4th From The Sun

Mars Explained Simply

Mars is a cold desert today, yet dry valleys, layered rocks, minerals formed in water and buried ice show that it once had rivers, lakes and a thicker atmosphere. That change makes Mars more than the “Red Planet”: it is a preserved investigation into how a potentially habitable world can lose heat, air and surface water. Orbiters, landers and rovers now read its rocks like pages of history while engineers study the real difficulties of sending people there—radiation, low pressure, toxic dust, limited power and a journey lasting months. This guide separates what missions have measured from what scientists still hope to discover about ancient life.

Rocky Planet 4th From The Sun Beginner Friendly

Have You Ever Wondered?

Have you ever wondered why Mars is red, whether people could live there, or whether your phone would work on the Red Planet? Mars looks familiar in some ways, but it is much harsher than Earth.

The Simple Answer

Mars is a cold, dry rocky planet with red dust, thin air and evidence that water once flowed across its surface.

Mars At A Glance

Position From Sun 4th
Type Rocky Planet
Diameter 6,779 km
Distance From Sun 228 million km
Length Of Day 24h 37m
Length Of Year 687 Earth days
Number Of Moons 2
Average Temperature About -63°C average

Where Is It?

Sun MercuryVenusEarthMarsJupiterSaturnUranusNeptune

What Does It Look Like?

Mars has red dust, rocky plains, craters, giant volcanoes, deep valleys and ice caps near its poles. Its sky can look pinkish because dust is often lifted into the thin atmosphere.

Journey Behind The Scenes

Mars formed from dust and rock about 4.5 billion years ago. It once had volcanic activity, flowing water and a thicker atmosphere. Over time, much of that atmosphere was lost.

Could Humans Live There?

Humans cannot breathe on Mars because the air is mostly carbon dioxide and extremely thin. Future explorers would need habitats, oxygen systems, radiation protection, food production and reliable power.

Gravity Explained

Gravity is the pulling force that gives you weight. If you weigh 100 kg on Earth, your weight on Mars would feel roughly like 38 kg. Your body has not changed; the planet's gravity has changed how strongly it pulls on you.

Compared With Earth

Earth

Earth has a thick atmosphere, stable liquid oceans and an active magnetic field that help protect the surface and support a working water cycle. Weather and plate tectonics erase much of the planet’s oldest history, but they also keep reshaping an environment where life can thrive.

Mars

Mars is about half Earth’s diameter and has a thin carbon-dioxide atmosphere with less than 1% of Earth’s surface pressure. Liquid water is unstable on most of its surface today, yet ancient river channels and lake deposits remain visible because geological change is much slower.

Moons

Mars has two small, irregular moons: Phobos and Deimos. They may be captured asteroid-like bodies or material left from an ancient impact, and scientists are still testing those possibilities. Phobos orbits so close that it crosses the Martian sky quickly and is gradually spiralling inward; in tens of millions of years it may break apart or strike Mars. Studying both moons helps researchers reconstruct the planet’s early history and plan future missions that could use them as scientific destinations.

Space Missions

  • 1965: Mariner 4 completed the first successful flyby.
  • 1976: Viking landers reached the surface.
  • 1997: Pathfinder and Sojourner showed mobile exploration was possible.
  • 2004: Spirit and Opportunity explored the surface.
  • 2012: Curiosity began studying habitability.
  • 2021: Perseverance landed and began collecting samples.

Why Mars Is So Interesting

Mars is a cold desert world with red dust, giant volcanoes, deep canyons and strong evidence that liquid water once flowed across its surface.

Surface And Landscape

Mars has rocky plains, dunes, craters, dried river valleys, the enormous canyon Valles Marineris and Olympus Mons—the largest volcano known in the Solar System.

Atmosphere And Weather

Mars has a thin carbon-dioxide atmosphere. It experiences winds, clouds, frost and planet-wide dust storms, but surface pressure is far too low for humans to breathe.

What Is Inside Mars?

Rocky crust Mantle Metal-rich core A crust containing evidence of ancient magnetic fields

Have Humans Ever Been To Mars?

No human has landed on Mars. Robots have explored it for decades, and Mars is the main destination discussed for future crewed planetary missions.

How We Have Explored It

  • Viking achieved the first successful long-lasting Mars landings.
  • Spirit, Opportunity, Curiosity and Perseverance explored the surface.
  • Orbiters continue mapping minerals, water ice, weather and possible landing areas.

Did You Know?

  • Mars has two tiny moons: Phobos and Deimos.
  • A day on Mars is only about 39 minutes longer than an Earth day.
  • Mars has seasons because its axis is tilted.
  • Water ice exists at the poles and below parts of the surface.
  • The red colour comes mainly from iron minerals that have oxidised—similar to rust.

Questions About Mars

Why is Mars red?
Its soil contains iron oxide, which is similar to rust. That gives the surface a reddish colour.
Can humans breathe on Mars?
No. The atmosphere is too thin and mostly carbon dioxide, so humans would need oxygen supplies and protected habitats.
Does Mars have water?
Mars has frozen water and signs of ancient rivers and lakes. Liquid water is not stable on most of the surface today.

Mars Is A Planet With A History Written On Its Surface

Mars matters because it preserves evidence of a very different past. Today it is cold, dry and wrapped in a thin carbon-dioxide atmosphere, yet spacecraft have photographed dried river channels, deltas and minerals that form in the presence of water. Those clues show that liquid water once moved across parts of the surface. The important scientific question is therefore not simply “Is there water on Mars?” but “What changed, and was ancient Mars ever suitable for life?”

One major difference from Earth is size. Mars is smaller, so it cooled more quickly and its interior became less active. It no longer has a strong global magnetic field like Earth's. Without that magnetic protection and with weaker gravity, the Martian atmosphere became vulnerable to being stripped away over very long periods by particles from the Sun. As the atmosphere thinned, stable liquid water became much harder to maintain at the surface.

Put Yourself On Mars

A Martian day is only about 39 minutes longer than an Earth day, which would make daily schedules surprisingly familiar. Everything else would remind you that you are on another planet. Gravity is about 38% of Earth's, the air is far too thin to breathe, average temperatures are far below freezing and radiation is much stronger because there is no thick atmosphere or global magnetic shield. Dust can remain suspended for long periods and sometimes grows into storms that spread across much of the planet.

The red colour comes mainly from iron minerals that reacted with oxygen, producing compounds similar to rust. If you picked up the soil it would not be bright red like paint; much of it is brown, orange and dusty. Mars also contains Olympus Mons, the largest known volcano in the Solar System, and Valles Marineris, a canyon system thousands of kilometres long.

Why Robots Go Before People

Robotic missions answer questions and test technology without risking human lives. Orbiters map landing sites and study weather. Landers measure conditions in one location. Rovers can travel, drill rocks and examine layers of ancient terrain. Curiosity has studied whether ancient environments were habitable, while Perseverance is collecting carefully selected rock samples for possible future return to Earth. These missions are not random sightseeing: each measurement reduces uncertainty for the science and for any future human mission.

Myth

People could live on Mars by simply wearing an oxygen mask because the surface looks like a cold desert on Earth.

Fact

Oxygen is only one requirement. Mars’s air pressure is far too low for an unprotected body, temperatures can be severe and the surface receives more radiation than Earth. A working habitat would need pressure, temperature control, shielding, water recycling, food systems, reliable power and protection from fine dust.

Myth

Photographs of dry river valleys prove that liquid water—and therefore life—still exists openly on the Martian surface today.

Fact

The valleys and minerals are strong evidence that water flowed long ago, when Mars had different conditions. Water ice still exists, but present surface pressure and temperature make stable open lakes or rivers unlikely. Evidence of ancient habitability is not the same as proof of past or present life.

Questions People Ask About Mars

Is there liquid water on Mars today?
Stable liquid water is difficult on the surface because pressure is so low and temperatures are usually cold. Mars has abundant water ice, especially near the poles and below the surface, and scientists continue to study possible short-lived salty flows.
How long would a trip to Mars take?
With current mission designs, a one-way journey commonly takes roughly six to nine months depending on the spacecraft, launch window and chosen trajectory.
Could plants grow directly in Martian soil?
Not like a normal garden. Martian soil chemistry, low pressure, cold temperatures, radiation and lack of organic nutrients mean crops would need a controlled habitat and carefully managed growing medium.

What Mars teaches us

Mars is valuable because its surface records change. Dry valleys, ancient lake beds and water-bearing minerals show that the planet once had very different conditions. Its thin atmosphere, cold climate and weak global magnetic protection help scientists investigate how a once wetter world became dry.

Keep these connections

  • Mars still contains abundant water ice, but stable surface liquid is difficult today.
  • Robots study radiation, chemistry, weather and geology before people travel there.
  • A human base would need pressure, heat, radiation shielding and reliable life support.
  • Evidence of past habitability is not the same as evidence of past life.

Planet Scorecard

Human Friendly ★☆☆☆☆
Scientific Interest ★★★★★
Easy To Visit ★★☆☆☆
Similar To Earth ★★★☆☆

Continue Your Journey

Continue from Mars to the giant planets, where thick atmospheres, rings and extensive moon systems replace solid surfaces.

Previous: Earth Next: Jupiter

Compare Mars’s lost surface water with Earth’s long-lived oceans, then see how Venus followed a very different climate path. To understand how orbiters, landers and rovers produced the evidence described here, continue with space exploration.