Subject: Physics Online Discussion Topic: Is life on Earth, really life from earth? Topic: Physics Online Topic
Author: John Date: 25 November 2011 9:32 AM
In this module you are looking at the similarities between the planets Mars and Earth. This might seem strange to some of you but you must never forget that we as inhabitants of planet Earth are indeed part of a vast universe and perhaps we are not alone at all!!
This online topic for discussion is actually a very really field of science that is called Astrobiology. The central aim of astrobiology is to look habitable planets both within and beyond our solar system and also to decipher how life on earth evolved. This is an exciting field of science that is multidisciplinary encompassing biology, genetics, physics, chemistry and other major fields of science.
It is such an important branch of science that the USA s premier research organization National Aeronautics and Space Administration (NASA) has a whole branch dedicated to this scientific field (http://astrobiology.nasa.gov/).
I will briefly outline two examples from the journal Astrobiology (available online through the UOW library) of current applications in the field of Astrobiology.
Blair et al. (2008) searched for formaldehyde clouds in the far outer galaxy as an indicator of the distance at which life can exist in the universe. It seems that it is well known that formaldehyde is a prebiotic molecule important in the development of amino acids (the building blocks of DNA).
The second example is from the work of Parro et al., (2008) who used an antibody array system to detect bacteria found on earth from drilling samples taken on Mars. Their results indicate that the Gram-negative bacterium Leptospirillum ferrooxidans which is found on Earth was also found on Mars. Suggesting that complex life forms can exist on Mars.
So what does this mean in terms of how life evolved on Earth? No doubt there is ample fossil and genetic evidence of organismal evolution on earth, but what about pre-evolution on earth? It seems that possibly some organisms on Earth are not from earth. This means that some of the science fiction movies are not science fiction rather they are science fact movies.
I wanted to know what NASA, the world famous US scientific space agency, had to say about this, so I posed the very question Is life on Earth, really life from earth? And resident NASA Astrobiology senior scientist Dr David Morrison gave this answer: There is no evidence one way or the other on the possibility of panspermia ” the exchange of life with other nearby planets like Mars. All we know for sure is that all life on Earth today is descended from a single common ancestor, and that life has existed on this planet for approximately 4 billion years. Most astrobiologists think the most probable location for the origin of Earth life is on Earth itself. However, we cannot exclude the possibility that life was exchanged between planets early in the history of the solar system. If by panspermia, however, you mean life crossing interstellar distances, this is extremely unlikely. The complex molecules of life can t survive the long times required for interstellar travel, nor the exposure to cosmic rays.
2nd writing in the topic
Auther: student 1
Scientists generally agree that the beginning of life on Earth was between 4.4 and 3.5 billion years ago. It is known that the life came to exist after the presence of liquid water on Earth. However, Scientists generally have different ideas about how life came to exist. There are many theories about this issue with different degrees of scientific credibility. The seven following theories are the most famous theories on the Origin of Life
1. Electric Spark
This theory suggests that life on Earth might have created by that lightning. According to some scientists, the Electric sparks can help to create the key building blocks of life because they generate sugars and amino acids from an atmosphere loaded with methane, water, hydrogen and ammonia.
2. Community Clay
This theory suggests that the first molecules of life might have met on clay which have concentrated the organic compounds together and organize them.
3. Deep-Sea Vents
This theory suggests that life might have begun in the deep-sea water were the hydrogen-rich molecules and chemical and thermal energy are exist.
4. Chilly Start
This theory suggests that the Ice covered the oceans 3 billion years ago, might have protected organic compounds for long time and helped them reacting with each other or with other compounds to create the life.
5. RNA World
Some scientists suggested that life might have begun with the RNA which could have spontaneously arisen on Earth.
6. Simple Beginnings
This theory suggests that life might have begun with smaller molecules interacting with each other in cycles of reactions and over time more complex molecules have formed.
This theory suggests that life did not begin on Earth at all, but was brought here from the space. Many scientists have suggested that life might have hitchhiked on comets from other star systems.
To conclude, earth has rich supply of carbon, water and other important elements to support a rich diversity of life. And as it is known, all living things on earth possess carbon within them and they need water to survive. Currently there are no strong evidences that comets and other planets do have such supporting life conditions. According to that it is more possible that the life on earth is from earth.
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