Mars: The Ultimate Guide

Star Walk
9 min readOct 6, 2021


The red planet Mars has been known to humans since ancient times. It has been the target of dozens of space missions and will hopefully soon become the first planet astronauts will land on. In this article, we’ll tell you everything you need to know about Mars and answer the most common questions related to the Red Planet. Let’s get started!

Mars Facts

  • Planet type: terrestrial
  • Radius: 3,396 km
  • Mass: 6.417 × 10²³ kg
  • Aphelion: 249.2 million km
  • Perihelion: 206.6 million km
  • Average distance from the Earth: 225 million km
  • Surface temperature: −143 °C to 35 °C
  • Solar day length: 24 h 39 m 35 s
  • Sidereal day length: 24 h 37 m 22 s
  • Year length: 686.98 Earth days
  • Age: 4.503 billion years
  • Named after: Roman god of war

How big is Mars?

Mars is the second smallest planet in the Solar System — only Mercury is smaller. Let’s measure this planet and compare it to the Earth.

Mars’ size

Mars has a diameter of 6,792 km; the planet’s circumference around the equator is 21,326 km. Thus, if you’re moving at a speed of about 100 km per hour, it will take you about nine days to travel around the planet’s equator.

Is Mars bigger than the Earth?

No, it’s not. The diameter of Mars is only about half of the Earth’s diameter, which is 12,742 km. Also, Mars is only about two times bigger than our Moon, which is 3,474 km in diameter.

Mars’ orbit and rotation

Every planet in the Solar System has its own orbital period (that determines the length of year) and rotation period (that determines the length of a day-night cycle). Let’s take a look at how fast Mars revolves around the Sun and spins on its axis.

How long is a year on Mars?

As Mars is located farther away from the Sun than the Earth, it takes longer for the Red Planet to complete one orbit around the Sun. A year on Mars lasts for about 687 Earth days, which equals 1.88 Earth years.

How long is a day on Mars?

Mars rotates on its axis at almost the same speed as the Earth. For this reason, daily cycles on these two planets are quite similar. One Martian day (called a sol) lasts 24 hours 39 minutes, which is only 39 minutes longer than a day on the Earth.

Does Mars have seasons?

As you probably know, seasons are caused by the tilt of a planet’s axis of rotation. Mars’ axial tilt is very similar to the Earth’s: the Red Planet is tilted at 25.2°, while the Earth’s axial tilt is about 23.5°. For this reason, Mars has four distinct seasons: spring, summer, fall, and winter. However, each season on Mars lasts about two times longer than on the Earth. That’s because it takes almost two Earth years for Mars to travel around the Sun once.

How far away is Mars?

Mars is the fourth planet from the Sun and one of the Earth’s two closest neighbors (the other one being Venus).

How far is Mars from the Sun?

Due to the high eccentricity of the Red Planet’s orbit, there’s a significant difference between Mars’ closest and farthest points from the Sun, which equal 206.6 million km and 249.2 million km, respectively. On average, Mars is positioned 228 million km away from our star, which equals 1.5 astronomical units.

How far is Mars from the Earth?

The distance between Mars and our planet is constantly changing. The farthest distance between Mars and the Earth equals 401 million km. The closest distance the two planets can get to each other is 54.6 million km. However, such a close approach never happened in recorded history. The closest approach between Mars and the Earth in almost 60,000 years occurred in 2003 when the two celestial bodies were 55.7 million km away from each other.

How long does it take to get to Mars?

The duration of a trip to Mars depends on when it is taken. The best time to launch a spaceship to Mars is about three months before the Red Planet gets closest to the Earth. Such a moment happens about every two years, around Mars’ opposition. According to NASA, an average trip to Mars takes about nine months.

The two fastest trips to Mars were taken by Mariner 6 (five months) and Mariner 7 (four months). However, these two spacecraft performed flybys of Mars and so didn’t need to slow down as orbiters, landers, and rovers do. The latest rover to land on Mars, Perseverance, reached the planet in about seven months.

Missions to Mars

As the Earth’s close neighbor, Mars has been the destination of numerous space missions. Since 1960, about 50 missions have been sent to the Red Planet, though only about half of them have been successful. Let’s take a look at the most significant ones.

NASA’s Mariner 9 entered Mars’ orbit in 1971, becoming the first spacecraft to orbit another planet. Mariner 9 mapped 85% of the Martian surface and sent more than 7,000 images back to the Earth.

The first human-made object to reach the Martian surface was the Soviet Union’s Mars 2, launched the same year as Mariner 9. Unfortunately, the speed at which Mars 2 approached the planet was too high; as a result, the descent system malfunctioned, and the spacecraft crashed into the Red Planet’s surface.

The first spacecraft to successfully land on Mars was NASA’s Viking 1. This spacecraft operated on the planet from 1976 to 1982 and sent back more than 57,000 images.

NASA’s Sojourner, which arrived on Mars in 1997 as part of the Pathfinder mission, became the first rover to operate on another planet. The Sojourner rover operated for 83 sols, making scientific measurements and taking pictures.

NASA’s twin rovers Spirit and Opportunity reached the Red Planet in 2004. The rovers were tasked with studying the planet’s climatic history and looking for evidence of past water activity. Originally, the mission was planned to last 90 days. However, both rovers exceeded their planned mission lifetimes by many years: Spirit operated until 2010, and Opportunity stopped working only in 2018.

In 2012, NASA’s rover Curiosity arrived at the Gale crater on Mars. The rover investigated the Martian climate and geology and found out that the planet once had conditions favorable for microbial life. Curiosity has been active on Mars for more than three thousand sols; as of 2021, the rover is still operational.

In 2021, China successfully landed its first spacecraft on Mars as part of the Tianwen-1 mission. The rover named Zhurong became the first spacecraft not launched by NASA to operate on Mars.

Also in 2021, NASA’s Perseverance rover landed on the Red Planet. Apart from the rover, a helicopter called Ingenuity also takes part in the mission. On April 19, 2021, Ingenuity performed the first-ever powered, controlled flight on another planet.

What is Mars made of?

Like the other three terrestrial planets (Mercury, Venus, and the Earth), Mars is a rocky celestial body. Let’s take a closer look at the planet’s physical peculiarities.

Formation of Mars

Mars formed together with the other Solar System planets. About 4.5 billion years ago, a giant cloud of interstellar gas and dust collapsed under its own gravity and flattened into a protoplanetary disk. Mars and the other rocky planets formed in the inner part of this disk, while the gas giants settled in the outer regions of the young Solar System.

Mars’ structure

Mars has a central core, a mantle, and a crust. The Red Planet’s core is made of iron, nickel, and sulfur. It is surrounded by a rocky mantle and a crust made of iron, magnesium, aluminum, calcium, and potassium.

Mars’ surface

Mars’ surface is primarily composed of basalt. The prevalence of iron oxide in the Martian soil gives the planet its distinct red color.

The Red Planet has many surface features similar to our planet: valleys, deserts, mountains, and polar ice caps. There are even former river deltas that suggest that Mars was a watery planet in the past.

Mars’ atmosphere

The atmosphere of Mars is much thinner than the Earth’s. It is composed primarily of carbon dioxide (95%), while our planet’s atmosphere is rich in nitrogen and oxygen. Thus, humans would not be able to breathe on Mars.

However, in April 2021, NASA’s rover Perseverance successfully converted a small portion of the Martian atmosphere into oxygen. In the future, this technology might be able to provide astronauts with breathable air.

Does Mars have a moon?

Mars has two moons: Phobos and Deimos. Both of them were discovered by American astronomer Asaph Hall in 1877. The moons of Mars are among the smallest moons in the Solar System: for reference, the Earth’s Moon has a diameter more than 100 times greater than that of Phobos, the larger Martian moon. Like our Moon, Phobos and Deimos are tidally locked to their planet and always show only one side to it.

Upcoming Events

October 7: Mars at solar conjunction

On October 7, 2021, at 03:35 GMT, Mars will pass close to the Sun in the sky. At the closest approach, the Red Planet will be positioned at only 0°39' from our star. Due to such proximity to the Sun, Mars will become unobservable for several weeks. If the planet could be observable, it would appear at its smallest and faintest — that’s because at the time of solar conjunction, Mars will reach its most distant point from the Earth.

December 2: Conjunction of the Moon and Mars

On December 2, 2021, at 00:27 GMT, Mars will pass close to the Moon in the sky. The separation between the two celestial bodies will equal 0°41'. The Moon will be shining at a magnitude of -8.9, while Mars will have a magnitude of 1.6. Both sky objects will be positioned in the constellation Libra. You’ll be able to observe the conjunction with the naked eye or with a pair of binoculars.

December 31: Lunar occultation of Mars

On December 31, 2021, at 19:52 GMT, the Moon will pass in front of Mars in the sky. You can observe the lunar occultation of Mars with binoculars. Unfortunately, this celestial event will only be visible from parts of Australia.


What is the gravity on Mars?

The gravity on Mars is 62% lower than on the Earth. This means that a person who weighs 80 kg on our planet would weigh only 30 kg on Mars. Although it would be much easier for humans to walk on Mars, such low gravity can have other not-so-pleasant effects on hypothetical Mars colonists — like causing muscle deterioration and osteoporosis.

What color is Mars?

The predominant color of the Martian surface is red. It is explained by the prevalence of iron oxide — more commonly known as rust — in the planet’s soil. Other colors on Mars include golden, brown, and tan.

What is the temperature on Mars?

Overall, Mars is a very cold place. The average temperature on the Red Planet equals -62 °C. However, according to Michael Mischna, a research scientist at NASA’s Jet Propulsion Laboratory, the air temperature on Mars wouldn’t feel the same as on the Earth. There’s little water vapor and few air molecules on Mars, so -70 °C would feel like -34 °C. To better understand temperature conditions on Mars, check this infographic made by NASA.

How many rovers are on Mars?

As of October 2021, there are six rovers on the Red Planet. Five of them (Sojourner, Spirit, Opportunity, Curiosity, and Perseverance) belong to NASA and one (Zhurong) — to China National Space Administration.

Did you know?

  • Mars can boast the largest volcano in the entire Solar System — Olympus Mons. With a height of 21 km, it stands about 2.5 times taller than Mount Everest.
  • Mars’ larger moon, Phobos, gradually gets closer to the planet at a rate of about 2 cm per year. In 50 million years, Phobos will either crash into Mars or disintegrate to form a ring around the Red Planet.
  • Billions of years ago, Mars looked very similar to the Earth. Large portions of the planet’s surface were covered with liquid water, and there may have been primitive life forms in the oceans. However, eventually, the Red Planet lost most of its atmosphere and dried up.
  • During the late 19th and early 20th centuries, many astronomers observed a network of canals on the Martian surface. Some believed them to be irrigation canals constructed by an alien civilization. However, it turned out to be an optical illusion.

We hope that you’ve discovered something new about the Red planet. Don’t hesitate to share this article on social media if you liked it. Also, you’re welcome to watch our educational cartoon with fun facts about Mars. We wish you clear skies and happy observations!



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