Transcript Planet Earth

Planet Earth
A story of formation and
the evolution of
microbial life
Lets get it on….
Solar nebula accreted to form
the solar system
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
Stromatolites
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