AST101H1 Chapter Notes - Chapter 24: Martian Meteorite, Martian Soil, Terrestrial Planet

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST101H1
• Professor: Michael Reid

Document Summary

Ancestors of modern life probably could not have arisen much earlier than the end of the heavy bombardment. Last major impacts occurred 4. 2 and 3. 9 billion years ago. Radiometric dating confirms the relative ages (deeper layers formed earlier and contain more ancient fossils) Fossil evidence for the early origin of life. Harder to detect earlier life because older rocks are much rare than younger rocks because most of earths surface is geologically young. When old rocks are found they have been subject to transformations that would of destroyed fossil evidence they may have contained. All life prior to few hundred million years ago was microscopic and those fossils are hard to detect. Carbon isotope evidence suggests that life was present more than 3. 85 billion years ago. Earth arose within no more than few hundred million years. Individual variation: this unequal reproductive success is called natural selection.