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COSMIC COLLISIONS AND DINOSAURS
Dr. Adriana Ocampo
March 2015
OVERVIEW
•  Cosmic collision and dinosaurs
•  Getting to know our neighborhood up to 5 AU
•  Exploring our Solar System beyond 5 AU
WHAT IS PLANETARY GEOLOGY?
•  Planetary geology, alternatively known
as astrogeology or exogeology, is a
planetary science discipline concerned
with the geology of the celestial bodies
such as the planets and their moons,
asteroids, comets, and meteorites.
•  Eugene Shoemaker is credited with
bringing geologic principles to planetary
mapping and creating the branch of
planetary science in the early 1960s,
the Astrogeology Research Program,
within the U.S. Geological Survey.
•  Shoemaker is one of the founders of
Planetary Science and made important
contributions to the field and the study
of impact craters, Lunar Science,
asteroids, and comets.
WHAT IS LIFE?
•  Life is a product of atoms and gravity
obeying natures laws of physics,
chemistry and biology!
A molecular cloud, or stellar nursery (if star
formation is occurring within), is a type of
interstellar cloud,
MOLECULAR CLOUDS = STAR
NURSERY
•  the density and size of which permit the
formation of molecules, most commonly
molecular hydrogen (H2).
•  it appears that the chemical precursors to life
are formed here long before planetary
systems develop around stars.
•  Before it was thought that molecules
required a terrestrial planet in a habitable
zone of a star to enable there formation
More research is required in theoritical and
experimental chemistry to explain the now
seemingly common identification of life
molecules in space.
Carina Nebula, HST 1999
EARTH OUR EVOLVING PLANET @ 1AU
Although more than 99 percent of all species that ever lived on the planet are estimated to be extinct
there are currently 10–14 million species of life on the Earth.
EARLIEST EVIDENCE OF LIFE
•  The earliest evidence for life on
Earth is
•  graphite found to be biogenic in
3.8 billion-year-old
metasedimentary rocks
discovered in western
Greenland and
•  microbialmats fossils
(stromatolites) found in 3.48
billion-year-old sandsotones
discovered in Western Asutralia.[
Biological graphite
Living Stromatolites:
Fossilized Stromatolites
WHEN DID LIFE STARTED ON
EARTH?
•  The earliest evidence for life found
so far is in a 3.7 billion-year-old rock,
the Isua sediments, found in western
Greenland.
•  The evidence for life in these rocks
does not come from fossilized
remains, but from a peculiar
chemical signature of living
organisms.
•  These rocks were deposited on the
surface of an oceanic crust on what
was thought to be a deep ocean.
• 
the Greenland Isua sediments are
actually an ancient sea-floor.
WHAT IS A MASS EXTINCTION?
•  Mass extinctions are:
•  periods in Earth's history when
abnormally large numbers of species
die out simultaneously or within a
limited time frame.
•  The most severe occurred at the end of
the Permian period (245Ma) when 96%
of all species perished.
EARTH GEOLOGICAL HISTORY
In 1982 J. Sepkoski and D.
Raup landmark publication
identified five mass extinctions
Earth mass extinctions had five
(5) major mass extinction
•  Ordovician ~438Ma (O/S)
•  Devonian ~360Ma (late D)
•  Permian ~245Ma (P/Tr)
•  Triassic ~208Ma (Tr/J)
•  Cretaceous ~66Ma (K/Pg)
MASS EXTINCTIONS
Characteristics of a
mass extinctions:
•  Global effect
•  It happens relatively fast
•  An exceptionally large number of
species disappear
•  Many environments are affected
causing extinction of many types
of species
•  identified by a sharp change in
the diversity and abundance of
macroscopic life.
•  extinctions are clustered in a
short amount of geological time
(a few million years is very short
in terms of geological time).
Pr/Trilobite Dv/Armored Fish
Pr/Sea scorpion
Tr/Dimetrodon
O/Nautiloid
ORDOVICIAN – SILURIAN 450-440MA
•  Ordovician–Silurian extinction events (End
Ordovician or O-S): 450–440 Ma at the OrdovicianSilurian transition.
•  Two events occurred that killed off 27% of all families,
57% of all genera and 60% to 70% of all species.
•  Together they are ranked by many scientists as the
second largest of the five major extinctions in Earth's
history in terms of percentage of genera that went
extinct.
LATE DEVONIAN 375-360MA
•  Eliminated about 19% of all families, 50%
of all genera and 70% of all species.
•  This extinction event lasted perhaps as
long as 20 Ma, and there is evidence for a
series of extinction pulses within this period
or , a prolonged series of extinctions
happened
PERMIAN TRIASIC – “THE GREAT DYING” 252MA
•  Earth's largest extinction or the "Great Dying" , killed 90% to
96% of all species (about 96% of all marine species and an
estimated 70% of land species, including insects).
•  The evidence of plants is less clear, but new taxa became
dominant after the extinction] had enormous evolutionary
significance: on land, it ended the primacy of mammal-like
reptiles.
•  The recovery of vertebrates took 30 million years, but the vacant
niches created the opportunity for other species to become
dominant.
•  The whole late Permian was a difficult time for at least marine
life, even before the "Great Dying".
The Earth became too hot, global warming has being linked to the Pr-T mass extinction.Ocean surface
temperatures reach 40C- a near lethal temp when marine life dies and photosynthesis stops
TRIASSIC-JURASSIC 201MA
• 
About 70% to 75% of all species went extinct
( 55% of marine genera).
•  Most non-dinosaurian archosaurs, and most of
the large amphibians were eliminated, leaving
dinosaurs with little terrestrial competition.
•  Non-dinosaurian (archosaurs) continued to
dominate aquatic environments.
CRETACEOUS-PALEOGENE 66MA
•  The K–T event (66Ma) is now officially called the Cretaceous–
Paleogene (or K–Pg) extinction event in place of CretaceousTertiary.
•  About 75% of all species became extinctTertiary
•  In the seas it reduced the percentage of non-mobile (sessile)
animals to about 33%.
•  On land all non-avian dinosaurs became extinct during that time.
•  Mammals and birds emerged as dominant land vertebrates in the
age of new life.
EXTINCTIONS ARE PART OF THE LIFE PROCESS ON
EARTH: BACKGROUND EXTINCTIONS
•  Extinction may seem catastrophic.
but over the grand sweep of life on
Earth, extinction is part of the process
of life..
•  Extinctions occur continually,
generating a "turnover" of the species
living on Earth. This normal process
is called background extinction.
•  Sometimes, however, extinction
rates rise suddenly for a relatively
short time a Mass extinctions
takes place leaving empty niches
left which allows diversification of
life on Earth.
HOW LONG DOES IT TAKE FOR A PLANET TO
RECUPERATE??
• 
Generally, biodiversity recovers 5 to 10 million years after the
extinction event. In the most severe mass extinctions it may take
15 to 30 million years.
•  Weedy (opportunistic) species: ability to reproduce quickly,
disperse widely, live in a variety of habitats, establish a
population in strange places, succeed in disturbed ecosystems
and resist eradication once established.
•  Fungus
•  Lichens
•  ferns
LIFE AND MASS EXTINCTIONS
•  There is the possibility that there may not have
been continuity of life. So the 'life' identified in
the Isua Greenland (sediments 3.8 billion years
ago or in Western Australia 3.5 billion years ago)
may not be an ancestor of you or me.
•  It's possible this life was destroyed and life had
to start again somewhere else at a later stage.
MANY QUESTIONS REMAIN
•  Why do mass extictions happen?
•  Do mass extinctions happen on a
cycle?
•  Can a mass extinction happen again?
Stromatolites Today: have lived for 3.5 Bya
THE VOYAGE BEGINS