ASTR 104 Lecture Notes - Lecture 36: Radiometric Dating, Radar Imaging, The Strongest
Document Summary
Earliest life: carbon isotope evidence pushes the origin of life to more than 3. 85 billion years ago, the oldest fossils show that bacteria-like organisms were present over 3. 5 billion years ago. Heavy bombardment solar system"s history: asteroids and comets today are a small fraction of what existed early in our. In the young solar system, some were flung into space through gravitational encounters: many others collided with planets, most collisions occurred in the first few hundred million years after the solar system formed, during the heavy bombardment period. What is life: all living organisms on earth share some key properties, order, reproduction, growth and development, energy utilization, response to environment, evolutionary adaptation, a simple definition of life, something that can reproduce and evolve. Necessities for life: as a whole, the different forms of life on earth require , nutrient source, energy, sunlight, chemical reactions, internal heat, liquid water, or possibly some other liquid, hardest to find on other planets.
