The red planet

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

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 Earth.

Size of Mars

Mars has a diameter of 6792 km and the circumference of the planet around the equator is 21 326 km. Therefore, if you move at a speed of about 100 km per hour, it will take about nine days to go around the planet’s equator.

Is Mars bigger than Earth?

No, it is not. The diameter of Mars is only half that of Earth, which is 12 742 km. Also, Mars is only about twice as big as our Moon, which is 3474 km in diameter.

The orbit and rotation of Mars

Each planet in the Solar System has its own orbital period (which determines the length of the year) and rotation period (which determines the length of day and night). Let’s see how fast Mars revolves around the Sun and spins on its axis.

How long is a year on Mars?

Because Mars is located farther from the Sun than the Earth, the red planet takes longer to complete one orbit around the Sun. A year on Mars lasts about 687 Earth days, which is equivalent to 1.88 Earth years.

How long is a day on Mars?

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

Does Mars have seasons?

As you probably know, seasons are due to the tilt of a planet’s axis of rotation. The axial tilt of Mars is very similar to that of the Earth: the red planet is tilted 25.2°, while the axial tilt of the Earth is about 23.5°. For this reason, Mars has four distinct seasons: spring, summer, autumn and winter. However, each season on Mars lasts about twice as long as on Earth. This is because it takes Mars almost two Earth years to go around the Sun.

How far away is Mars?

Mars is the fourth planet from the Sun and one of the two closest to Earth (the other is Venus).

How far is Mars from the Sun?

Due to the high eccentricity of the red planet’s orbit, there is a significant difference between Mars’ closest and farthest points from the Sun, which are 206.6 and 249.2 million km, respectively. On average, Mars is 228 million km from our star, which is equivalent to 1.5 astronomical units.

How far is Mars from Earth?

The distance between Mars and our planet is constantly changing. The farthest is 401 million km, and the closest the two planets can be is 54.6 million km. However, there has never been a closer approach in recorded history. The closest approach between Mars and Earth in almost 60 000 years occurred in 2003, when the two celestial bodies were 55.7 million km from each other.

How long does it take to get to Mars?

The duration of a trip to Mars depends on the timing of the trip. The best time to launch a spacecraft to Mars is about three months before the red planet approaches Earth. This time occurs approximately 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 made by Mariner 6 (five months) and Mariner 7 (four months). However, these two spacecraft performed flybys of Mars and therefore did not need to slow down as in the case of orbiters, landers and rovers. The last rover to land on Mars (the Perseverance) reached the planet in about seven months.

Missions to Mars

As a close neighbor of Earth, Mars has been the destination of numerous space missions. Since 1960, some 50 missions have been sent to the red planet, although only 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 7000 images back to Earth.

The first man-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 to the surface of the red planet.

The first spacecraft to land successfully on Mars was NASA’s Viking 1. This spacecraft worked 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 (it did so for 83 sols), making scientific measurements and taking photographs.

NASA’s twin rovers, Spirit and Opportunity, arrived on the red planet in 2004, with the mission to study the planet’s climate history and look for signs of past water activity. Initially, the mission was to last 90 days. However, both rovers exceeded their planned mission duration by many years: Spirit operated until 2010 and Opportunity reached 2018.

In 2012, NASA’s rover Curiosity arrived at Mars’ Gale Crater. Its job was to investigate Martian climate and geology and it discovered that the planet once had favorable conditions for microbial life. Curiosity has been active on Mars for more than three thousand sols; in 2021, the rover is still operating.

In 2021, China successfully landed its first spacecraft on Mars as part of the Tianwen-1 mission. The Zhurong rover became the first non-NASA-launched spacecraft to circle Mars.

Also in 2021, NASA’s Perseverance rover landed on the red planet. In addition to the rover, a helicopter called Ingenuity is also participating in the mission. On April 19, Ingenuity performed the first engine-controlled flight on another planet.

What is Mars made of?

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

Formation of Mars

Mars formed together with the other planets of the Solar System. About 4.5 billion years ago, a gigantic 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.

Structure of Mars

Mars has a central core, a mantle, and a crust. The core of the red planet consists of iron, nickel, and sulfur. It is surrounded by a rocky mantle and a crust of iron, magnesium, aluminum, calcium, and potassium.

The surface of Mars

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

The red planet has numerous surface features similar to our planet: valleys, deserts, mountains and ice caps. There are even ancient river deltas suggesting that Mars was once a water planet.

The atmosphere of Mars

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

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

Does Mars have a moon?

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

Upcoming events

June 22: Moon-Mars conjunction

On June 22, at 18:16 GMT, the conjunction of the waning Moon and Mars (magnitude 0.5) will occur. They will be in the constellation of Pisces at 1° from each other. Jupiter (magnitude -2.2) will be nearby and will add to the scene.

Observers in the northern hemisphere will have a couple of hours before sunrise to enjoy the Moon and the Red Planet shining low over the horizon. In the southern hemisphere, the Moon and Mars will rise around 1-2 a.m. local time and move higher in the sky all night.

Frequently Asked Questions

What is the gravity on Mars?

Gravity on Mars is 62% lower than on Earth. This means that a person weighing 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 may have other not-so-pleasant effects on hypothetical Mars colonists, such as 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 – better known as rust – in the planet’s soil. Other colors on Mars are gold, brown and tan.

What is the temperature on Mars?

In general, Mars is a very cold place. The average temperature on the red planet is -62 °C. However, according to Michael Mischna, a research scientist at NASA’s Jet Propulsion Laboratory, the air temperature on Mars would not feel the same as on Earth. There is little water vapor and air molecules on Mars, so -70 °C would feel like -34 °C. To better understand the temperature conditions on Mars, check out 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 the China National Space Administration.

Did you know?

• Mars boasts the largest volcano in the entire solar system: Olympus Mons. With a height of 21 km, it is 2.5 times higher than Everest.

• Mars’ largest moon, Phobos, is gradually approaching the planet at a rate of about 2 cm per year. In 50 million years, Phobos will either collide with Mars or disintegrate to form a ring around the red planet.

• Billions of years ago, Mars looked very similar to Earth. Much of the planet’s surface was covered with liquid water and there may have been primitive life forms in the oceans. However, over time, the red planet lost its atmosphere and dried out.

• In the late 19th and early 20th centuries, a large number of astronomers observed a network of canals on the Martian surface. Some believed that they were irrigation canals built by an extraterrestrial civilization. However, it turned out to be an optical illusion.