Mercury
Mercury is the smallest and fastest planet in our solar system. It has a diameter of 4,879 km, which is only slightly larger than Earth’s moon. It orbits the Sun at a speed of 29 miles (47 kilometers) per second.
Mercury has a very long day and a very short year. A day on Mercury lasts 176 Earth days, while a year on Mercury takes only 88 Earth days. This means that one day on Mercury is longer than two years on Mercury!
Mercury has a very eccentric orbit, meaning that it is not a perfect circle but more of an oval shape. This causes its distance from the Sun to vary from 46 million km to 70 million km. This also causes its temperature to range from -173°C to 427°C [-279°F to 801°F].
Mercury has no moons or rings, and almost no atmosphere. This makes it vulnerable to impacts from asteroids and comets, which have created many craters on its surface. Some of these craters contain water ice, which can survive in the dark and cold regions near Mercury’s poles.
The existence of water ice on Mercury was first suggested by radar observations from Earth in 1991. It was later confirmed by NASA’s MESSENGER probe, which orbited Mercury from 2011 to 2015. MESSENGER also collected data on Mercury’s surface, atmosphere, magnetosphere and geology. MESSENGER was the second mission to explore Mercury, after Mariner 10, which flew by the planet three times in 1974 and 1975. Mariner 10 was the first to image Mercury’s surface and measure its magnetic field. The current mission to Mercury is BepiColombo, a joint project of ESA and JAXA. It launched in 2018 and will arrive at Mercury in 2025. It consists of two orbiters: one to study Mercury’s surface and exosphere (MPO), and one to study its magnetosphere (MMO)
Mercury is named after the Roman messenger god, who was known for his speed and agility. He wore winged sandals and a winged hat, and carried a staff called a caduceus.
Venus
Venus is the second planet from the Sun, and it is the second brightest object in the night sky after the Moon. It is often referred to as the Earth's sister planet due to their similar size and mass.
Venus is the sixth in size and mass. It is sometimes called Earth’s “sister” or “twin” planet as it is almost as large and has a similar composition. It has a diameter of 12,103.6 km (7,520.8 mi) and a mass of 81.5% of Earth’s.
Venus has a very thick atmosphere, mainly composed of carbon dioxide and nitrogen, with traces of sulfuric acid clouds. The atmospheric pressure on Venus is about 92 times that of Earth’s, which is equivalent to being 900 m (3,000 ft) underwater on Earth.
Venus has a very high surface temperature, averaging at about 462°C (864°F). This is due to its proximity to the Sun and its strong greenhouse effect, which traps heat in its atmosphere. Venus is hotter than Mercury, even though Mercury is closer to the Sun.
Venus has a very slow rotation, taking about 243 Earth days to complete one spin on its axis. This means that one day on Venus is longer than one year on Venus, which takes only 225 Earth days to orbit the Sun. Moreover, Venus rotates in the opposite direction of most other planets, which means that the Sun rises in the west and sets in the east on Venus.
Venus has no moons or rings, but it has many volcanoes and mountains on its surface. The highest mountain on Venus is called Maxwell Montes, which reaches about 11 km (7 mi) above the mean surface level. The largest volcano on Venus is called Maat Mons, which has a diameter of about 290 km (180 mi) and a height of about 8 km (5 mi)
There have been 46 space missions to Venus, including flybys and orbiters. The first mission to Venus was Mariner 2, which flew by the planet in 1962 and scanned its cloud-covered surface2. The most recent mission to Venus was Akatsuki, which entered orbit around Venus in 2015 and is studying its atmosphere and weather. The most successful missions to Venus were conducted by the Soviet Union, which landed several probes on the planet’s surface between 1970 and 1985. The first probe to land on Venus was Venera 7, which transmitted data for 23 minutes before succumbing to the harsh conditions. The longest-lasting probe was Venera 13, which survived for more than two hours and sent back the first color images of Venus. The most comprehensive mission to Venus was Magellan, which orbited the planet from 1990 to 1994 and mapped its surface with radar. Magellan revealed that Venus has many volcanoes, mountains, craters and valleys, as well as evidence of tectonic activity2. The future missions to Venus include DAVINCI+ and VERITAS, which were selected by NASA in 2021. DAVINCI+ will descend through Venus’s atmosphere and measure its composition, while VERITAS will orbit the planet and map its geology with radar. These missions will shed light on how Venus became so different from Earth over time.
Earth
Earth is the third planet from the Sun and the fifth largest planet in the Solar System. It is the only planet known to have life, and it is the only place in the universe where humans can live.
Earth is the third planet from the Sun and the fifth largest planet in the solar system in terms of size and mass. It has a diameter of about 12,742 km (7,918 mi) and a mass of about 5.97 x 10^24 kg. It takes about 365.25 days to orbit the Sun and about 24 hours to rotate on its axis.
Earth has one natural satellite: the Moon🌙 which orbits Earth at an average distance of about 384,000 km (238,900 mi). The Moon has a diameter of about 3,474 km (2,159 mi) and a mass of about 7.35 x 10^22 kg. The Moon takes about 27.3 days to orbit Earth and rotates at the same rate as it orbits, which means that it always shows the same face to Earth. The Moon affects Earth’s tides by creating bulges in its oceans due to its gravitational pull.
Earth has an atmosphere that consists mainly of nitrogen (78%) and oxygen (21%), with traces of other gases such as argon, carbon dioxide and water vapor. The atmosphere protects Earth from harmful radiation from space and regulates its climate by trapping heat near its surface. The atmosphere also contains clouds that produce precipitation such as rain🌧️ snow❄️ or hail☄️ depending on temperature and humidity levels.
Mars
Mars is the fourth planet from the Sun and the second smallest planet in the Solar System. It is known as the Red Planet due to its reddish appearance. It is home to the tallest mountain in the Solar System, Olympus Mons.
Mars is named for the Roman god of war and has a reddish color due to iron oxide in its surface dust. It has a diameter of about 6,779 km (4,212 mi) and a mass of about 6.39 x 10^23 kg. It takes about 687 days to orbit the Sun and about 24 hours and 37 minutes to rotate on its axis.
Mars has a thin atmosphere that consists mainly of carbon dioxide (95%), with traces of other gases such as nitrogen, argon and oxygen1. The atmosphere is too thin to support liquid water on the surface, but there is evidence of past water activity such as dried riverbeds, lakes and glaciers.
Mars has many surface features such as impact craters🌑 valleys🏞️ dunes🏜️ volcanoes🌋 and polar ice caps❄️. The largest volcano on Mars is Olympus Mons which rises 22 km (14 mi) above the surrounding plains and has a diameter of 600 km (373 mi). The longest valley on Mars is Valles Marineris which stretches for 4,000 km (2,485 mi) along the equator and reaches depths of up to 7 km (4 mi).
Mars has two small irregularly shaped moons: Phobos☾ which orbits at an average distance of 9,377 km (5,827 mi) from Mars’s center and has a diameter of 22.2 km (13.8 mi), and Deimos☽ which orbits at an average distance of 23,460 km (14,580 mi) from Mars’s center and has a diameter of 12.6 km (7.8 mi). Both moons are thought to be captured asteroids that were pulled into orbit by Mars’s gravity.
Mars
Mars is the fourth planet from the Sun and the second smallest planet in the Solar System. It is known as the Red Planet due to its reddish appearance. It is home to the tallest mountain in the Solar System, Olympus Mons.
Mars is named for the Roman god of war and has a reddish color due to iron oxide in its surface dust. It has a diameter of about 6,779 km (4,212 mi) and a mass of about 6.39 x 10^23 kg. It takes about 687 days to orbit the Sun and about 24 hours and 37 minutes to rotate on its axis.
Mars has a thin atmosphere that consists mainly of carbon dioxide (95%), with traces of other gases such as nitrogen, argon and oxygen1. The atmosphere is too thin to support liquid water on the surface, but there is evidence of past water activity such as dried riverbeds, lakes and glaciers.
Mars has many surface features such as impact craters🌑 valleys🏞️ dunes🏜️ volcanoes🌋 and polar ice caps❄️. The largest volcano on Mars is Olympus Mons which rises 22 km (14 mi) above the surrounding plains and has a diameter of 600 km (373 mi). The longest valley on Mars is Valles Marineris which stretches for 4,000 km (2,485 mi) along the equator and reaches depths of up to 7 km (4 mi).
Mars has two small irregularly shaped moons: Phobos☾ which orbits at an average distance of 9,377 km (5,827 mi) from Mars’s center and has a diameter of 22.2 km (13.8 mi), and Deimos☽ which orbits at an average distance of 23,460 km (14,580 mi) from Mars’s center and has a diameter of 12.6 km (7.8 mi). Both moons are thought to be captured asteroids that were pulled into orbit by Mars’s gravity.