HISTORY OF SOLAR SYSTEM

THE SOLAR SYSTEM is the region of space that falls within the gravitational influence of the sun.After the Sun itself,the most significant objects in the solar system are planets.Most of the planets are orbited in turn by moons,while a large number of smaller lumps of rock and ice also follow their own courses around the sun.On the broiling surface of the Sun,a cataclysmic release to magnetic energy triggers a solar flare - a violent outburst of radiation and high energy particles that will reach Earth within hours.
                            THE SOLAR SYSTEM IS THOUGHT to have begun forming about 4.6 billion years ago from a gigantic cloud of gas and dust,called the solar nebula.This cloud contains several times a huge amount of mass of the present day Sun.over million of years it collapsed to a flat,spinning disc,which had a dense,hot central region.The central part of the disc eventually became the Sun while the planets and everything else in the solar system formed from a portion of the remaining material.

Formation of the solar system:
Solar nebulas
the solar nebula from which the solar system formed due to collapsing.As it collapsed the cloud flattened into a pancake-shape disc with a bulge at it's center.The central region also became hotter and denser,in the parts of the disc closer to this hot central region only rocky particles and metals cloud remain in solid form.Other materials are vaporized.The rocky and metallic particles gradually came together to form inner planets (Mercury,Venus,Earth,Mars).In the cooler outer region of the disc,a similar process occurred,but the solid particles that came together to form planetesimals contained large amount of various ices,such as water,ammonia and methane ices,as well as rock.These materials are arranger eventually to form the gas-giant  planets (Jupiter,Saturn,Uranus,Neptune).Once the planetesimals were a few kilometers in diameter,their gravity was strong enough to attract more and more materials in a run away process.Many of the planetesimals came together to form moon sized bodies called protoplanets.it containing both rock and ice,were massive enough to pull in vast amounts of hydrogen,helium and other gases.which attracted onto the planetary cores to form the dense atmospheres.Pluto may have formed from materials not used in the gas giants or may have been captured by the solar system at a later time.

  • BRIEF DISCUSSION ABOUT MERCURY
    Mercury is the second smallest planet in the solar system, the closest planet to the Sun, and richest in iron.The surface environment is extremely harsh.There is hardly any shielding atmosphere and the temperature rises to 430 degree celsius during the day than plummets to an air freezing of -180 degree celsius at night.No other planets experiences such a wide range of temperature.

    STRUCTURE:
    Mercury has very high density i.e. it is rich in iron.This iron is sank to the center, producing a huge core (3,600 km in diameter).The solid rocky mantle is about 550 km thick and makes up most of the outer 25% of the planet.The mantle and the thin crust mainly consists of the silicate mineral another site, just like the old lunar highlands.The whole iron of the Mercury has gone into its core, which produces a magnetic field with a strength that is about 1% of Earth's magnetic field.Mercury rotates 3 times in two orbits (there are three Mercurian days in two Mercurian years).Mercury passes directly between the and the Sun about 13 times a century.Its axis of rotation is almost vertical, this means that the planet has no seasons and some craters close to the poles never receive any Sunlight and are permanently cold.

    ATMOSPHERE:
    Mercury has a very thin temporary atmosphere because the planets is too small for an atmosphere to persist.Its day time temperature is extremely high, reaching 430 degree celsius.Very few amount of oxygen helium and hydrogen is present in its atmosphere.The hydrogen and helium are captured from solar wind of gas that is constantly escaping from the Sun.The atmospheric gases are much denser on the cold night side of the planet than on the hot day side, as the molecules have less energy to escape.Oxygen is the most abundant gas followed by sodium and helium.However loss and regeneration of gases is continuous and the atmospheric composition can vary drastically over time.

    FEATURES:
    Mercury Is covered with impact craters ranging in size from small bowl shaped craters to a basin that is a quarter of the diameter of the planet.Its flat plains (called planitiae) were formed when lava flooded low-laying regions.In the last billion years,the impact rate has greatly decreased, and the surface has changed little.Impact craters cover Mercury's visible surface.Its surface gravity is about twice that of the Moon,so the ejecta blankets are closer to the parent craters and thicker than those found on the moon.The craters are interspersed by at least two generations of flat plains of solidified basaltic lava,like the lunar maria.Eventually most of the vents were covered by the lava.Mercury's surface also has several ridges, which are up to 1 to 3 km  high and 500 km long.


    Caloris Basin:
    The formation of this huge multi-ring basin, which is larger than the US state of Texas.It is similar to the Orientale basin on the moon.The tremendous impact that produced Caloris led to seismic waves being focused on the opposite of the planet, causing an Earthquake.The waves were then reflected back to the basin and fractured the surrounding waves.The basin is now about 2 km.The center of the Caloris basin lies to the left of the mosaic.




    Brahms Crater:
    A large, mature,complex crater to the north of the Caloris basin, Brahms has a prominent central mountainous peak about 20 km across.The walls have slipped inwards, forming a series of elaborate, concentric, stair like terraces and highly irregular rim.





    Bach Crater:
    This two-ringed basin represents an intermediate class of craters between the slightly smallest ones with central mountainous peaks and larger with multiple rings.Bach was formed to wards the end of the period of heavy bombardment.Lava later flooded the crater, producing the smooth floor. 



    Degas Crater:
    This bright ray crater is relatively young, and it overlies the slightly larger Bronte Crater to its north.The rays extend out readily for several hundred kilometers.These highly reflective wispy streaks were caused by the fine pulverized rock ejected from Degas churning up the soil surface on impact.It will take about a billion years for the solar wind to erase them.



    • BRIEF DISCUSSION ABOUT VENUS
    Venus is a second planet from the Sun and Earth's inner neighbour.Venus's thick,reflective clouds enable the planet to shine brightly,so that from a distance it looks beguiling and beautiful.The two planets are virtually identical in size and composition but these are very different worlds.An unbroken blanket of dense clouds permanently envelops Venus.underneath lies a gloomy lifeless, dry world with a scorching surface,hotter then that of any other planet.



    STRUCTURE:
    Venus has formed from the same material as Earth about 4.5 billion years ago and has differentiated into distinct layers in a similar way to Earth.Venus's orbital path is least elliptical then other planets.Venus takes 224.7 Earth days to complete one orbit.Venus spins extremely slowly on its axis compared to other planets.it takes 243 Earth days for just one spin.That5 means that a Venusian day is longer then a Venusian year.However the time between one Sunrise and the next on Venus is 117 Earth days.That means one spot on the surface faces the Sun every 117 Earth days.Venus does not have seasons as it moves through its orbits.This is because of it's almost circular path and the planets small axial tilt.Venus is within 100 times the distance of the moon.Venus is a dense,rocky world just smaller than Earth and with less mass.It is seen that the most of the structure of Venus is similar to that of Earth.So Venus's metal core is thought to have a solid inner part and a molten outer  part.As compared to Earth to Earth Venus has no detectable magnetic field.Venus's internal heat generated early in the planet's history and from radio active decay in the mantle,is lost through the crust by conduction and volcanism.heat melts the subsurface mantle material,and magma is released onto the surface.  



    ATMOSPHERE:
    Hemispheres of Venus
    Venus's atmosphere contains such as carbon dioxide,nitrogen,sulphur dioxide,argon and water vapour.Venus's carbon dioxide rich atmosphere stretches up from the ground for about 80 km.The lower layer is the densest and contains large droplets.and the top layer has small droplets.close to the planet's surface,the atmosphere moves very slowly and turns with the planets spin.The clouds speed round Venus once every four Earth days.Venus's equator receives more solar heat then its polar regions.The cloud reflects the majority of Sunlight reaching Venus back into space and so this is an overcast orange-coloured World.Venus's thick cloud layers trap heat and help produce the planet's high surface temperature.only 20% of Sunlight reaches the surface ,it warms of the rock .heat in the form of infrared radiation is then released but it can't escape adds to the warming process.



    Geography:
    Venus has expected as similar to Earth,but it does not having any moving plates.Venus has hundreds of volcanoes such as Maat Mons,to small nameless domes.There has been volcanic activity as recently as about 500 million years ago,and it is possible that some of the volcanoes could be active.Venus's tallest volcano,Maat Mons,rises to almost 5km above the surrounding terrain and is 8km above the planet's mean surface level.There are hundreds of impact craters are present on Venus,this total is low compared to that for the Moon and the Mercury.The orange colour of Venus is due to the atmosphere filtering out the blue light.The planet has three main highland regions,termed terra.They are Aphrodite,which dominates the equatorial zone, and Lada and Ishtar. Over 20 smaller,upland areas, termed regio, are found around the planet.

    Ishtar Terra:
    It is a highland terrain,it's age is under 500 million years and it's length is 5610 km.Ishtar Terra is a large plateau about the size of Australia, which stands 3.3 km above the  surrounding low lands.It is the nearest thing on western region is the elevated plateau Lakshmi Planum.The steep sided Maxwell Montes range makes of the eastern part of Ishtar Terra, along with a deformed area.It is likely that beneath Ishtar there is cooled, thickened crust that is kept up by a rising region of mantle.




    Devana Chasma:
    It's age is under 500 million years,length is about 4600 km and it is Fault in nature.Devana Chasma is a large Fault, that cuts through Beta Regio.It is similar to the great Rift Valley on Earth.Devana Chasma slices through Rhea Mons and Theia Mons.The Fault is over 2 km deep and about 80 km wide near Rhea Mons.It continues to the high land region Phoebe Regio and reaches depth of 6 km.Fault and Grabens cut through and fan out from parts of the Rift Valley.




    Maxwell Montes:
    It's age is under 500 million years, length is 797 km and it is a mountain range type.The Maxwell Montes mountain range forms the eastern boundary of Lakshmi Planum.It is the highest point on Venus, rising over 10 km above the surrounding low lands.The western side is a complex of grooves and ridges and is particularly steep-Magellan data revealed that the south western flank has aslope of 35 degree.The mountain range was  formed by compression and crustal foreshortening, which produced folding and thrust faulting.




    Gula Mons:
    It's age is under 500 million years, height is 3 km and it is a Shield volcano type.Gula Mons is the larger of the two volcano that dominate the high land rise western Eistla Regio.This shield volcano is encircled by hundreds of kilometers of lava flows.The volcano is also at the center of an array of crustal fractures.Guor Linear is a rift system that extends for at least 1000 km from the southeast flank.




    Lakshmi Planum:
    It's age is under 500 million years, length if 2,345 km and it is volcanic plain type.This is a smooth plateau, 4 km high formed by extensive volcanic eruptions.This massive plain covers an area that is about twice the size of Earth's Tibetan Plateau.There are just a few planums on Venus.







    Eistla Regio:
    It's age is under 500 million years,length is 8,015 km and it is volcanic highland type.Eistla Regio is one of Venus's smaller upland areas, which are located in the lower basin land separating the major highland areas.It lies in the equatorial region to the west  of the major highland, Aphrodite Terra.An unusual type of volcanic dome, unique to Venus is found within Eistla Regio.

    Fortuna Tessera:
    It's age is under 500 million years, length is 2,801 km and it is Ridged Terrain type.Fortuna Tessera is an area of north-south trending ridges about 1000 km wide.The distinctive pattern made by the region's intersecting ridges and grooves led to this types of Terrain originally being called Parquet Terrain.







    Sachs Patera:
    It's age is under 500 million years, length 65 km and it is Caldera type.Sachs Patera is about 130 meter deep and is surrounded by scarps spaced 2 to 5 km apart.Solidified lave flows extend 10 to 25 km to the north and northwest of those scarps.






    Beta Regio:
    It's age is under 500 million years, length is 2,869 km and it is a Volcanic highland.Beta Regio is a large highland region dominated by Rhea Mons and Theia Mons.The Rhea which is lies 800 km to the north of Thea, was originally thought to be a volcano but Magellan data revealed it to be an uplifted massive cut through by a Rift Valley, the Devana Chsma.

    Akna Montes:
    It's age is under 500 million years, length is 830 km and it is a mountain range.The Akna Montes is a ridge belt that appears to be the result of folding due to northwest-southeast compression.The mountain building is hought to have occured after the plains formed,as the plains in this region seem to be deformed.






    Sacajawea Patera:
    It's age is under 500 million years, diameter is 233 km and it is caldera type.The Sacajawea Patera is an elliptically shaped volcanic caldera on Lakshmi Planum.It is thought to have formed when a large under ground chamber was drained of magma and then collapsed.The resulting caldera then sagged.The depression is about 1.2 km deep and is enclosed by a zone of concentric troughs and scarps that extend up to 100 km in length and are 0.5 km to 4 km apart.

    Sapas Mons:
    It's age is under 500 million years, height is 1.5 km and it is Shield Volcano. It rising 1.5 km above the surrounding terrain and with a diameter of about 217km. These are shaped like a shield of inverted plate, with a broad base and gently sloping sides. Sapas Mons is located in the Atla Regio, a broad volcanic rise just north of Venus's equator with an average elevation of 3km. Sapas mons is covered with in lava flows and grew in size as the layer of lava accumulated.




    Miralaidji Corona:
    It's age is under 500 million years, diameter 300 km and it is Corona type.This large volcanic was formed by a plume of magma rising under the Venusian surface.The corona of Venus range in size from about 50 to 2,600 km across and are circular to elongate in shape.




    Dali Chasma:
    It's age is under 500 million years, length 2,077 km and it is a Fault.The Dali Chasma lies in western Aphrodite Terra.It is a system of canyons and deep troughs coupled with high mountain that makes a broad, curving cut through more than 2,000 km of the planet's surface.The mountain ranges associated with the canyons rise for 3 to 4 km above the surrounding terrain.The canyons are 2 to 3 km  deep.


    Ovda Regio:
    It's age is under 500 million years, diameter 5,280 km and it is a highland Terrain.Ovda Regio is a highland area in Venus's equatorial region.It forms the western  part of Aphrodite Terra.It rises 3 km above the mean surface level.Ovda Regio is one of a handful of highland region on Venus that displays a type of complex ridge terrain known as tessera.


    Lada Terra:
    It's age is under 500 million years, length 8,615 km and it is a Highland Terrain.Lada is the second largest of three highland region on Venus.It is in the south polar region of the planet.Lada Terra includes some typical tessera terrain of crisscrossing troughs and ridges.Lada includes three large coronae called as Quetzalpetlatl, Eithinoha and Otygen.


    Artemis Corona:
    It's age is under 500 million years, diameter 2,600 km and it is a corona. Artemis is more than twice as big as the next largest corona on Venus, Heng-o. A near circular trough, Artemis Chasma which has a raised rim, marks it's boundary.Within it are complex systems of fractures, volcanic flows and small volcanoes are present.





    IMPACT CRATERS:
    Impact Craters on Venus range in size from 7 km to 270 km.The largest are multiringed, those of intermediate size have central peaks and the smaller ones have smooth floors.Some of the craters are explained below.


    Jeanne Crater:
    It's age is under 500 million years, diameter 19.4 km and it is a central peak crater.An asteroid travelling from the southwest smashed into the Guinevere Planitia obliquely and created Jeanne Crater.Ejecta pushed out of the impact basin produced a distinctive triangular shape.


    Balch Crater:
    It's age is under 500 million years, diameter 40 km and it is a central-peak crater.Most impact craters on Venus have remained unchanged since they were formed and have sharply defined rims.However a relatively small number have been modified by volcanic eruptions and other kinds of tectonic activity.Balch Crater is one of them.The western of the crater remains intact but most of the eastern half was destroyed.The crater was initially called Somerville.




    Wanda Crater:
    It's age is under 500 million years, diameter 21.6 km and it is a central peak crater.Wanda Crater is in the northern part of the Akna Montes mountain range.The crater has a large, rugged peak in the center of its smooth lava flooded floor.About one-third of all Venusian Craters have such peaks.







    Riley Crater:
    It's age is under 500 million years, diameter 25 km and it is a central peak crater.Riley crater is one of the few Venusian craters to have been precisely measured.25 km wide craters floor lies 500 meter below the surrounding plain, the rim is 620 meter above it and the peak is 536 meter high.




    Cleopatra Crater:
    It's age is under 500 million years, diameter 105 km and it is a double ring crater.Cleopatra is located on Maxwell Montes,Venus's highest mountain range, and stands out as a smooth eye like feature against the rough mountainous terrain.It was one of several circular features that resembled both an impact crater and a volcanic feature.



    Alcott Craters:
    It's age is under 500 million years, diameter 66 km and it is a Degraded Crater.Alcott is one of the few craters on Venus that has been modified by volcanic activity not associated with the crater's production. In Alcott's lava erupted elsewhere and then flowed over the crater. About half of the crater's ring is still visible along with Ejecta from the original impact lying to the south and east.





    Saskia Crater:
    It's age is under 500 million years, diameter 37.1 km and it is a central peak crater. Saskia is a middle sized crater and its Ejecta pattern is typical for its aize. The crater has central peaks, formed as the planet's surface recoiled after being pushed down by the energy released during the impact. The original crater rim has collapsed and formed Terraced walls. In this crater rough areas appear light while smooth ones look dark.

    Stein Crater Field:
    It's age is under 500 million years, diameter 14 km and it is a crater field. Small asteroids heading for Venus's surface can be broken up by the planet's dense atmosphere. The resulting fragments continue heading towards the surface , striking it simultaneously within a relatively small area to form a crater field. The Stein Field consists of three small craters. Material melted by the impacts has formed flow deposits, also lying to the northeast.




    Mead Crater:
    It's age is under 500 million years, diameter 270 km and it is a Multi-ringed crater. Mead is the largest impact crater on Venus. It has two distinct rings. Ejecta lies between them and beyond the outer ring. Mead is a multi-ringed crater whose inner ring is the rim of the crater basin. This encloses a smooth, flat floor, which hides a possible central peak. There is a drop of only about 1 km between the crater rim and the crater center.


    Addams Crater:
    It's age is under 500 million years, diameter 87 km and it is a central peak crater. The large circular Addams crater measures almost 90 km across but it is it's long tail that makes this crater unusual. Additionally impact melt Ejecta and lava extend out from about a 3rd of the rim, creating a mermaid-style tail to the east. The molten material flowed downhill for about 600 km from the impact site. Venus's high surface temperature of about 464 degree celsius allows Ejecta to remain molten for a longer time then if it were on Earth. However once the material cools below about 1000 degree celsius it becomes so viscous and it stops flowing.
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