Terrestrial Worlds of Solar Systems - Space and Space Travel | ESS 102, Study notes of Environmental Science

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N otes • “H ow to Reference D ocum ent” for papers now online • W ater Rocket Launches today and tom orrow • Papers due D ec3/4 • Test 3 D ec7 (study guide w ill be online on Fri) T errestrial W orlds of the S olar S ystem : Relevant w ebsites: http://en.w ikipedia.org/w iki/Terrestrial_planets http://w w w .nineplanets.org/ Tidally Locked V enus O rbit 117 Earth days= 1 V enus solar day 243 Earth days= 1 V enus sidereal day (360 degree rotation around its axis) 225 Earth days = V enus orbital period around Sun N ight/day Tem p difference m oderated greatly by greenhouse effect Tidally Locked M oon O rbit O rbital Period = Rotation Period = 27.3 Earth D ays W e alw ays see sam e side of m oon from Earth T he M oon: • The M oon doesn’t qualify as a planet, and it is the sm allest of the m ajor terrestrial bodies. • It is the only natural satellite of a terrestrial body and both its origins and evolution are unique. • The lack of Iron is a sym ptom of how w e now believe the m oon form ed. • In a large im pact event betw een the Earth and a M ars-sized protoplanet. W here did Earth’s w ater com e from ? Tw o possible sources: 1. O utgassing of w ater vapor from surface condensed in liquid w ater 2. Com ets colliding w ith Earth during first 500 m illion years of solar system W e don’t know which source was dom inant! M ars: • M ars has generated m ore interest than any other terrestrial w orld. • M ars is the m ost studied object in the solar system after the m oon (barely). • It is a study in contrasts, w ith m oon-like features but evidence of a m ore Earth-like past. • This past has m any scientists m ore interested in w here M ars has been than w here it is, w hich is too bad. G eology and E volution: • Like m ost objects in the solar system , M ars is a study in extrem es. • The m artian interior is sim ilar to other terrestrial bodies. • How ever, it’s sm aller relative size (about 11% the m ass of the Earth) seem s to have contributed to it largely cooling since its form ation. • The topography of M ars suggests a unique history. • The North is low er and younger. • The South is older and higher. T he T harsis R idge: • The dom inant features on M ars are all related to its m ost obvious form of geologic activity. • The Tharsis ridge and another sm aller region (the Elysium planitia) w ere form ed from a m antle plum e. • There are m antle plum es on the Earth (Iceland and Haw aii), but the crustalplates m ove o ver them , lim iting the size of the volcanos. T he V alles M arineris: • To the East of the Tharsis ridge is the longest channel system in the solar system . • The Valles M arineris is m ore than 3000 km long (as w ide as the continental USA). • Its depth reaches 8 m iles. • Valles M arineris is a rift valley sim ilar to regions like the Red Sea on Earth. • Despite appearances the Valles M arineris w as not form ed by w ater. It is there because the w eight of the Tharsis Ridge on the rest of the crust caused a failure • This show s that M ars has never had plate tectonics. A W et E arly M ars? • A look at the m odern M artian surface show s signs that w ateronce flow ed there. M ars Earth • But flow s do not m ean that open w ater existed on the surface… . Sum m ary of terrestrial planets From A rny, 1998 G as G iant P lanets and T heir S atellites: Jovian Planets – A Brief Inventory: The largest planets in the solar system are the ones w e are least likely to visit in person. • The prim ary distinguishing feature of Jovian (or gas giant) planets is their lack of a surface. • Their com position is sim ilar to the Sun (m ostly H and He, w ith sm all am ounts of everything else). This is a rem nant of how they form ed. • Their densities are also sim ilar to the Sun (1 gm cm -3) • They are also flu id b o d ies like the Sun, w hich m eans that they rotate d ifferen tially. • W here the clouds form is a function of tem perature and pressure in the planet’s atm osphere. • Different colors probe different levels in the atm osphere! Clouds and M apping the Jovian Planets. The depth of the cloud and aerosol layers is determ ined by the tem perature and pressure profiles of the atm osphere. • Jupiter is the w arm est of the Jovian planets, and it’s clouds are at the highest altitudes. This enhances their contrast. • W atching the m ovem ent of the clouds tells us about the underlying convection patterns of the atm osphere. • The banded structure show s zo n es an d b elts of convective m otion in the atm osphere • O n Saturn the clouds are deeper and the contrast low er. • Uranus and Neptune have clouds very deep and very few visible features in their atm ospheres (especially Uranus). Cooling Dow n: The interiors of the Jovian planets are very hot (5,000-20,000 K). • Unlike the terrestrial planets, w hich are shielded by their crust, the heat escapes from gas giants via co n vectio n, just like on the Sun. • If this happened on Earth, it w ould be a cold rock today. • All the Jovian planets produce m ore energy than they receive from the Sun except Uranus. Cooling Dow n: The interiors of the Jovian planets are very hot (5,000-20,000 K). • Unlike the terrestrial planets, w hich are shielded by their crust, the heat escapes from gas giants via co n vectio n, just like on the Sun. • If this happened on Earth, it w ould be a cold rock today. • All the Jovian planets produce m ore energy than they receive from the Sun except Uranus. So w here does the energy com e from ? • Partly it com es from the initial form ation of the planets. For the m uch cooler Jovian w orlds (50-150 K), it takes longer for this heat to escape. • Som e energy is generated by on-going differentiation, w here heavy m aterial falls to the center of the planet. • And yet m ore energy com es from sim ple contraction. A cooler interior com presses m ore. W hat Happened to Uranus? Uranus is one of the strangest objects in the solar system . • It’s rotational axis is tilted alm ost 90°from the norm into the plane of its orbit. This m eans that its seasons are the m ost extrem e of any planet. • Uranus’ m agnetic field is offset from its center and tilted by 59°. • Uranus produces less heat than the other jovian planets.