Tori M. HoehlerNASA 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 ChemistryEvolution and Continuity

Although we often thinkof them in

cataclysmic terms, impacts

and volcanoes are tied to the story of life in both negative and

positive ways.

Heavily Cratered SurfaceSuggests Little Evidence

of Recent Volcanismon Mercury

Radar Images SuggestRecent Volcanism

on Venus

Active RockVolcanismon Earth

Little Evidenceof Volcanismon The Moon

Mars clearly hadvolcanism once, buthow active is it now?

Sulfur Volcanism on Io

IceVolcanismon Enceladus?

Liquid NitrogenVolcanismon Triton?

Volcanism is a way of transporting heatby 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

Vent Biology Origin of Life Chemistry?

Atmospheric (Stratospheric!) Chemistry

Ocean Composition Crustal Alteration

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 super-heated water (a great solvent, remember?)

= Salty Ocean

HydrothermalAlteration

+

Rock Weathering(Bases)

Volcanic Outgassing(Acids)

+

A chemically differentiated planetis 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

year

century

million yr.

billion yr.

ten thousand yr.

100 millionmillion10,00010010.01

Hiroshima

Tunguska

K/T

TNT equivalent yield (MT)

Global catastrophe

Tsunami danger

(Credit: D. Morrison)

Size matters – and so does time

Terrestrial ImpactFrequency

Impact typematters, too

Impacts deliver energy

(Sometimes a little,Sometimes a lot . . . )

Heat energy

TitanEarth

Apply heat here to maketemporarily inhabitable?

Apply heat here to maketemporarily uninhabitable

Ejection of MaterialKinetic energy

Release from Impacted Planet?Suspension in atmosphere?

Impacts deliver materials and chemistryfrom elsewhere in the solar system

cometsasteroids

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

(Image credit: David Deamer)

Impacts can deliver organic chemicals – possible importance for origins of life?

Organics found in the Murchison

meteorite form cell-like vesicles when they contact liquid

water

EEffects of Impacts on

Established Life:

Impact Frustration of

Life

D’oh

year

century

million yr.

billion yr.

ten thousand yr.

100 millionmillion10,00010010.01

Hiroshima

Tunguska

K/T

TNT equivalent yield (MT)

Global catastrophe

Tsunami danger

(Credit: D. Morrison)

Terrestrial ImpactFrequency

“Armageddon” Impact(Texas-sized!)

“Catastrophic” depends on who you are and where you live . . .

“Catastrophic” depends on who you are and where you live . . .

Temperature (°C)

Dep

th (

km)

2

0

200

1

1000

Geotherm

al Gradient

Surface-Sterilizing Impacts

(Sleep & Zahnle, 1998)

Habitable

Heat-Sterilized

Impact Heating

Effects of Impacts on

Established Life:

Interplanetary Transfer of Life?