2. Origin of life

It is still a challenge for scientists and philosophers to define the term “life”, since it must include all life we are familiar with, but also not exclude life forms that might be fundamentally different from life on earth (= Aliens).

Life can be defined as:

• A network of regulatory mechanisms (negative feedbacks) inferior to the potential of expansion and reproduction (positive feedbacks).

• Things with the capacity for metabolism and motion

• Matter that can reproduce itself and evolve as survival dictates

• A way to hydrogenate carbon dioxide

• Living things that are self organizing and autopoietic (produce and maintain without help)

The Kepler Project was a NASA space mission to discover Earth-like planets by monotoring the brightness of stars and detecting planets through the transit method.

It revolutionized our understanding of exoplanets by identifying thousands of planets, many of them potentially habitable.

The experiment simulated the conditions of the early earth’s atmosphere to see if these conditions may have favoured the chemical reactions that synthesised amino acids and other live-forming compounds.

They created the conditions by circulating a mixture of methane, ammonia, hydrogen and water vapor through a closed glass apparatus.

• water was boiled to mimic the ocean

• Electrical sparks were discharged into the gas mixture to simulate lightning as an energy source.

• The gasses passed through a condenser, causing them to cool and return as liquid, creating a continuous cycle.

• Eventually the liquid contained amino acids and other organic molecules.

This demonstrated that essential biomolecules can arise spontaneously under plausible prebiotic conditions.

The experiment provided the first experimental support for chemical evolution and remains foundational to studies on the origin of life.

• Discovery of the Cell by Robert Hooke (1665)

• Discovery of a Virus (1892)

• Penicillin discovered (1928)

• Creation of the first DNA molecule in a Lab (1972)

Life might have originated from these vents, in which an early form of metabolism took place.

The synthesis of amino acids could have occurred deep in the earth’s crust, they were then brought up into cooler waters where the presence of clay minerals have lead to the formation of peptides and protocells.

The hypothesis is supported by the fact that, Methane (CH4) and Ammonia (NH3) were not present in the vents, in contrast to the earth’s primitive atmosphere.

Life is a characteristic organism that exhibit all of the following phenomena:

1. Order

2. Metabolism

3. Regulation

4. Growth and development

5. Reproduction

6. Adaption

7. Movement

8. Response to stimuli

6 non-metallic elements account for >98%

CHNOPS:

• Carbon: Backbone of organic molecules

• Hydrogen: Part of water and all organic molecules

• Nitrogen: Constituent of all proteins and nucleic acids

• Oxygen: Respiration, part of water, in nearly all organic molecules

• Phosphorus: Constituent in DNA and RNA, high energy bond in ATP

• Sulfur: Important in protein structure

Yes it would be possible.

• Terrestrial life is based on carbon and water. (Presumed pre-conditions for life)

• Terrestrial planets, such as Earth, are formed from “stardust” in a process that allows for the possibility of other planets having formed with compositions similar to Earths.

• So it is assumed that sufficient quantities of carbon, water and the other major life-forming elements, may enable the formation of living organisms on other planets with a chemical make-up and temperature range similar to earth.

• An alternative to carbon would be silicon based life, since it has many properties similar to carbon.

• Water required as the solvent for biochemical reactions.

• Carbon as scaffolding element that creates the overall structure and shape of biomolecules.

Distance from a star where an earth-like planet can maintain liquid water on its surface and potentially earth-like life.

Important because liquid water is essential for life.

• Physical Evolution:

  • 13.8 billion years Bigbang

  • 4.6 billion years Origin of earth

  • 4.4 billion years Oceans form

• Chemical Evolution (abiogenesis):

  • Formation of complex biomolecules

  • Vesicles

  • Probionts

• Biological Evolution:

  • 4.2 -3.6 billion years life emerges

  • 3.4 billion years oldest traces of life found in fossils

• Formation of biomolecules from non-organic precursors

• Genesis of the cell

• Emergence of the interdependence of function (enzymes) and information (RNA, DNA)