Exploring Mars

Past and Active Missions

Mariner Missions (1964-1972)

NASA’s Mariner 4 mission sent back the first close-up images of Mars in 1964, revealing a terrain covered in impact craters. 

In 1969, Mariners 6 and 7 imaged the equatorial and south polar regions of Mars and analysed the martian atmosphere. 

In 1971, Mariner 9 became the first spacecraft to orbit Mars. Despite a dust storm that obscured the whole planet for the first month after its arrival, Mariner 9 mapped almost the whole martian surface over the course of a year. It revealed that large features, observed since the late 19^th century, were huge volcanoes and discovered the vast ‘Valles Marineris’ canyon system, which was named in the mission’s honour. Mariner 9 also provided the first closeup images of the two moons of Mars, Phobos and Deimos.

Mars 2 and 3 (1971-2)

The Soviet Union’s Mars 2 and 3 missions each involved an orbiter, a lander and a rover. Both orbiter missions succeeded, sending back images and data. They were just beaten to Mars by Mariner 9 and, like the NASA mission, initially had their view obscured by a global dust storm. The Mars 2 lander crashed into the martian surface. However, Mars 3 made the first successful soft landing on Mars on 2 December 1971. It transmitted a partial picture of the martian surface, before it stopped working less than 30 seconds after landing. 

Viking Missions (1975-1982)

Viking 1 and 2 were identical missions, each consisting of a lander and an orbiter. Viking 1 landed in the flat lowlands of Chryse Planitia in the northern hemisphere. Viking 2 landed in one of the largest impact basins on Mars, Utopia Planitia. Both landers returned images of the martian surface and also conducted experiments to detect potential signs of life. The experiments indicated that there was chemical activity in the soil at the landing sites but found no evidence of the presence of life. 

The Viking missions continued far beyond their designed 90-day lifetime, with the Viking 2 lander operating for seven years on the surface of Mars. 

Mars Pathfinder (1996-7)

NASA’s Mars Pathfinder landed in 1997 in the Ares Vallis, an outflow channel believed to have been formed by water. The mission successfully deployed the first rover, Sojourner, on the martian surface. 

Mars Pathfinder returned more than 17,000 images, more than 15 chemical analyses of rock and soil, and significant data on martian weather. Key findings from Mars Pathfinder include geological evidence of surface water in Mars’s past, the discovery of magnetic airborne dust, meteorological measurements of dust devils, the presence of ice clouds, and dramatic temperature fluctuations in the martian mornings. 

Mars Global Surveyor (1996-2006)

NASA’s Mars Global Surveyor orbiter carried a suite of scientific instruments designed to study the martian interior, surface, and atmosphere. The mission revealed gullies and debris flow that indicated that liquid water was once present at or near the surface. Data from the onboard magnetometer showed that, although Mars does not have a global magnetic field, areas of the martian crust have localised magnetic fields. Observations from the camera onboard also showed that Mars has weather patterns that repeat at roughly the same time each year. 

Mars Global Surveyor sent more than 240,000 images of Mars back to Earth, which were important in identifying potential landing sites for future rover missions such as Mars Exploration Rovers (Spirit and Opportunity) and Mars Science Laboratory (Curiosity rover).

2001 Mars Odyssey (2001- )

Still operating today, NASA’s 2001 Mars Odyssey orbiter is currently the longest running spacecraft at Mars. The mission made the first global map of elements and minerals on the martian surface. This has helped scientists to identify regions of interest that may hold clues into the wetter past of Mars and to discover pockets of water ice beneath the martian surface. 

The orbiter has acted as a communication relay to send data back to Earth from numerous rovers and landers on Mars. 

Mars Express (2003- )

ESA’s Mars Express was Europe’s first mission to Mars. Although a lander, Beagle 2, was unsuccessful, the Mars Express orbiter is the second longest-serving Mars mission and is still in operation after more than 20 years. 

Since arriving at Mars in 2003, Mars Express has provided a map of the chemical composition of the martian atmosphere, detected traces of methane gas, found evidence of water ice in the south polar ice cap, and detected underground water ice, buried impact craters, and layered deposits. 

Mars Exploration Rovers (2004-2018)

NASA’s twin Mars Exploration Rovers, Spirit and Opportunity, aimed to look for evidence that water existed on Mars in the past. They landed in 2004 on opposite sides of the planet: Spirit landed at Gusev Crater, an impact crater believed to have once been a lake, whilst Opportunity landed in Meridiani Planum, a large plain that contains minerals indicative of the past presence of water. 

Spirit’s investigations indicated that impacts, volcanism, and subsurface water were present on an early Mars. Despite breaking a wheel in 2006, Spirit continued to operate until 2010. Its immobile wheel scraped away bright patches hidden under the martian soil, which were found to have silica-rich properties. On Earth, similar deposits are found in hydrothermal systems where microbial life thrives. 

During its 15-year lifetime, Opportunity studied more than 100 craters and detected minerals that form in water, such as hematite and gypsum. The rover discovered that Endeavour Crater contains clays that formed from water with a neutral pH, meaning it may once have been a habitable environment. Opportunity also found the Eagle and Endurance craters contained sulfate-rich evaporates, indicating that they had, at times, been lakes that dried out. 

The rovers exceeded their designed lifetime of 90 days, with Spirit lasting over 6 years and Opportunity 14.5 years. By the time Opportunity’s mission ended the rover had travelled a total of 45.16 km, the current record holder for furthest distance travelled on the surface of Mars. 

Mars Reconnaissance Orbiter (2005- )

In 2005, NASA launched Mars Reconnaissance Orbiter (MRO) to search for evidence that water was present on Mars long enough to provide an environment that was habitable for life. It remains operational and is the third longest-serving spacecraft to orbit Mars.

MRO’s powerful camera has enabled scientists to investigate small-scale features on Mars in detail, as well as identify potential obstructions to landers and rovers on the martian surface. Instruments carried by the orbiter have helped identify minerals on the martian surface and locate subsurface water. 

MRO is also used by multiple spacecraft as a communications bridge back to Earth in the first step towards an “interplanetary internet”.  

Mars Phoenix (2007-2008)

NASA’s Mars Phoenix landed in 2008 in the northern polar region, Vastitas Borealis. The mission’s aim was to study the history of water on Mars and search for evidence of habitability in the planet’s arctic plains. 

Mars Phoenix scooped up martian soil samples, using robotic arm, and analysed them in an onboard laboratory.  Results confirmed the presence of water ice in the martian subsurface and found traces of the chemical perchlorate, a possible energy source for microbes and a potential resource for future human explorers.

Mars Science Laboratory/Curiosity (2012- )

NASA’s Mars Science Laboratory mission and Curiosity rover landed in 2012 in Gale Crater, just south of the martian equator. Curiosity is still active on Mars today, continuing long beyond its primary mission time of 687 Earth days (1 martian year), and continues to relay important scientific data back to Earth.  

Curiosity’s main science goal is to determine if Mars has ever had the right environmental conditions to support microbial life. The rover is equipped with multiple cameras, spectrometers, radiation detectors, environmental sensors, and atmospheric sensors.  These instruments allow Curiosity to locate and analyse rocks that may contain indicators of past habitability on Mars. 

Significant findings from Curiosity include the analysis of rounded pebbles and mudstones, which show that water was present for long periods on the martian surface. Chemical analysis of a mudstone called ‘Sheepbed’ has revealed the presence of key elements for life, including sulfur, nitrogen, oxygen, phosphorus and carbon. Sheepbed contains clay minerals and a low salt content indicating that fresh and possibly drinkable water was once present in Gale Crater. 

Curiosity has found organic molecules, the building blocks of life, in rocks from Mount Sharp. Although this highlights that the elemental ingredients required for life to flourish were once present on Mars, it does not confirm the presence of past or current life. Curiosity has also measured quantities of methane in the martian atmosphere; the origin of this methane, and whether it might be geological or biological, is still under investigation. 

Curiosity is still active on Mars today, continuing beyond its primary mission time of 687 Earth days (1 martian year). The rover continues to relay important scientific data back to Earth.  

Mars Orbiter Mission (Mangalyaan) 

The Mars Orbiter Mission, also known as Mangalyaan, was India’s first mission to Mars. From 2014-2022, the orbiter studied the martian surface and atmosphere, and provided new insights into dust storms. 

MAVEN (Mars Atmospheric and Volatile EvolutioN)

Since 2014, NASA’s Mars Atmospheric and Volatile EvolutioN (MAVEN) orbiter mission has collected data on the martian atmosphere to understand how the climate has changed over the planet’s history. MAVEN has provided critical insights into how Mars lost most of its atmosphere to space, resulting in the thin CO₂-rich atmosphere we observe today.

ExoMars Trace Gas Orbiter (2016 -)

ESA’s ExoMars 2016 mission consisted of the successful Trace Gas Orbiter (TGO), which continues to operate around Mars, and the Schiaparelli lander, which was lost on landing. 

TGO is studying the martian atmosphere for traces of gases that may indicate the presence of life. To date, it has not found evidence of biomarker gases, such as methane or phosphene. However, it has made detailed maps of carbon monoxide and water vapour in the atmosphere, along with several other molecules, and revealed how dust storms can transport water and ice high into the martian atmosphere. The second part of ESA’s ExoMars mission, the Rosalind Franklin rover, is scheduled to arrive on Mars by 2030.

InSight (2018-2022)

NASA’s InSight mission landed in 2018 in Elysium Planitia, a smooth plain just north of the martian equator. InSight’s main objective was to study the internal structure of Mars to help understand how the planet formed and evolved. 

InSight carried the first seismometer to Mars, which studied the martian crust, mantle and core by detecting changes to seismic waves as they travelled through the interior of the planet. Over its 4-year lifetime, InSight detected more than 1300 ‘marsquakes’, the shaking of the martian surface caused by meteorite impacts, movement of magma or cracking in the martian crust.

The mission collected unique data on the composition, temperature, and pressure of the layers that make up Mars. Scientists can now confirm that the planet’s core is molten, with a radius of 1,830 km. The thickness of the mantle and crust have also been determined to be around 1560km and 50 km respectively. 

Hope Orbiter (2020- )

The Hope Orbiter, also known as the Emirates Mars Mission, is the first spacecraft sent to Mars by the United Arab Emirates. The Hope Orbiter is studying the martian atmosphere, including daily and seasonal variations, how Mars is currently losing its atmosphere to space, and what the link between weather change and atmospheric loss can reveal about how climate of Mars has changed over its history

Tianwen-1 (2020- )

The Tianwen-1 orbiter and Zhurong rover make up China’s first mission to Mars. In 2021, the Zhurong landed in Utopia Planitia, where NASA’s Viking 2 landed over 40 years ago. Zhurong is using a radar to search for evidence of subsurface water that may contain life, as well as conducting chemical analyses of rocks. Tianwen-1 is conducting investigations into the martian surface, atmosphere and magnetic field, and also serves as a communication relay between Earth and Zhurong. 

China aims to build on its experiences with Tianwen-1 and Zhurong to develop its own sample return mission. 

Mars 2020/Perseverance (2020- ) 

The Mars 2020 Perseverance rover is the first stage of the Mars Sample Return Campaign, which aims to bring samples of martian rock and regolith back to Earth for analysis. Perseverance touched down on Mars in 2021 in Jezero Crater. Early in the history of Mars, Jezero held a deep lake into which a river flowed, creating a delta. This landing site was chosen from over 60 potential targets as it is a promising location to search for evidence of past life. 

Future Missions

Martian Moons eXploration (MMX) Mission

JAXA’s Martian Moons eXploration (MMX) mission will explore the two martian moons, Phobos and Deimos. MMX consists of an orbiter, lander, and sample return mission. If successful, the first samples from Phobos could be returned to Earth in the early 2030s.  

The mission aims to help scientists resolve questions about the origin of the moons. The two main theories are that Phobos and Deimos are either captured asteroids or debris from a large impact with Mars. Samples from Phobos and Deimos returned by MMX will also hold clues to the composition of the martian surface, since the moons will have accumulated material ejected from impacts with Mars over billions of years. 

ExoMars Rover and Surface Platform

ESA’s ExoMars Rosalind Franklin rover and Surface Platform lander is expected to launch in 2028.

Rosalind Franklin will land in Oxia Planum, a clay-rich region of the martian surface that is thought to have once contained water. Rocks in the region are estimated to be around 3.9 billion years old. The mission’s main goal is to determine if any organic material has been preserved from this early time on Mars. Samples at depth are more likely to preserve signature of past life as they have been protected from processes at the martian surface. Rosalind Franklin will be the first rover able to drill down to a 2-m depth below the martian surface.

Tianwen-3

China proposes to launch the Tianwen-3 sample return mission in 2030. If successful, Tianwen-3 will be the first spacecraft to return samples from Mars to Earth.