ERTH 6 (Jan 23)

Typed

What was earth like across the Archean

• The Archean Eon (4.0 to 2.5 billion years ago) featured a vastly different Earth, characterized by a hot and inhospitable environment.

• The atmosphere was primarily composed of methane, ammonia, and other gases, with very little free oxygen.

• Early continents were small and fragmented, largely consisting of volcanic islands and continental crust that gradually formed over time.

• Life began to emerge during this period, with the first simple microorganisms, such as stromatolites, appearing in the oceans.

Silicate weathering feedback

Why do we live in a planet with a large range of temperature

When rain water falls it some thimes has carbonic acid, and weathers rock and take ions with them, this water then flows into the ocean , this will promote the precipitation of CaCO3

Plate tectonics

’ allows for a constant resupply of fresh material to earths surface

Those resupply is essential for a constant stream of nutrients to the ocean

Plate tectonics also maintains certain environments

Paleomagnetic evidence for modern-like plate motion velocities

A prediction of plate tectonics is that the movement of tectonic plates will continue to shape the distribution of oceanic and continental features, impacting marine ecosystems and global climate patterns.

Volcanoes have been popping up and are all oriented towards earth magnetic field, older volcanoes that have existed for millions/billion years are pointed in a variety of directions

Metabolism

A set of cheical reaaction that power life

Metabolisms are th eset of chemical reactions that turn food ionto energy powers cellular functions

But what are metabolisms and how do they differ among various organisms? Metabolisms can be broadly classified into two categories: catabolism, which breaks down molecules to produce energy, and anabolism, which uses energy to construct components of cells such as proteins and nucleic acids.

This is how microbials get energy

Certian Microbials use Nitriogen

Certain microbials live of of Iron

Certain Microbials use sulfur

Clasification:

Three question to remember

WHat are the odds this fossil is the first or last appearance of this organism

Is this actually a fossil

Is this fossil in a place

There are numerous occurrences of puprotired Archean microfossils and in some cases authors have even attempted to assign them metabolism

In realty each case is placed under intense scrutiny and it is exceedingly difficult to prove that a certain structure is 100% life

It is also extremely challenging to assign metabolism.

Other biosignatures

1. Is the signal real?

   • Noise ?

   • Analytical noise -I.e, the sensitivity of your instrument

   • USer error

   • Sample heterogeneity - Variability in the sample composition that can affect the accuracy of measurements.

   • Other materials causes interference

2. What is the signal/what doe sit mean?

   • What are we measuring ? A concentration a specific molecule ? An isotopic values

The rest of the lecture was bascily just emphasizing that we are very unsure on how we know what is and what isnt life, we will alwasy second guess and try to disprove that certain evidince is incorrect or otherwise in our quest to understand the origins of life and the conditions that support it. This uncertainty leads us to continually refine our methods and approaches in measuring concentrations and isotopic values, ensuring that we remain critical and open-minded in our interpretations.

KAi

Introduction

• The lecture begins with a brief recap of previous classes, discussing the late heavy bombardment, the evidence of rocks, and early life origins.

• Focus shifts to understanding rock records through various methods, such as molecular clocks and biomarkers.

Rock Records

• Molecular Clocks: Uses DNA to trace evolutionary histories and similar species sharing common ancestors, such as various cancers.

• Biomarkers: Refers to stubborn molecules that provide clues to the past since they resist decomposition.

The Geological Context

• Discussion on plate tectonics, how it influences geological features, distinguishes land and ocean regions, and its importance for climate.

• The model estimates for geological processes account for crust differentiation, water depth variation, and implications for life.

• Highlight of silicate weathering feedback: the interaction of increased CO2 levels in the atmosphere with water, leading to chemical reactions that affect climate stability.

• When CO2 levels rise, the weathering process increases, supplying calcium to oceans, which helps regulate atmospheric CO2 through carbonate minerals.

Plate Tectonics and Life

• Explanation of plate boundaries: spreading ridges, subduction zones, and transform boundaries, emphasizing their relation to geophysical events like earthquakes.

• Without plate tectonics, nutrient supply to Earth’s surface is disrupted, limiting biological growth and diversity, particularly phosphorus.

• Tectonics also plays a role in weathering processes crucial for maintaining life in various environments.

Emergence of Life

• The exploration of how life emerged on Earth, focusing on the Archaean era and the predominance of microbials like archaea and bacteria.

• Metabolic pathways and classifications are discussed (chemoautotroph, phototroph, etc.), focusing on energy sources and electron donors.

• Modern interpretations of early metabolic pathways help trace the evolution of life.

Evidence of Early Life

• Rock records serve as a historical timeline documenting the evolution of life, though fossil evidence is subject to the 'signor-lipps effect,' where the absence of evidence does not equate to absence of species.

• Discussion about how fossils can be misinterpreted over time due to limitations in technology.

• The significance of careful analysis of ancient rocks to avoid over-interpretation of abiotic structures that may appear life-like but are not.

Studying Ancient Life

• Comparison of structures in ancient rocks versus modern analogs, noting that similar morphology can arise from abiotic processes.

• The challenge of discerning true biogenic features from abiotic formations.

Current Understanding of Early Life

• General consensus leans towards microbial life existing shortly after Earth’s formation, but debates continue regarding the nature of early life and its metabolic processes.

• Emphasis on the uncertainty of when various biosignatures appeared but a broad agreement that necessary conditions for life were present in the geological record.