacterial spores with particles of clay, red sandstone, Martian meteorite or simulated Martian soil to make small lumps a centimeter across. The lumps were then exposed via the satellite to outer space. After two weeks of exposure, researchers found that nearly all of the bacterial spores mixed with red sandstone were able to survive. Another study showed that bacterial spores could survive the extreme conditions of outer space for six years if they were protected from extraterrestrial solar UV radiation. This would be possible if the spores traveled within comets or meteorites.

However, interplanetary distances are large, so the time a bacterial spore would have to spend in a meteorite or comet before hitting a host planet could range in the millions of years. Two studies involving the isolation of bacterial spores, either from the abdomen of extinct bees preserved in amber or from a brine inclusion in an old salt crystal from the Permian Salado formation, suggest that bacterial spores can remain viable for up to 250 million years. Thus, bacterial spores could potentially account for life on earth.

But are there bacterial spores floating through space? One study focused on the heat radiation emitted from Halley’s Comet's dust particles as the comet approached the sun. The particles' radiation fingerprint corresponded surprisingly well to that of bacteria heated to elevated temperatures – no material other than bacteria matched the observed spectrum. As comets are known to have collided with Earth at different points in the past, this observation presents an interesting argument for panspermia. While this study does not provide conclusive evidence for presence of life in outer space, it does raise the possibility that our galaxy may be littered with bacterial spores.

An important thing to note about the panspermia hypothesis is that it gives no explanation for how life that arrived on Earth came to be. Even if we are able to show that life on Earth was a result of panspermia, the question of where and how life originated will be a lot harder to answer. So far our knowledge of the solar system suggests that life is unique to Earth, but, as science and technology advance, we will have to modify ideas that we currently regard as facts. It remains to be seen if the questions regarding the origin of life on Earth and the origin of life in the universe have the same answer.

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Of course life started else

<p>Of course life started else where. The bible is a book of intervention, and even explains how Adam and Eve were abducted and got their memories back after eating from the tree of knowledge. They only recognized they were naked because their memories came back to them after eating a fruit that was familliar to them, not because it was a magical tree. God had lots of help, there are lots of aliens, including God, mentioned in the bible. 34 versus are about aliens.</p>

You are assuming the bible

<p></p><p>You are assuming the bible (sic) is a credible source of science, hsiotory and the origin of life. You can't use the bible as a basis for an argument. The Bible is an ethnocentric, supremacist, sexist, racist book of regional myths. you can take a quote from the bible and use it as proof for anything. e.g, The devil can quote cripture to suit his purpose. Did life originate in the Garden of Eden? &nbsp;Did Man give life to woman? Out of HIS rib? &nbsp;do snakes, trees talk&nbsp;<span style="background-color: #e7e7e7; color: #333333; font-family: Tahoma, Calibri, Verdana, Geneva, sans-serif; font-size: 14px; font-weight: bold; line-height: 32px;">Judges 9:8–15</span><span style="line-height: 1.5;">&nbsp;and donkeys talk? was there an all encompassing worldwide simultaneous flood? do snakes eat dirt? was Noah 900 yrs old? did the aged Lot have sex with his daughters,( in a drunken stste) two days in a row? How did language develop? I can go on... who did god create first , man or beast? what came first the moon or the sun?</span></p><p>DON"T CHERRY PICK! is the earth really 6000 yrs old?</p><p>&nbsp;who are the Nephalim?</p>

I don't know how life is

I don't know how life is formed, how the Sun shines, the wind blows or a thought is formed but I see that it is, they do and are, so the means for their existence therefore exists. The question is not how but why and this brings me to know that God exists and created man with a purpose in mind. Since science does not yet have the answers; think it through for yourself...

Well said. And science shows

Well said. And science shows the marvels that God did/does whether it's through evolution or whatever theory. In the end he knows all forms of creating things out of "nothing" and/or something that he already had created.

As a matter of fact,

As a matter of fact, extraterrestrials aren't proved and is yet a theory... but i want to know where did these idea of aliens came from. did it just pop out of nowhere and a a billion trillion people around the world said 'Aliens must be true and there is such thing like that and we must prove and find it!!". whose idea is it, the panspermia? and where did they get the idea of aliens in the universe?

Religion is for people who do

Religion is for people who do not have the ability to think for themselves, or to think beyond the scope of simplicity. Sure, people are afraid of being alone, so they need some "god" to not feel that way. Everything in the bible is nonsense, and there are numerous things in the bible that go against the facts of science. The reason why so many theories exists is because we need a billion pieces more of evidence, and we've barely started..."because of religion holding us back." Through the span of over 500 years, many people have been killed because they dare to go against the belief of some "god." If they were left to open their minds and discover new things, we would probably be a little farther ahead by now. We will never become a level 1 civilization with religion.

Relying fully on religion as

Relying fully on religion as a source to how life came upon earth isn't a good source of evidence. Our earth s made of much more complex things that not even the bible would be able to explain. The bible is there, yes. It offers another look into the world, but it's the only thing that leads us to believe how life originated on earth. Life on earth is way more complex than people dare to think, you have to open your mind to the possibilities from how life was created, why we are here today?

Life on Earth as we know it

Life on Earth as we know it today consists of way too many people believing in way too many different things with regards to HOW WE ARE HERE... WHO BROUGHT US HERE... WHY ARE WE STILL HERE... WHERE ARE WE GOING... Religion and its many different forms and structures have led to WAR... DEATH... MURDER... SUICIDE... CULTS... So many indescribable atrocities that have hindered mans ability to progress to the next level of being and consciousness. Panspermia is in no way a fantasy as it has been proven that bacterial spores can lie dormant for hundreds of millions of years and still remain viable as a life form in that they can be awakened into being again as if they went into dormancy just yesterday. Thinking that we are the only LIVING (INTELLIGENT) beings in the entire universe is not only foolish and naïve but also short sighted and premature... We are an experiment that has been on going for millions of years and when we hit a stumbling block that once again hinders our growth as a species and the intellectual growth that we as a species crave and need, HELP is administered to us through a suggestion or the sudden appearance of a miracle cure or invention that allows us to take the next step towards our own advancement as a species... As Terrence McKennan's theory of Psilocybin Mushrooms may have allowed evolution to take the next step out of the trees onto the planes of Africa and for Apes to become intelligent enough to form languages and become the stepping stone towards the beings we are now, so will the next step be shortly realized as something is about to happen to us as a species on this beautiful blue planet we call home, as all these new discoveries being made all of a sudden, cures being found, strange sightings and occurrences around the world are rapidly increasing, changing weather patterns, climate change, magnetic disturbances from within the planet itself and so on, a global phenomenon of planetary proportions is looming and we are going to be in for a massively life changing event that will be either our downfall or projection into the next level of being as a species... Think about the next time you see something beautiful on the side of the road like a field full of bright coloured flowers that during your lifetime driving past the same field you have never seen flowers there before... for some reason those flowers have decided to grace the world with there presence... appreciate it for as long as you can because you never know when something like that will happen again in your lifetime... Signs of an intervention from an outside entity or entities is becoming more and more evident each day that passes us by and we must buckle up and hold on tight and enjoy the ride...

I believe in god and am a

I believe in god and am a christian. That does not mean i do not also think that science has nothing to do with it. I think that god may have a limited controll over the universe. There is also a 100% chance aliens evist. i mean, the universe is so massive life is bound to exist elseware. it is scientificaly plausable becasue it has happened on earth already.

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