Astrobiology – Introduction


Like I said, I’d like to blog not only about my poems and lyrics, but also about science I’m interested in. I would like to start a little series on Astrobiology, even though I’m not sure if I know enough about this topic, since I’ve learned it all by myself. Lectures are hard to find, especially in Germany. There were some lectures in Cologne some years ago, but they stopped them. Since it’s hard to study Astrobiology, I study Biology now and will later try to specialize on this field. Not sure how this will work out, but for now I try to learn as much as I can about this topic. And now I will try to explain some of the stuff to you, because, honestly, it’s pretty awesome stuff.

Since I never actually studied Astrobiology, there is no guarantee that what I say is correct, I will, however, try to have and name a reliable source.

So, what exactly is Astrobiology (or Exobiology, both terms are used)? The word consists of Astro/Exo and Biology, so this alone indicates that we talk about life outside of earth. So, what life? Until today, there was no life found outside of earth, and 20 years ago, scientists were pretty sure that there is no life within our solarsysten. There are, however, newer studies which show that life is much more persistent than thought and that life could be possible at a few spots in our solarsystem. I will come to this again later.

When we talk about life outside earth, were not talking about Aliens from movies. Were talking most of the time about bacteria. Of course  man did not find bacteria on other planetary bodies, but what scientist have found indicate that it could be possible to find them.

But let’s start at the beginning. Before we can start to find life outside earth, we have to define what life actually is. There is no definite definition and a lot of smart people argue about exactly this topic. The most general accepted definition was given by the NASA Exobiology Program in 1992, which stated that

Life is a self-sustained chemical system capable of undergoing darwinian Evolution.”¹

This definition implies that the system uses external matter and energy which must be provided by the environment. Considering this, primitive life could be described as an open chemical system capable of evolving and reproduction. For evolving, some sort of mechanism must exist, which transfers information from one system to another system, however, at random some errors can occur and the systems evolves into something more complex or efficient or better adapted.

Life on earth is a based on a carbon chemistry in water. It’s used as a reference to provide guidelines when searching for extraterrestrial life. Essential to life on earth are only a few of the elements existing on earth. The most important are Hydrogen (H), Oxygen (O), Carbon (C) and Nitrogen (N). Those four elements deliver more than 96% of the body mass. There are some other elements like Sulfur (S), Magnesium (Mg) or Natrium (Na), which are essential for life but not in the same way as the four organic molecules.²

The most important thing is probably water. It serves as solvent, it favors diffusion and exchange of organic molecules, they establish hydrogen bonds with molecules containing  hydrophilic groups. Another important fact is that molecules containing both hydrophilic and hydrophobic groups self organize them according to this properties. This is essential for forming lipidmembranes.

Besides the H-bonding water also exhibits a large dipole moment which favors the dissociation of ionizable groups like NH2 and COOH, which can form additional H-bonds with water molecules improving their solubility.

Water was the key feature for the evolvement of live on earth, serving as basic solvent, heat dissipator and a powerful hydrolytic agent, which allowed chemical combinations which would have not happened in organic solvents. Thus, liquid water is considered as prerequisite for the existence and emergence of life.³

We now know what life is and of what it contains, what it needs to emerge and why it needs this.

I will continue this series over the time, and try to give you an overview over astrobiology.

Sebastian

1: Complete Course in Astrobiolgy, WILEY-VCH Verlag, Weinheim, 2007, P.3
2: http://www.en.wikipedia.org/wiki/Dietary_mineral ; Lecture in Cellbiology, 2010, JGU Mainz
3: Complete Course in Astrobiolgy, WILEY-VCH Verlag, Weinheim, 2007, P.4
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