The inner planets of our solar system, also known as the terrestrial planets, are the four planets closest to the Sun. They include Mercury, Venus, Earth, Venus. These planets are rocky and have solid surfaces, distinguishing them from the gas giants in the outer solar system. They are made of dense metallic minerals and rich in iron and magnesium. They have thin atmosphere. They move faster and have a shorter period of revolution. They have very few natural satellites or no satellites.
1. Mercury:
Closest planet to the Sun.
It is named after the ancient Roman god Mercurius (Mercury): Messenger of the gods.
Smallest and lightest planet in the solar system.
Has a very thin atmosphere, primarily composed of oxygen, sodium, hydrogen, helium, and potassium.
Surface temperatures vary drastically, from extremely hot during the day to extremely cold at night.
Its special feature is the presence of magnetic field in it.
It is visible two hours before sunrise.
Mercury has no natural satellite.
No water on it.
No protective blanket like Ozone around it to prevent us harmful radiations.
Its largest crater: Caloris Planitia
Mercury's sidereal year (88.0 Earth days) and sidereal day (58.65 Earth days)
One solar day (sunrise to sunrise) on Mercury lasts for around 176 Earth days
The first telescopic observations of Mercury were made by Thomas Harriot and Galileo from 1610.
The first spacecraft to visit Mercury was NASA's Mariner 10 (1974–1975).
2. Venus:
Second planet from the Sun.
Similar in size and structure to Earth but with a thick, toxic atmosphere primarily composed of carbon dioxide, with clouds of sulfuric acid.
The hottest planet in the solar system due to a runaway greenhouse effect.
Surface pressure is about 92 times that of Earth.
Venus is one of two planets in the Solar System, the other being Mercury, that have no moons.
One solar day (sunrise to sunrise) on Venus lasts for around 224.7 Earth days
It is also known as the ‘Morning star’ or the ‘Evening star’.
It is surrounded by a thick cloud cover, hence known as ‘Veiled Planet’
Also known as the ‘Earth’s twin.’
It also rotates clockwise like Uranus.
The highest point on Venus, Maxwell Montes, the coolest point on Venus.
Venus is often visible to the naked eye during the day due to its brightness. In 1716, Edmund Halley calculated Venus's maximum brightness.
It is named after the Greek goddess Aphrodite of love and beauty
3. Earth:
Third planet from the Sun.
Largest of the inner planets and the fifth largest planet of our solar system.
The only planet known to support life.
Earth is about 4.54 billion years old.
Diameter is approximately 12,742 kilometers (7,918 miles).
Earth is an oblate spheroid, meaning it is slightly flattened at the poles and bulging at the equator.
Gravity is 9.8 m/s², which is strong enough to hold an atmosphere.
One natural satellite, the Moon.
Earth orbits the Sun at an average distance of about 93 million miles (150 million kilometers) in a nearly circular orbit.
It takes 23 hours 56 minutes and 4.091 seconds to rotate on its axis with a speed 1,610 km/h, resulting in day and night.
Impact of Earth’s Rotation Speed:
Making of day and night
The tides come twice a day
Differences in longitude and time, deviations in winds and currents
Earth moves from perihelion on January 3rd to aphelion on July 4th.
Day and night are equal on Earth: 21 March 23 September
Biggest day: 21 June
Shortest day: 22 December
Earth's axis is tilted by 23.5 degrees, and thus makes 66.5 angle, which causes the seasons.
Mean velocity 29.8 km/sec.
It takes 365 days 5 hours and 48 minutes to revolve around the Sun.
Impacts of Earth’s Revolution Speed:
Season changes
Difference in the duration of day and night
Determination of the duration of the year
The rays of the sunshine straight and diagonally
Determination of Cancer and Capricorn
Known as the ‘watery planet’ and ‘blue planet.’
Earth's crust is composed mainly of oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium.
Below the crust lies the mantle, composed of silicate rocks rich in magnesium and iron.
Earth's core is primarily made of iron and nickel. The outer core is liquid, while the inner core is solid.
The atmosphere on Earth is divided into five main layers: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
It is composed of 78% nitrogen, 21% oxygen, and trace amounts of other gases, including argon, carbon dioxide, and neon.
Located in the stratosphere, the ozone layer absorbs and scatters ultraviolet solar radiation.
About 71% of Earth's surface is covered by water, with oceans holding about 97% of it.
The Earth's oceans are divided into five major parts: the Pacific, Atlantic, Indian, Southern, and Arctic Oceans.
The Mariana Trench in the Pacific Ocean is the deepest point on Earth, reaching about 36,000 feet (10,972 meters).
Earth has seven continents: Asia, Africa, North America, South America, Antarctica, Europe, and Australia.
Mount Everest is the highest point on Earth, at 8,848 meters (29,029 feet) above sea level.
Mauna Kea in Hawaii is the tallest volcano when measured from its base on the ocean floor.
Earth has several climate zones, including tropical, temperate, polar, arid, and Mediterranean.
The planet's average temperature has risen about 1.2°C (2.2°F) since the late 19th century, largely due to human activities.
Life on Earth is thought to have begun more than 3.5 billion years ago, with single-celled organisms.
Earth's magnetic field protects the planet from solar and cosmic radiation.
Earth is home to over 7.8 billion people.
4. Mars:
Mars is named after the Roman god of war, reflecting its red, blood-like appearance.
The second-smallest planet in the Solar System after Mercury.
The fourth planet in the Solar System.
Mars has flat from both sides.
A day on Mars, known as a "sol," is approximately 24.6 hours, just slightly longer than an Earth day.
A year on Mars takes about 687 Earth days, nearly twice as long as a year on Earth.
Known as the "Red Planet" because of its reddish appearance, which is due to iron oxide (rust) on its surface.
Mars is home to the tallest volcano and the highest known mountain in the Solar System, Olympus Mons.
Also has a massive canyon system called Valles Marineris.
Mars has polar ice caps made of water and dry ice (frozen carbon dioxide) that expand and contract with the changing seasons.
Has a very thin atmosphere, composed mostly of carbon dioxide (95.3%), with traces of nitrogen (2.7%) and argon (1.6%).
The atmospheric pressure on Mars is only about 0.6% of Earth's at sea level, making it impossible for liquid water to exist for long on the surface.
Mars has two small moons, Phobos and Deimos.
Unlike Earth, Mars does not have a global magnetic field, which makes its atmosphere vulnerable to solar wind and radiation.
India launched its first Mars Orbiter Mission (MOM) from Sriharikota on 5 November 2013 through the polar satellite launch vehicle PSLV C-25. Mangalyaan was the name of the spacecraft.