1. Life in our Solar System

2. 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.”

3. Formation 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

4. Life on Earth Life appears on Earth soon after heavy bombardment ends in the form of marine fossils Oldest fossil 3.5 Billion years

5. Life 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

6. Life on Earth ~540 Million years ago, sudden appearance of animals during Cambrian explosion – Nearly complete disappearance at ~500 My ago

7. Life 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

8. Requirements of Life Think-Pair Share Activity: 1.Water 2.Access to appropriate raw materials 3.Energy source (solar or chemical)

9. Helpful 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?)

10. Life 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

11. Mercury Daytime temp: 800 °F Nighttime temp: -300 °F No liquid water Magnetosphere less than 1/1000 of Earth No plate tectonics No atmosphere

12. Venus 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

13. Moon 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

14. Mars 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)

15. Mars Past Unknown temperatures Liquid water at the surface Strong magnetosphere No plate tectonics Thicker atmosphere (similar to Earth)

16. Mars In Detail Evidence for Past Water: 1.Gullies - Water flow down crater walls

17. Mars In Detail Evidence for Past Water: 1.Gullies 2.Tributaries - Caused by rain?

18. Mars In Detail Evidence for Past Water: 1.Gullies 2.Tributaries 3.Flow Channels - Carved by huge amounts of flowing water?

19. Mars In Detail Evidence for Past Water: 1.Gullies 2.Tributaries 3.Flow Channels 4.“Blueberries”

20. Mars In Detail Evidence for Past Water: 1.Gullies 2.Tributaries 3.Flow Channels 4.“Blueberries” 5.“White powder” -Pure silicon dioxide -Ancient hot spring?

21. Jupiter Gaseous surface – Not solid Huge magnetosphere High radiation environment

22. Jupiter’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

23. Europa In Detail Europa Evidence points toward deep subsurface ocean Very thin atmosphere Possible plate tectonics In Jupiter’s magnetosphere

24. Jupiter’s Moons Callisto About the size of Mercury Possible thin subsurface ocean Very thin atmosphere No plate tectonics In Jupiter’s magnetosphere

25. Saturn Gaseous surface – Not solid Large magnetosphere High radiation environment Very similar to Jupiter

26. Saturn’s Moons Titan 1.5x size of the Moon Possible thin subsurface ocean Thick atmosphere Extremely cold (-290 °F) Weathering and erosion

27. Titan In Detail Titan Surface lander Huygen’s probe Atmosphere possibly similar to ancient Earth’s Methane lakes Cryo-volcanism (volcanoes of water)

28. Saturn’s Moons Enceladus 1/7 size of Earth’s Moon Possible subsurface water (cryo-volcanism) No atmosphere Extremely cold

29. Outer planets Uranus, Neptune, Pluto – Very, very, very cold – Likely no liquid water – No atmosphere – No plate tectonics