A Walking Tour of the Solar System Lou Mayo, NASA, Goddard

How Did the Solar System Form?

0.4AU 0.7AU 1AU 1.5AU 5AU 10AU 20AU 30AU -185C/370C 600C -70C /50C -161C/0C -153C -180C -210C -210C

Mercury Density = 5.4 cm-3 implies a metal-rich interior, perhaps 70% iron-nickel and 30% silicate Because of the relatively large density of Mercury, the core must occupy a larger fraction of the planet than is the case for the Earth. Mercury is smaller than the Earth, it should have cooled more rapidly and its solid inner core should be an even larger fraction of the radius of the liquid core than is the case for the Earth. Day and night side temperatures vary greatly! Tenuous oxygen, sodium, helium, and potassium atmosphere is created by solar wind blasting particles off the surface which quickly escape into space

Venus Venus weak magnetic field is an induced field from direct interaction between the solar wind and the ionosphere. Equator to pole temperatures vary by only a couple of degrees Thick CO2 and H2SO4 atmosphere obscures the surface in visible light The solar wind and high atmospheric temperatures contributed to the almost complete loss of any water. Size and Mass ~ Earth’s Magellan Radar Images show evidence for vulcanism

Earth WATER HEAT ATMOSPHERE LIFE MAG FIELD CIRCULAR ORBIT

Mars - Predictor of Earth’s Future? Mars no longer has a dynamo to generate a global magnetic field. Strong localized magnetic fields imbedded in the crust provide some protection for the atmosphere against disassociation and mass loss But Mars probably lost most of its atmosphere and oceans from solar wind particle collisions Dead Volcanos CO2, H2O Ice caps River beds 2 Moons Dust Storms Thin CO2 atmosphere

Exploring Mars

Jupiter and its Moons Lou Mayo NASA GSFC

Io Orbits within intense Jovian radiation belt Jovian magnetosphere strips away about 1 ton per second of volcanic gases and other materials. Causes auroras on Jupiter Most volcanic body in Solar Systen Sulfurous plumes reach over 500 kilometers. Generates electric current (3M amperes that flows along Jovian magnetic field

Europa Must occasionally be resurfaced by tidal warming of its global ocean. Conditions under ice crust may be suitable for life. Completely covered with a frozen ocean 100 kilometers thick. Few craters are visible. Surface ice has been resurfaced, fractured, and rearranged in "recent" history.

Old, dark and cratered terrain. Grooved with few craters terrain. Thick water mantle which may have behaved like the Earth's mantle. Crust thickened more slowly than Callisto's. Slightly larger size yields greater heat retention. Ganymede was closer to Jupiter -- which was very warm initially from the heat of its formation. May have experienced some tidal heating. Active geology persisted for the first billion years until the crust thickened to the point that it could no longer be fractured through to the water mantle. Ganymede

Callisto Callisto is heavily cratered and shows now signs of significant ice volcanism or tectonism on its surface. Callisto's crust formed early and thickened quickly. Callisto formed farther from Jupiter where the "proto-jovian" nebula was cooler.

Cassini Saturn March 27, million miles

Composite Infrared Spectrometer (CIRS)

Titan

Latest Cassini Images of Titan

Titan’s surface is visible only in certain infrared frequency bands and in radar SS objects look different in different wavelengths of light

Uranus The Uranian magnetic field is tilted 60 deg. from its rotation axis The magnetotail is twisted by the planet's rotation into a long corkscrew shape behind the planet. Tipped on its side 11 Known Rings Magnetic Field Aurora H2, He, CH4, NH3 15 moons

Neptune Magnetic field generated by motions of conductive material (probably water) in its middle layers. Tilted (47 deg) Auroras occur over wide regions of the planet 700mph winds detected 3 rings - composed of dark material 8 moons (7 + Triton) H2, He, CH4, NH3

Pluto

Comets Comet tails provided the first evidence for a solar wind Composed of water and CO2 ice, NH3, silicates, organics Dust tail Ion tail Comet Hale Bopp Originate outside the orbit of Pluto in Kuiper belt and Oort cloud Likely a prime source of water on Earth and perhaps amino acids

Heliosphere (Where the solar system ends)