Tori M. Hoehler
NASA Ames Research Center
POP!
BIG BANG
A few things have to happen,
and a few conditions must be
met, to get from there to here.
Understanding what these
“things” and “conditions” are,
and how frequently they occur,
is astrobiology
The Road to Life?
Habitability
Origin of Life Chemistry
Evolution and Continuity
Although we
often think
of them in
cataclysmic
terms, impacts
and volcanoes are
tied to the story
of life in both
negative and
positive ways.
Heavily Cratered Surface
Suggests Little Evidence
of Recent Volcanism
on Mercury
Radar Images Suggest
Recent Volcanism
on Venus
Active Rock
Volcanism
on Earth
Little Evidence
of Volcanism
on The Moon
Mars clearly had
volcanism once, but
how active is it now?
Sulfur Volcanism on Io
IceVolcanism
on Enceladus?
Liquid Nitrogen
Volcanism
on Triton?
Volcanism is a way of transporting heat
by moving material (when radiation or
conduction just aren’t enough)
Bigger bodies cool more slowly, and
may have more active or longer lasting
volcanism as a result
Heat is transported by
moving hot material from
place to place – the
material itself may be of
great importance
On a differentiated planet, the hot material may
come from a chemically different region
Volcanoes Bring Mantle Chemistry to the Surface
Atmospheric (Stratospheric!) Chemistry
Ocean Composition
Vent Biology
Crustal Alteration
Origin of Life Chemistry?
Creation of Atmosphere
(example: Io)
Introduction of H2O and CO2
(oceans and greenhouse)
Introduction of Sulfur and other “heteroatoms”
(weather, salt balance, weathering)
Acids
Much of Earth’s “volcanic”
activity occurs at the ocean bottom
Submarine volcanism
is often manifested by
transport of superheated water (a great
solvent, remember?)
+
Rock Weathering
(Bases)
Volcanic Outgassing
(Acids)
+
Hydrothermal
Alteration
= Salty Ocean
A chemically differentiated planet
is like a battery . . .
=
Hydrothermal vents transport chemical
energy (they tap the Earth’s battery), and this
can be harnessed by some microorganisms
Impacts . . .
Like volcanoes, impacts transport
“stuff” from place to place
Size matters – and so does time
Hiroshima
year
Terrestrial Impact
Frequency
Tunguska
century
Tsunami
danger
ten thousand yr.
Global
catastrophe
million yr.
K/T
billion yr.
0.01
(Credit: D. Morrison)
1
100
10,000 million 100 million
TNT equivalent yield (MT)
Impact type
matters, too
Impacts deliver energy
(Sometimes a little,
Sometimes a lot . . . )
Heat energy
Earth
Titan
Apply heat here to make
temporarily uninhabitable
Apply heat here to make
temporarily inhabitable?
Kinetic energy
Suspension in atmosphere?
Ejection of Material
Release from Impacted Planet?
Impacts deliver materials and chemistry
from elsewhere in the solar system
asteroids
comets
Volatiles are
“frozen out” in
the cold outer
reaches of the
solar system, and
can be delivered
to the inner solar
system by
comets
Methane and nitrogen ice coat the surface of Triton
Impacts can deliver organic chemicals –
possible importance for origins of life?
Organics found in
the Murchison
meteorite form celllike vesicles when
they contact liquid
water
(Image credit: David Deamer)
E Effects
of
Impacts on
Established Life:
Impact
Frustration of
Life
D’oh
Hiroshima
year
Terrestrial Impact
Frequency
Tunguska
century
Tsunami
danger
ten thousand yr.
Global
“Catastrophic” depends on who you are and where
you live . . .
catastrophe
million yr.
“Armageddon” Impact
(Texas-sized!)
K/T
billion yr.
0.01
(Credit: “Catastrophic”
D. Morrison)
1
100
10,000 million 100 million
yield
dependsTNT
on equivalent
who you are
and(MT)
where you live . . .
Surface-Sterilizing Impacts
0
Depth (km)
Heat-Sterilized
1
Habitable
2
0
100
Temperature (°C)
200
(Sleep & Zahnle, 1998)
Effects of
Impacts on
Established Life:
Interplanetary
Transfer of Life?