Mars: a planet full of riddles

Mars has always inspired the imagination of mankind. It is more similar to Earth than any other planet in the Solar System. Scientists have been trying to uncover the secrets of Mars for more than 50 years using unmanned spacecraft. Water – essential for the development of life as we know it – has left clear marks on the surface of the planet. Searching for these traces is one of the goals of ESA's Mars Express mission. It has been returning measurement data and images reliably from our planetary neighbour since 2004. The images from the HRSC camera on board the spacecraft offer new possibilities for investigating the complex geological history of the Red Planet.

Join us on a trip to our planetary neighbour. See breathtakingly beautiful pictures of its surface. Find out more about its geology, climatic history and moons, and learn about the history of its exploration.

Mars Earth
Diameter 6792.4 km (Equator) 12756.32 km (Equator)
Surface area 144 × 106 km2 510 × 106 km2
Mass 6.419 X 1023 kg 5.974 X 1024 kg
Gravitational acceleration 3.69 m/s2 9.78 m/s2
Mean distance from Sun 227.9 X 106 km 149.6 X 106 km
Orbital period 687 days 365.24 days
Rotation period 26.62 hours 23.93 hours
Axis inclination 25.2° 23.4393°
Topography -8000 m to 21,200 m -11,000 m to 8850 m
Temperature -60 °C (-133 °C to 27 °C) 15 °C (-88 °C to 58 °C)
Mean atmospheric pressure 6.35 mbar 1013 mbar
Atmospheric composition 95% CO2, 3% N2, 2% Ar 78% N2, 21% O2, 1% Ar
Density 3.934 g/cm3 5.534 g/cm3

Mars in 3D - The High Resolution Stereo Camera

HRSC Camera
HRSC Camera

The first all-European mission to another planet – Mars Express – was launched on 2 June 2003. On board the spacecraft was the High Resolution Stereo Camera (HRSC), which was developed by the DLR Institute of Planetary Research. HRSC was the first camera system on a planetary mission to systematically acquire high-resolution, three-dimensional image data in colour.

The objective of the HRSC experiment is the global topographic mapping of Mars at a resolution of at least 40 metres per pixel. Large areas of the planet have also been recorded at 20 and even 10 metres per pixel. The stereo image data can be used to generate digital terrain models. The combination of the height information obtained with the high-resolution image data enables researchers to draw significantly improved conclusions about the geological evolution of the planet during its four-and-a-half-billion year history.

This highly accurate 3D mapping is achieved using an observation technique that is being employed in planetary research for the first time. As the spacecraft flies by the planet, the HRSC scans the Martian landscape with nine linear CMOS sensors arranged transversely with respect to the flight direction. Four of these sensor channels have fields of view that point forward along the spacecraft ground track by differing amounts, while another four look obliquely backward. Between these two sets of channels, the nadir channel looks vertically down and delivers images with the highest possible resolution.

Missions to Mars

Why is Mars a barren desert planet today? Where did the water that was once there go? Could life ever have existed on Mars, and could it still do so today? Mars presents us with many questions, but missions like Europe’s Mars Express provide important new data on the geology, mineralogy and atmosphere of Mars to help resolve the most important issues in Mars research.

On board Mars Express is the High Resolution Stereo Camera (HRSC), operated by DLR. The images are a valuable and unique resource for current and future Mars research. The discoveries made so far have massively changed our view of the geological and climatic development of the Red Planet.

In these interviews, DLR scientists report on their research and on the intriguing discoveries made so far using the HRSC data.


Mars 1

The Soviet spacecraft was intended to carry out research in the vicinity of Mars. It was the first spacecraft to approach Mars, although radio contact was lost before arriving at its destination.

Mariner 3

Mariner 3

On the Mariner 3 mission, the first US attempt to fly to Mars, the shell failed to separate, preventing the solar panels from unfolding. Radio contact was lost nine hours after launch.

Mariner 4

Mariner 4

This is the first close-up picture ever taken of Mars. Mariner 4 provided a total of 22 images of the surface during its flight, at a distance of 10,000 kilometres. In addition, it demonstrated that the thin Martian atmosphere consists primarily of carbon dioxide, and that there are weak traces of a magnetic field.

25.02.1969 und 27.03.1969
Mariner 6 and 7

Mariner 6 and 7

Mariners 6 and 7 were designed as a twin mission. The Mariner 6 spacecraft flew 3437 kilometres above the Martian equator, and Mariner 7, 3551 kilometres above the Martian South Pole. Both spacecraft investigated the surface and atmosphere (structure and composition), and delivered over 200 images of the surface.

Mariner 8

Mariner 8

This US mission was not successful; a malfunction with the Centaur upper stage prevented the spacecraft from reaching Earth orbit. Mariner 8 was intended to map Mars.


Mars 2

The Soviet Mars 2 orbiter and lander mission operated for 362 orbits. The orbiter provided data until 1972, including images acquired with a camera using film that was chemically developed on board, and subsequently scanned with a TV camera. The descent module separated from the orbiter on 27 November 1971, but plummeted to the Martian surface, as the descent system malfunctioned and the parachute did not deploy. Despite the crash landing, it was the first time a capsule reached the surface of Mars.

Mars 3

Mars 3

Mars 3 reached Mars on 2 December 1971. The lander was separated from the orbiter and landed successfully, but the transmission lasted less than 20 seconds. The orbiter, however, continued sending data back to Earth until August 1972.

Mariner 9

Mariner 9

Part of the Mariner Mars 71 project, consisting of the Mariner 8 and 9 probes. When Mariner 8 was lost during the launch, Mariner 9 had to combine the work of both missions (mapping 70 percent of the surface of Mars as well as investigating its atmosphere and surface). The mission provided 7329 images of the surface, with a maximum resolution of 100 metres per pixel. It mapped 100 percent of the planet, including the first detailed images of the volcanoes of Mars, Valles Marineris, the polar caps, as well as the first images of the Martian moons Phobos and Deimos.

07/08 1973

Mars 4 to 7

The Soviet Mars 4 to 7 missions were intended to succeed in landing a capsule on the surface of Mars for the first time. The missions were not successful.

Viking 1

Viking 1

The NASA Viking mission consisted of two spacecraft, Viking 1 and Viking 2, both equipped with a lander and an orbiter. The main aim of the mission was to search for traces of life on the surface of Mars, as well as to acquire high-resolution images of the surface, and determine the structure and composition of the planet’s atmosphere and surface. Viking 1 reached Mars orbit on 19 June 1976. The lander touched down on Chryse Planitia on 20 July 1976. Operations were terminated on 17 August 1980, but the lander continued functioning until 13 November 1982.

Viking 2

Viking 2

Viking 2 reached Mars orbit on 7 August 1976. The lander touched down in the north of Utopia Planitia on 3 September 1976. Both landers sent back panoramic views. The missions delivered over 55,000 images (including of the moons), covering the entire surface with a resolution of 100-200 metres per pixel, and a few down to 8 metres. The orbiter functioned until 25 July 1978, and the lander until 11 April 1980.


Phobos 1

This Soviet mission was intended to investigate the Martian moon Phobos. It was lost en route to Mars as a result of an incorrect command signal.


Phobos 2

This spacecraft reached Mars orbit, delivered thermal images of a roughly 1500 kilometre-wide strip of terrain at the equator, and took nine images of Phobos. Radio contact was lost on 27 March 1989.

Mars Observer

Mars Observer

Radio contact was lost shortly before reaching Mars orbit.

Mars Global Surveyor

Mars Global Surveyor

The replacement for Mars Observer spent seven years mapping the surface of Mars in high resolution. Using the principle of laser altitude measurements, the first global topographical map of Mars was produced.


Mars 96

Russian mission with important European participation. Malfunction in the 4th stage of the carrier rocket, unstable Earth orbit. The spacecraft plunged into the ocean. The replacement vehicle for this mission was cost-effectively converted for the Mars Express spacecraft, with the German HRSC camera on board.

Mars Pathfinder

Mars Pathfinder

Landed in the delta region of Ares Vallis and Tiu Vallis on 4 July 1997. It was the first time that a spacecraft landed using airbags. The lander and Sojourner rover operated for 84 days.


Mars Climate Orbiter

Lost entering Mars orbit. Its objectives included the investigation of the weather and climate, water and the properties of the mainly carbon dioxide atmosphere.


Mars Polar Lander

Same mission goals as Mars Climate Orbiter. Landing was not successful.

2001 Mars Odyssey

2001 Mars Odyssey

Orbiter mission with the aim of carrying out a detailed mineralogical investigation of the surface and surrounding radiation. The Mars orbiter also acted as a communications relay for subsequent Mars missions. In 2010, Odyssey achieved the record for being the spacecraft operating for the longest period around Mars. In 2012, the mission supported the landing of the Mars Science Laboratory.

Mars Express

Mars Express

European orbiter and lander mission. Landing of Beagle 2 was not successful. The orbiter mission was successful and provided important new data on the geology, mineralogy and atmosphere of Mars. Using the HRSC camera developed by DLR, Mars was mapped globally in high resolution, 3D and in colour. The images and the first global topographical mapping based on stereo image data reached a resolution of down to 10 metres per pixel.


Spirit (Mars Exploration Rover A)

US rover mission, landed in Gusev Crater on 4 January 2004. Spirit carried numerous scientific instruments on board, and had a range of 100 metres a day. It studied the surface looking for traces of life, and the climate and geology of Mars. All attempts to contact the rover ceased on 25 May 2011.


Opportunity (Mars Exploration Rover B)

Rover landed in Meridiani Planum on 25 January 2004. Same mission goals as Spirit.

Mars Reconnaissance Orbiter

Mars Reconnaissance Orbiter

The orbiter reached Mars on 10 March 2006. It is investigating the climate and the surface, using a camera system providing the highest resolution images of the surface of Mars to date. It is also looking for landing sites.



Small stationary lander that touched down in the northern polar region on 25 May 2008. Investigated the role of water and the surface at high latitudes. It discovered ice and frost deposits by taking samples of the polar surface.



The objectives of the Russian mission were to map the Martian moon Phobos and land on the Martian satellite, taking images in the process to send back to Earth. The probe malfunctioned in Earth orbit and did not enter its planned transfer orbit.

Mars Science Laboratory

Mars Science Laboratory

The Mars rover Curiosity landed in Gale Crater on 6 August 2012. It was the first landing using a flying crane to lower the rover the last eight metres onto the surface. The intention is to use 10 instruments to search for traces of the chemical constituents for life and discover how friendly or hostile Mars was to life in its past - and might be for future manned missions.

Video (external link)

November 2013


The US mission will investigate the atmosphere of Mars, and clarify how the loss of atmospheric gases into space has influenced climate change on Mars.



The US mission will mainly see geophysical experiments being carried out on and under the surface of Mars, for example measuring the speed of seismic waves or heat flow, using the ‘Mole’ developed by DLR that is capable of boring up to five metres into the Martian surface. The aim is to improve our understanding of the structure and state of the core and mantle, as well as the thermal development of Mars.

2016 and 2018


The ExoMars mission is intended to look for traces of life and carry out geophysical investigations on the interior structure of Mars, for example.

From 2020 onwards

Mars Sample Return

The aim of the Mars Sample Return mission is to collect surface samples on Mars and return these to Earth.

Mars exploration – the current status

Why is Mars a barren desert planet today? Where did the water that was once there go? Could life ever have existed on Mars, and could it still do so today? Mars presents us with many questions, but missions like Europe’s Mars Express provide important new data on the geology, mineralogy and atmosphere of Mars to help resolve the most important issues in Mars research.

On board Mars Express is the High Resolution Stereo Camera (HRSC), operated by DLR. The images are a valuable and unique resource for current and future Mars research. The discoveries made so far have massively changed our view of the geological and climatic development of the Red Planet.

In these interviews, DLR scientists report on their research and on the intriguing discoveries made so far using the HRSC data.

  • Prof. Dr. Tilman Spohn
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    Prof. Dr. Tilman Spohn

    The possibility of life on Mars

    Tilman Spohn is head of the DLR Institute of Planetary Research. In this interview he talks about the possibility of life, not just on Mars, but also on other planets and moons as well.

  • Prof. Dr. Ralf Jaumann
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    Prof. Dr. Ralf Jaumann

    The history of the climate of Mars

    Ralf Jaumann is head of the Planetary Geology department at the DLR Institute of Planetary Research. He is the experiment manager and co-investigator for the HRSC on Mars Express, focusing on the climatic history of the Red Planet.

  • Ernst Hauber
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    Ernst Hauber

    Volcanism on Mars

    In this interview, Ernst Hauber, a planetary geologist at the DLR Institute of Planetary Research, talks about the geology of Mars, its long-lasting volcanism, its tectonics and the development of the crust of the planet.

  • Dr. Laetitia Le Deit
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    Dr. Laetitia Le Deit

    Landing sites on Mars

    Laetitia Le Deit, a planetary geologist at the DLR Institute of Planetary Research, investigates sites on the surface of Mars that are well suited for landers and are of particular interest to research.

  • Harald Hoffmann
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    Harald Hoffmann

    The Mars moons Phobos and Deimos

    In this interview, Harald Hoffmann, a planetary geologist at the DLR Institute of Planetary Research, reports on the current debate on the formation and future of the Martian moons Phobos and Deimos.

  • Dr. Daniela Tirsch
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    Dr. Daniela Tirsch

    The weather and climate on Mars

    In this interview, Daniela Tirsch, a planetary geologist at the DLR Institute of Planetary Research, explains how wind and weather continue to leave their mark on the surface of Mars today.

  • Ulrich Köhler
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    Ulrich Köhler

    The history of Mars exploration

    Ulrich Köhler, a planetary geologist at the DLR Institute of Planetary Research, gives us an overview of the history of the exploration of our planetary neighbour.

  • Klaus Gwinner
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    Klaus Gwinner

    The cartography of the surface of Mars

    In this interview, Klaus Gwinner, a planetary geologist at the DLR Institute of Planetary Research, reports on the 3D modelling and cartography of the surface of Mars based on data from the HRSC camera.

Those worlds in space are as countless as all the grains of sand on all the beaches of the Earth. Each of those worlds is as real as ours and every one of them is a succession of incidents, events, occurrences which influence its future.

Carl Sagan, 1934-1996 US astronomer and astrophysicist, visionary
Driving force behind the 1976 Viking lander missions to Mars

The Martian globe

One of the most conspicuous features on Mars is its topographical division, or dichotomy, into a northern region of lowland plains and the older southern highlands, featuring numerous impact craters. The processes leading to what we see today are still not clear. The transition from the highlands to the lowlands takes place along a narrow zone. Here, erosion by flowing water, wind, ice and ground water has created a remarkable landscape of furrowed buttes, deeply cut valleys and smaller areas of elevated ground.

This false-colour global map of Mars displays the altitude variations of the surface. The data to produce this was acquired with NASA’s Mars Global Surveyor. The lowest lying regions are shown in blue, such as the floor of the 8000-metre-deep Hellas impact crater in the southern hemisphere. The highest points on Mars are coloured red, pink, brown and grey, and are located in the Tharsis volcanic region, which is home to the majority of volcanoes on Mars, including Olympus Mons – the highest mountain in the Solar System, at 26 kilometres above the surrounding plains.

Interesting features on Mars that have been imaged by the HRSC stereo camera on the Mars Express spacecraft are marked on the globe. By clicking on the relevant location, you will see a short description and further information on the feature.

Mars Surface - Projection
Mars Surface - Projection
Mars Express

The Martian surface

Of all the planets in the Solar System, Mars is the most similar to Earth. It has seasons, ice-covered pole caps and an atmosphere. Numerous geological structures present on Earth are also visible on its surface: volcanoes, canyons, valley systems and deserts.

But today, there is no water on Mars to act as the driving force behind the multiple erosion and sedimentation processes that are continually reshaping Earth’s surface. Also, plate tectonics, which are responsible for creating mountain ranges here on Earth, are absent on Mars. We can still see numerous craters on Mars that are billions of years old – on Earth, however, the traces of impacts are erased after a few million years. Furthermore, the enormous volcanoes on Mars have not been active for a long time.

What we see on Mars today is a kind of freeze-frame image of its early history, which gives us information about the Solar System's geological past. The High Resolution Stereo Camera, which was developed by DLR and is on board ESA’s Mars Express spacecraft, has been in operation since 2004, delivering high-resolution, three-dimensional colour images, the spatial resolution of which surpasses previous topographical image data. These images enable scientists to analyse details with an altitude accuracy of down to 10 metres and thus acquire new knowledge about the geological development and climatic history of Mars.

  • Volcanoes Zoom


    On Mars there are numerous volcanoes and large areas covered in solidified lava. Using the images received, the HRSC science team has discovered that volcanic activity on Mars lasted a long time, from its beginnings, over three and a half billion years ago, to the most recent geological past.

    There could even be residual volcanic activity today; this is further indicated by spectrometer data that provided evidence of short-lived methane gas above volcanic regions. It is likely that the gas is being produced by volcanic foci beneath the surface of Mars, and consequently finds its way into the atmosphere.

  • Valleys and valley systems Zoom

    Valleys and valley systems

    Numerous deep valleys stretching from the Martian highland to deltas in the lowland indicate that water must have flowed on Mars in the past. Often more than 1000 kilometres long, these valleys have a constant gradient and are strongly reminiscent of river courses and flood valleys on Earth.

    However, it is not yet clear where this water went. It may have trickled into depressions in the northern plains, or it may still be there today, as a layer of ice beneath the surface.

    However, it is very probable that a large proportion of the original water evaporated and escaped into space.

  • Impact craters Zoom

    Impact craters

    During the first 700 million years of Mars' history, there was a phase of heavy bombardment by asteroids and comets; this is indicated by the numerous craters in the Southern Highlands. Counting and analysing these enables scientists to draw conclusions about the age of the Martian surface. The presence of numerous craters in a region implies that it must be very old.

    By studying the craters, the scientists can gain an insight into the climatic history of the planet. Many show traces of water or ice that was located beneath the surface at the time of impact.

  • Wind phenomena Zoom

    Wind phenomena

    Today, the surface of Mars is most strongly shaped by wind power.

    Mars' atmosphere is much thinner than Earth's; nevertheless, the weather is characterised by intense storms that pick up dust and the smallest grains of sand from the surface, transport them around the globe, and deposit them.

    Dunes are therefore a common phenomenon on the desert planet. They are often dark-coloured or black, as they consist of small grains of dust from eroded volcanic rock. The rocks and stones have been abraded for hundreds of millions of years by the small but nevertheless erosive power of the wind.

  • Ice and glaciers Zoom

    Ice and glaciers

    Ice – on and under the dusty surface near the Martian Polar Caps – was discovered using spectrometers.

    Images acquired with the HRSC camera also clearly show evidence of how the surface was shaped by ice mixed with rock debris, sand and dust that once slid down the slopes – rock glaciers – filling craters and carving valleys.

    Some of these structures are located at the relatively warm equator and are geologically very young, often less than 100 million years old. This shows that variations in the tilt of Mars’ rotational axis have very often led to dramatic changes in the climate.

    It is unclear whether there is still ice under the rock glaciers’ protective layer of dust and debris today, but this is probably the case.

  • Tectonics Zoom


    In many places, the Red Planet's surface reflects the processes occurring in its interior.

    As magma slowly rises from the depths and exerts pressure on the rigid crust of Mars, it forms large localised bulges. The consequence of this is stress that sometimes leads to tearing of the surface. A pattern of grabens and columns often forms on the surface along such stretch zones. In the meantime, blocks of crust begin to subside – often by several thousand metres. Volcanoes frequently form on Mars, as they do in rift zones on Earth.

    Studying such tectonic structures enables scientists to draw conclusions about the early development of the crust, and to gain an insight into the interior and dynamics of a planet.

In addition to giant volcanoes and deep rift valleys, Mars has even more spectacular landscapes. Experience the various features of this planet in fascinating images acquired with the High Resolution Stereo Camera on board the Mars Express spacecraft.

More information

Here you will find links to websites providing information about Mars, the various missions, current research results and images of its surface.