Image in header: Basic diagram of universal cellular catabolism (breakdown of organic food to extract ernergy). Source: https://www.slideshare.net/slideshow/cell-metabolism/6630810 (uploaded by iamchi001)
You are reading my course, so you would like to know more about (the possibility of) extraterrestrial life? Nice. But then you will first have to understand more about the basics of terrestrial life. After all, the only kind of life we have come to know so far is full of universal properties that make a lot of sense. These properties are probably universal in terrestrial life because they were the most likely choices if you respect the laws of physics and chemistry. So chances are that these properties can also be found (or variants of them but with d same basic principles) in other places in the Solar System.
Hence this Part 2, on“Life (on Earth), the essential characteristics“. But before we start looking at what life has invented on our planet, and how this has enabled its evolution into an earthly paradise, we need to delve a bit into the most fundamental features. If you’re not a biologist or other dyed-in-the-wool biology nerd, definitely don’t skip this first block of Part 2. You will need the understanding of basics to understand the rest.
If you read other courses or books on astrobiology, you often have to first go through an extensive chapter asking “What is life”? I myself have always found that a bit tedious. I didn’t want to spend my time going over hypothetical alternatives to the kind of life we already know here on Earth. Above all, I wanted to know whether this -our known- kind of life also exists elsewhere. So therefore, here is no introduction to what life could be (the alternatives to what we already know), but rather a chapter on“life as it is“, as we know it. Especially within the Solar System, I think this is a better way to go about the search for extraterrestrial life. It allows us to focus better in our search. Besides, it is fascinating enough when we base our search on what we already know, without having to take into account all the hypothetical alternative life forms. But in saying this, of course, I have not said that alternatives could not exist.