As we continue to move through the solar system, we next reach Mars. The fourth planet from the Sun is a dusty, cold, red desert. Mars is easy to spot in the night sky, it looks like a bright reddish orange star.
Mars is one of the most explored bodies in our solar system and the only planet we have sent rovers to so far. Due to Mar’s red color, the ancient Romans were inspired to name it after their god of war, as its color is evocative of blood.
Table of Contents
- 1 Mars Facts
- 2 Size and Distance
- 3 Orbit and Rotation
- 4 Moons
- 5 Space Probe Flybys of Mars
- 6 Structure and Surface
- 7 Geological History of Mars
- 8 Water on Mars
- 9 Atmosphere and Magnetosphere
- 10 Potential for Life on Mars
- 11 Exploring Mars
- 12 History of Mars Observation
- 13 NASA’s Commercial Partnerships for Mars Exploration
Mars Facts
- Mars is almost half the size of Earth
- Mars has two Moons
- There is a canyon on Mars that would span the width of the United States
- Mars is the most explored planet besides Earth
- Mars’ surface is rusted, giving it its red color
Size and Distance
Mars is about half the size of Earth at 2,106 miles (3,390 km) in radius. On average the Sun is 142 million miles (228 million km) from the Mars. It takes sunlight 13 minutes to reach Mars.
Orbit and Rotation
A day on Mars is almost the same length as a day on Earth, 24.6 hours. A Martian day is called a sol. It takes 687 Earth days for Mars to orbit the Sun, or 669.9 sols. Another similarity to Earth is the tilt of Mars’ axis at 25 degrees from straight up and down, where Earth’s is 23.4 degrees.
This tilt gives Mars distinct seasons and its longer orbit around the Sun makes these seasons last longer than our seasons here on Earth. Mars’ orbit is more elliptical, and egg shaped than Earth’s orbit so the seasons on Mars vary in length whereas Earth’s seasons are evenly spread throughout our year. Spring in Mars’ northern hemisphere is 194 sols long and is its longest season. Mars’ shortest season is fall in the northern hemisphere at 142 sols.
Moons
Mars has two small moons, Deimos and Phobos. It is suspected that these moons may be asteroids captured by Mars’ gravity. Both moons are small and potato shape because they are too small to have enough mass and gravity to pull themselves into a spherical shape.
Phobos is the larger of the two moons and is covered in many deep craters. Phobos is slowly moving towards Mars and will eventually crash in about 50 million years. While Mars does not currently have any rings, when Phobos crashes into Mars, it will create a dusty ring surrounding the planet.
Deimos is half the size of Phobos and is two and a half times further from Mars. Deimos’s surface is covered in loose dirt that fills the craters making its surface appear smoother than Phobos.
Space Probe Flybys of Mars
On March 1, 2025, NASA’s Europa Clipper, Psyche space probe, and ESA’s Hera mission executed a flyby of Mars. These maneuvers are part of gravitational slingshot techniques, which are used to adjust the trajectory of spacecraft en route to distant celestial targets.
Structure and Surface
Like Earth, Mars is a rocky terrestrial planet that has a central metal core. Mars’ core is made of iron, nickel, and sulfur. Surrounding this core is a rocky mantle and then a crust.
The Red Planet gets its rusty color from exactly that, rust. Mars’ surface has iron in its rocks, dust, and regolith (the name for soil on Mars). This iron on the surface rusts due to the exposure just as metal rusts when left outdoors.
Geological History of Mars
Mars features a rich geological history, with evidence suggesting significant tectonic activity. The formation of the Tharsis volcanic plateau points to ancient volcanic eruptions shaping the planet’s surface. Thousands of feet high, these massive volcanoes hint at a less active current state but reveal a tumultuous past. Missions like the Mars Global Surveyor have provided key insights into these ancient processes, changing our understanding of the Red Planet.
While Mars is smaller than Earth it has very large features covering its surface. There is a large canyon system named Valles Marineris that is more than 3,000 miles (4,800 km) long, long enough to stretch the width of the United States.
The Valles Marineris is 200 miles (320 km) at its widest and is 4.3 miles (7 km) at its deepest, making this canyon 10 times larger than the Earth’s Grand Canyon. Olympus Mons is the largest volcano in the solar system is found on Mars. Olympus Mons is three times taller than Mt. Everest.
Water on Mars
Liquid water once flowed on the Martian surface, carving detailed valleys and patterns. Recent missions have detected recurring slope lineae, indicating the seasonal flow of briny water. Furthermore, radar from orbiting spacecraft has revealed significant subsurface ice deposits across Mars. This remarkable finding suggests that the planet could still host liquid water under certain conditions, keeping the possibility of life an engaging scientific inquiry.
Mars’ surface shows the scars of a watery past in its ancient, dried river valleys and lakebeds. There are also rocks and minerals found on the surface that could only have been formed in liquid water. Water can still be found on Mars today in the form of water ice just below the surface near Mars’ north and south poles.
Atmosphere and Magnetosphere
Mars has a thin atmosphere that does not provide much protection to the planet from impacts from meteorites and asteroids. This thin atmosphere does not hold in heat from the Sun very well. Temperatures on Mars range from -225 degrees Fahrenheit (-153 degrees Celsius) to 70 degrees Fahrenheit (20 degrees Celsius).
Earth’s magnetosphere is generated by the rotation of our hot central metal core this is called a geodynamo. Mars’ central metal core no longer has an active geodynamo and therefore does not generate a magnetic field around the planet. However, there are areas of the Martian crust that are highly magnetized indicating that Mars once did have a magnetic field.
Potential for Life on Mars
The potential for life on Mars remains a lively area of research. Discoveries of methane spikes in the atmosphere suggest active processes that might indicate microbial life. Spacecraft like the Curiosity rover are key in this search, analyzing surface rocks and soil. The possibility of life, now or in the past, continues to inspire both scientific exploration and public imagination.
Exploring Mars
From the ancients to modern astronomers, humans have studied Mars more than any other planet, except Earth. Both orbiting in space and on the surface, Mars has a fleet of spacecraft exploring the planet.
The Perseverance rover, equipped with the Ingenuity helicopter, continues to explore the Martian surface. Ingenuity, which successfully scouted sites for investigation, concluded its mission in 2024. The Curiosity rover remains active, conducting scientific research and exploration.
History of Mars Observation
Early observations of Mars date back to 1610 with Galileo Galilei’s telescopic study. His findings laid the groundwork for future explorations. In the late 1800s, astronomer Percival Lowell famously mapped what he thought were canals on Mars. These so-called canals fueled speculation about intelligent life on Mars, though they were later dismissed as optical illusions. Mars has fascinated both scientists and enthusiasts, prompting a continued quest to uncover its mysteries.
NASA’s Commercial Partnerships for Mars Exploration
In April 2024, NASA initiated collaborations with several companies to research commercial services aimed at advancing robotic science on Mars. This initiative is part of NASA’s strategy to enhance scientific studies and involves leveraging commercial innovations.
- In Orbit: There are three NASA spacecraft in orbit, Mars Reconnaissance Orbiter, Mars Odyssey, and MAVEN.
- On the Ground: NASA has sent five rovers to the surface of Mars. In order they are: Sojourner, Spirit and Opportunity, Curiosity, and Perseverance.
- International Missions: The United Arab Emirates sent the Hope orbiter in 2021. China’s Tianwen-1 mission included an orbiter, lander, and rover. China became the second nation after the United States to successfully land on Mars in 2021 with its Zhurong Mars rover. The ESA’s missions to Mars include Mars Express and ExoMars Trace Gas Orbiter. India has the Mars Orbiter Mission.
SpaceX continues to advance its goal of routine Mars travel as part of a colonization effort. In 2024, the development of the Starship program progressed, featuring integrated test flights aimed at achieving full reusability. SpaceX plans to use Starship’s significant payload capacity for sustained operations on Mars, supported by resources both from Earth’s resupply and on-site production.
More recently, NASA’s Insight lander has focused on studying Mars’ interior. By analyzing seismic activity, Insight provides fresh data on the Martian crust and mantle. This groundbreaking mission aims to deepen our understanding of how rocky planets form and evolve. These findings about Mars’ seismic waves offer a novel perspective on the structure beneath its rugged exterior.
