Post on 20-Jan-2016
IntroductionIntroduction
The Solar System is ordered in that the The Solar System is ordered in that the planets form two main families: planets form two main families:
• solid rocky inner planets andsolid rocky inner planets and
• gaseous/liquid/icy outer planetsgaseous/liquid/icy outer planets
From observations, astronomers believe From observations, astronomers believe the Solar System formed some the Solar System formed some 4.5 4.5 billion years agobillion years ago out of the collapse of a out of the collapse of a huge cloud of gas and dusthuge cloud of gas and dust
Components of the Solar SystemComponents of the Solar System
The SunThe Sun
• The Sun is a star, a ball of incandescent gas The Sun is a star, a ball of incandescent gas whose output is generated by nuclear whose output is generated by nuclear reactions (fusion) in its corereactions (fusion) in its core
• Composed mainly of H (71%) and He (27%), Composed mainly of H (71%) and He (27%), and traces of nearly all the other elementsand traces of nearly all the other elements
• It is the most massive object in the Solar It is the most massive object in the Solar System – 700 X the mass of the rest of the System – 700 X the mass of the rest of the Solar System combinedSolar System combined
Components of the Solar SystemComponents of the Solar System
The PlanetsThe Planets
• Planets shine primarily by reflected Planets shine primarily by reflected sunlightsunlight
• Orbits are Orbits are almostalmost circular lying in circular lying in nearly the same plane – Pluto is the nearly the same plane – Pluto is the exception with a high inclination exception with a high inclination (17°) of its orbit(17°) of its orbit
Components of the Solar SystemComponents of the Solar System
The PlanetsThe Planets• All the planets travel counterclockwise All the planets travel counterclockwise
around the Sun (as seen from high around the Sun (as seen from high above the Earth’s north pole)above the Earth’s north pole)
• Six planets Six planets rotaterotate counterclockwise; counterclockwise; Venus rotates clockwise (retrograde Venus rotates clockwise (retrograde rotation), and Uranus and Pluto appear rotation), and Uranus and Pluto appear to rotate on their sidesto rotate on their sides
Components of the Solar SystemComponents of the Solar System
Two types of planetsTwo types of planets• Inner planetsInner planets
–Mercury, Venus, Earth, MarsMercury, Venus, Earth, Mars–Small, rocky (mainly silicon and Small, rocky (mainly silicon and
oxygen) bodies with relatively thin oxygen) bodies with relatively thin or no atmospheresor no atmospheres
–Also referred to as Also referred to as terrestrial terrestrial planetsplanets
Components of the Solar Components of the Solar SystemSystem
Outer (Jovian) planetsOuter (Jovian) planets• Jupiter, Saturn, Uranus, Neptune, Jupiter, Saturn, Uranus, Neptune,
and and Pluto*Pluto*• Gaseous, liquid, or icy (HGaseous, liquid, or icy (H22O, COO, CO22, ,
CHCH44, NH, NH33) composition, do not have ) composition, do not have a well-defined surfacea well-defined surface
• Thick atmospheresThick atmospheres• Ring systemsRing systems• Many moonsMany moons
Components of the Solar SystemComponents of the Solar SystemBode's LawBode's Law• Predicts the spacing of the planets in the Predicts the spacing of the planets in the
Solar System. Solar System.
• The relationship was first pointed out by The relationship was first pointed out by Johann Titius in 1766 Johann Titius in 1766
• Formulated as a mathematical expression Formulated as a mathematical expression by J.E. Bode in 1778. by J.E. Bode in 1778.
• Lead Bode to predict the existence of a Lead Bode to predict the existence of a planet between Mars and Jupiter (we now planet between Mars and Jupiter (we now recognize as the asteroid belt).recognize as the asteroid belt).
Components of the Solar SystemComponents of the Solar SystemAsteroids and CometsAsteroids and Comets• AsteroidsAsteroids are rocky or metallic are rocky or metallic
bodies ranging in size from a few bodies ranging in size from a few meters to 1000 km across (about 1/10 meters to 1000 km across (about 1/10 the Earth’s diameter)the Earth’s diameter)
• CometsComets are icy bodies about 10 km are icy bodies about 10 km or less across that can grow very long or less across that can grow very long tails of gas and dust as they near the tails of gas and dust as they near the Sun and are vaporized by its heatSun and are vaporized by its heat
Components of the Solar SystemComponents of the Solar System
Locations of Comets and AsteroidsLocations of Comets and Asteroids
• Most asteroids are inMost asteroids are in asteroid beltasteroid belt between Mars and Jupiter indicating that between Mars and Jupiter indicating that these asteroids are the failed building-these asteroids are the failed building-blocks of a planetblocks of a planet
Components of the Solar SystemComponents of the Solar System
Locations of Comets and AsteroidsLocations of Comets and Asteroids
• Most comets orbit the Sun far beyond Most comets orbit the Sun far beyond Pluto in thePluto in the Oort cloudOort cloud, , a spherical shell a spherical shell extending from 40,000 to 100,000 AU extending from 40,000 to 100,000 AU from the Sunfrom the Sun
• Some comets may also come from a disk-Some comets may also come from a disk-like swarm of icy objects that lies beyond like swarm of icy objects that lies beyond Neptune a region called theNeptune a region called the Kuiper BeltKuiper Belt
•It is second to Pluto in eccentricity
•It takes 88 days to orbit the Sun
•So if you are 10 years old on Earth, you would be 42 years old on Mercury!
•Mercury’s rate of rotation is 59 Earth days (tidal lock w/ sun)
•Combined effect: 1 solar day = 176 Earth days
•Axial tilt = 0°
•Mercury has no atmosphere to speak of
•It does trap some H and He from the solar wind
•Extreme temperatures: 700°C daytime and –100°C nighttime
•Ancient surface: many impact craters (like our moon)
•Gravity = 38% of Earth’s•If you weighed 100 pounds on Earth, you would weigh 38 pounds on Mercury
•There are inter-crater plains
•This indicates there once was volcanic activity on Mercury
•Presence of scarps suggest the crust cooled, shrank and split
•Most prominent geologic feature: Caloris Basin
•It is a large bull’s-eye crater caused by the impact of a large asteroid
•Mariner 10 flew by Mercury 3 times in 1974 and 1975
•Future: MessengerMessenger – launched in the summer of 2005; flew by last January (’08) and September; Goes into orbit 2011
http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php
The Surface of Venus
•It takes 223 days for Venus to orbit the Sun
•If you were 10 years old on Earth, you would be 16 years old on Venus
•Since its orbit lies within Earth’s, it is called inferior
•The rate of rotation is 243 days
•It also shows retrograde rotation
•So the Sun rises in the west and sets in the east
•Atmospheric Pressure is 90 times that of Earth
•The clouds are made of sulfuric acid
•The atmosphere is almost entirely made of CO2
•Due to the high CO2 content, there is a runaway greenhouse effect
•Temperatures are >900°F at all times
•We learned of the greenhouse effect from Venus studies
•Venus has two “continents” – Ishtar and Aphrodite Terras
•These “continents” rise above the rest of the terrain
•It has a “younger” surface – it has undergone some erosion, etc.
•Surface gravity is 91% that of the Earth’s
•If you weighed 100 pounds on Earth, you would weigh 91 pounds on Venus
•Evidence of Volcanism exists
•There are shield volcanoes•Volcanic flows imaged by the Magellan spacecraft
•Lightning was detected by the Venera spacecraft
Venera: Venera: •16 missions (1960’s – 16 missions (1960’s –
’80’s)’80’s)•8 were landers8 were landers
Magellan:Magellan:•Orbiter (1990 – ‘94)Orbiter (1990 – ‘94)•Radar mapped sfcRadar mapped sfc
•It takes Mars 1.88 Earth years to orbit the Sun
•If you were 10 years old on Earth, you would be about 5 ½ years old on Mars
•A day on Mars is 24.6 hours•Its axial tilt is 24°•Mars has seasons just like the Earth, but last twice as long
•Ice caps on Mars come and go with the seasons; made mostly of dry ice
•The atmosphere on Mars is very thin
•Atmospheric pressure is only 0.1 of Earth’s
•It is composed mainly of CO2
•No ozone = sterilization of surface
Mars has 2 moons:•Phobos (means fear)•Deimos (means panic)•Did not form when Mars formed – captured by gravity
•Northern Hemisphere – rolling volcanic plains
•Southern Hemisphere – heavily cratered highlands
•Mars appears red due to iron oxide rich soil
•Largest volcanoes in the solar system are found on Mars
•The largest of these is Olympus Mons– It measures 700 km across its base and is 25 km high
– It is an example of a shield volcano
Valles Marineris•A.K.A. Mariner Valley•4000 km long•120 km across at it widest•7 km deep
Two types of flow features:•Runoff channels•Outflow channelsOther evidence:•Sub-surface outflows•Erosional evidence
•Mariner (fly-by)•Viking (landers)•Mars Pathfinder (Lander and rover)
•Mars Global Surveyor
Mars Exploration Rovers:•Spirit•Opportunity•Both landed on Mars in early 2004
•Both are still working; Spirit is stuck!
Phoenix Lander•Landed in 2008•3-month mission turned into 5-months
•Search for water, life