Contents
1. Introduction
2. Earth
3. Other planets of the Solar system
4. Conclusion

Introduction
Solar system includes nine planets each of them is a unique space object which possess features that make them different from each other. Probably the most particular planet is Earth, which is the only planet where variety forms of life co-exist. At the same time other planets are also interesting to explore and compare that will provide an opportunity to better understand the solar system at large, its origin and the processes it undergoes in particular. It is particularly important to compare Earth with other planet because of its uniqueness and such a comparison will probably reveal the mystery of the only planet where life exists.
Earth
Earth is one of the most particular planet of the solar system. It is also known as Terra, or else it is called the third planet from the Sun because among the nine planet of the solar system it is the third closest to the star. It is the largest of the solar system’s terrestrial planets and it is the only planetary body that modern science confirms as harbouring life. The planet is relatively young in astronomic terms for it was formed around 4,5 billion years ago and shortly thereafter acquired its only natural satellite, the Moon.
Speaking about the structure of the planet, it should be said that the Earth consists of several atmospheric, hydrologic and mainly geologic layers. However, in comparative analysis of the Earth and other planets geologic layer would be particularly noteworthy since other planets basically lacks atmosphere and hydrologic layers identical to terrestrial. On analysing the structure of the Earth, it should pointed out that it is chemically divided into an outer silicate crust, a highly viscous mantle, a liquid outer core that is much less viscous than mantle and a solid inner core. The liquid outer core gives rise to a weak magnetic field due to the convection of its electrically conductive material.
It is noteworthy that an important source of information about the inner structure of the Earth are volcanoes and cracks in the ocean floors as well as the analysis of the mountains structure for many of the rocks now making up the Earth’s crust formed less than 100 million years ago. At the same time it should be pointed out that the oldest known mineral grains are 4.4 billion years old, indicating that the Earth has had a solid crust for at least that long.
It should be emphasized that the average density of the Earth is 5515 kg/m3, making it the densest planet in the Solar system. The average density of the surface is only 300 kg/m3 indicates at the presence of denser materials within the core of the earth. The core is divided into inner and outer. The former is believed to be solid and consists of iron and some nickel while the latter is liquid and consists of liquid iron mixed with liquid nickel and lighter materials. It is believed that convection in the outer core, combined with the rotation of the Earth, gives rise to the Earth magnetic field. The mantle is believed to be solid/plastic rich in iron and magnesium.
Furthermore, it should be pointed out that the surface of the Earth is constantly changing and several processes influence the shaping of the Earth’s surface. One of it has been already mentioned and it is volcanic activity which results in volcanic eruptions on the surface of the planet that changes it dramatically. At the same time volcanic eruptions are to a significant extent the effect of the seismic activity of the Earth’s crust which leads to cracking of the crust in some places. Another consequences of seismic activity of the crust are earthquakes which also change the surface. Also there are natural processes which impact independently from inner-Earth processes, erosion may be named among them. Erosion leads to the gradual destruction of the surface of crust, including mountains and rocks and naturally other parts of the Earth’s surface.
All these factors create a uniqueness of the planet making it different from others.
Other planets of the Solar system
Obviously it would be logical to compare the Earth to other planets of the Solar system in order to fully realize its uniqueness.
First of all, Mercury is the closest planet to the Sun at the same time it is the second-smallest planet in the Solar system. Physically, Mercury is similar in appearance to the Moon as it is heavily cratered. It has no atmosphere and no natural satellites. The planet has a large iron core which generates a magnetic field about 1% as strong as that of the Earth. Surface temperature on Mercury range from about 90 to 700 K, with the sub solar point being the hottest and the bottoms of the craters near the poles the coldest.
The second planet from the Sun is Venus. It is sometimes referred to as the Earth’s ‘sister planet’, as the two are very similar in size and bulk composition. A remarkable feature of the planet is its atmosphere which basically consists of carbon dioxide and a small amount of nitrogen, with the pressure at the surface about 90 times that of Earth. The solar radiance is much lower than on the Earth because the planet thick cloud cover reflects the sunlight back into space. Another remarkable feature of the planet is the fact that it has slow retrograde rotation, i.e. it rotates from east to west and not vice versa as other major planets do. Its magnetic field is very weak compared to other planets.
Probably the most mysterious planet is Mars. Its particular feature is its red color. The red, fiery appearance of the planet is caused by iron oxide on its surface. Mars has only a quarter of the surface area of the Earth and only one-tenth the mass, though its surface area is practically equal to that of the Earth’s dry land because Mars lacks oceans.
Jupiter is the fifth planet from the Sun and by far the largest in the Solar system. This planet is characterised by a particularly great mass which is 2.5 times more than all the other planets combined. It also has the fastest rotation range. But it’s best known feature is probably the Great Red Spot, a storm larger than Earth that is a permanent feature of the planet which is perpetually covered with clouds and may not have any solid surface.
Saturn is the sixth planet from the Sun. It is a gas giant, the second-largest planet in the Solar system. Its particular feature is the system of rings, consisting of mostly ice particles and rocky debris.
Uranus is the seventh planet from the Sun and it is a gas giant as Saturn. The planet is the third largest by diameter and fourth largest by mass. It is primarily composed of rocks and various ices.
Neptune is the eights or occasionally the ninth planet from the Sun due to Pluto’s eccentric orbit. It is the outermost gas giant in the Solar system. Although the planet is the smallest among gas giants, it is more massive than Uranus since its stronger gravitation field has compressed it to a higher density. Faint dark rings have been discovered around the planet though they are less substantial than those of Saturn. It also has a Great Dark Spot comparable to Jupiter’s Great Red Spot.
And finally Pluto, it is the ninth and probably the most disputable planet in the Solar system. Pluto has an eccentric orbit that is highly inclined in respect to the other planets and takes it inside the orbit of Neptune. Currently Pluto is classified as a trans-Neptunian object.
Conclusion
In conclusion it is possible to say that each planet of the Solar system is unique and compared to the Earth other planets have one main feature which make them absolutely different from the third planet from the Sun, namely it is the lack of conditions for life, at least in its terrestrial forms.

Bibliography:
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2. Freedman, David H. “When is a Planet Not a Planet?”, Atlantic Monthly, February 1998.
3. Scott, George L. The Solar System. LA: Routledge, 2002.