civil service materials: Indian GEOGRAPHY1

THE PLANETS

Mercury
1. Closest planet to the Sun
2. Smallest planet
3. No satellites
Venus
1. Very dense atmosphere
2. Hottest planet (over 400 C)
3. Large amount of greenhouse gases
Earth
1. Hydrosphere unique among rock-based planets
2. Only planet where plate tectonics observed
Mars
1. Atmosphere made mainly of carbon dioxide
2. Red colour comes from iron oxide
3. Geological activity such as volcanoes as recently as 2 million years ago
Jupiter
1. 2.5 times the masses of all other planets combined
2. Composed mainly of hydrogen and helium
3. Great Red Spot in atmosphere created by strong internal heat
4. 63 known satellites. Ganymede, Callisto, Io and Europa show similarities to terrestrial planets such as volcanism and internal heating
5. Ganymede is the largest satellite in the solar system. It is larger than mercury
6. Has planetary ring system
Saturn
1. Extensive ring system
2. Rings made by small particles of water ice clumped together
3. Rings first observed by Galileo
4. Least dense planet in solar system
5. 60 satellites
6. Titan is the only satellite in the solar system with a substantial atmosphere
Uranus
1. Orbits the sun on its side
2. Very cold core, radiates little heat
3. 27 satellites
4. Has planetary ring system
Neptune
1. Smaller in size but more massive and more dense than Neptune
2. 13 known satellites
3. Has planetary ring system

OTHER COMPONENTS

Asteroids
1. Small objects composed of rocky and metallic minerals
2. Small asteroids are called meteoroids
3. Main asteroid belt occupies orbit between Mars and Jupiter
4. Asteroid belt is sparsely populated. Spacecraft routinely pass through belt without incident
5. Ceres is the largest body in the asteroid belt. Classified as a dwarf planet
Comets
1. Small bodies composed of volatile ices
2. Coma of a comet (tail) is observed when proximity to the sun causes the icy particles to sublimate and ionize
3. Hale-Bopp comet was visible to the naked eye for 18 months. It was the most widely observed and brightest comet recorded
Interplanetary medium
1. It Is the interplanetary atmosphere created by the stream of charged particles emitted by the Sun (called solar wind)
2. Aka Heliosphere
3. Stretches out to 100 AU
4. Space weather is created by geomagnetic storms on the Sun’s surface which disturb the heliosphere
5. Earth’s magnetic field prevents solar wind from stripping away the Earth’s atmosphere
Kuiper belt
1. Ring of debris, similar to asteroid belt, but composed mainly of ice
2. Present in the area beyond Neptune
3. Pluto is the largest object in the Kuiper belt

Located in the Milky Way galaxy, a spiral galaxy. Milky Way diameter 100000 light years. Contains about 200 billion stars
Solar System resides in one of the outer arms, called Orion Arm
Sun lies around 25,000 light years from galactic centre. Completes one revolution every 250 million years (aka Cosmic Year)
Closest star is Alpha Centauri triple star system
Largest star close to Sun is Sirius
Closest sun-like star is Tau Ceti
Closest extra-solar planet is Epsilon Eridani b, which orbits the star.r Epsilon Eridani

Venus
1. Ishtar Terra and Aphrodite Terra: two continents on Venus
2. Maxwell Montes: highest mountain on Venus
Mars
1. Adirondack: first rock chosen to be explored by the first Mars rover Spirit in Jan 2004
2. Gusev Crater: crater on Mars, site of landing of the Mars rover Spirit, Jan 2004
3. Sleepy Hollow: circular, shallow depression on Gusev crater
4. Olympus Mons: tallest volcano and mountain in the Solar System. About 3 times as tall as Mount Everest (88000 ft)
5. Meridiani Planum: Landing site of second Mars rover Opportunity. May indicate the presence hot springs or liquid water in the past
Moon
1. South Pole – Aitken basin: largest crater on the Moon, on the far side
2. Shackleton crater: Site where the Moon Impact Probe from Chandrayaan landed and found water, Nov 2008.
  Located at the South Pole, where the rim gets continuous sunlight while the interior is in perpetual shadow.
3. Cabeus crater: Site where the LCROSS spacecraft landed and confirmed significant presence of water, Oct 2009.Located at the south pole

1957: Sputnik 1, first Earth Orbiter
1961: Vostok 1, first manned Earth orbiter
1966: Luna 9, first Lunar Lander
1969: Apollo 11, first manned lunar landing
1970: Luna 17/Lunokhod 1 – first Lunar Rover
1971: Mars 3 – first Mars Lander
1976: Helios 2 – closest Solar approach
1977: Voyager 2 – first to leave Solar System
1978: International Cometary Explorer – first comet flyby (comets Giacobini-Zinner and Halley)
1996: Mars Pathfinder – first Mars Rover
2001: Genesis – first Solar wind sample return

2137 BCE: Chinese astronomers record solar eclipse
2^ND millennium BCE: Heliocentric solar system, with Sun at the centre, proposed in the Vedic texts
499 CE: Aryabhata, in his Aryabhatiya, propounds heliocentric solar system of gravitation, elliptical orbits for planets, and suggests that moon and planets shine due to reflected light
500: Aryabhata accurately computes the earth’s circumference, solar and lunar eclipses and length of earth’s revolution around the Sun
620: Brahmagupta recognizes gravity as a force of attraction and describes law of gravitation
628: Brahmagupta calculates motion and position of various planets
1150: Bhaskara, in the Siddhanta Shiromani, calculates longitudes and latitudes
1514: Copernicus states his Heliocentric theory in Commentariolus
1610: Galileo Galilee discovers Callisto, Europa, Ganymede and Io, sees Saturn’s rings
1656: Christiaan Huygens: identifies Saturn’s rings as rings and discovers Titan
1705: Edmund Halley predicts the periodicity of Halley’s Comet
1755: Immanuel Kant formulates the Nebular Hypothesis of Solar System formation
1930: Clyde Tombaugh discovers Pluto
1946: American launch of a camera-equipped V2 rocket provides the first images of the Earth from space

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