The Masses Of The Terrestrial Planets Biology Essay


Venus is the second planet in the solar system from the sun, following Mercury. Venus is the brightest - brighter than most stars - object in space, after the moon, the reason why in the ancient times astronomers have refer it to as the morning star due to its bright colour during the day. Scientists believe that both Venus and Earth were created at around the same time and that they may have evolved from the same nebula, hence, in the astronomical world Venus is known as the Earth's sister planet. However, later in time after studies they have convinced themselves that this was the end point of the sisterhood of both planets.

Another interesting fact about Venus is the origin of its name. It has been named after the Roman goddess of Love and Beauty.

In this section of this investigation, various points such as the properties of Venus will be examined in order to inform the reader about such body present in the solar system. This section of the investigative report will be covering specific points about the surface and geology of Venus. Then will pass on to a brief information on the atmosphere of Venus from its composition to how it shapes the planet. The volcanism activity and craters found in Venus will also be covered since they are they what make Venus distinguishable from other planets in the solar system.

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In order to start this investigation, it is important to be aware of some similarities between Earth and Venus, simply to help position you in terms of magnitude and the meaning of some features present in the planet. For instance, size, mass, average density, volume and interior composition of both planets are very similar, hence, many scientist before starting their study about Venus thought that many function that arise from these properties would be similar to that n Earth. Let us take the interior composition of both planets; they are both made of iron core and massive silicate mantle, yet, Venus has no magnetic field whereas Earth possess of a strong one.

The above example is just an idea of the route to which this investigative report will take in order to educate you about Venus.

Venus is a terrestrial planet

If one were to observe the solar system from above, one would notice that planets orbit in a circular fashion around the Sun. Observing more attentively, it would be evident that Mercury, Venus, Earth and Mars orbit very tightly to the sun compared to the rest of the planets present in the solar system. These planets are therefore referred to as the inner planets. Moreover, they are classified as the terrestrial planets due to their similarities to Earth.

In its turn, Venus - a terrestrial planet - has similar properties such as diameter, mass and average density compared to the rest of the inner planets in the solar system. Incidentally, the diameter of Venus is known to be as 12,100 km (NASA. 2007), which is about 600 km (NASA. 2007) less than Earth. Notice that these figures were obtained by mathematical calculation involving an angular diameter and distance of Venus from Earth. For instance, on March 16, 2007, when Venus was 1.97-108 km away and an angular diameter of 12.7 arcsec from Earth (Freedman, R, 2008 p.162; Kaufmann III, 2008 p.162), hence by using the small angular formula and the figures such obtained the diameter of Venus can be calculated.

Silicate mantle

Iron core

Similarly, the masses of the terrestrial planets will have figures more closely related to each other, than comparing to the Jovian planets. Venus has as its mass 4.8685 x 1024 kg (NASA. 2007), this is of Earth's mass. In general, masses of planets may be measured by the period of the satellite of the planet and Kepler's Third Law. Interestingly, Venus and Mercury are the only planets that do not possess a satellite, hence, the mass of Venus was calculated by sending a spacecraft, and then, by the amount of deflection of the satellite due to the gravitational pull in Venus, the mass was calculated.

Rocky surface

Fig 3. - interior compsiton of Venus

Lastly is the average density of the terrestrial planets that differs slightly from one to another, in fact, they possess the highest average density in the solar system. Interestingly their individual components are lighter that the overall average density, for instance, a typical Venusian rock has an average density of 3000 kgm-3 against 5240 kgm-3. It is thought that this happens because of the interior composition of such planets possess of rocky surface and dense iron core and silicate mantle.

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In summary, all terrestrial planets resemble Earth through their interior structure, mass and density. For this reason, some analysis, such as the diameter, may be made from earth using technology or by comparison.

Venus is enveloped by a heavy atmosphere

In many ways Venus is found to be similar to Earth. However their similarities do not extend further than their physical properties, for instance, their atmospheres differ greatly from each other. Venus is said to have atmospheric pressure of 92.1 barometers (Adams, D. Et al., 1994 p.126) which it is evidently 92 times greater than Earth's that is 1.01 barometers (Adams, D. Et al., 1994 p.126) at sea-level. In spite of this comparison to Earth's atmospheric pressure, Venus owns an out of the ordinary atmospheric composition.

Fig.1 - image of the heavy clouds hindering the view of the Venusian surface. Once it was considered that scientific investigations of the structure of Venus was impeded by the heavy clouds that form its atmosphere, hence, for many years scientists have studied its composition and thus unveiling the clouds that hinder such analysis. Then, being familiar with the chemistry of this atmosphere would be imperative for one to understand its composition.

In order to get the latter statement a Russian spacecraft - Venera - was sent to Venus to carry out investigations. Thereupon, it was found that the Venusian atmosphere has an unusual atmospheric structure of two distinct tropospheric areas that carry out distinct chemical reactions. Such structure goes as follows: the upper troposphere is exposed to sun rays thus carries out dissociation related chemical reaction whereas the lower troposphere is protected from the solar light hence traps heat and carries out heat related chemical reactions. In conclusion, such reactions that take place together with the abundant carbon dioxide (CO2) in the Venusian troposphere are vital in order to create species such as oxides of nitrogen (NOx) and produce sulphuric acid (H2SO4) droplets that make up the clouds veiling Venus.

Fig. 2 - percentage of the Venusian atmospheric compositionAs said before, Venus shows an unsual atmosphere, yet, interesting. During the production of sulphuric acid (H2SO4), believed to come from volcanic eruption that has as by-products sulphur dioxide and itself sulphuric acid, water (H2O) is used up, hence leaving only traces of water (H2O) but no hard evidence of its existence. Finally, this leads to the idea of Venus having very thick and dense clouds hence heavy atmosphere composed of 96.5% of carbon dioxide (CO2) and 3.5% of Nitrogen (N2).

Venus has a high surface temperature of 465oC

The latter section discussed the structure and the chemistry of the Venusian atmosphere. Thereupon, it can be recalled that the Venusian atmosphere is composed of dense clouds with sulphuric acid (H2SO4) droplets produced from plenty carbon dioxide (CO2) and oxides of nitrogen (NOx) in the atmosphere.

Fig 4. - Surface of VenusScientists examined the Venusian atmosphere and found out that above the clouds the temperature is about 13oC, in contrast, at the surface of Venus the temperature gets as high as 465oC. It is believed that the principle cause of the extreme surface temperature is the consequence abundant carbon dioxide (CO2) in the atmosphere. Scientists concluded that Venusian atmosphere undergoes greenhouse effect. In essence, the heat delivered from the Sun enter the atmosphere and is radiated out, then again, it does not leave the atmosphere due to its heavy clouds that impede it from such. For this reason, Venus' surface temperature is higher than that on Mercury - higher than any other planet! - leaving no chance of life.

In addition to no life expected to exist in Venus, such high temperature allows the rocks to weaken preventing the formation of any tectonic plates, instead, it forms flaky plates!

High temperatures account for Venusian flaky crust

Fig 5. - convention current in Venus' crust Due to high temperature at the surface of the planet, dynamic convention currents take place, weakening the planet's crust and causing it to break into flakes. From this originates the so called flaky plates that in turn to do not mountains to be formed - like its sister planet Earth does. Although Venus does not show any tectonic plates, it is believed that the flaky plates have undergone some king of activity that deformed Venus' surface and form faulty ridges.

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The fact that mountainous land are not regular in Venus, puzzles astronomers that believe that Venus being 'twin' to Earth, should have enough heat in order to maintain molten interior and sustain convention currents that form the tectonic plates and therefore chain of mountains should be present. However it contains thousand of volcanoes!

85% of Venusian surface is covered by volcanoes

Fig. 6 - Lava found in Venus which covers major part of its surface.Through Magellan, a radar telescope that it sent to orbit Venus, scientists have noted more than 1600 volcanoes were present on the Venusian plains. Moreover, some young lava flows was also observed with the images provided by Magellan. This suggests astronomers that there has been some volcanic activity, even though, it is thought that many of the volcanoes are, at the moment, inactive. Hence, Venus and its sister planet are the only ones with active volcanoes in the whole solar system.

Volcanoes and lava flow characterise to the Venusian surface. More that 80% on Venus surface are flat plains thought to come from some volcanic activity. For instance, thousands of shielded volcanoes may be observed on Venus's surface. These are not regular volcanoes - like the ones on earth - on the contrary of long slating sides, these volcanoes have rather shorter sides that are considered to arise from molten mantle that tend to bring to the fore the surface above it, then, overlaying it sides and as final results short slopes of accumulated magma. Such volcanoes, in Venus, are estimated to have a diameter of 0.8 km - 240 km (NASA. 2007). Venus is not completely made of shielded volcanoes it also contains also some 100s large volcanoes covering its surface

One of the consequences of the presence of volcanoes on 80% of the surface of Venus is that huge lava is deposited on its surface, thus, the endless flat plains. This lava may extend for hundreds of kilometres forming bendy channels as it travels along the surface of Venus. The other major consequence of volcanoes on the surface of Venus is the deposit of sulphuric acid (H2SO4) in its atmosphere. This is the major contributor to the green house effect, thus, the extremely high temperature in its surface.

Putting all together, Venus is rich of flat plains completed mostly by shield volcanoes and some of large volcanoes. Although they promote a pleasant surface to the planet, these volcanoes are the main source of limited resources for life, since high temperatures take up all the water, and poisonous gas are formed then deposited in the atmosphere.

Venus presents small craters less than two kilometres

Venus is the second planet close to the sun after mercury. Like all other planets in the solar system Venus orbits around the sun in roughly circularly. However other object found in space do not orbit in such fashion. Incidentally, asteroids and comets tend to orbit the sun elliptically, hence, at some point in space the lines of orbit intercept. When this happens, interplanetary debris collide with the surface of Venus, craters are formed.

A large number of craters dot the surface of Venus. In spite of this, such craters tend to be very small, about 2 kilometres in diameter almost non-existent. The reason why some craters in Venus are almost non-existent in the surface of Venus is due to its thick atmosphere. Large special debris enter the atmospheric area of Venus to make contact with its surface, but as it makes its way through it is burn off by the abundant sulphuric acid (H2SO4) present thus causing such small craters. However, if such large debris break while penetrating the atmosphere, a cluster of craters, this is, overlaid craters are formed.

Interplanetary debris impact on the surface of Venus does not only cause craters but in addition, flows of lava. Because the surface of Venus is dramatically hot, as the craters are formed the rocks melt, then again since surface rocks found in Venus are the result of dry lava, it is molten hence the flow of lava after the impact.

Lastly, scientists have found that the more craters are found on the surface of a planet, the older the planet is present in the solar system. They also spot a relationship between craters and internal activity. For instance, Venus has small craters because the debris, after impact with its surface, interacts with its heavy atmosphere and the surface temperature. Hence this suggests that Venus has some interior activity that generates sufficient geological activities that limits the entry of craters, in other words, the surface of Venus is somewhat young and alive. Otherwise, it would be dull with little internal activity. From this it is fair to say that the more the geological activity the smaller the craters are on the surface of the planet.


Venus is a very simple planet, yet, many complexions shape the planet in order to bring to light its uniqueness. It was learnt that Venus has a much heavier atmosphere compared to that of Earth's, in its turn, it is the abundance of sulphuric acid in the clouds of Venus that produces the clouds that veils Venus and gives its unique charm. From this section, it was also informed that the surface temperature in Venus is tremendously high which give its unique property of flaky crust compared to the hard solid that its sister planet has. Again, its temperature is so high that takes up all the water existent and lives no chance of life in its planet.

Interesting enough, Venus has no mountains, but yet, it has more than 80% of its plain land filled with volcanoes and lava. The craters that indentify its surface also told the reader the age of Venus. Venus is about 500 million years old (NASA. 2007), scientists learnt this by studying the deepness and consequence of debris impact in the surface of Venus.

All the properties and similarities of Venus to Earth, help scientists to unveiled the mysteries and fantastic properties of this planet and now we are able to delight ourselves with such knowledge.