Tag: archean

Geological time scale part 2

Posted on by Kuhan Chandru

Before starting the second part, i  would like to apologize for the delay. I was not super busy or anything, just being plain lazy without any excuses.

Moving on, When did life actually started? No one can actually tell. However scientists believe that life could have started or originated on multiple occasion and scenarios, only to be denied by major impacts. Despite this, it is speculated that life must have started around 3.8 billion years ago, when the LHB seized.

As mentioned in the previous post, the Archean period indicates, that earth has more water and minerals to make life plausible but, before that the atmosphere and the ocean has to form and cool off from HLB impacts. Only after this events, life could kick-start. Prebiotic chemistry happened during this time where the formation of lipids and peptides aggregates were formed. The idea of a “prebiotic soup” also must have happened here too. Many models were designed to imitate this period as well.

The protocell or LUCA (last universal common ancestor); could have emerged right after the prebiotic chemistry has taken place with metabolic diversification (which is about 3.8 -2.5 billion years ago). However, these are all scientific hypothesis, there are no fossilized records what so ever. Overall the origin of life idea is based on several hypothesis to build the prebiotic world and it’s chemistry. This grey area is where many chemical astrobiologist (like me) are focusing on. The idea however, is heavily supported by present knowledge of chemistry and geology with the power of models.

The earliest Stromatolites which is considered as the earliest micro fossils we have, is hypothesized (with heavy dispute) to have occurred right after this . The cyanobacteria rose with the power of photosynthesis giving an influx of oxygen to earth’s atmosphere, the very reason we have oxygen now. However, it should be noted that oxygen is toxic, meaning that other life forms utilizing non- oxygen metabolism during that time, must have went extinct without evidence. The Proterozoic eon starts here. The Cambrian explosion also starts here with the increasing of oxygen, leading to life forms which were well fossilized such as Opabinia and Marrella. Watch the video above to see how these creatures look like.

There are plenty of scientific evidence here. I will not be elaborating further on what happened after this. Many studies have been done, it is an establish science. We pretty much know what happened after the Cambrian explosion, but not what happened before that.

That’s all for now. The next post is about the possible sites of life’s origin.

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Geological time scale (part 1)

Posted on by Kuhan Chandru

I first knew about the geological time scale during my college years, back then the only geological time i knew was “Jurassic” due to a certain Hollywood movie. Learning it was fun but memorizing it for exams was horrible. The lecturers will first show the scale like the one here (very very boring btw), and they will explain one by one what happened with pictures of dinosaurs, plants, ancient humans and etc. It was remarkable, but how did geologists came to this scale always puzzled me, it still does, as we have loopholes in it too. The scale is basically a convention agreed by geologists based on research which were agreeable from time to time.

Here i will briefly explain some key events and how they got there. Most importantly i will put emphasis on how and when life started, the rest is evolution which you can read/view elsewhere. I will be also breaking this topic to a few parts for easy understanding.

Lets start,

After the big bang, the HADEAN period named after Hades begin. The sun was already formed and the rise of giant planets (Jupiter and Saturn) could have happened during this time. This is based on “numerical models“. After the formation of Mars, earth was finally formed in it’s hottest state (hot as hell). It is also postulated that the moon was also formed right after this, and her origins came from earth. Check out the video below on how this could have happened

From here on, our primitive atmosphere begin to arise, which is absolutely hypothetical in case you were wondering. After this particular sequence of events, the building of the habitable earth begins. The first proto ocean were already in play after the cool down effects on earth . There are some speculation that life could have started here; but right after this, the late heavy bombardment (LHB) of comets and meteorite came showering on earth, the planet was destroyed, water evaporated completely and it was a mess. This phenomena is also observable on the moon .If you have wondered why the moon has craters, its because of LHB (despite not having tectonic plates etc).

Now, The ARCHEAN period begins, which is generally the post HLB. Earth during this time has a lot of minerals and more water because of the LHB. In other words, she has received more materials to allow life to flower.

The rest of story is to be continued in the near future, stay tuned

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