Unit 2: Why Life on Earth is Possible Accretion Accretion is one of the leading theories for the formation of planet Earth. It is a process that occurs when gravity attracts tiny bits of matter towards an object. Accretion forms planetesimals, which form protoplanets. A protoplanet is a planetary embryo that consists of collection of matter, from which a planet is formed. The Steps of Accretion Homogeneous Accretion It is when Earth accreted from materials of the same composition after condensation. Heterogeneous Accretion It is when Earth accreted during condensation, forming a differentiated planet as it grew in size. Homogeneous Accretion Evidences It provides a mechanism that explains the presence Loopholes The hypothesis cannot explain the abundance of elements such as osmium, Heterogeneous Accretion of volatile elements in the core. It qualitatively explains the density differences among terrestrial planets. iridium, ruthenium, and rhodium in the mantle. Accretion must be very fast (103 to 104 years for completion). This rate does not coincide with the occurrence of large impact craters. Also, the abundances of iron, calcium, titanium, and aluminum do not coincide with what was predicted by the theory. Water: The Medium of Life The Hydrosphere The hydrosphere includes all of Earth’s water. Bodies of water are classified into either saltwater or freshwater, based on salinity. Saltwater Saltwater (oceans and seas) primarily have high salt content. 97.5% is saltwater Freshwater It has zero to very little salt content. 2.5% is freshwater Properties of Water These properties make aquatic habitats a stable place for organisms to live in, since aquatic habitats can somewhat resist temperature changes. 1. Density - Water is at maximum density at 3.98°C. 2. Heat Capacity - Water has a relatively high heat capacity, which allows it to resist temperature changes. The Origin of Water on Earth The prevailing hypothesis on the origin of water on Earth suggests that water came from comets that collided with Earth. Other studies suggest that water was already present within Earth since formation as volatiles trapped in magma. Sun as the Main Source of Energy Albedo All objects can either absorb or reflect light. This is a property known as albedo. It has a value that ranges from 0-1. The Sun The Sun is the Earth’s main source of energy, and powers many of the processes in the planet. Plants are dependent on the Sun for photosynthesis. Solar Energy is Renewable o As long as the sun shines, solar energy is available for everyone to utilize. o This is advantageous since the sun is an environmentally- friendly source of energy. Earth’s Energy Budget Earth’s energy budget is the balance of energy absorbed and energy reflected. 30% of the energy from the sun is reflected and scattered by clouds, atmosphere, and Earth’s light-colored surfaces. Factors Affecting Earth’s Energy Budget There are certain factors that affect Earth’s energy budget such as: the amount of light colored surfaces amount of radiation received Earth’s axial tilt presence of greenhouse gases Earth's Atmosphere Atmospheric Composition The bulk of the atmospheric composition of Earth is nitrogen and oxygen in which together comprises 99%. Only 0.9% is argon and the remaining 0.1% is trace gases. Carbon dioxide and ozone, although available in minute amounts, are very essential to life on Earth. Layers of the Atmosphere Troposphere is where humans and most of the biosphere reside, and is the lowest layer. Stratosphere contains the ozone layer. Mesosphere is where meteorites burn up. Thermosphere is a layer with extremely high temperatures. Exosphere is the outermost layer of the atmosphere, and the layer in contact with outer space. The Stratospheric and Tropospheric Ozone Stratospheric ozone is good while tropospheric ozone is bad. These harmful ozones when inhaled, can irritate the lungs and breakdown lung tissues. Plants are also affected by this tropospheric ozone. Atmosphere’s Role in the Hydrologic Cycle The atmosphere is a crucial part of the water cycle. It serves as the reservoir of large amounts of water. Therefore, the atmosphere is an efficient medium to move water around the globe. Unit 3: Introduction to Earth System Science Earth System Science It is the study of Earth as an integrated system. It seeks to understand the past, current, and future state of our planet. The interdisciplinary nature of ESS led to the development of new ideas for research, as well as promoting scientific studies to people of different backgrounds. The Gaia Hypothesis The Gaia Hypothesis states that the Earth is a self-regulating system. Organisms interact with their surroundings and other organisms. These interactions make Earth self-sustaining. Vladimir Vernadsky - a Russian mineralogist and geochemist, who popularized the term noosphere or the sphere of human consciousness and reason Alexander von Humboldt- a 19th-century German geographer and naturalist, who helped establish the foundation for Earth system science through his observations of nature James Hutton the Father of modern geology, was a Scottish farmer and naturalist conceptualized the process of weathering introduced the concept of uniformitarianism James Lovelock- a British environmentalist proposed the Gaia hypothesis or Gaia principle, which is a postulate that Earth works as a self-regulating system Lynn Margulis - an American biologist and evolutionary theorist, further developed Lovelock’s Gaia hypothesis NASA ESS Committee NASA scientists aim to understand Earth’s systems by using satellites for long-term observations. NASA continuously collects data through their satellites. Scientists and data analysts process the data for human use. Examples of uses are for weather, atmospheric analysis, and many more. Satellite Imagery Satellites can take photos of the Earth from space for various purposes. Four Subsystems of Earth The Atmosphere The atmosphere makes up of all the gases on Earth. The atmosphere has different layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere Atmosphere o Greek word ‘atmos’, which means gas o Karman line- separates the atmosphere and outer space o Nitrogen (78.1%), Oxygen (20.9%), noble gases (Ar- 0.9%), Carbon dioxide and other gases (0.1 The Geosphere Geosphere comes from the Greek word geo which means ground. It includes all the soil, rocks, and minerals present in the crust to the core of Earth. Layers of the Geosphere Crust- This is the outermost layer, and is solid. Mantle- This is the middle layer, and is liquid. Core- This is the innermost layer, and is solid. Three Layers of the Geosphere Crust- made mostly of silicate materials (oceanic-5 to 10 km and continental- 15 to 70 km thick) Mohorovicic discontinuity or Moho – Croatian scientist, Andrija Mohorovicic; boundary between crust and mantle Mantle (2 900 km)- mostly made up of silicate rocks rich in magnesium and iron Upper Mantle- cold and brittle Lithosphere asthenosphere Lower Mantle - hotter and denser than the upper mantle but it remains solid because of the immense pressure Gutenberg Discontinuity - boundary between mantle and core (Beno Gutenberg) Core (3 480 km-radius)- made up of iron and nickel outer core- liquid iron and nickel Inner core- hot, dense ball of mostly iron Bullen Discontinuity (Keith Edward Bullen)- boundary between inner and outer core. The Hydrosphere It is composed of all water on Earth in any form: water vapor, liquid water, and ice. It is comprised of 97.5% saltwater and 2.5% freshwater. The Biosphere It includes all the organisms on Earth.
