Location-Location-Location

• Defining aspect – region where we neither freeze nor boil the planet’s oceans– Campfire Analogy

• Drifting HZ: 1-3 billion years and Earth will be outside this zone

Temperature Distance to the sun (campfire), Atmosphere, Solar output

Atmosphere CO2-silicate (rock) cycle – as temps warm increased weather removes more CO2 from the atmosphere – negative feedback cycle

UV Shield from harmful radiation – O3

Constant Conditions Orbits, seasons, etc.

Solid/Liquid core • Metal core – magnetic field protects surface from radiation from space

• Liquid core – radioactive heat from core, mantle and crust fuels tectonic activity.

Elements of Life CHNOPS

6 most abundant elements in humans

Land Mass Tectonics – provide/recycle elements.

Habitat, Carbon cycling (weathering)

Water Liquid form

Not too many extinctions

Protection from Asteroids - Jupiter

Jupiter is our solar system’s largest planet. And it creates both good and bad conditions for earthly life. On the one hand, Jupiter’s powerful gravity prevented space rocks orbiting near it from coalescing into a planet, and that’s why our solar system has an asteroid belt. Today, Jupiter’s gravity continues to affect the asteroids – only now it nudges them toward the sun, where they have the possibility of colliding with Earth.

On the other hand, Jupiter’s gravity also protects us. Long-period comets enter the solar system from its outer reaches. Jupiter’s gravity slings most of these fast-moving ice balls out of the solar system before they can get close to Earth. So long-period comets are thought to strike Earth only about every 30 million years. Without Jupiter nearby, long-period comets would collide with our planet up to 1000 times more frequently.

Earth’s Surface Temperature Sans Atmosphere

• T = (S* (1-a) / r2 / 4 / SB)1/4

– S is the solar constant in Watts m-2 ~ 1367• The actual direct solar irradiance at the top of the

atmosphere fluctuates by about 6.9% during a year due to the Earth's varying distance from the Sun

• 1.412 kW/m² in early January • 1.321 kW/m² in early July a is Earth’s albedo ~ 30%

– r is the average Earth-Sun distance = 1 AU– SB is Stefan-Boltzmann's constant = 5.67e-08

• The result is 254.86 K – what is that in Celsius? -18°C– In Fahrenheit? 0°F

Protection from Asteroids - Jupiter• Jupiter is our solar system’s largest planet.

– It creates both good and bad conditions for earthly life. • On the one hand, Jupiter’s powerful gravity prevented space rocks

orbiting near it from coalescing into a planet, and that’s why our solar system has an asteroid belt.

• Today, Jupiter’s gravity continues to affect the asteroids – only now it nudges them toward the sun, where they have the possibility of colliding with Earth.

• On the other hand, Jupiter’s gravity also protects us. Long-period comets enter the solar system from its outer reaches. Jupiter’s gravity slings most of these fast-moving ice balls out of the solar system before they can get close to Earth. So long-period comets are thought to strike Earth only about every 30 million years. Without Jupiter nearby, long-period comets would collide with our planet up to 1000 times more frequently.