Planet Earth A story of formation and the evolution of microbial life Lets get it on….
Earth accreted (probably from solar nebula) about 4,600 million (i.e. 4.6 billion) years ago due to electromagnetic and gravitational forces – self organization
Earth is the third planet out from the Sun Diameter of 12,776 kilometres Geologic record begins 3,900 million (3.9 billion) years ago
Early Earth, over 4 billion years ago, was molten and meteorites impacted the surface
Lighter liquids floated to the surface Heavier liquids sank to core, such as iron and nickel
Planet Earth - 0 to 3.5 billion years Lighter liquids gassed out of volcanoes and formed early atmosphere Stable crust formed at surface
Early atmospheric gases from volcanoes were carbon dioxide, carbon monoxide, water vapour (i.e. steam) and methane - but no oxygen. A hot humid and violent place.
Earth has a solid crust on a molten liquid core The crust is segmented into floating continental plates The molten core drove continental drift in a process called tectonics
As the Earth cooled to below 100 degree centigrade, water vapour from volcanoes probably condensed out to form oceans. Early Earth life may have started without oxygen, in the seas – algae over 3,500 thousand years (about 3.5 billion years) ago – that is, life had already started by 30% of the current age of the Earth
Photons from the Sun are thought to have provided the energy for water vapour to split into oxygen and hydrogen leading to oxygen-feeding life forms about 2 thousand million years ago
The molten core causes a magnetic field around Earth which protects Earth from radiation and allowed the atmosphere to develop…
Planet Earth - the last 500 million years Starting about 500 million years ago, the oceans became steady-state chemical sources of life Two-thirds of the Earth is covered by the oceans The sea floor spreads and continents drift on their plates
Planet Earth - the last 150,000 years Dramatic climate changes have occurred from full Ice Ages and glacial coverage to non-glacial warm periods Transitions from Ice Age to warm periods have occurred in less than 10,000 years and we do not know the reasons.
Humans have expanded across the planet since the last Ice Age, over the last 20,000 years, taking advantage of the highly favourable period between Ice Ages
Stanley Miller A.I. Oparin J.B.S. Haldane Harold Urey
“The essential difference between life and non-life is replication. There are other differences, but this is the essential one”. Stanley Miller