Meet Mars - The Fourth Planet in The Solar System

Introduction to Mars

Mars is the fourth planet from the Sun, orbiting at an average distance of about 142 million miles (228 million kilometers) or 1.52 AU while Earth is 1 AU away from the Sun. It is important to note that its orbit is not as circular as ours meaning that it ranges between 1.38 and 1.67 AU from the Sun throughout its orbit.

Although it has been observed in our sky since ancient times, it was first explored by a spacecraft in 1964 by Mariner 4’s flyby and then when we landed Viking 1 in 1975. Since then it has been explored by landers, rovers, and even probe satellites in orbit around the planet in addition to long-range observatories like telescopes.

Since it is only one stop away and a rocky planet with a more hospitable environment than Venus, it has been the subject of many different research missions delving into topics such as:

• The search for life (past or present off Earth)
• The evolution of Mars’s surface and atmosphere and the potential for similar evolution here on Earth
• The possibility of humans on Mars in the near future and using it as a testing ground and launch pad for other human space exploration misisons
• Developing new technologies for living and working in extreme environments
• Better understanding the formation and evolution of rocky planets

Physical Characteristics

All in all, Mars is 1.9 times smaller than Earth, or almost half the size. If Earth were the size of a nickel, Mars would be about as big as a raspberry. Its volume is about 15 percent. Its gravity is less than half of ours. Its density is about 72% of ours and its mass is about 11% of ours.

What’s the surface like?

Dry, rocky, and cold as it is a cold desert planet. At half an AU further away from the Sun than us on average, sunlight takes 13 minutes to reach its surface as opposed to the 8 minutes and 20 seconds it takes to reach us. This also means it’s not quite as bright or warm.

While it appears red due to the oxidation or rusting of iron in its rocks, regolith (Martian “soil”), and dust, the surface actually features a variety of colors including brown, gold, and tan, which we see in “close-up” images. The oxidized dust is easily swept up into the atmosphere and therefore from a distance (such as observing from Earth) appears mostly red.

While Mars has only about half the diameter of Earth, its surface has nearly the same area as Earth’s dry land. This surface, features volcanoes, impact craters, and crustal movement. It has also been heavily eroded and shaped by atmospheric conditions like dust storms.

What about its atmosphere?

Today, Mars’s atmosphere is much thinner than ours, meaning it loses more of the heat it receives from the Sun than us and it cannot offer much protection from impacts from meteorites, asteroids, and comets. 

While our atmosphere is primarily Nitrogen and Oxygen, the atmosphere on Mars is mostly Carbon Dioxide (98%), Argon, and Nitrogen with only a small amount of Oxygen and water vapor. This means that spacesuits are required for humans to breathe on Mars. The air would also be hazy and red due to the amount of dust that is suspended in the air versus the blue on Earth. 

Surface pressure was found to be equal to about 19 miles (30.5 kilometers) above Earth’s surface during Mariner 6’s flyby.

Is there a magnetic field?

We have found areas of the Martian crust in the southern hemisphere that are highly magnetized, indicating that there was a magnetic field 4 billion years.

However, Mars has no global magnetic field today. In fact, evidence suggests that this loss of magnetic field is intertwined with the loss of its atmosphere and surface water, all effects of some cataclysmic change in Mars’s ancient past. 

Is there water?

Today there is water-ice in the polar regions and we have found evidence of briny water flow during seasonal melts. So, yes, there is water on Mars!

There is evidence to indicate there used to be massive bodies of liquid water on the surface of Mars in its ancient past, but those no longer exist today.

Days and Years or Rotation and Orbit

Mars is about half the size of Earth, but completes a full rotation in 24.6 hours. This means that its day is just slightly longer than our own.

With an average distance from the Sun of 142 million miles (228 million kilometers), Mars is 1.5 AU from the Sun, and takes 687 Earth days or 669.6 Mars days called sols to complete its orbit, again keeping in mind its eccentric orbit which varies greatly in distance from the Sun. 

Formation and Geology

How did Mars form?

Similar to all other planets in our solar system, Mars formed about 4.5 billion years ago when the centrifugal gravitational forces of the Sun shortly after it started nuclear fusion pulled swirling gas and dust into larger clumps throughout the area that would become the solar system. 

Mars Over Time

Our exploration of Mars has continued to show us that the barren cold desert we see today is not the way Mars has always been. In fact, evidence of various forms indicates that Mars used to be very similar to Earth, including having large bodies of liquid water on its surface, a thicker atmosphere, and a magnetic field. Something happened in its past that stripped all of those away. One of the main research interests in Mars is understanding what happened to turn a world very similar to ours to the Red Planet we see today. 

As you may have already guessed, if Mars was similar to Earth in its past, it is also one of our greatest contenders for life in some form in the past, present, or future. This is a related topic that is of great interest to scientists and has fueled many of our past, present, and upcoming missions.

What is inside Mars? Is it similar to Earth?

Similar to its fellow terrestrial planets, Mars has a central core, rocky mantle, and solid crust. The ratios are where each planet differs.

Mars core: Between 930 and 1,300 miles (1,500 to 2,100 kilometers) in radius made of iron, nickel, and sulfur

Mars rocky mantle: Surrounding the core is the mantle between 770 and 1,170 miles (1,240 to 1,880 kilometers) thick

Mars crust: Above the mantle is a crust between 6 and 30 miles (10 to 50 kilometers) deep made of iron, magnesium, aluminum, calcium, and potassium

Interesting Topography

Mar features some of the most interesting topographical features in the solar system!

• Valles Marineris: a massive canyon system as long as the distance from California to New York (over 3,000 miles/ 4,800 kilometers!), 200 miles (320 kilometers) at its widest and 4.3 miles (7 kilometers) at its deepest. All in all, it’s about 10 times the size of the Grand Canyon.
• Olympus Mons: the largest mountain/ volcano in the solar system
• Ancient river valley networks, deltas, and lakebeds indicating the presence of liquid water in its past and a lot of it! In fact, some features suggest there were huge floods about 3.5 billion years ago.
• Polar Ice Caps: While the Martian atmosphere is too thin for liquid water to exist long, there is water-ice just under the surface in the polar regions and some of this flows down hillsides and crater walls in briny saly flows during seasonal melts

Thanks to all the exploration of Mars (explained in more detail later), there are several amazing resources to help you virtually explore the topography of the Red Planet.

• NASA Eyes on the Solar System- Mars
• NASA Visualization Technology Applications and Development (VTAD) 3D model of Mars
• NASA Solar System Exploration Mars Interactive module and Galleries
• NASA Mars 3D Resources
• NASA Solar System Treks
• Wikipedia Template: Features and artificial objects on Mars

Moons of Mars

A first in our Planetary In-Depth Series (Mercury and Venus): Mars has moons! Mars has two small moons that may be captured asteroids named Phobos and Deimos.

Phobos is the bigger of the two and orbits closer to Mars. It has many craters and deep grooves. It is slowly moving toward Mars and will either crash into it or break apart from the stress in about 50 million years.

Deimos is about half the size of Phobos and orbits two and a half times further away than its brother. In contrast, Deimos is more irregularly shaped and covered in loose dirt which fills the craters, making it appear smoother.

While Mars currently has no rings, when Phobos crashes into Mars or breaks apart, it could create a dust ring.

Climate

Temperatures

Similar to how Mercury’s lack of atmosphere results in drastic temperature shifts from the day to night side, Mars also experiences temperature variations due to a thin atmosphere.

It can be as high as 70 degrees Fahrenheit (20 degrees Celsius) or as low as about -225 degrees Fahrenheit (-153 degrees Celsius). And this fluctuation doesn’t just apply to the day and night side. Heat escapes so easily from the planet that if you were standing on its surface on the equator at noon, it would be 75 degrees Fahrenheit or 24 degrees Celsius at your feet and 32 degrees Fahrenheit or 0 degrees Celsius at your head! 

Weather

While the atmosphere is thin, there is weather on Mars, primarily in the form of dust storms. As mentioned earlier, the dust is easily picked up from the surface and when winds get strong enough, they can create practically planet-wide dust storms, covering virtually any surface features from view even from large telescopes. Even once these storms officially dissipate, it can be months before all of the dust settles.

Seasons

Its axial tilt is slightly greater than Earth (25.2 versus our 23.44), creating distinct seasons with slightly more extreme differences. Similar to here on Earth, the season depends on which hemisphere you are in with the Northern Hemisphere having the opposite season as the Southern Hemisphere. Each season is longer since it takes Mars longer to orbit the Sun, but these seasons are not as evenly spread as they are here on Earth. While each season on Earth is about 3 months (a quarter of a year), seasons on Mars vary in length due to the more elliptical, erratic orbit causing it to vary much more in the distance from the Sun than we do here on Earth.

Northern (Hemisphere) Spring/ Southern (Hemisphere) Autumn: 194 sols (Mars days)

Northern Autumn/ Southern Spring: 142 sols

Northern Winter/ Southern Summer: 154 sols

Northern Summer/ Southern winter: 178 sols

Exploration of Mars

Mars has been the most intensely studied planet in the solar system besides Earth. Recorded observations of Mars date back to Ancient Egypt over 4,000 years ago, charting its movements in the night sky. Telescopes greatly increased our understanding of this planet, bringing to light amazing features that fueled our questions regarding life beyond Earth. But that wasn’t enough and as part of the space race, we began sending spacecraft to study Mars in more detail.

The following lists some of the relevant details about successful Mars missions. Failed missions such as Mariner 3, Mariner 8, Mars Observer, Mars Climate Orbiter, and Mars Polar Lander are not included.

To sum up, Mars has been greatly explored and today, NASA’s current monitoring of Mars includes spacecraft:

• On the ground: landers and rovers including Perseverance, Curiosity exploring Mount Sharp in Gale Crater, Insight probing the interior of Mars from the Elysium Planitia
• In the air: the Ingenuity helicopter was taken to Mars by Perseverance and has made over 50 flights in the Martian atmosphere since it marked the landmark of the first aircraft in history to make a powered, controlled flight on another planet
• In orbit: NASA has three spacecraft in orbit, studying Mars: Mars Reconnaissance Orbiter, Mars Odyssey, and MAVEN

Current international Mars missions include:

• The Hope orbiter from the United Arab Emirates at Mars since Feb. 9, 2021
• China’s Tianwen-1 mission arrived on Feb. 10, 2021, including an orbiter, a lander, and a rover. In May 2021, Zhurong Mars rover touched down, making it only the second nation to do so.
• ESA missions: ExoMars Trace Gas Orbiter and Mars Express
• India: Mars Orbiter Mission (MOM) orbiting Mars since 2014

Explore all of these in real time in Mars Now.

Mars in Popular Culture

No other planet has quite captivated us like Mars. The red dot fascinated our ancient ancestors who bestowed upon it the names of their gods, often relating to war, including the Roman name we use today. Since we first discovered canal-like features on the Martian surface in the late 1800s, many dreamed of intelligent species on the Red Planet, which they believed might be a water world to explain the canals. 

Mars in Mythology

The Red Planet was named by the ancient Romans after their god of war since the striking color was so reminiscent of blood. In fact, many other cultures named it relating to the color or related to the feelings or associations with this color. The Egyptians called it “Her Desher” which means “the red one”.

Mars in Literature

Mars has been a setting in fiction since at least the mid-1600s and is easily the most portrayed planet in a myriad of ways in various forms of fiction. Some of the most popular or noteworthy of these works include:

• • The 1656 work Itinerarium exstaticum by Athanasius Kircher
  • The anonymously published 1839 novel A Fantastical Excursion into the Planets

• Gulliver’s Travels by Jonathan Swift features astronomers studying the moons of Mars over a hundred years before we actually discovered them

• The 1903 novel The Certainty of a Future Life in Mars by Louis Pope Gratacap
• The Barsoom/ John Carter of Mars Series by Edgar Ric Burroughs
• The 1897 novel The War of the Worlds by H. G. Wells
• The 1950 novel The Martian Chronicles by Ray Bradbury
•  Joe Haldeman’s 2008 novel Marsbound
• Stranger in a Strange Land by Robert Heinlein

Mars in TV, Film, and Radio

It would be remiss of me not to mention the 1938 radio drama, “The War of the Worlds” which some listeners who really believed the world was being invaded by Martians. While it would be quite exhaustive to list all the movies, tv shows, and more that feature Mars or inhabitants of Mars, here are some famous and notable titles:

• • Total Recall (1990 and 2012)
  • “The Expanse” TV series based on the novel series by the same name

• The Martian (2015) easily one of the best space and astronaut movies focuses on a stranded astronaut who has to survive on the Red Planet (based on the 2014 book of the same title by Andy Weir)

• Mars Attacks! (1996)

• John Carter (2012)

• • War of the Worlds (1953 and 2005) and War of the Worlds 2 (2008)
  • Mission to Mars (2000)
  • Invaders from Mars (1953 and 1986)

• Robsinson Crusoe on Mars (1964)

• Abbott and Costello Go to Mars (1953)

• Flash Gordon: Mars Attacks the World (1938)

• Marvin the Martian has been a mainstay of the Looney Tunes since 1948 (his design is based on the Hoplite style of armor usually worn by the Roman god)
• “My Favorite Martian” TV Series

Mars in Comics

What’s a better home for Mars than in comic books? Between superheroes and far-off adventures, comic books create the perfect media for imagining the red planet. Here are just a few of the numerous examples of Mars in comics:

• Mars is a 1984 American comic series focused on a group of explorers and engineers sent to Mars to terraform it

• Various John Carter Comics of the famous John Carter from Edgar Rice Burroughs including: John Carter, Warlord of Mars (1977), John Carter: The Gods of Mars (2011-2012), and John Carter of Mars: A Princess of Mars (2011-2012)

• • Mars has a rich history within the Marvel universe ranging from ancient aliens who seeded it with light to invasions that Captain America and Golden Girl must thwart to alien space ships and races on and around Mars including the mutant nation of Arakko.
  • Similarly, it has also been utilized throughout the DC universe. There are various arcs with invading Martians of various types. It is often most well-known for the Skrulls, particularly the Martian Manhunter J’onn J’onnzz the only peaceful member of his war-like race of conquerors with psionic and shapeshifting abilities. Supergirl even uses Viking 1 as part of her plans to trick Lex Luthor.

• War of the Worlds has been adapted multiple times, first by “Classics Illustrated” in 1955, but other publishers include Marvel, Eternity, and Dark Horse

Mars in Video Games

The popularity of Mars as a sci-fi setting has translated to video games as well. A few notable examples include:

• • The Red Faction games
  • The 2014 game Destiny
  • The Doom games

• Call of Duty: Infinite Warfare

• Daffy Duck: the Marvin Missions

• Mars Rising

• Mass Effect 3

• Surviving Mars

• Monuments of Mars

Mars in Music

Besides the famous bombastic Mars, the Bringer of War sequence in Gustav Holst’s suite The Planets, Mars has also been used in music in a variety of ways, including artist names, including

• The Rise and Fall of Ziggy Stardust and the Spiders of Mars by David Bowie

• Bruno Mars: pop artist
• Charlie Mars: country and folk pop artist
• Thirty Seconds to Mars band
• “Life on Mars” song from David Bowie’s Hunky Dory album

You could also check out the sounds of Mars from NASA

Mars word associations

Did you know Tuesday is actually Mars Day? The ancient Babylonians first created the week and each of the seven days was named for one of the seven known moving bodies in the sky (the sun, the moon, Mars, Mercury, Venus, Jupiter, and Saturn). 

While English may not seem to keep this tradition, Tuesday is actually for Tyr, the Norse god of war, or “Tews” the English version. Other languages have kept a more noticeable link to Mars Day such as Mardi in French, Martedi in Italian, and Martes in Spanish.

Did you know the month of March is also named after Mars? While January 1st is New Year’s Day in most cultures today, from Roman times until recent centuries, March was the new year, because it was seen as a time of renewal, of spring from winter. The Romans named this first month of the year after their god of war because the spring weather meant battles could begin.

Observing Mars in the Night Sky

In planetary observing, there are a couple of important terms to remember since we have to consider the location of the desired planet, the Sun, and the Earth to understand how and when the planet will be visible and how. First, astronomers typically group the planets into two subsets to determine their viewing schedule:

Superior Planets: those past Earth going away from the Sun meaning Mars and beyond

Inferior Planets: the two planets closer to the Sun than the Earth (Mercury and Venus)

Then we look at the location of the desired planet, Earth, and the Sun with a few line-ups that determine their visibility: 

Planetary Opposition occurs when a planet is directly opposite the Earth from the Sun meaning that they line up with the Earth between the Sun and the other planet. This is typically the best time to view the planets as it is when they will appear the brightest since the planet is the closest to Earth and fully illuminated by the Sun. Only superior planets experience oppositions while inferior planets experience 2 conjunctions. Very close oppositions for Mars occur every 15 to 17 years.

Planetary conjunction occurs when a planet is directly in line with the Sun from the Earth meaning the Sun lies directly in between the 2 planets for superior planets. For superior planets, like Mars, we see the following interactions.

• Superior Conjunction is when the planet is on the opposite side of the Sun from the Earth (behind the Sun from our perspective). The planet appears as a full disk like a full Moon, but smaller since it is further away.
• Inferior Conjunction is when the planet is on the same side of the Sun as the Earth.

Greatest Elongation is when the planet is at its greatest observed angle between it and the Sun when viewed from the Earth. This occurs both in the eastern and western sky. Otherwise, it is too close to the Sun and you can harm your eyes by staring close at the Sun. Make sure that you have a solar filter on telescopes or binoculars to protect yourself.

Quadrature: An elongation of 90° and a planet can be at either the eastern or western quadrature, depending on if the planet lies to the east or the west of the Sun when viewed from the Earth. 

Closest Approach: When Mars is closest to Earth. There are many factors to consider here including the fact that both our orbits are not perfectly circular, but rather elliptical or egg-shaped, and more so with Mars. In addition, both of our orbits are tilted. Closest Approach is an ideal time to view Mars typically as it will appear brighter, especially when it lines up with Opposition. 

However, with all the variables of our orbits, not all closest approaches are equal. Some will be better than others depending on how the factors line up. In addition, despite the common hoax that is often circulated, Mars will never be as big as our full moon in the night sky. Closest Approaches are also utilized for launching spacecraft to Mars as it takes advantage of the shortest distance between us.

Opposition is the best time to view Mars and other superior planets. The last Mars close approach and opposition was December 2022 and the next will be January 12, 2025 at a distance of 59,703,892 miles (96,084,100 km). Be sure to mark it on your calendar for some good Mars observing.

It’s worth noting that Mars is one of the five planets that can be seen without a telescope.

How to find Mars in the night sky?

Like many other astronomical objects, Mars will not always be visible. Since we passed the last opposition and closest approach in December 2022, Mars has been slowly fading away both in magnitude and whether or not it will be up in the night sky in your location. 

For instance, while in late August you should still be able to spy it in the western sky in the early evenings, it will be gone in October, overpowered by the sunset’s glare. It’ll pass behind the sun on November 18, but will be back in the east before sunrise, in early 2024. 

Be sure to check out star charts and apps when wanting to spy Mars or other planets. They will all lie in the ecliptic band across the sky, which the sun, moon, and the zodiac constellations pass through, making it often easier to starhop from more noticeable landmarks to the red planet (just make sure it’s not Antares in Scorpius!).

Mars is a fantastic astronomical object for telescope observing, with features to spy. For more information on how to view Mars with a telescope, check out our Observing Mars with a Telescope guide. Check out all of our planetary observation guides for more information on how to observe our celestial neighbors.

Upcoming conjunctions

We also have planetary conjunctions when a planet appears close to another astronomical object (typically another planet) in the night sky. 

Solar conjunction: Nov. 11 to Nov. 25 where Mars will be so close to the Sun it will be invisible to us, making communication with our spacecraft around or on it difficult as data will be inevitably lost. No new commands are given during this time and many instruments will be turned off.

We had a Mercury-Mars conjunction on Autsut 13, but the next upcoming ones are all in 2024. 

January 27, 2024: Mercury-Mars

February 22, 2024: Venus-Mars

April 10, 2024: Mars-Saturn

April 29, 2024: Mars-Neptune

July 15, 2024: Mars-Uranus

August 14, 2024: Mars-Jupiter

Transits

Since Mars does not lie between us and the Sun, we will not see it pass in front of the Sun from our perspective, creating the opportunity for a transit event.

Summary and Future Prospects

Mars has fascinated us since ancient times and continues to do so. Its close proximity and less toxic environment than Venus has allowed us to explore it up close in orbit, on the surface, and even in the Martian air. 

This Red neighbor used to be strikingly similar to us but now lies as a barren icy desert, prompting questions about its evolution and how ours might be on a similar path. Research concerning Mars will continue with an eventual goal of putting humans on the surface by the 2040s, possibly eventually providing at least some of our descendants with a second home or waystation for other human space exploration missions. 

Fun Facts About Mars

1. Mars is the only planet in our solar system to be completely inhabited by robots!
2. According to NASA, if the Sun were as tall as a typical front door, Earth would be a dime and Mars would be an aspirin tablet.
3. Phobos and Deimos, the two moons of Mars meaning Fear/ Panic and Dread/ Terror. Some versions say they are the sons of Ares (the greek counterpart of Mars) while other versions say they are the horses that pulled the chariot of Ares. 
4. Due to the reduced gravity on Mars, you could jump almost three times higher!
5. Mars is home to Olympus Mons, the highest mountain in the solar system and 3 times higher than Mount Everest!
6. Due to its thin atmosphere allowing heat to escape, your feet could be experiencing spring temperatures while your head experience winter!