Lecture 5

ERTH 1009/1011 Lecture Overview

  • Lecture Date: 5/23, Winter 2025

  • Instructor: Peter Crockford

Upcoming Events

  • Carleton Geology Society Meeting

    • Date: Wednesday, Jan 29th

    • Time: 12:00 PM

    • Location: HP 2110

  • Women in Earth Science Check-in Meeting

    • Date: Tuesday, Jan 28th

    • Time: 11:30 AM

    • Location: HP 2130

    • Notes: Timbits and hot cocoa provided.

Quiz 1 Overview

  • Quiz Content:

    1. Characterization of Earth during the Hadean.

    2. Characteristics of Continental Crust (Felsic, Quartz, Feldspar) and Oceanic Crust (Mafic, Pyroxene, Olivine).

    3. True/False on geologic timescale and fossil biozones.

    4. True/False on Earth's differentiation and magnetic field.

    5. Sequence of events from Big Bang to Earth's complete differentiation.

    6. Importance of lunar samples from Apollo Era.

Quiz Answers

  • Answers Summary:

    1. Hadean characterized by a molten surface, cooling over time.

    2. Continental crust is Felsic; Oceanic crust is Mafic.

    3. True/False: Geologic time scale was not based solely on fossil zones. Answer: FALSE.

    4. True/False: Earth's differentiation is responsible for magnetic field. Answer: TRUE.

    5. Event Sequence: Big Bang -> Supernova -> Protoplanetary Disk -> Sun ignites -> Planetesimals -> Core formation -> Moon Formation -> Earth completion.

    6. Lunar samples provided isotopic evidence supporting the giant impact hypothesis.

The Archean Earth and Life Origins

  • Learning Goals for Today:

    1. Review of Earth's history up to now.

    2. Definitions and terminology relevant to life.

    3. Hypotheses on the origin of life.

    4. Tools available for evidence of early life.

    5. Life on Mars considerations.

    6. Outstanding questions on the topic.

Essential Definitions in Biology

  • Life Defined:

    • NASA's definition of life as a self-sustaining chemical system capable of Darwinian evolution, emphasizing independence in basic functions (e.g., metabolism).

  • Koshland’s 7 Pillars of Life:

    1. Program (DNA)

    2. Improvise (mutation)

    3. Compartmentalize (membranes)

    4. Energy (metabolism)

    5. Regeneration (compensation for losses)

    6. Adaptability (daily changes)

    7. Seclusion (specificity)

Biology's Central Dogma

  • Process Overview:

    • DNA -> RNA -> Proteins

    • Transcription, translation, and replication processes.

  • Mutations:

    • Occur at a rate of 1 in 10,000 replications in bacteria.

    • Can affect fitness and adaptability of organisms.

Hypotheses for the Origin of Life

  • Leading Candidates:

    1. Hydrothermal Vents:

      • Stable energy sources and potentially conducive environments for life.

    2. Soda Lakes:

      • Alkaline conditions, rich in nutrients, foster organic molecule synthesis.

    3. Puddles:

      • Temporary and suitable for initial biochemical processes.

    4. Other Planets (Panspermia):

      • Suggests Earth was seeded with life from extraterrestrial sources.

Evidence & Tools for Detecting Life

  • Biomarkers:

    • Stubborn molecules in geological records indicating past life.

    • Requires control of data quality and recognizable organic signatures.

  • Fossils:

    • Valuable in understanding past life; however, microbial fossils are challenging to interpret.

  • Molecular Clocks:

    • Utilize mutation rates to estimate divergence times of species from LUCA (Last Universal Common Ancestor).

Summary of Key Concepts

  • Life's central dogma summaries processes of how information is transformed from DNA to functional proteins.

  • Definitions of life are diverse, with no consensus on all forms.

  • Main hypotheses for the origin of life include conditions on early Earth, such as those found in hydrothermal vents and soda lakes.

  • Various tools exist to explore the history of life, each with their own challenges and benefits.