Neptune and Pluto (Important Facts) {Part-21}

NEPTUNE IS the furthest planet from the Sun at an average distance of about 4,500 million kilometres. Neptune is the smallest of the giant planets and is thought to consist of a small rocky core surrounded by a mixture of liquids and gases. Seven transient cloud features have been observed in its atmosphere.

Neptune

The Largest of these were Green Dark Spot, which was as wide as the Earth, the Small Dark Spot, and the Scooter. The Great and Small Dark Spots were huge storms that were swept around the planet by winds of about 2,000 kilometres per hour. The Scooter was large area of Cirrus cloud. Neptune has six tenuous rings and 13 known moons. Triton is the largest Neptunian moon and the coldest object in the Solar System, with a temperature of -240^oC. Unlike most moons in the Solar System, Triton orbits its mother planet in the opposite direction to the planet's rotation.

Structure of Neptune

Rings of Neptune

Moons of Neptune

The region extending out from Neptune's orbit is populated by Kuiper Belt objects and Dwarf planets. They make a dough-nut shaped belt called Kuiper Belt. The Kuiper Belt objects are a mix of rock and ice, irregular in shape, and less than 1,000 kilometres across.

Kuiper Belt

The larger dwarf planets, which include Pluto, are almost round bodies. Pluto was the first object discovered beyond Neptune and was considered a planet until the dwarf planet category was introduced in 2006. It is made of rock and ice and is 2,274 kilometres across. It has three known moons. The largest, Charon, is about half Pluto's size and the two probably had a common origin.

Pluto

Moons of Pluto

Pluto and Charon structure

Pluto Surface's

Uranus (Important Facts) {Part-20}

URANUS IS THE SEVENTH PLANET from the Sun and the third largest, with a diameter of about 51,000 kilometres. It is thought to consist of a dense mixture of different types of ice and gas around a solid core. Its atmosphere contains traces of methane, giving the planet a blue-green hue, and the temperature at the cloud tops is about -210^oC. Uranus is the most featureless planet to have been closely observed: only a few icy clouds of methane have been seen so far.

Uranus

Uranus is unique among the planets in that its axis of rotation lies close to its orbital plane. As a result of its strongly titled rotational axis, Uranus rolls on its side along its orbital path around the Sun, whereas other planets spin more or less upright. Uranus is encircled by main rings that consist of rocks interspersed with dust lanes and too distant outer rings made of dust. The rings contain some of the darkest matter in the Solar System and extremely narrow, making them difficult to detect: most of them are less than 10 kilometres wide, whereas most of Saturn's rings are thousands of thousands of kilometres in width.

Rings of Uranus

There are 27 known moon Uranian moons, all of which are icy and most of which are further out the rings. The 13 inner moons are small moons and dark, with diameters of than 160 kilometres, and the five major moons are between about 470 and 1,600 kilometres in diameter.The major moons have a wide variety of surface features. Miranda has the most varied surface, with cratered areas broken up by huge ridges and cliffs 20 kilometres high. Beyond these are nine much more distant moons with diameters less than 150 km.

5 major moons of Uranus

Composition of Uranus

Saturn (Important Facts) {Part-19}

SATURN IS THE SIXTH PLANET from the Sun. It is a gas giant almost as big as Jupiter, with a equatorial diameter of about 120,500 kilometres. Saturn is thought to consist of a small core of rock

Saturn

and ice surrounded by an inner mantle of metallic hydrogen (liquid hydrogen that acts like a metal). Outside the inner mantle is an outer mantle liquid hydrogen that merges into a gaseous atmosphere. Saturn's clouds from Belts and Zones similar to those on Jupiter, obscured by overlying haze. Storms and eddies, seen as red or white ovals, occur in the clouds. Saturn has an extremely thin but wide system of rings that is less than 1 kilometre thick but extends towards to about 420,000 kilometres from the planet's surface. The main rings comprise thousands of narrow ringlets, each made up of icy rock lumps that range in size from tiny particles to chunks several metres across. The D, E and G rings are very faint, the F ring is brighter and the A, B and C rings are bright enough to be seen from Earth with binoculars.

Saturn's Rings,Belts and Zones system

In 2009, a huge dust ring was discovered 6 Kilometres (4 million miles) beyond the Main system. Saturn has more than 60 known moons, some of which orbit inside the rings and are thought to be exert a gravitational influence on the shapes of the rings. Unusually, 7 of the moons are co-orbital- they share an orbit with another moon. Astronomers believe that such co-orbital moons may have originated from single satellite that broke up.

Structure of Saturn

Atmosphere of Saturn

Jupiter (Important facts) {Part-18}

JUPITER IS THE FIFTH PLANET from the Sun and the outermost of the four giant planet, with a diameter about 11 times that of the Earth and a mass about 2.5 times the combined mass of the seven other planets. Jupiter is thought to have a small rocky core surrounded by a inner mantle of metallic hydrogen (liquid hydrogen that acts like a metal). Outside of the inner mantle is an outer mantle of

Jupiter

Jupiter-Earth Comparison

liquid hydrogen and helium that merges into the gaseous atmosphere. Jupiter's rapid rate of rotation causes the clouds in its atmosphere to form belts and zones that encircle the planet parallel to the equator. Belts are dark, low-lying, relatively warm cloud layers and zones are bright, high-altitude, cooler cloud layers. Within the belts and zones, turbulence causes the formation of cloud features such as White ovals and Red spots, both of which are huge storm systems. The most prominent cloud feature is a storm called the Great Red Spot, which consists of a spiraling column of clouds three times wider than than the Earth that rises about 8 kilometres above the upper cloud layer.

Jupiter-Belt and Zone system

Jupiter has a thin, faint, Main ring, inside which is a tenuous halo ring of tiny particles. Beyond the main ring's outer edge is a broad and faint two-part Gossamer ring.

Jupiter's Ring

Structure of Jupiter

There are 63 known Jovian moons. The four largest moons (called the Galileans) are Ganymede, Callisto, Io, and Europa. Ganymede and Callisto are cratered and icy. Europa is smooth and icy 
and is thought to have a subsurface water ocean. Io covered in bright red, orange and yellow splotches. This colouring is caused by sulphurous material from active volcanoes that shoot plumes of lava hundreds of kilometres above the surface.

4 largest moons of Jupiter

Moons orbiting Jupiter

Note:- You can watch a Hollywood movie- "Europa Report" (Sci-fi movie) which is about the life on Europa- a moon of Jupiter.  

Mars (Important Facts) {Part-17}

MARS, KNOWN AS THE RED PLANET, is the fourth planet from the Sun and the outermost rocky planet. In the 19th century astronomers first observed what were thought to be signs of life on Mars.

Mars

These signs included apparent canal-like lines on the surface, and Dark patches that were thought to be Vegetation. It is now known that the "Canals" are an optical illusion, and the Dark patches  are areas where the red dust that covers most of the planet has been blown away. The fine dust particles are often whipped up by winds into dust into dust storms that occasionally obscure almost all the surface. Residual fine dust in the atmosphere gives the Martian sky pinkish hue. The northern hemisphere of Mars has many large plains formed of solidified volcanic lava, whereas the southern hemisphere has many craters and large impact basins. There are also several huge, extinct volcanoes,

Martian sky

including Olympus Mons, which, at 600 kilometres across and 25 kilometres high, is the largest known volcano in the Solar System. The surface also has many canyons and branching channels. The canyons were formed by movements of the surface crust, but the channels were thought to be have been formed by flowing water that has now dried up. The Martian atmosphere is much thinner than Earth's, with only a few clouds and morning mists. Mars has two tiny, irregularly shaped moons called Phobos and Deimos. Their small size indicates that they may be asteroids that have captured by the gravity of Mars.

Moons of Mars

Internal structure of Mars

Earth-Mars atmosphere comparison

Craters of Mars

Journey to Mars

The Moon (Important Facts) {Part-16}

THE MOON IS THE EARTH'S only natural satellite. It is relatively large for a moon, with a diameter of about 3,470 kilometres- just over a quarter that of the Earth. The Moon takes the same

The Moon

time to rotate on its axis as it takes to orbit the Earth 27.3 days and so the same side (the near side) always faces us. However, the amount of the surface we can see- the phase of the Moon - depends on how much of the near side is in sunlight. The Moon is dry and barren, with negligible atmosphere and water. It consists mainly of solid rock, although its core may contain molten rock or iron. The surface is dusty, with highlands covered in craters caused by meteorite impacts, and lowlands in which large craters have been filled by solidified lava to form dark areas called Maria or Seas.

Phases of the Moon

Craters of the Moon

Moon's Craters Name

Maria occur mainly on the near side, which has a thinner crust than the far side. Many of the craters are rimmed by mountain ranges that form the crater walls and can be thousands of metres high.

Internal Structure of the Moon

The Earth (Important Facts) {Part-15}

THE EARTH IS THE THIRD of the eight planets that orbit the Sun. It is the largest and densest rocky planet, and the only known to support life. About 70% of the Earth's surface is covered by

The Earth

water, which is not found in liquid from on the surface of any other planet. There are 4 main layers:-
(i).The Inner Core
(ii).The Outer Core
(iii). The Mantle
(iv). The Crust

At the heart of the planet the solid Inner Core has a temperature of about 6,600^oC. The heat from this Inner core causes material in the molten outer core and mantle to circulate in convection currents. It is thought that these convection currents generate the Earth's magnetic field, which extends into space as the Magnetosphere.

Magnetosphere

The Earth's atmosphere helps screen out some of the harmful radiation from the Sun, stops most meteoroids from reaching the planet's surface, and traps enough heat to prevent extremes of cold. The Earth has one natural Satellite, the Moon, which is thought to have formed when the huge asteroid impacted Earth in the distant past.

Formation Of Earth

Chemical composition of the Earth

Venus (Important Facts) {Part-14}

VENUS IS A ROCKY PLANET and the second planet from the Sun. Venus spins slowly backwards

Venus

as it orbits the Sun, causing its rotational period to be the longest in the Solar System, at about 243 Earth days. It is slightly smaller than the Earth and probably has similar internal structure, consisting of a semi-solid metal core, surrounded by a rocky mantle and crust. Venus is the Brightest object in the sky after the Sun and Moon because its cloud reflect sunlight strongly. The main component of the atmosphere is Carbon dioxide, which traps heat in a greenhouse effect far stronger than that on the Earth. As a result, Venus is the hottest planet, with a maximum surface temperature of about 480^oC. The thick cloud layers contain droplets of Sulphuric acid and are driven around the planet by winds

at speeds of up to 360 kilometres per hour. Although the planet takes 243 Earth days to rotate once, the high-speed winds cause the clouds to circle the planet in only four Earth days. The high temperature, acidic clouds and enormous atmosphere pressure (about 90 times grater at the surface than that on the Earth) make the environment extremely hostile. However, Space probes managed to land on Venus and photograph its dry, dusty surface. The Venusian surface has also been mapped by

Venusian Suface (By a space probe)

probes with radar equipment that can "see" through the cloud layers . Such radar maps reveal a terrain with craters, mountains, volcanoes and areas where craters have been covered by plains of Solidified volcanic lava. There are two large highland regions called Aphrodite Terra and Ishtar Terra.

Aphrodite Terra and Ishtar Terra
(two highland regions in Venus)