Exploration of Mars

• 1. Introduction

  ›

  Mars has been sending spacecraft to its grave since 1960. From the earliest Soviet probes that barely left Earth's atmosphere to orbiters that fell silent just short of their goals, roughly sixty percent of all spacecraft ever aimed at the red planet have failed before completing their missions. That staggering loss rate earned an informal name: the Mars Curse. Yet the failures have never stopped the attempts. And the successes, when they came, were sometimes extraordinary. Spirit and Opportunity, the twin Mars Exploration Rovers, were designed to operate for a defined period. They kept going for years beyond it. What drives this relentless push toward a planet half the size of Earth, with a thin atmosphere and a surface cold enough to freeze most machinery? The answers run through decades of Soviet failures, American reinventions, and an expanding cast of space agencies from Europe, India, China, and the United Arab Emirates. And they circle around one central question: did Mars ever hold liquid water, and could it once have harbored life?

• 2. The Mars Curse

  ›

  On the 2nd of September 1988, mission controllers waited for a routine communications session with Phobos 1. It never came. The problem traced back to a software error that deactivated the spacecraft's attitude thrusters. Without them, the solar arrays drifted away from the Sun, the batteries died, and the mission was over. Phobos 2, launched alongside it, fared better at first. It survived cruise and Mars orbital insertion, gathered data on the Sun, the interplanetary medium, and Mars itself. But just as the spacecraft was preparing to approach within 50 meters of Phobos's surface and release two landers, contact was lost. A computer malfunction ended the mission on the 27th of March 1989. These were not isolated disasters. In 1992, Mars Observer failed as it approached Mars. In 1999, the Mars Climate Orbiter burned up in the Martian atmosphere because engineers mixed up U.S. customary units with metric ones. The same year, Mars Polar Lander and the Deep Space 2 penetrators also suffered fatal errors. Fobos-Grunt, launched in 2011 carrying both a Russian sample-return vehicle and the Chinese Yinghuo-1 satellite, suffered a complete control failure shortly after launch and fell back to Earth, disintegrating over the Pacific Ocean on the 15th of January 2012. The pattern was consistent enough that scientists coined the phrase "Galactic Ghoul" for the fictitious space monster that supposedly fed on Mars probes. The joke acknowledged a real and punishing engineering challenge: interplanetary distances are vast, mission timelines are long, and a single software line, a single unit conversion, can destroy years of work.

• 3. First Contact

  ›

  Mariner 4 flew past Mars on the 14th of July 1965, and sent back the first close-up photographs ever taken of another planet. The pictures, played back to Earth from a small onboard tape recorder, showed impact craters and revealed a surface atmospheric pressure of about one percent of Earth's. Daytime temperatures were estimated at around negative 100 degrees Celsius. No magnetic field was detected. The data forced engineers to go back and redesign planned Martian landers, and it made clear that surviving on Mars would be far harder than anyone had hoped. Mariner 9 followed in 1971, becoming the first spacecraft to orbit another planet. When it arrived, a planet-wide dust storm was raging, so controllers turned the waiting time into an opportunity and had the probe photograph Phobos. Once the storm cleared, Mariner 9's images showed what appeared to be ancient river valleys and channels, the first detailed evidence that liquid water might once have flowed on the surface. During the storm, one feature had remained visible above the dust: Nix Olympica, which the new images revealed to be the tallest volcano in the Solar System. It was reclassified as Olympus Mons. On the Soviet side, Mars 3 achieved the first soft landing on the 2nd of December 1971, but its transmission was cut off after just 14.5 seconds. Mars 2, which arrived days earlier, crash-landed and became the first human-made object to reach the Martian surface. The race to Mars in the early 1970s produced both landmark achievements and a toll of broken hardware.

• 4. Viking's Long Watch

  ›

  Viking 1 and Viking 2 lifted off in 1975 and touched down on Mars in 1976. Each carried an orbiter and a lander, and the landers were dramatically larger than anything that had come before: Viking 1 weighed 3,527 kilograms, compared to the 358 kilograms of the Mars 3 lander. From the surface, they took the first color panoramas of Mars. Viking 1 remained operational for about six years, finally going silent on the 11th of November 1982, after receiving a faulty command. Viking 2 operated for over three years before its mission ended in early 1980. The landers measured temperatures ranging from negative 86 degrees Celsius before dawn to negative 33 degrees Celsius in the afternoon. Martian winds were slower than scientists had predicted from observing global dust storms; neither lander recorded gusts over 120 kilometers an hour, and average velocities were considerably lower. The orbiters sent back more than 52,000 photographs, while the landers contributed over 4,500. Together they revealed that large floods of water had once carved deep valleys into the Martian surface, eroding grooves into bedrock and traveling thousands of kilometers. Branched stream patterns in the southern hemisphere suggested that rain once fell. The landers also detected nitrogen in the atmosphere for the first time and recorded atmospheric pressure swinging by 30 percent over the Martian year as carbon dioxide condensed and sublimed at the polar caps. The biological experiments the landers carried were designed to search for signs of life. Their results were inconclusive. A reanalysis of the Viking data published in 2012 suggested signs of microbial life, but no definitive answer has ever been established.

• 5. Water, Ice, and Biosignatures

  ›

  Mars Global Surveyor launched on the 7th of November 1996, and entered orbit on the 12th of September 1997. After a year and a half adjusting its trajectory from an ellipse into a circular polar orbit, it began its primary mapping mission in March 1999. Among its most striking finds were gullies and debris flow features suggesting possible current sources of liquid water near the surface, similar to an aquifer. Magnetometer readings showed that Mars has no global magnetic field; instead, magnetism is localized in patches of the crust. In January 1999, laser altimeter data gave scientists their first three-dimensional views of Mars's north polar ice cap. The mission returned more data about Mars than all previous missions combined before a software error uploaded in June 2006 caused the spacecraft to orient its solar panels incorrectly, overheating the batteries. NASA lost contact on the 5th of November 2006, and ended restoration efforts on the 28th of January 2007. Mars Odyssey, arriving in 2001, detected large amounts of hydrogen in the upper meter or so of Martian regolith, indicating vast deposits of water ice within 60 degrees latitude of the south pole. In early 2004, the Mars Express orbiter detected methane in the Martian atmosphere, a potential biosignature. ESA announced in June 2006 the discovery of aurora on Mars. Phoenix landed on the north polar region on the 25th of May 2008, and its robotic arm confirmed the presence of water ice directly on the 20th of June 2008. The mission ended on the 10th of November 2008. Beagle 2, which had been declared lost in February 2004, was located in January 2015 by the HiRISE camera aboard Mars Reconnaissance Orbiter; it had landed safely but failed to fully deploy its solar panels, blocking its antenna.

• 6. Rovers and Persistence

  ›

  Spirit and Opportunity landed in January 2004 and both exceeded all their scientific objectives. Among the most significant returns was conclusive evidence that liquid water existed at some time in the past at both landing sites. Martian dust devils and windstorms occasionally swept clean their solar panels, extending the rovers' lives well beyond their original specifications. Spirit operated until 2010, when it became stuck in a sand dune and could no longer reorient itself to recharge its batteries. Mars Pathfinder had preceded them in July 1997, carrying Sojourner, a 10.6 kilogram wheeled robot and the first rover to operate on the Martian surface. Pathfinder also tested an airbag landing system and automated obstacle avoidance, both later used by the Mars Exploration Rovers. The Mars Science Laboratory mission delivered Curiosity to Aeolis Palus in Gale Crater on the 6th of August 2012. The rover carries instruments designed to assess whether Mars could support or have supported life. The Mars 2020 mission, launched on the 30th of July 2020, delivered Perseverance to Mars on the 18th of February 2021, after a journey of 293 million miles. Perseverance is nuclear-powered and about one ton in mass, equipped with a robotic arm that reaches about seven feet, zoom cameras, a chemical analyzer, and a rock drill. By the 19th of October 2021, it had captured five hours of sound from Mars: wind gusts, rover wheels on gravel, and motors moving the spacecraft's arm. Alongside it, the Ingenuity helicopter scouted sites for the rover to study before its mission ended in 2024.

• 7. A Global Endeavor

  ›

  India's Mars Orbiter Mission, also known as Mangalyaan, launched on the 5th of November 2013, and reached Mars orbit on the 24th of September 2014. It was completed at a budget of 71 million dollars, making it the least expensive Mars mission to date. India became the fourth space agency to reach Mars after the Soviet Union, NASA, and ESA, and the first country to succeed in its maiden attempt. The mission concluded on the 27th of September 2022. The United Arab Emirates launched the Hope Mars Mission in July 2020 on a Japanese H-IIA booster. It entered Mars orbit on the 9th of February 2021, and is studying the planet's atmosphere and weather patterns. China's Tianwen-1, launched on the 23rd of July 2020, placed an orbiter, lander, and the 240 kilogram Zhurong rover at Mars. Zhurong landed on the 14th of May 2021, deployed on May 22, and traveled 1,921 meters over 347 Martian days before entering hibernation. It has not moved since. In April 2024, NASA selected several companies to study providing commercial services for robotic science on Mars. SpaceX is targeting its first uncrewed Starship launches to Mars no earlier than 2026, with crewed flights planned no earlier than 2028. ESA's Rosalind Franklin rover, delayed indefinitely after the 2022 Russian invasion of Ukraine disrupted the partnership with Roscosmos, received additional funding in 2024 and is now planned for a 2028 launch. China's Tianwen-3 mission aims to return samples of Martian soil to Earth, launching in late 2028 and returning samples by July 2031.