To commemorate the 20th anniversary of ESA’s Mars Express mission, the team behind the High Resolution Stereo Camera (HRSC) has created a remarkable new global color mosaic that presents Mars in a way never seen before. This stunning mosaic provides intricate details of the planet’s surface color and composition. The darker areas, characterized by shades of grey, reveal basaltic sands of volcanic origin, while lighter patches showcase clay and sulfate minerals. Additionally, the mosaic showcases Valles Marineris, the expansive scar stretching across Mars. Image credit: ESA/DLR/FU Berlin/G. Michael, CC BY-SA 3.0 IGO
In celebration of two decades of exploration, ESA’s Mars Express mission has released a vivid and detailed mosaic of Mars that offers a diverse range of colors and highlights the planet’s composition. Utilizing high-altitude images, this mosaic reveals unprecedented variations in color and provides insights into Mars’ distinct geological features. The imagery showcases reddish oxidized iron, dark volcanic basaltic sands, and bright regions that suggest the presence of past liquid water. The mission is set to continue its exploration until at least 2026.
This new Mars mosaic, which captures the planet’s color and composition with exceptional detail, was generated using data acquired by the High Resolution Stereo Camera (HRSC) aboard Mars Express. Ordinarily, HRSC captures images of Mars’ surface from an altitude of approximately 300 km during the spacecraft’s elliptical orbit, resulting in images covering areas around 50 km in width. However, for this particular mosaic, HRSC adopted a different approach. By collecting 90 images at higher altitudes ranging from 4,000 to 10,000 km, HRSC was able to capture regions approximately 2,500 km wide. These images were then skillfully merged to form a comprehensive global view.
Typically, large-scale images of this nature are obtained to study Mars’ weather patterns. However, even in the absence of atmospheric phenomena, they offer breathtaking glimpses of the planet’s surface. The image provided here exemplifies the high-altitude HRSC imagery used to construct the global mosaic, taken during HRSC orbit 21,688. The grey terrain represents data from NASA’s Mars Orbiter Laser Altimeter, while the HRSC data is displayed as two colored slices. Geographical coordinates of Mars are indicated around the discs to provide contextual information. On the left, a red-green-blue composite depicts the visible light surface appearance, with the light blue color in the northern and southern limbs resulting from the camera’s shallower view through the Martian atmosphere. These regions were excluded from the global mosaic. On the right, an infrared-red-green composite offers an unconventional view that allows examination of Mars’ surface reflectivity in different wavelengths. These images were also inspected to identify any artifacts or data gaps present in the global mosaic. Image credit: ESA/DLR/FU Berlin/MOLA Science Team, CC BY-SA 3.0 IGO
A heightened perspective of colors
This latest view accentuates the variations in color and contrast across Mars’ surface by enhancing local color details. The HRSC possesses nine imaging channels, enabling the visualization of Mars not only in three dimensions but also in color. However, the ever-changing opacity of the Martian atmosphere poses challenges in accurately determining surface colors from orbit. Dust particles scatter and reflect light, causing colors to shift between images and creating a patchwork-like effect when assembling a mosaic.
Traditionally, this effect has been suppressed during image processing, resulting in reduced color variations among different regions of Mars. However, to create this particular mosaic, the HRSC team utilized a different approach. Each constituent image was color-referenced to a color model derived from high-altitude observations, enabling the preservation of color variations and providing an unprecedentedly rich and vibrant view of Mars’ colors.
The image displayed here is a close-up of the mosaic, showcasing stretched contrast and featuring the Valles Marineris canyon system. Surface details such as sulfate deposits, haze and fog, and cloud cover are annotated. Valles Marineris, stretching more than 4,000 km east-west and up to 700 km north-south, represents the largest and most awe-inspiring canyon system in the entire Solar System. Faint bright-to-light blue areas indicate the presence of clouds in the atmosphere. The depths of Valles Marineris are also covered by fog and haze, which tend to form in Martian surface depressions during this time of year. Image credit: ESA/DLR/FU Berlin/G. Michael, CC BY-SA 3.0 IGO
Every color signifies a distinct material
While the mosaic captivates viewers with its visual splendor, it also provides valuable insights into the composition of Mars, revealing an unparalleled variety and level of detail in its surface colors.
Mars is renowned for its reddish hue, primarily due to the high levels of oxidized iron present. However, large portions of the planet depicted in the mosaic appear darker and bluish. These areas consist of grey-black basaltic sands originating from volcanic sources, forming extensive layers of dark sand that traverse Mars’ surface. These sand deposits accumulate as they are transported by the wind, creating impressive sand dunes and dune fields within impact craters.
Conversely, materials weathered by water tend to exhibit lighter colors. Clay and sulfate minerals, the two most common water-weathered minerals on Mars, appear notably bright in these color composites. The presence of these minerals was established through observations made by the OMEGA spectrometer aboard Mars Express. Their existence signifies the prolonged presence of liquid water on Mars, which weathered and altered rocks over time, resulting in the formation of significant clay deposits like Mawrth Vallis (not visible in this particular view but previously observed by HRSC).
Sulfate minerals can be seen within the Valles Marineris canyon system, as evident in the annotated image. However, they are covered by a thin layer of dark sand, obscuring their impressive color variations. Unlike clay deposits, sulfate minerals indicate more acidic environmental conditions that would be less conducive to supporting life.
Artist’s impression of Mars Express. Credit: Alex Lutkus
Two decades of Mars exploration
Launched in 2003, Mars Express has been orbiting the Red Planet for the past 20 years, capturing images of Mars’ surface, mapping its minerals, analyzing the composition and circulation of its tenuous atmosphere, investigating beneath its crust, and exploring various interactions within the Martian environment.
The High Resolution Stereo Camera (HRSC) on board the spacecraft has played a vital role in revealing Mars’ diverse surface features over the past two decades. Its images have showcased numerous geological wonders, including Ascraeus Mons, Mars’ second-tallest volcano, and the majestic Valles Marineris canyon system, as well as deep fractures, water-carved valleys, impact craters, tectonic faults, river channels, and ancient lava pools.
Over the course of its mission, Mars Express has made significant contributions, enhancing our understanding of our neighboring planet in ways never before achieved. Originally slated for a single Martian year, approximately 687 Earth days, the mission has far surpassed its initial objectives. With the mission extended until at least the end of 2026, we eagerly anticipate the unveiling of more breathtaking and insightful snapshots of Mars in the years to come.
20 years and counting: Mars Express in numbers. Credit: ESA
The development and operation of the High Resolution Stereo Camera (HRSC) are led by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR).
The creation of the color model method and processing of the mosaic were performed by Greg Michael of the HRSC team at Freie Universität Berlin. The acquisition and planning of the high-altitude images were carried out by the camera operations team at the German Aerospace Center (DLR) in Berlin-Adlershof. The georeferenced dataset will be made available through the ESA guest storage facility upon the publication of the forthcoming scientific paper on the mosaic.
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Frequently Asked Questions (FAQs) about Mars Express mission
What is the Mars Express mission?
The Mars Express mission is a space exploration mission conducted by the European Space Agency (ESA) to study Mars. It involves an orbiter called Mars Express that has been orbiting the Red Planet since 2003.
What is the purpose of the global color mosaic created by Mars Express?
The purpose of the global color mosaic created by Mars Express is to provide a detailed and unprecedented view of Mars’ surface color and composition. It allows scientists and space enthusiasts to observe the planet in remarkable detail, highlighting various geological features and providing insights into its composition.
How was the global color mosaic of Mars created?
The global color mosaic of Mars was created using data captured by the High Resolution Stereo Camera (HRSC) onboard Mars Express. The HRSC gathered a series of high-altitude images of Mars, which were then stitched together to form a comprehensive view of the entire planet.
What does the global color mosaic reveal about Mars?
The global color mosaic reveals a wealth of information about Mars. It showcases the diverse colors present on the planet’s surface, including the reddish hue caused by oxidized iron. It also highlights the presence of basaltic sands, clay and sulfate minerals, and features such as Valles Marineris, the largest canyon system in the Solar System.
How long will the Mars Express mission continue?
The Mars Express mission has been extended until at least the end of 2026. This means that there will be continued exploration and data collection from Mars Express, providing further insights into the Red Planet and its mysteries.
