One of the most significant topics in science today is the exploration of the vast and endless solar system. The most recent and highly anticipated topic is the discovery of a new planet whose atmosphere mimics one like Earth’s. This is important because it is one of the many threats that could come about in the near or distant future. As the population continues to rise, Earth could one day hit its population limit and cause common peril. Improvements in medicine and industrial farming are causing a decrease in mortality rate and an increase in life expectancy. As population numbers grow, there will be an increase in degradation of the environment causing harmful side effects like increase carbon dioxide levels which could be linked to global warming. Another possibility is the destructive behavior we humans display every day. As the population increases so do the many hurtful activities like pollution, which taints water supplies, air purity, and soil quality. So, it is obvious why many companies and astronomers are determined to find more planets for humans to inhabit. A suitable atmosphere is critical to find the perfect planet. The primary atmosphere of terrestrial planets was once made of the gasses secreted during initial formation, “that is 94.2% Hydrogen, 5.7% Helium and everything else less than 0.1%” (Schombert). However, this primary atmosphere was lost on terrestrial planets due to multiple factors such as the surface temperature, atoms masses, and each planet’s escape velocity. The lighter atoms on the planets were able to move fast enough to reach escape velocity and leak out into space. The warmer terrestrial worlds do not contain hydrogen and helium in their secondary atmospheres. The elements that do remain are often contained in rocky minerals or packed ice. The terrestrial planets that we have in our solar system up to date include Mercury, Venus, Earth, and Mars.
Mercury, also known as “Swift Planet,” is credited as being the smallest terrestrial planet in our solar system, only being about one-third the size of Earth. The atmosphere of Mercury is fragile. This thin atmosphere causes Mercury to experience dramatic weather changes from burning hot temperatures to below freezing temperatures. The planet itself is known to be very dense with the crust being made up of various metals including iron and nickel. At the core of the terrestrial planet is iron, increasing the overall density. It has an extremely low magnetic strength which equates to roughly one percent of Earth’s.
Along with low magnetic strength, the gravity on Mercury is low as well. In addition to the gravity being low on Mercury, it makes holding in the atmosphere extremely challenging. The atmosphere is saturated with “sodium, magnesium, and calcium… traces of hydrogen, helium, and potassium” (Redd). The unanswered question about mercury is how it loses and regenerate its atmospheres.
Mars is known to contain the gigantic mountains in the solar system, raising nearly 78,000 feet above its surface. Most of its surface is old and has a large number of craters. Regardless of this, recently, geographically new surfaces have been discovered. At the pole of Mars, are the polar ice caps that have size variation especially during the Martian springs. In the planet, morning clouds appear in the western limb. These were discovered to form overnight especially when Martian temperatures decrease and water in the surface of the atmosphere freeze to form ice crystal clouds (Aguilar &David 23). These clouds tower more than 25KM above the surrounding plains, mountains in the mars’ atmosphere. Compared to the earth, Mars is less dense and has smaller magnetic fields which are an indication of a solid core rather than earth’s liquid/molten core. Regardless of scientist finding no evidence of life, Mars is known to have water ice as well as organics- living things matter. Recently, evidence of methane has been discovered in some parts of the surface. Methane is known to be produced from processes of both non-living and living organisms. In its atmosphere, mars contain two moons- Deimos and Phobos; which are small in size compared to earth’s moon (Wordsworth et al. 2013). Popularly known as the red planet, mars had been a popular destination of spacecraft given that there is some evidence that the planet might have been inhabited many years ago. Some of the things that remain misty are the sources of methane in Mars atmosphere when there is no evidence of life in the planet, additionally, regardless of mars having liquid water, does the water flow since no evidence of rivers like in the earth.
Another terrestrial planet is Venus. This is the second planet from the sun and orbits the sun every 224.7 earth days. It has the most extended period of rotation compared to any other planet of the solar system. The planet is very terrestrial and sometimes known as “earth sister.” It has a thick carbon dioxide (96%), in its atmosphere that can trap most of the heat from the sun thus making it the hottest planet in the solar system-run way greenhouse effect. As a result, temperatures experienced in the planet reached as high as 465 degrees Celsius, a temperature which can melt lead.
Additionally, its surface is composed of sulphuric acid, and recently, scientists have detected traces of water in the atmosphere. Venus had no moon, and most of its surface is covered with deep canyons and volcanos. Some of the most significant canon on Venus stretch more than 4000 miles across the surface. It was recently observed that some of its eruptions are still active. The human quest for research has been met with challenges since only a few spacecraft have penetrated Venus thick atmosphere and survived due to the extreme temperatures.
Moreover, Venus has a vertex at each pole. The north vertex has double eye shape surrounded by a collar of air which is cool. Studies conducted in Venus suggest that the atmosphere contains strong winds (350 km) at the cloud tops through the winds at the surface of the planet are slow to a few kilometers per hour. In its surface, are rolling plains and several depression and two large highland areas among other features. Some of the misty in the planet are; the age of the surface of the planet, and the precise composition of the Venus atmosphere and whether it has a variation on different attitudes.
The earth is one of the terrestrial and the biggest of the terrestrial planets. Past studies indicate that the earth contains atmospheric layers which are divided into five main layers. The troposphere is one of the layers closest to the earth surface and lies between 4-12 miles from the earth surface. The stratosphere is another layer second in the earth atmosphere ending at almost 50 kilometers from the earth surface. Mesosphere starts at the 31st mile from the earth surface and extends to 53 miles high. Other layers include the thermosphere which extends about 56 miles, and its temperature reaches almost 1500 degrees Celsius. Lastly is the exosphere which is the most top layer and is extremely thin where the earth merges with the outer space. Its composition is mainly helium and hydrogen. It contains large regions of terrestrial liquid water which is necessary for life which is abundant on earth (Shizgal et al. 95). Like the other planets, earth has a rocky surface with canyons and mountains as well as a massive metal core. The atmosphere of the earth contains water vapor which is essential in moderating daily temperatures.
Moreover, the earth has regular seasons for most parts of its surface. Regions which are closer to the equator tend to be worm while areas to the poles are mostly cool and during the winter they become icy. Recently, studies have shown that the earth atmosphere is worming at a higher rate due to climate changes associated with greenhouse gases which are human generated. These gases act as a trap of heat in the atmosphere. The earth has poles, and at the northern pole, there is a magnetic pole which is wandering considerably by several miles a year. In recent studies by scientists at the Russian space research institute by orbiting the solar and hemispheric observatories for some decades discovered that gaseous layer at the earth atmosphere reaches more than 630,000 kilometers way in the space. This means that it is not only fifty times the diameter of the earth but also covers the moon’s atmosphere. At the part that the atmosphere merges with outer space, there is a hydrogen cloud called the geocorona. The geocorona is associated with ultraviolet radiation as the atoms of hydrogen scatters light rays in all directions. Some of the unanswered question about the earth atmosphere include whether the oceans and seas will continue absorbing carbon dioxide that is daily increasing. Additionally, will this process lead to seas saturation will carbon dioxide and what will happen next?
Gammon, Katharine. “Terrestrial Planets: Definition & Facts About the Inner Planets.” Space.com, Future US, 8 Feb. 2019, www.space.com/17028-terrestrial-planets.html.
Redd, Nola Taylor. “Mercury’s Atmosphere.” Space.com, Space, 18 Oct. 2016, www.space.com/18644-mercury-atmosphere.html.
Schombert, J. “Terrestrial Atmospheres.” Astronomy 121: The Formation and Evolution of the Solar System, University of Oregon, 29 Apr. 2019, abyss.uoregon.edu/~js/ast121/lectures/lec14.html.
Aguilar & David A. 13 Planets: The Latest View of the Solar System. National Geographic Books, 2011.
Shizgal, B., R. Sospedra-Alfonso, and A. Yau. “Energetic Oxygen in the Terrestrial Exosphere.” EGU General Assembly Conference Abstracts. Vol. 14. 2012.
Wordsworth, Robin D., and Raymond T. Pierrehumbert. “Water loss from terrestrial planets with CO2-rich atmospheres.” The Astrophysical Journal 778.2 (2013): 154.