Imagine a robot the size of a small car, rolling slowly across a rusty-red desert on another planet, drilling into rocks, taking photographs, and sending back clues about whether life once existed there. It sounds like science fiction, but it is happening right now. Several robotic explorers have already travelled across the surface of Mars, and two of them, Curiosity and Perseverance, are still working there today.
Mars has fascinated people for centuries. It is the most Earth-like of our neighbouring planets, and it is the most likely place in our solar system, besides Earth, where life might once have existed. Sending humans there is still years away, so robotic rovers act as our eyes, hands, and laboratories on the Martian surface.
In this guide, we will meet the rovers one by one, look at the most important things they have taught us, and explain what questions remain open. It is written for beginners, so there is no need for any science background.
What Is a Mars Rover?
A rover is a robotic vehicle designed to drive across the surface of another world. Unlike a lander, which stays in one place, a rover can travel to different locations to study different kinds of rocks, soil, and landscapes. Each rover carries cameras, scientific instruments, and a power source, and it is controlled by teams of scientists and engineers back on Earth.
Why use robots instead of people? Mars is extremely hard to reach and dangerous. It is at least 55 million kilometres away at its closest, and a journey takes about seven months. The planet has a very thin atmosphere with almost no oxygen, no liquid water on the surface, average temperatures around -60°C, and strong radiation. Robots can survive in these conditions and cost far less than a crewed mission.
There is also a communication delay. Radio signals take between about 4 and 24 minutes to travel one way between Earth and Mars, depending on where the planets are in their orbits. That means you cannot “drive” a rover with a joystick. Instead, engineers send commands in batches, and the rover carries them out on its own, with increasing help from on-board autonomy and, more recently, AI-assisted route planning.
Meet the Rovers
Six rovers have successfully operated on Mars so far. Let us go through them in order.
Sojourner (1997): The Pioneer
The first Mars rover was Sojourner, which landed on 4 July 1997 as part of the Mars Pathfinder mission. It was tiny, about the size of a microwave oven and weighing only about 10.5 kilograms. It was designed to last about a week, but it kept working for around 83 days.
Sojourner travelled only a few metres from its lander, but it proved something huge: a rover could drive on Mars and study rocks up close. It tested the rock and soil with a chemical instrument and showed that this kind of exploration was practical.
Spirit and Opportunity (2004): The Overachievers
In January 2004, two identical NASA rovers, Spirit and Opportunity, landed on opposite sides of Mars. Each was about the size of a golf cart and planned for a 90-day mission.
They performed far beyond expectations. Spirit worked for about six years, until it became stuck in soft sand in 2009 and eventually fell silent in 2010. During its time, it found evidence of ancient hot springs, including bright silica-rich soil that on Earth is often linked to hot, watery environments where microbes can thrive.
Opportunity lasted almost 15 years. It kept going until a giant planet-wide dust storm in 2018 blocked the sunlight its solar panels needed, and NASA declared the mission complete in February 2019. In total, it drove about 45 kilometres, farther than any other vehicle on another world at the time.
Opportunity’s major discovery was proof that liquid water once soaked the Martian surface. It found small round mineral balls, nicknamed “blueberries,” and layered rocks containing minerals that form only in the presence of water. Together, the two rovers showed that ancient Mars had environments that were wet and, at times, possibly habitable.
Curiosity (2012): The Mobile Laboratory
Curiosity is a much bigger rover, about the size of a small car and weighing roughly 900 kilograms. It landed on 6 August 2012 inside Gale Crater, using a remarkable landing method called the sky crane. A rocket-powered platform hovered above the surface and lowered the rover on cables, then flew away to crash at a safe distance.
Instead of solar panels, Curiosity is powered by a small nuclear battery that turns heat from decaying plutonium into electricity, which lets it work day and night, in any season. After more than a decade, it is still exploring, climbing the slopes of Mount Sharp, a mountain in the middle of Gale Crater that is made of layers of rock like a giant history book.
Curiosity carries a full science laboratory, including a drill, a laser that zaps rocks to study their makeup, and instruments that heat samples to identify chemicals.
Perseverance (2021): The Life Hunter
Perseverance landed on 18 February 2021 in Jezero Crater, a place chosen because it once held a lake and has a fan-shaped delta where a river flowed in. On Earth, deltas are excellent places to preserve traces of life, so scientists thought this would be an ideal place to look.
Perseverance is similar in size to Curiosity, weighing about 1,025 kilograms, and uses the same type of nuclear power. Unlike earlier rovers, its main purpose is directly about astrobiology, the search for signs of past life. It has a drill that collects rock core samples and seals them in tubes to be left on the surface for a possible future trip back to Earth.
It arrived with a travelling companion: a small helicopter named Ingenuity. On 19 April 2021, Ingenuity made the first powered, controlled flight on another planet. It was meant to fly only five times, but it completed 72 flights before suffering damage to its rotor blades in January 2024, ending its mission. It proved that flying on Mars, where the air is about 100 times thinner than on Earth, is possible.
Zhurong (2021): China’s First Rover
China joined the club in May 2021 with the Zhurong rover, part of the Tianwen-1 mission. It explored a region called Utopia Planitia and studied the terrain with ground-penetrating radar. It went into planned hibernation in 2022 during the Martian winter and did not wake up again, but its mission made China the second country to operate a rover on Mars.
What Have the Rovers Taught Us? The Big Discoveries
Now for the exciting part. After decades of exploring, what do we actually know about Mars that we did not know before?
1. Mars Was Once Wet and Warmer
This is the single biggest lesson. Today Mars is a cold, dry desert, but the rovers have shown that billions of years ago it was very different. They have found:
- River valleys, deltas, and lake beds, carved by flowing water.
- Minerals that only form in water, such as clays and sulphates.
- Evidence of groundwater, including mineral veins running through rocks. Curiosity has also found web-like patterns in rock that are thought to have been shaped by ancient groundwater.
- Rocks formed in lakes, including the mudstones that Curiosity studied in Gale Crater.
About 3 to 4 billion years ago, parts of Mars appear to have had a thicker atmosphere, rivers, lakes, and possibly even seas. Then the planet lost most of its atmosphere and surface water, slowly becoming the dry world we see today.
2. Mars Once Had Habitable Environments
In 2013, within its first year, Curiosity drilled into a rock at a place called Yellowknife Bay. The analysis showed that the area was once an ancient lakebed with fresh water and contained key chemical ingredients for life, such as carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus. The water was neither too acidic nor too salty.
In other words, it was an environment where simple microbes could have lived. This does not mean life existed there, only that conditions were suitable. It was a landmark result, because it answered the question “Could Mars ever have supported life?” with a clear “Yes, it could have.”
3. Organic Molecules Exist on Mars
Organic molecules are chemicals built around carbon, and they are the building blocks of life as we know it. Importantly, they can also be made by non-living processes, so finding them is exciting but not proof of life.
Curiosity has detected organic molecules in several rocks, and in recent years it has reported larger and more varied ones than ever seen on Mars before. The results show that organic material can be preserved in Martian rock for billions of years, which is encouraging for the search for ancient life. Perseverance has also found organic compounds in the rocks of Jezero Crater, in places where water once flowed.
4. A Possible Sign of Ancient Life, but Not a Confirmation
In 2024, Perseverance examined a rock in an ancient river channel, nicknamed Cheyava Falls, which showed unusual patterns of spots, sometimes described as “leopard spots,” and a mix of minerals and organic compounds. On Earth, similar features can be linked to chemical reactions involving microbes. NASA scientists described this as a potential biosignature, meaning something that might be a sign of past life.
It is crucial to understand what “potential” means here. The same patterns can also be explained by chemical reactions that do not involve life. Scientists are cautious, and extraordinary claims need extraordinary evidence. The best way to settle the question would be to study the collected samples in laboratories on Earth, using instruments far too large to send to Mars.
5. Jezero Was a Lake, and the Rocks Tell a Long Story
Perseverance’s exploration confirmed that Jezero Crater was a lake fed by a river, and the rocks there record both volcanic and watery history. The crater floor is made of volcanic rock that was later altered by water, and the delta preserves layers of sediment, including boulders swept in by ancient floods. Some studies also suggest that the area’s rocks were altered by water more than once, hinting at a long and complex watery history.
6. Mars Weather, Dust, and Sound
The rovers have also taught us a lot about the Martian environment. They have tracked dust devils, seasonal changes, and strong dust storms that can cover the whole planet. They have measured radiation levels, which is vital information for planning human missions. Perseverance carries microphones, and it recorded the first sounds from the surface of Mars, including wind, the crunch of its wheels, and the laser striking rocks. These recordings revealed that sound travels more slowly on Mars, and that higher-pitched sounds fade faster in its thin carbon dioxide air.
7. Methane Mystery
Curiosity has detected small, changing amounts of methane in the Martian air. On Earth, most methane is produced by living things, though it can also come from geological processes. The measurements have been puzzling, as methane seems to appear and disappear with the seasons. Scientists are still working out the source, and it remains one of Mars’s open mysteries.
8. Making Oxygen from Martian Air
Perseverance also carried an experiment called MOXIE, which successfully produced breathable oxygen from the carbon dioxide in the Martian atmosphere. It was a small device, but it showed that future explorers might be able to make some of their own oxygen on Mars, which would save huge amounts of cargo weight.
What the Rovers Have Learned About Surviving on Mars
Beyond science, the rovers have taught engineers valuable lessons.
- Dust is a challenge. Dust can cover solar panels, as it did for Opportunity, and sticks to equipment.
- Wheels wear out. Curiosity’s aluminium wheels suffered unexpected damage from sharp rocks, and engineers changed the design of later wheels and adjusted how Curiosity drives.
- Landing is the hardest part. Many Mars missions have failed. Entering the atmosphere, slowing down, and landing safely takes only a few minutes, which engineers sometimes call the “seven minutes of terror,” and it has to work automatically.
- Autonomy is powerful. Newer rovers can choose their own paths and even work out their own location, which lets them explore faster without waiting for instructions from Earth.
The Rovers at a Glance
| Rover | Landed | Location | Status | Key Highlights |
|---|---|---|---|---|
| Sojourner | 1997 | Ares Vallis | Ended 1997 | First Mars rover |
| Spirit | 2004 | Gusev Crater | Ended 2010 | Hot spring signs |
| Opportunity | 2004 | Meridiani Planum | Ended 2019 | Proof of ancient water |
| Curiosity | 2012 | Gale Crater | Still active | Habitable lake environment, organics |
| Perseverance | 2021 | Jezero Crater | Still active | Sample collection, possible biosignature |
| Zhurong | 2021 | Utopia Planitia | Inactive since 2022 | China’s first rover |
The Big Open Questions
Despite all that we have learned, many questions remain.
Did life ever exist on Mars? This is the biggest question of all, and rovers alone may not be able to answer it. The samples being collected by Perseverance could provide the answer if they can be returned to Earth. Bringing them home, a plan known as Mars Sample Return, is difficult and expensive, and its future approach has been under review, so it is wise to check the latest news from NASA and other space agencies.
Where did the water go? We know Mars lost most of its atmosphere, probably because it lacks a strong global magnetic field to protect it from the solar wind. Scientists are still refining the details of how and when this happened.
Is there life today? Most scientists think that present-day life on the surface is unlikely, but there may be tiny microbes underground, where there is more protection and possibly liquid water. That is a question for future missions.
What Comes Next?
Mars exploration is far from over. Curiosity and Perseverance continue to explore, and new missions are in preparation. Europe’s ExoMars rover, named Rosalind Franklin, is being developed with the ability to drill up to two metres below the surface, where organic molecules may be better protected from radiation. Space agencies are also studying how to return samples to Earth, and, longer term, how to send astronauts there. Every lesson the rovers teach us about dust, radiation, terrain, and resources will help make that possible.
How You Can Follow the Rovers Yourself
You do not need to be a scientist to take part.
- Browse the raw images. NASA publishes the rovers’ photos online, often within hours of being taken. You can scroll through them like a photo album of another planet.
- Follow the rovers on social media. The mission teams share updates, often with a bit of humour and personality.
- Watch the landing and mission videos. The sky crane landings are available online and are thrilling to watch.
- Try a Mars map. Interactive maps and 3D tools let you see where each rover has travelled.
- Look at Mars in the night sky. Mars appears as a steady reddish point of light. Knowing that robots are driving around on its surface right now makes it feel wonderfully close.
A Gentle Final Thought
The Mars rovers are a story about patience, teamwork, and curiosity. They were built by thousands of people, launched across space, and set down on a world no human has visited. Slowly, one rock and one photograph at a time, they have transformed Mars from a mysterious red dot into a place with a rich history of rivers, lakes, and chemistry.
What we have learned so far is only the beginning. The next discoveries may come from rocks that are still waiting to be drilled, or from samples that may one day reach laboratories on Earth. Keep following the story, keep asking questions, and remember that every great discovery starts with someone wondering what lies beyond the next hill.