Jupiter Versus the Earth: Composition & Structure

JUPITER VERSUS THE EARTH: COMPOSITION & STRUCTURE Randy Gladstone Southwest Research Institute, San Antonio TX 78238

NASA Space Science Workshop Explore! Jupiter’s Family Secrets May 4-5, 2010 Springfield, MO

Solar System Architecture Warm

Solar Nebula Temperature

Rock

Cold

Ice + Rock

Frost Line

Pluto

Neptune

Ice Dwarf

Uranus

Saturn

Giant Planets

Jupiter

Sun

Mercury Venus Earth Mars

Terrestrial Planets

How Do We Know What’s Inside a Planet? • For planets other than Earth, there are only a few ways to determine what’s inside • From the mean density (the total mass divided by the total volume) it is possible to constrain the internal structure based on models of likely composition • From the gravity field (determined by watching how satellites orbit) it is possible to tell more about how the mass inside a planet is distributed (e.g., whether it has a core, etc.)

• For Earth, most of our knowledge of the interior come from the study of seismic waves (as are generated by large earthquakes)

Terrestrial Planet Interiors

Venus (5250 kg/m3)

Mars (3940 kg/m3)

Earth (5520 kg/m3)

Mercury (5420 kg/m3)

Earthquake Waves Probe Earth’s Interior

Inside Earth The major regions in the Earth are the crust, mantle, outer core, and inner core: • The outer crust is relatively thin (~30 km thick in the continents and ~5 km thick in the oceans) • The mantle is ~3000 km thick (almost halfway to the center of the Earth) and is made of a dense rock called peridotite; it has plastic-like properties and its slow overturning drags along the crust, causing plate tectonics (i.e., continental drift) • The liquid outer core is 2300 km thick and is a mixture of iron (90%) and nickel (10%); motions in the liquid give rise to the Earth’s magnetic field • The solid inner core at Earth’s center has a 1200 km radius and is made of iron (90%) and nickel (10%); the temperature at the Earth’s core is ~5700 K and the pressure there is ~3.6 million atmospheres

Earth

Jupiter (1310 kg/m3)

Saturn Uranus Neptune (690 kg/m3) (1190 kg/m3) (1660 kg/m3)

Jupiter Interior vs. Earth Interior

Inside Jupiter Jupiter is still cooling off (and contracting) from its formation 4.5 billion years ago (it emits 1.7 times as much energy as it receives from the Sun)! • The atmosphere (the outermost ~5000 km at