01:750:109 Chapter 15.1: The Cosmic Perspective Fundamentals: The Search for Life in the Solar System
The Search for Life in the Solar System
●No other world in our solar system has ever been home to a civilization
●Some of these worlds have conditions that could allow more primitive life to survive
What are the necessities of life?
●First step
in the search for life in our solar system is deciding what it is that we are looking for
○Initial searches focused on looking for life that is similar to that of Earth's and on living
conditions to those required by life forms on Earth
The Nature of Life on Earth
●All life on Earth shares a few common characteristics:
○Uses DNA as its genetic material
○Builds proteins from the same set of building blocks, known as amino acids
●Beyond this, life on Earth is diverse
●People generally assume all living organisms belong to either the plant kingdom
or animal
kingdom
○But found out that most microbes don’t belong to either
●Tree of life
that depicts the relationships among all living species
○3 major domains: bacteria, archaea, eukarya
○Offers key lessons that help us search for life beyond Earth:
■First: Tells us that the plant and animal life with which we are most familiar is
not typical of most life on Earth. In fact, most life is microscopic
■Suggests that we are far more likely to find microscopic life on other
worlds than large life forms similar to plants or animals
■Second: All life on Earth appears to be related
■Suggests that all life evolved from a common ancestor
■Organisms on branches closer to the root of the tree of life must contain
DNA that has changed less over time, suggesting that these organisms
more closely resemble the organisms that lived early in Earth's history
■Today, organisms that lie closest to the root are microbes that
live in very hot water around seafloor volcanic vents in the deep
oceans
■Don’t depend on sunlight for life, but obtain energy
from chemical reactions in water heated volcanically by
Earth itself
■AKA conclude that sunlight is not necessary for life
■Other: most organisms live under conditions that seem "extreme" to animals
like ourselves
Document Summary
The search for life in the solar system. No other world in our solar system has ever been home to a civilization. Some of these worlds have conditions that could allow more primitive life to survive. First step in the search for life in our solar system is deciding what it is that we are looking for. Initial searches focused on looking for life that is similar to that of earth"s and on living conditions to those required by life forms on earth. All life on earth shares a few common characteristics: Builds proteins from the same set of building blocks, known as amino acids. Beyond this, life on earth is diverse. People generally assume all living organisms belong to either the plant kingdom or animal kingdom. But found out that most microbes don"t belong to either. Tree of life that depicts the relationships among all living species. Offers key lessons that help us search for life beyond earth:
