Posted on Thursday, February 06, 2014
By Kadri

Young Sun, Early Earth and the Origins of Life by Muriel Gargaud, Hervé Martin, Purificación López-Garcia, Thierry Montmerle and Robert Pascal

Rating: 9/10

Carl Sagan wrote in his book “Cosmos” : “If you want to make an apple pie from scratch, you must first invent the universe.”

This book about astrobiology is written in a way that seems to be following Carl Sagan's thought.

This far the only example of life we have is the one now present on Earth, in the Solar System. As usual in a system objects interact with each other and so it's important to look at the whole system to understand more about the parts of it.

The book starts with the formation of the Sun, some 4.7 billion years ago in a molecular cloud that the young Sun shared with many other stars that have left the Sun's vicinity since that time. First we learn about the stars, how they form and evolve and how the stars initial mass affects how long the fusion processes in the star will keep going.

As it is now known many stars have planetary systems and explaining how the planets form is the next step on the way to finally understanding the necessities for life.
Nowadays, when some stars have been observed with the protoplanetary disks (Vega in the constellation Lyra, having been the first), scientists understand planet formation better than they did about a hundred or even just fifty years ago, when one of the theories for planet formation involved a giant comet passing by the sun really close and tearing away gases from the Sun that would eventually lead to the planets forming.

In the present it is thought that the planets form from the same disk of left-over mass around a star that will be sticking together ass time passes and they'll start forming little chunks of matter, that through numerous collisions will eventually become protoplanets. There are some questions still in the theory as collisions of larger objects tend to rather break the objects apart than combine then in an even bigger object.

However we end up having a planetary system and now we get to the planet Earth, and it's geologic history, what kind of processes were taking place on Earth billions of years ago – how would it have looked like on Earth during the Heavy Late Bombardment, the scars of which can still be seen on the Moon, and when did Earth actually have conditions that might have been suitable for life to evolve.

It is an interesting read as astrobiology combines research in so many different areas such as biology, chemistry, geology and astronomy, and while the book starts with astronomy, it continues on with geology and such interesting topics as how the Earth's crust has formed – although the formation of the oceanic and continental crust is a topic that is covered in high-school and sometimes even middle-school geography or Earth science lessons, then it's taught as it is happening in the present, but not how the processes were in the beginning of the Earth's geologic history – since the conditions were different, then even the crust that formed was not the same as it is now.

We also find out about the atmosphere on the early Earth, and how do scientists even get information about it. Also the environment on Earth was very different in other ways as well, not just in the atmosphere's content – the internal energy generated inside the Earth was about four times as much as it is now, but the Sun was about 20% fainter.

So how is it that we've ended up with a planet with exactly this kind of atmosphere and life and a average global temperature of about 15 degrees centigrade? Now we also dive into molecular biology and chemistry to find out how can organic molecules form in certain conditions, and how did RNA evolve and how did the simplest life forms evolve into more complex life.

We also go through some catastrophic events on the Earth such as asteroid impacts and ice ages and glaciation, which seemingly brings as to the present time.

The book ends with an exploration of the topic of exoplanets and which are found monthly now of various sizes and characteristics.

Overall this book is a great source of information that nicely links up everything that you need to know about in astrobiology, and it's accompanied by many schematics and illustrations that help a lot in understanding the text, as well it comes with a very helpful glossary in the end of the book.

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