Planetary Satellites

In order to compare the atmospheres of the terrestrial planets, first we have to understand what terrestrial planets are. They are characterized by having a mostly solid surface, unlike gaseous ones, whose surface is mostly liquid or gas. Earth is the only rocky planet that has an active hydrosphere, that is, water above and below the surface. The main characteristic of terrestrial planets is that they are formed mostly by silicates. Silicates are the most abundant group of minerals, and also the one of greatest geological importance, since they are petrogenic, that is to say, they are the minerals that form the rocks. Another characteristic shared by the rocky planets is their structure under the surface: a metallic core, mostly made of iron, and a series of silicate layers that surround it.

The terrestrial planets are those that are closest to the Sun: Mercury, Venus, Earth and Mars. They are also known as telluric planets or rocky planets. The structure of the terrestrial planets is very similar in all of them: they have a metallic nucleus and a silicate mantle that surrounds them. On its surface they have craters, mountains, valleys and volcanoes. Craters are less visible on Earth due to the action of atmospheric agents and vegetation. Mercury and Venus have no natural satellites to accompany them. Instead Earth has a satellite, the Moon, which is the fifth largest satellite in the Solar System. Mars has two natural satellites, Deimos and Phobos, which are believed to be two captured asteroids and have an irregular shape.

There are many other bodies in the Solar System with characteristics similar to those of terrestrial planets, such as transneptunian objects, which have a solid surface, or the dwarf planet Ceres of the asteroid belt. Transneptunian objects are mostly ice due to their long distance from the Sun. Some large satellites of the Solar System are also similar to terrestrial planets and rock formations, but can not be considered as such. It is believed likely that there were many more terrestrial planets (planetasimals) during the formation and evolution of the Solar System but they were merged or destroyed by the main current terrestrial planets.

Mercury is the terrestrial planet closest to the Sun, so it only takes 88 days to travel its orbit. In addition, it is the smallest planet in the Solar System. Its rotation period is 58.7 Earth days.

Venus is the second planet in the Solar System, and its journey around the Sun is about 225 days. Its size and mass are similar to those of Earth, however, it is the planet that has the longest day in the Solar System, since its rotation period is 243 Earth days. Earth is the third planet in the Solar System and is the largest of the four terrestrial planets. In 365 days it travels through the Sun's orbit and its rotation period is 24 hours, a terrestrial day. The Earth is home to thousands of species and has a unique natural satellite: the Moon. Mars is the fourth planet of the Solar System. The orbital route of Mars is 687 Earth days, and it is the most Earth-like in many aspects, as for example that its rotation period is 24 hours and 37 minutes. Deimos and Phobos are its two natural satellites, which from the surface of Mars, move from west to east.

Astronomers, always helped by technologies that were advancing to achieve a better knowledge of the universe that surrounds man (and let us say with a great deal of curiosity on their part) as they discovered new planets, which fit the characteristics that they established themselves to identify which ones were and which were not, named each one with names that come from Greek mythology and Roman mythology, as is the case of Mars (Roman god of war) or Venus (Roman goddess related to love). It is important for Astronomers to know the different type of terrestrial planets and their differences mainly because us, humans, live in one of them. We have to be able to know in what we are living, the components of earth, what is harming our planet so that we can take care of it and know what could damage it. And secondly because with the advance of technology we keep discovering things and facts we did not know before and that is what keeps developing new theories that could keep leading to a better understanding of life.

So far, the Earth is the only planet in the Solar System in which life develops, although for years scientists have been studying and investigating whether in other planets of the same System the development of living beings can be feasible, especially looking for signs of the existence of water and also taking into account the seriousness of each of them, which is what we, who live on Earth, allows us to be on it seated and not floating through the air, as for example if it happens on the Moon, and that it was clearly seen when American astronauts came to it in 1969 to explore it. If astronomers keep searching and investigating terrestrial planets, we might be able to find new form of life. And that is why terrestrial planets are important in this field. To keep investigating new possibilities of life. Today Mars is considered a dry planet. On its surface, however, we can still find the vestiges of some rivers that supposedly flooded the planet millions of years ago. Now, new research points to the possibility that we have underestimated the abundance of water on the red planet. A new study, published a few days ago in the journal “Science Advances”, suggests that Martian rivers became wider than we can find on Earth today. The data collected from the Martian river basins on which there is more data reveals the ancient rivers of Mars were approximately twice as wide as terrestrial rivers. This situation could have occurred at different stages of Martian history. 3.6 billion years ago and 1 billion years ago, specifically. In these periods, the data obtained indicate that the flow of the Martian rivers was intense. This means that in these formations they could run between 3 and 20 liters of water per square meter per day. This phenomenon seems to have taken place in the whole planet, reason why the experts discard that it was a short episode or located.

These findings, according to the researchers responsible for this new study, suggest that there may have been rainfall on Mars even during the time when researchers believe that the planet was losing its atmosphere and was drying up. If the data on these massive rivers are correct, the findings could suggest that the last stage of the Mars atmosphere disappeared faster than previously estimated, or that there were other precipitants of precipitation in low atmosphere conditions.

As it was established before, it is very important to study the planets, not only to understand how and why the different natural phenomena occur, habitats, food chains, among many other aspects. But also the study of the earth, allows us to even understand other planets possible planets, understanding that in theory certain physical, mathematical, chemical and even biological laws are universal. It is worth saying that the study of it gives us the possibility to carry out projects in favor of taking care of it. Artificial satellites have revolutionized our world in almost any aspect that you can pose. Weather satellites allow us to follow the development of hurricanes and warn when there is a danger, saving thousands of lives. Communications satellites offer us instant access to information from around the world via radio, television and telephones. Many of us would be lost without the GPS system, ect. Exploring the other planets of the Solar System helps us to better understand ours and to see how our own actions affect it. One day our own existence as a species could depend on being able to detect and move an asteroid to an orbit that does not pose a danger of impact against the Earth. From the point of view of technology, computers, communications, and many other fields have benefited enormously from the developments created for space research. Some estimates say that for every dollar that was invested in the Apolo program a return of more than 20 was obtained. But above all we are curious and we want to learn, explore, challenge the limits of what is possible and see what is beyond it. And the Universe is huge, beautiful, mysterious and, above all, understandable. Even if the other reasons did not exist, this should be enough to encourage us to continue our exploration.

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