Origin of Life & Astrobiology: Essential Concepts
Essential Compounds for Life
Inorganic Compounds
Water and mineral salts are essential for the function of living beings.
Organic Compounds
Found only in living beings, characterized by covalent bonds.
- Polymers: Macromolecules formed by monomers.
- Carbohydrates: Primary source of energy.
- Lipids: Store energy and have regulatory functions.
- Proteins: Perform transport, structural, and hormonal functions; enzymes act as chemical catalysts.
- Nucleic Acids: Store and transmit genetic information.
Defining Life and its Origins
A living being is an organized and complex system that exchanges matter and energy with the environment.
Key Characteristics of Living Beings
- Cellular Organization: Unicellular or Multicellular.
- Interaction: Response to stimuli.
- Metabolism: Obtaining matter and energy.
- Homeostasis: Regulation of the internal environment.
- Reproduction: Production of new organisms.
Theories on the Origin of Life
- Spontaneous Generation: Discredited myth, thanks to experiments by Redi and Pasteur.
- Panspermia Hypothesis: Life arrived on Earth from space.
- Abiogenesis: Life originated from simple molecules.
- Oparin’s Hypothesis: The Miller-Urey experiment, now considered a discredited myth.
- Current Hypothesis: Protocells formed in underwater hydrothermal vents.
Protocells
Characterized by a semipermeable membrane, internal metabolism, and genetic material.
First Evidence of Photosynthetic Organisms
- Stromatolites: 3.5 billion years old.
- Formation of Iron Bands: 2.4 billion years ago.
- Endosymbiosis: Led to the rise of eukaryotic cells.
Conditions for Habitability on Earth
- Liquid Water: Requires an energy source, placing Earth in the habitable zone (neither too hot nor too cold).
- Bioelements: CHONPS (Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur).
- Atmosphere: Protects from solar radiation and maintains necessary gases.
- Magnetic Field: Protects from solar winds and cosmic rays.
- Internal Activity: Tectonic plates, volcanoes, and energy flow.
- Moon: Regulates weather and tides.
- Elliptical Orbit: Minimal variation, resulting in seasons.
Earth as a System
Earth is an open system, exchanging matter and energy with outer space. It is dynamic, due to the interaction of subsystems (Atmosphere, Hydrosphere, Geosphere, Biosphere), and self-regulatory, through interaction and recycling between components.
Astrobiology: The Search for Life Beyond Earth
Astrobiology is the science that studies the origin, evolution, distribution, and future of life in the universe.
- Exoplanets: Over 5000 discovered.
- Extremophile Organisms: Organisms that can survive in extreme conditions.
- Biomolecules: Chemical compounds, objects, or patterns resulting from the presence of life.
- Cellular Structures: Organic biomolecules or photosynthetic pigments.
- Oxygen on Earth: Originates from photosynthetic organisms.
Methods for Detecting Extraterrestrial Life
- Observation from Earth: Astronomical observatories.
- Observations from Space: James Webb Telescope.
- Space Laboratories: International Space Station.
- Space Exploration: Space probes exploring planets.
- Explorers on Planets: Rovers searching for signs of life.
- Human Missions (Moon): Soil samples brought back.
Potentially Habitable Planets and Moons
- Mars: Formerly had water, seasons, and polar caps.
- Europa: May have a frozen ocean.
- Titan: Its atmosphere contains methane instead of water.
- Enceladus: May have an ocean and internal activity.
- Exoplanets: Many more exoplanets are being discovered in the habitable zone.