Mars Express

Mars Express is a space exploration mission by the European Space Agency (ESA) that has been studying the planet Mars and its moons since 2003. It was the first mission of its kind attempted by ESA. The mission had two parts: the Mars Express Orbiter and Beagle 2, a lander meant to study the surface of Mars. Although the lander did not work as planned, the orbiter has been sending important scientific information since early 2004.

The orbiter has helped scientists make detailed pictures of Mars, map its minerals, study its atmosphere, and look at what lies beneath the surface. Because it has provided so much valuable information, the mission has been extended many times. The most recent extension, approved in March 2023, allows the spacecraft to keep working until the end of 2026, with a possible extension to 2028.

Now, more than 22 years after it arrived at Mars, Mars Express is the second longest-operating spacecraft in orbit around a planet other than Earth. It has also helped other missions by acting as a communication link in Mars orbit. It has worked with spacecraft from NASA, ESA, Roscosmos, China, and Japan, making it an important part of Mars exploration.

Name

The word "Express" in the name refers to how quickly and efficiently the spacecraft was built. It also describes the spacecraft's fast trip to Mars. This happened because Earth and Mars were closer together than they had been in about 60,000 years when the spacecraft was launched.

Background

The Mars Express mission was created to study Mars, looking at its inside, surface, air, and surroundings. The spacecraft carried seven science tools, a small lander, a lander communication system, and a Visual Monitoring Camera. These tools help solve the mystery of Mars's missing water.

Some tools on the spacecraft, like cameras and certain spectrometers, were based on designs from a failed Russian mission called Mars 96 in 1996. European countries helped provide tools and money for that mission. The Mars Express mission also aimed to achieve some of the science goals from that failed mission, including research with Beagle-2.

The design of Mars Express was based on ESA's Rosetta mission, which helped save time and money. The same design was later used for ESA's Venus Express mission. The budget for Mars Express, not including the lander, was €150 million. The main builder of the Mars Express orbiter was EADS Astrium Satellites.

Orbiter and subsystems

The Mars Express orbiter is a cube-shaped spacecraft with two large solar panel wings. It was launched with a total weight of 1,223 kg, including the main spacecraft, a small lander, and fuel for its journey. The main body is made of strong aluminium and measures about 1.5 m by 1.8 m by 1.4 m. The solar panels stretch out to about 12 m from tip to tip.

The spacecraft uses solar panels to create electricity, which powers everything on board. Even though there was a small problem that reduced its power, it still works well for its science tasks. The spacecraft keeps its instruments at the right temperatures using special blankets and heaters. It also has smart computer systems that help decide when and how to send data back to Earth.

Lander

The Beagle 2 lander aimed to study the rocks, minerals, and chemicals at its landing site on Mars. It also planned to look at the atmosphere, weather, and search for signs of life. Sadly, the landing did not go as planned, and the lander could not send back data.

Later, in 2015, a spacecraft called the Mars Reconnaissance Orbiter found Beagle 2 on the surface of Mars. One of its solar panels may not have opened fully, which stopped it from communicating with Earth. Even though it didn’t work as intended, Beagle 2 was an important step for both British and European space exploration.

Scientific instruments

The Mars Express mission has several tools to study Mars. These tools help scientists learn about the planet’s surface, atmosphere, and what lies beneath. The tools include a camera that takes detailed pictures, a spectrometer that looks at minerals, and a radar that searches for frozen water under the surface.

Other tools study the atmosphere’s composition and how it interacts with sunlight and space. There is also a radio system that helps study Mars’s atmosphere and surface using signals.

Operations of the spacecraft

Operations for Mars Express are managed by a team of engineers from ESA's Operation Centre (ESOC) in Darmstadt. They started getting ready for the mission about 3 to 4 years before it launched. This included setting up the equipment on Earth and planning how the mission would work.

The Mission Control Team includes several groups, such as the Flight Control Team and the Flight Dynamics Team. These teams are based at ESOC, but some other teams helped design and build the spacecraft. The Flight Control Team has a Spacecraft Operations Manager, six Operations Engineers, one Spacecraft Analyst, and six spacecraft controllers who also help with other missions like ExoMars Trace Gas Orbiter, BepiColombo, and Solar Orbiter. The team was put together four years before the launch, with engineers coming from different missions, mostly those that worked on satellites around Earth.

Mission timeline

Mission preparation

Before the launch, many teams of experts worked together to prepare the spacecraft and the ground systems. They made sure everything worked well together, from the smallest details to the big picture. They tested the control system, checked the satellite, and ran many simulations to be ready for launch.

Launch

The spacecraft launched on June 2, 2003, from Baikonur Cosmodrome in Kazakhstan using a Soyuz-FG/Fregat rocket. It first went into a circle around Earth, then the rocket fired again to send it toward Mars. The solar panels were deployed, and the spacecraft began its journey to Mars. This was the first successful Russian-launched probe to leave Earth’s orbit since the Soviet Union.

Near Earth commissioning phase

After launch, the spacecraft went through checks to make sure everything worked. This included deploying the solar arrays and checking the instruments one by one. This phase lasted about one month.

The interplanetary cruise phase

For five months, the spacecraft traveled toward Mars. Although planned to be quiet, this phase had many events, including star tracker problems, power issues, extra maneuvers, and a big solar flare that hit the spacecraft.

Lander jettison

The Beagle 2 lander was released on December 19, 2003, to land on Mars. It entered the atmosphere on December 25 but could not be contacted after landing. It was later declared lost.

Orbit insertion

Mars Express arrived at Mars after traveling 400 million km. On December 20, it fired its engines to start orbiting the planet. The orbit was adjusted several times to get the right path around Mars. After 100 days, the orbit was changed again to make the spacecraft’s path around Mars shorter.

Routine phase: science return

Since entering orbit, Mars Express has been doing science work. It points toward Mars to collect data and then turns to send the information to Earth. Some instruments can work even while the spacecraft points toward Earth.

Timeline of notable discoveries and events

For more than 20,000 orbits, the Mars Express payload instruments have been regularly operating. The HRSC camera has been consistently mapping the Martian surface with unprecedented resolution and has acquired many images.

First decade

2004

• January 23: ESA announced the discovery of water ice in the south polar ice cap, using data collected by the OMEGA instrument.
• January 28: Mars Express orbiter reaches final science orbit altitude around Mars.
• March 17: Orbiter detects polar ice caps that contain 85% carbon dioxide ice and 15% water ice.
• March 30: A press release announces that the orbiter has detected methane in the Martian atmosphere. Although the amount is small, about 10 parts in a thousand million, it has excited scientists to question its source. Since methane is removed from the Martian atmosphere very rapidly, there must be a current source that replenishes it. Because one of the possible sources could be microbial life, it is planned to verify the reliability of these data and especially watch for difference in the concentration in various places on Mars. It is hoped that the source of this gas can be discovered by finding its location of release.
• April 28: ESA announced that the deployment of the boom carrying the radar-based MARSIS antenna was delayed. It described concerns with the motion of the boom during deployment, which can cause the spacecraft to be struck by elements of it. Further investigations are planned to make sure that this will not happen.
• July 15: Scientists working with the PFS instrument announced that they tentatively discovered the spectral features of the compound ammonia in the Martian atmosphere. Just like methane discovered earlier (see above), ammonia breaks down rapidly in Mars's atmosphere and needs to be constantly replenished. This points towards the existence of active life or geological activity; two contending phenomena whose presence so far have remained undetected.

2005

• In 2005, ESA scientists reported that the OMEGA instrument data indicates the presence of hydrated sulphates, silicates and various rock-forming minerals.
• February 8: The delayed deployment of the MARSIS antenna, planned for early May 2005, has been given a green light by ESA.
• May 5: The first boom of the MARSIS antenna was successfully deployed. At first, there was no indication of any problems, but later it was discovered that one segment of the boom did not lock. The deployment of the second boom was delayed to allow for further analysis of the problem.
• May 11: Using the Sun's heat to expand the segments of the MARSIS antenna, the last segment locked in successfully.
• June 14: The second boom was deployed, and on June 16 ESA announced it was a success.
• June 22: ESA announces that MARSIS is fully operational and will soon begin acquiring data. This comes after the deployment of the third boom on June 17, and a successful transmission test on June 19.

2006

• September 21: The High Resolution Stereo Camera (HRSC) has obtained images of the Cydonia region, the location of the famous "Face on Mars". The massif became famous in a photo taken in 1976 by the American Viking 1 Orbiter. The image recorded with a ground resolution of approximately 13.7 metres per pixel.
• September 26: The Mars Express spacecraft emerged from an unusually demanding eclipse introducing a special, ultra-low-power mode nicknamed 'Sumo' – an innovative configuration aimed at saving the power necessary to ensure spacecraft survival. This mode was developed through teamwork between ESOC mission controllers, principal investigators, industry, and mission management.
• October: In October 2006 the Mars Express spacecraft encountered a superior solar conjunction (alignment of Earth-Sun-Mars-orbiter). The angle Sun-Earth-orbiter reached a minimum on October 23 at 0.39° at a distance of 2.66 AU. Operational measures were undertaken to minimize the impact of the link degradation, since the higher density of electrons in the solar plasma heavily impacts the radio frequency signal.
• December: Following the loss of NASA's Mars Global Surveyor (MGS), Mars Express team was requested to perform actions in the hopes of visually identifying the American spacecraft. Based on last ephemeris of MGS provided by JPL, the on-board high definition HRSC camera swept a region of the MGS orbit. Two attempts were made to find the craft, both unsuccessful.

2007

• January: First agreements with NASA undertaken for the support by Mars Express on the landing of the American lander Phoenix in May 2008.
• February: The small camera VMC (used only once to monitor the lander ejection) was recommissioned and first steps were taken to offer students the possibility to participate in a campaign "Command Mars Express Spacecraft and take your own picture of Mars".
• February 23: As result of the science return, the Science Program Committee (SPC) granted a mission extension until May 2009.
• June 28: The High Resolution Stereo Camera (HRSC) has produced images of key tectonic features in Aeolis Mensae.

2008

• In March 2008, the Mars Express Team was the winner of the Sir Arthur Clarke Award for Best Team Achievement.
• During a Phobos flyby on 23 July 2008, Mars Express observed backscattering of solar wind protons at Phobos, a process previously reported at the Earth's Moon, suggesting that it is common at airless bodies covered by regolith. The next such observation occurred in January 2016.

2009

• February 4: The ESA's Science Programme Committee has extended the operations of Mars Express until December 31, 2009.
• October 7: ESA's Science Programme Committee has approved the extension of mission operations for Mars Express until December 31, 2012.

2010

• March 5: Flyby of Phobos to measure Phobos's gravity.

2011

• August 13: Safe mode following a Solid-State Mass Memory problem.
• August 23: Solid-State Mass Memory problem.
• September 23: Safe mode following a Solid-State Mass Memory problem.
• October 11: Solid-State Mass Memory problem.
• October 16: Safe mode following a Solid-State Mass Memory problem.
• November 24: Science operations are resumed using the Short Mission Timeline and Command Files instead of the Long Time Line resident on the suspect Solid-State Mass Memory.

2012

• February 16: Resumes full science operations. There is still enough fuel for up to 14 additional years of operation.
• In March 2012, a paper was published in JGR Planets documenting the first detection of a faint infrared glow above the winter poles of Mars. This discovery was based on Mars Express's OMEGA observations from 2004, 2005, and 2006.
• July: Solar corona studied with radio waves.
• August 5/6: Assisted US probes Mars Odyssey and Mars Reconnaissance Orbiter in data collection and transfer on the Mars Science Laboratory landing.

2013

• Mars Express produced a near-complete topographical map of Mars's surface.
• On 29 December, Mars Express performed the closest flyby to date of Phobos.

Second decade

2014

• In October 2014, ESA reported Mars Express was healthy after the Comet Siding Spring flyby of Mars on 19 October — as were all NASA Mars orbiters and ISRO's orbiter, the Mars Orbiter Mission.

2015

• January: Beagle 2 found by Mars Reconnaissance Orbiter.

2016

• During a Phobos flyby in January 2016, Mars Express again observed solar wind proton backscattering from the moon's surface. This was only second such observation by the spacecraft (first occurred in 2008) and, as of 2025, this intermittency remains unexplained.
• October 19: Assisted with data collection and transfer for the Schiaparelli EDM lander landing.

2017

• On 19 June, the spacecraft took a notable image spanning from the North Pole up to Alba Mons and even farther south. The image was released in December 20, 2017, and was captured by HRSC.

2018

• Activated new AOCMS software which includes a gyroless attitude estimator to prolong the lifetime of the spacecraft's laser gyros
• In July 2018, a discovery was reported based on MARSIS radar studies, of a subglacial lake on Mars, 1.5 km (0.93 mi) below the southern polar ice cap, and about 20 km (12 mi) wide, the first known stable body of water on Mars.
• December 2018: Mars Express relays images of the 80-kilometer wide Korolev Crater filled with approximately 2200 cubic kilometers of water ice on the Martian surface. Based on further evidence the crater ice is still part of much vaster ice resources at Mars poles.

2019

• Based on data from the HRSC camera, there is geological evidence of an ancient planet-wide groundwater system.

2020

• Between March and April 2020, Mars Express (along with other interplanetary missions by ESA) was briefly placed into a largely unattended safe configuration with science instruments turned off due to the worsening COVID-19 pandemic and the need to reduce on-site personnel at ESOC.
• In September 2020, a discovery was reported based on MARSIS radar studies, of three more subglacial lakes on Mars, 1.5 km (0.93 mi) below the southern polar ice cap. The size of the first lake found, and the largest, has been corrected to 30 km (19 mi) wide. It is surrounded by 3 smaller lakes, each a few kilometres wide.
• A study published in December 2020 in JGR Planets utilized the wide field of view of the Visual Monitoring Camera, in combination with other instruments on Mars Express and other orbiters, to describe the life cycle of a large elongated orographic cloud that grows and fades on a daily basis during spring and summer over Arsia Mons. A follow-up study published in 2022 used computational modeling to describe the physical mechanisms behind the cloud's formation.

2021

• Two studies published in December 2020 and January 2021, that analyzed SPICAM data, show that water escape to space is accelerated by dust storms and Mars's proximity to the Sun, and suggest that some water may have retreated underground.
• A study published in April 2021, that used SPICAM data to analyze the relationship between ozone and water vapour in the atmosphere of Mars, identified a previously unknown problem with climate models, that might be relevant also to studying the Earth's atmosphere.
• In November 2021, an experiment was performed to test whether Mars Express and the TGO lander relay communications radio could be used to perform radio occultation science, as well as a series of tests of data relay from the CNSA Zhurong rover.

2022

• In February 2022, a study was published in Earth and Planetary Science Letters demonstrating that liquid brines (water with perchlorate and chloride) are the best explanation for the MARSIS observations from 2018 interpreted as liquid water under the South pole of Mars. Such brines might not form actual underground lakes but could exist between grains of ice or sediment.
• On 14 February 2022, Mars Express observed a rare astronomical event — Deimos passing in front of Jupiter and its Galilean moons. Measuring the duration of the occultation enabled a more precise determination of the position and orbit of Deimos.
• In June 2022, an upgrade of the MARSIS instrument software was completed. The new version improved the performance of the instrument to push its performance beyond some of the old limitations.
• On 23 September 2022, Mars Express conducted a close flyby of Phobos and used the MARSIS instrument to probe the moon's subsurface structure from as close as 83 km. Operating MARSIS at such close distance was enabled by the recent software upgrade. The instrument was originally designed for studying Mars – at more than 250 km from the spacecraft.
• In November 2022, Mars Express performed data relay tests with NASA Perseverance rover, bringing the total number of other spacecraft supported by Mars Express in this way up to a record-breaking seven.

2023

• In January 2023, the first global high-resolution map of aqueous minerals (formed through interaction with water) at Mars was published using data from Mars Express's OMEGA and MRO's CRISM instruments.
• June 3: To celebrate the 20th anniversary of the spacecraft's launch, a livestream of images from the Visual Monitoring Camera was streamed online, marking the first livestream direct from Mars.

Third decade

2024

• Published in January 2024, a new research analysed MARSIS radar data collected over the preceding decade and concluded that the Medusae Fossae Formation at Mars equator, previously thought to be likely composed of dry deposits, instead includes a large amount of water ice.

• In May 2024, computers on Mars Express (as well as on another ESA mission, BepiColombo) reported a sharp increase in the number of memory errors, coinciding with a massive solar flare from the active region AR3664, at that time facing away from Earth. The event was also observed in detail by ESA's Solar Orbiter.

• During May 2024 solar storms, Mars Express and TGO were performing radio occultation experiments and managed to measure the response of the Martian atmosphere to the solar storm. The two orbiters observed a dramatic increase in electrons in two distinct layers of the atmosphere with a 45% increase in 110 km above surface and a 278% increase in 130 km.

• In June 2024, a new study was published in Nature Geoscience, providing first evidence for water frost near Mars equator, specifically atop the Tharsis volcanoes. This work used data from ESA's Mars Express and TGO missions.

• In July 2024, a study was published in Radio Science documenting the first routine use of mutual radio occultation technique at another planet, specifically the measurements of physical properties of the Martian atmosphere conducted using a radio link between ESA's Mars Express and TGO orbiters between 2020 and 2023.

• In September 2024, a new cloud atlas of Mars has been published, containing images of Martian clouds by Mars Express from the past 20 years.

2025

• In February 2025, a study was published in Nature Communications suggesting that the red color of Mars is caused by iron oxides containing water, known as ferrihydrite, and not by hematite that forms under dry conditions, as thought before. This work used data from Mars Express and other spacecraft.
• In May 2025, ESA updated the software solution from 2018 which was meant to prolong the lifetime of the spacecraft's gyroscopes. This new update could allow Mars Express to stay operational until 2034 and be ready to support the MMX spacecraft in 2029.
• In June 2025, a comprehensive data set from Mars Express—TGO radio occultation observations has been made publicly available with a publication of a new study in JGR Planets analysing 71 full vertical profiles from such observations.
• In September 2025, scientists presented a method for predicting the green visible light aurora on Mars, which they developed using data from Mars Express, MAVEN, and Perseverance.
• In October 2025, scientists published a catalogue of 1039 Martian dust devils observed by Mars Express and TGO during past two decades. Their analyses show near-surface wind speeds of up to 44 m/s, faster than ever observed by surface probes.

2026

• In April 2026, ESA published a new HRSC image of Utopia Planitia showing a fast spreading of dark volcanic ash across the area since it was photographed by the Viking orbiters in the 1970s, illustrating a rare large scale change on the surface of Mars in recent past.