Life in our Solar SystemLife in our Solar System

What is the definition of ‘Life’?What is the definition of ‘Life’?

“A collection of molecules that can undergo metabolism, be able to grow, respond to stimuli, reproduce, and adapt to their environments through natural selection.”

Formation of EarthFormation of Earth

• Earth was formed ~4.5 Billion years ago from smaller planetesimals crashing together.– Giant impact forms Moon ~4.4 Billion years ago– Earth continually bombarded by giant impactors

until 3.8 Billion years ago

Life on EarthLife on Earth

• Life appears on Earth soon after heavy bombardment ends in the form of marine fossils

• Oldest fossil 3.5 Billion years

Life of EarthLife of Earth

• Activity stays quiet until large amounts of stromatolite fossils found between 2.7 Billion years ago and 540 Million years ago

• Caused by sudden appearance of oxygen

Life on EarthLife on Earth

• ~540 Million years ago, sudden appearance of animals during Cambrian explosion– Nearly complete disappearance at ~500 My ago

Life on EarthLife on Earth

• 500 My - 250 My: animals getting substantially larger– Sharks, amphibians, reptiles

• 250 – 65 My: Age of the dinosaurs• 65 My – present: Age of the mammals– ~ 1 My ago: humans begin showing up

Requirements of LifeRequirements of Life

Think-Pair Share Activity:1.Water2.Access to appropriate raw materials3.Energy source (solar or chemical)

Helpful Conditions For LifeHelpful Conditions For Life

• Plate tectonics– Recycle nutrients– Allow for continents– Help maintain constant temperature

• Magnetosphere– Deflects dangerous radiation from Sun

• Atmosphere– Helps regulate temperature (carbon dioxide)– Contains oxygen (allows for large life forms?)

Life In Extreme EnvironmentsLife In Extreme Environments

We find microbes living in conditions of boiling water, low moisture (arid), ice, high acidity, high salt, no sunlight, and deep underground

Temp. Range of life on Earth: -5°F to 235°F

MercuryMercury

• Daytime temp: 800 °F• Nighttime temp: -300 °F• No liquid water• Magnetosphere less

than 1/1000 of Earth• No plate tectonics• No atmosphere

VenusVenus

• Daytime temp: 900 °F• No liquid water• Magnetosphere less than

1/1000 of Earth• Possible single plate surface• Thick carbon dioxide

atmosphere with surface pressure ~90 times Earth

MoonMoon

• Daytime temp: 225 °F• Nighttime temp: -245 °F• No liquid water (frozen water

in permanently shadowed craters)

• Within Earth magnetosphere• No plate tectonics• No atmosphere

MarsMars

Presently• Daytime temp: 0 °F• Nighttime temp: -180 °F• No liquid water found (frozen

water at the poles)– Possible underground water

• No magnetosphere• No plate tectonics• Thin atmosphere (1/100 of

Earth)

MarsMars

Past• Unknown temperatures• Liquid water at the surface• Strong magnetosphere• No plate tectonics• Thicker atmosphere (similar

to Earth)

Mars In DetailMars In Detail

Evidence for Past Water:1.Gullies

- Water flow down crater walls

Mars In DetailMars In Detail

Evidence for Past Water:1.Gullies2.Tributaries

- Caused by rain?

Mars In DetailMars In Detail

Evidence for Past Water:

1.Gullies2.Tributaries3.Flow Channels

- Carved by huge amounts of flowing water?

Mars In DetailMars In Detail

Evidence for Past Water:1.Gullies2.Tributaries3.Flow Channels4.“Blueberries”

Mars In DetailMars In Detail

Evidence for Past Water:1.Gullies2.Tributaries3.Flow Channels4.“Blueberries”5.“White powder”

- Pure silicon dioxide- Ancient hot spring?

JupiterJupiter

• Gaseous surface– Not solid

• Huge magnetosphere• High radiation environment

Jupiter’s MoonsJupiter’s Moons

Europa• Size of the Earth’s Moon • High radiation environment

at surface• Thin atmosphere• Evidence for water• Plate tectonics?• In Jupiter’s magnetosphere

Europa In DetailEuropa In Detail

Europa• Evidence points toward deep

subsurface ocean• Very thin atmosphere• Possible plate tectonics• In Jupiter’s magnetosphere

Jupiter’s MoonsJupiter’s Moons

Callisto• About the size of Mercury• Possible thin subsurface

ocean• Very thin atmosphere• No plate tectonics• In Jupiter’s magnetosphere

SaturnSaturn

• Gaseous surface– Not solid

• Large magnetosphere• High radiation

environment• Very similar to Jupiter

Saturn’s MoonsSaturn’s Moons

Titan• 1.5x size of the Moon• Possible thin subsurface

ocean• Thick atmosphere • Extremely cold (-290 °F)• Weathering and erosion

Titan In DetailTitan In Detail

Titan• Surface lander Huygen’s

probe• Atmosphere possibly similar

to ancient Earth’s• Methane lakes• Cryo-volcanism (volcanoes of

water)

Saturn’s MoonsSaturn’s Moons

Enceladus• 1/7 size of Earth’s Moon• Possible subsurface water

(cryo-volcanism)• No atmosphere • Extremely cold

Outer planetsOuter planets

• Uranus, Neptune, Pluto– Very, very, very cold– Likely no liquid water– No atmosphere– No plate tectonics