Mars has attracted more sustained spacecraft exploration than any planet beyond Earth. Since the first successful flyby in 1965, orbiters, landers, rovers and even a helicopter have transformed the Red Planet from a distant world seen through telescopes into a place whose rocks, atmosphere and ancient environments can be studied in extraordinary detail.
The history of Mars exploration has included spectacular successes as well as numerous failed missions. Yet each generation of spacecraft has built upon the last, revealing a planet that was once much wetter and potentially habitable. Here are ten milestones in the exploration of Mars.
1. Mariner 4 Returned the First Close-Up Images of Mars
NASA’s Mariner 4 made the first successful flyby of Mars on July 14, 1965. It returned 22 close-up photographs, giving humanity its first detailed spacecraft views of another planet.
The images showed a heavily cratered landscape and helped overturn earlier ideas that Mars might possess an Earth-like environment. Mariner 4 also found that the Martian atmosphere is extremely thin and composed primarily of carbon dioxide.
Later Mariner missions revealed that the cratered terrain photographed by Mariner 4 represented only part of a much more varied planet containing enormous volcanoes, canyons and evidence of ancient flowing water.
2. Viking Made the First Fully Successful Landings on Mars
NASA’s Viking 1 landed successfully on Mars on July 20, 1976, followed by Viking 2 on September 3. They became the first spacecraft to operate successfully for extended periods on the Martian surface.
Each mission consisted of an orbiter and a lander. Together they returned thousands of images, mapped much of the planet and studied the atmosphere, weather and surface chemistry.
The Viking landers also carried the first experiments designed specifically to search for evidence of Martian life. Their results proved difficult to interpret, but no convincing evidence of life was established.
3. Viking 2 Photographed Frost on the Martian Surface
Viking 2 landed much farther north than Viking 1, at Utopia Planitia. Its long operating life allowed the lander to observe seasonal changes in its surroundings.
During the Martian winter, Viking 2 photographed a thin layer of frost covering the ground. The observations provided an early close-up demonstration of the active exchange of volatiles between the Martian atmosphere and surface.
Decades later, other missions would establish that enormous quantities of water ice are present beneath parts of the Martian surface and within its polar regions.
4. Sojourner Became the First Rover to Explore Mars
NASA’s Mars Pathfinder landed in Ares Vallis on July 4, 1997. It carried a small six-wheeled rover named Sojourner, which became the first wheeled vehicle to operate on another planet.
Sojourner was only about the size of a microwave oven and was designed primarily as a technology demonstration. Nevertheless, it spent nearly three months exploring the area around the Pathfinder lander and examining Martian rocks and soil.
The mission demonstrated that a mobile robot could successfully navigate and conduct science on Mars, establishing an approach that would eventually lead to much larger and more capable rovers.
5. Spirit and Opportunity Survived Far Longer Than Expected
The twin Spirit and Opportunity rovers landed on opposite sides of Mars in January 2004. Each was designed to operate for just 90 Martian days.
Spirit continued exploring until communications ended in 2010. Opportunity survived even longer, remaining operational until a planet-wide dust storm ended communications in June 2018.
Opportunity ultimately traveled more than 45 kilometers (28 miles), setting a distance record for off-Earth wheeled travel at the time.
More important than their longevity were their discoveries. Both rovers found geological evidence that liquid water had affected ancient Mars. Opportunity’s observations at Meridiani Planum, in particular, revealed minerals and sedimentary rocks formed or altered in the presence of water.
6. Mars Reconnaissance Orbiter Gave Us an Extraordinary View From Above
NASA’s Mars Reconnaissance Orbiter (MRO) entered orbit around Mars in March 2006 and remains an active mission two decades later.
Its HiRISE camera can resolve remarkably small features on the Martian surface. MRO has photographed landslides, dunes, impact sites, rover tracks and geological layers while helping scientists investigate the planet’s history of water.
The spacecraft has also become an important communications relay. Data from surface missions can be transmitted to MRO and then sent back to Earth, making the orbiter part of the infrastructure supporting continued exploration of Mars.
7. Phoenix Confirmed Water Ice Beneath the Surface
NASA’s Phoenix lander touched down in the Martian arctic in May 2008 with a robotic arm capable of digging into the soil.
When Phoenix excavated shallow trenches, it exposed bright material just below the surface. Some of this material disappeared over several days, behavior consistent with exposed water ice sublimating directly into vapor.
Phoenix subsequently confirmed water ice in its samples. The discovery provided direct evidence that substantial frozen water exists immediately beneath the surface in parts of Mars.
8. Curiosity Showed That Ancient Mars Was Habitable
NASA’s car-sized Curiosity rover landed inside Gale Crater on August 6, 2012. Its central question was not whether life currently exists on Mars, but whether the planet ever possessed environmental conditions capable of supporting microbial life.
The answer has been increasingly clear: yes. Curiosity found evidence that Gale Crater once contained lakes and streams with liquid water and chemistry capable of supporting life as we know it.
It has also detected a range of organic molecules preserved in ancient Martian rocks. Organic compounds are not themselves proof of life—they can form through non-biological processes—but their survival demonstrates that important ingredients for life can be preserved on Mars.
Curiosity remains active in 2026, climbing through the layered rocks of Mount Sharp and investigating how Mars changed from a wetter ancient world into the cold desert seen today.
9. Perseverance and Ingenuity Opened a New Era of Mars Exploration
NASA’s Perseverance rover landed in Jezero Crater on February 18, 2021. Jezero was selected because orbital observations showed that it once contained a lake and river delta—an environment where evidence of ancient microbial life might potentially have been preserved.
Perseverance is studying the geology of this ancient environment and collecting carefully selected samples of Martian rock and regolith in sealed tubes. The rover remains active in 2026 as it explores increasingly ancient terrain beyond the original Jezero crater floor.
Perseverance also carried a small experimental helicopter called Ingenuity. On April 19, 2021, Ingenuity achieved the first powered, controlled flight on another planet.
The helicopter was intended to make only five experimental flights over about 30 days. Instead, it completed 72 flights during nearly three years of operations before rotor damage during its final landing ended its flying career in January 2024.
10. Rosalind Franklin Will Search Beneath the Martian Surface
The next major European rover mission is ESA’s Rosalind Franklin, part of the ExoMars program.
The rover is currently planned for launch in 2028 and arrival on Mars in 2030. Its most distinctive instrument is a drill designed to reach as deep as two meters (6.6 feet) below the surface.
That depth matters because Mars’s surface is exposed to intense radiation and oxidizing conditions that can destroy organic material. Samples buried underground may therefore preserve evidence that would long ago have disappeared from exposed rocks.
Rosalind Franklin will analyze those samples for evidence of past or potentially present life. If successful, it will extend a story that began with Mariner 4’s handful of photographs in 1965 into the direct investigation of potentially habitable environments beneath the Martian surface.