There are four terrestrial planets in our solar system, which are also the four closest to the sun: Mercury, Venus, Earth, and Mars.
Astronomy is a subject that fascinates us all. Studying the intricate workings of the cosmos is as rewarding as it is challenging, constantly trying to find answers to complex questions such as our place in the universe.
But before we can deal with such groundbreaking theories, we must first learn and understand the basics of astronomy upon which it is founded. And perhaps the most basic of them all is understanding planets, including the one we live in.
A planet, by definition commonly agreed, is a celestial body that is in orbit around the sun, is shaped in the form of a sphere, and has a gravitational field strong enough to clear out its orbital debris.
We know earth as a giant body of rocks and metals upon which we thrive. But we have to understand that not all planets are the same.
Most of them do not have conditions that deem them habitable for a plethora of reasons such as temperature and surface density. For example, a typical day on the planet Venus is 462 degrees Centigrade, enough to boil most earthly things.
Mars, on the other hand, has no Oxygen and is effectively a very thin atmosphere that makes living beings vulnerable to the deadly UV rays of the sun. To then think about our position on earth and how we have managed to survive and thrive as a species in this pale blue dot is profound.
As discussed, planets can be of varying physical and compositional properties that determine its habitability and surface conditions. Broadly speaking, planets within our solar system can be categorized into two categories based on their position with respect to the sun:
- Terrestrial Planets
- Gas giants or Jovian Planets
What are terrestrial planets
Terrestrial planets can typically be defined as Earth-like planets, primarily made up of rocks and have a hard surface. Most such planets also have a molten heavy-metal core, moons, and traditional topological features such as craters, valleys, and volcanoes.
In our solar system, there are four terrestrial planets that also happen to be the closest to the sun: Mercury, Venus, Earth, and Mars. These planets are also sometimes referred to as the inner ring planets.
Studies estimate that during the formation of our solar system there were likely more terrestrial planetoids that were either destroyed or merged with one of the planets.
Every single terrestrial planet has around a similar sort of structure: a focal metallic center made out of for the most part iron, with an encompassing silicate mantle.
Such planets have regular surface highlights, which incorporate gulches, cavities, mountains, volcanoes, and other comparable structures, contingent upon the nearness of water and structural movement.
Terrestrial planets likewise have optional climates, which are created through volcanism or comet impacts.
This likewise separates them from gas goliaths, where the planetary climates are primary and were captured directly from the original solar nebula.
Terrestrial planets are additionally known for having few or no moons. Venus and Mercury have no moons, while Earth has just one (the Moon).
Mars has two satellites, Phobos and Deimos, however, these are more likened to extensive space rocks than genuine moons. In contrast to the gas mammoths, earthbound planets likewise have no planetary ring frameworks.
Jovian planets
In our solar system, Jupiter, Saturn, Uranus, and Neptune make up what we call gas giants or Jovian planets. They typically do not have a solid surface and are partially or wholly made of condensed gases.
They are inhospitable to life as we know it and often have rings around them. Gas giants are usually bigger than terrestrial planets and have very thick atmospheres.
On Jupiter and Saturn, hydrogen and helium make up a large portion of the planet, while on Uranus and Neptune, the components make up only the external envelope.
The classification of terrestrial planets
Researchers have proposed a few classifications for ordering terrestrial planets. Silicate planets are the standard kind of terrestrial planet found in the Solar System, which is made principally out of a silicon-based rough mantle and a metallic (iron) center.
Iron planets
Are a hypothetical kind of terrestrial planet that comprises essentially of iron and thusly has a more noteworthy thickness and a littler range than other earthly planets of practically identical mass.
Planets of this sort are accepted to frame in the high-temperature areas near a star, and where the protoplanetary circle is wealthy in iron.
Mercury is a conceivable precedent, which is framed near our Sun and has a metallic center equivalent to 60– 70% of its planetary mass.
Coreless planets
Are another hypothetical kind of earthly planet, one that comprises of silicate shake however has no metallic center. At the end of the day, coreless planets are the inverse of an iron planet.
Coreless planets are accepted to shape more remote from the star where unstable oxidizing material is progressively normal. In spite of the fact that the Solar System has no coreless planets, chondrite space rocks and shooting stars are normal.
And after that, there are Carbon planets, a hypothetical class of planets that are made out of a metal center encompassed by essentially carbon-based minerals. Once more, the Solar System has no planets that fit this depiction, however, has a wealth of carbonaceous space rocks.
What are the terrestrial planets
Terrestrial please are Mercury, Venus, Earth, and Mars. Below we take a look in more detail.
Mercury
Mercury is the littlest planet in the nearby planetary group, about a third the extent of Earth. It has a meager climate, which makes it swing among consuming and frosty temperatures.
Mercury is additionally a thick planet, made for the most part out of iron and nickel with an iron center. Its magnetic field is just around 1 percent that of Earth’s, and the planet has no known moons.
The outside of Mercury has numerous profound pits and is secured by a slight layer of little molecule silicates. In 2012, researchers found broad proof of organics — the structure squares of life — as well as water ice in cavities, shaded from the sun.
Mercury’s meager climate and closeness to the sun mean it’s unimaginable for the planet to have a life as we probably are aware of.
Venus
Venus, which is about an indistinguishable size from Earth, has a thick, poisonous carbon-monoxide-ruled climate that traps heat, making it the most blazing planet in the nearby planetary group.
Venus has no known moons. A significant part of the planet’s surface is set apart with volcanoes and profound gullies.
The greatest canyon on Venus extends over the surface for 4,000 miles (almost 6,500 kilometers). What’s more, it’s conceivable that probably a portion of the planet’s volcanoes are as yet dynamic.
Scarcely any rocket has ever entered Venus’ thick climate and endured.
What’s more, it’s not simply spacecraft that experiences difficulty traversing the air — there are fewer meteor impacts on Venus than different planets in light of the fact that just the biggest meteors can make it.
The planet is threatening to life as we probably are aware of.
Earth
Of the four terrestrial planets, Earth is the biggest and the single one with broad districts of fluid water.
Water is vital for life and life is plenteous on Earth — from the most profound seas to the most elevated mountains.
Like the other rocky planets, Earth has a rough surface with mountains and gullies and a substantial metal center. Earth’s climate contains water vapor, which directs everyday temperatures.
The planet has standard seasons for a lot of its surface; locales closer to the equator will in general remain warm, while spots nearer to the poles are cooler and in the winter, frosty.
The Earth’s atmosphere, be that as it may, is heating up because of environmental change related to human-produced ozone-depleting substances, which act as a trap for escaping heat.
Earth has a northern magnetic pole that is meandering significantly, by many miles a year; a few researchers recommend it may be an early indication of the north and south magnetic poles flipping.
The last real flip was 780,000 years back. Earth has one moon that space travelers visited during the 1970s.
Mars
Mars has the biggest mountain in the nearby planetary group, rising 78,000 feet (about 24 km) over the surface.
A significant part of the surface is extremely old and loaded up with craters, however, there are topographically more up-to-date zones of the planet too. At the Martian, poles are polar ice tops that shrivel amid the Martian spring and summer.
Mars is less thick than Earth and has a smaller magnetic field, which is demonstrative of a strong center, as opposed to a fluid one. While researchers have discovered no proof of life yet, Mars is known to have water ice, and organics — a portion of the elements for living things.
Proof of methane has additionally been found in certain pieces of the surface. Methane is created from both living and non-living procedures.
Mars has two little moons, Phobos and Deimos. The Red Planet is additionally a well-known goal for the shuttle, given that the planet may have been livable in the old past.
What is beyond the solar system
Amid its lifetime, NASA’s Kepler space observatory found in excess of 2,300 affirmed outsider planets — and thousands of additional potential outcomes — as of January 2019.
Kepler came up short on fuel in 2018, however huge numbers of its conceivable planet revelations still should be affirmed with follow-up perceptions from different telescopes.
Utilizing the information from the telescope, researchers determined that there might be billions of Earth-like planets in the Milky Way cosmic system.
A successor mission to Kepler, called TESS (Transiting Exoplanet Survey Satellite), started activities in 2018.
The shuttle is intended to search for Earth-like planets that are just a couple of light-years from our planet, taking into account brisk perceptions by different telescopes on Earth. Starting in mid-2019, TESS has effectively found a bunch of planets; its initially affirmed find was in September 2018.
How is Venus different from Earth?
Venus is a rough planet, much like the Earth. Given its comparable size, mass, and thickness to our planet, researchers believe that its inside is much similar to Earth’s own.
Notwithstanding an outside layer essentially more seasoned than Earth’s continually evolving surface, Venus likely likewise sports a mantle and a center. The mantle is presumably rough, and the center is most likely fluid to some degree.
However, notwithstanding the planets’ similitudes, the magnetic field of Venus is far more fragile than on Earth’s.
The explanations behind that may have to do with the center. Some portion of it could basically have to do with movement.
The planet rotates at a very slow pace — with one day taking 243 Earth days — and the center may not turn quick enough to make a magnetic field the way the center of Earth and different planets do. The center may likewise be totally strong, or may not exist at all.
How old is the Earth?
Researchers have struggled through several years attempting to decide the age of the planet.
By dating the stones in Earth’s regularly evolving crust, just as the stones in Earth’s neighbors, for example, the moon and visiting shooting stars, researchers have determined that Earth is 4.54 billion years of age, with an error margin of 50 million years.