06-09-2025

Mars volcano captured with its head above the clouds in sunrise photo

Earth.com staff writer

NASA’s Mars Odyssey spacecraft has captured a view that, until now, existed only in the imagination: a sunrise panorama of Arsia Mons thrusting through a gauzy blanket of clouds on the Martian horizon.

Captured on May 2, 2024, the image shows the ice-tipped giant looming 12 miles (20 kilometers) above Mars’ surface – twice the height of Earth’s Mauna Loa – and wrapped in dawn-lit water-ice clouds.

Besides its cinematic beauty, the shot marks the first time any of the three colossal Tharsis Montes volcanoes has been photographed from the side rather than from directly overhead. This new perspective provides scientists with a fresh vantage on Martian weather.

Odyssey turns sideways

Launched in 2001 and still going strong, Mars Odyssey is the longest-lived orbiter at any world beyond Earth.

Beginning in 2023, mission engineers started performing an unusual maneuver. They rotate the entire spacecraft 90 degrees so that its downward-facing camera can instead look sideways.

By turning the Thermal Emission Imaging System (THEMIS) toward the limb of the planet, the team can photograph layers of dust and ice clouds stacked above the surface – and, when lucky, snag silhouettes of Martian landmarks.

Each horizon-pointing sequence creates a mosaic stitched from dozens of narrow, high-altitude frames. By repeating the experiment in different seasons, scientists watch how cloud decks grow, shrink, or migrate.

“We’re seeing some really significant seasonal differences in these horizon images,” said Michael D. Smith of NASA’s Goddard Space Flight Center. “It’s giving us new clues to how Mars’ atmosphere evolves over time.”

Clouds at the edge Mars

Mars boasts two primary kinds of clouds: flakes of frozen carbon dioxide – essentially dry ice – and plumes of water ice. The Tharsis Montes region, a volcanic plateau bigger than the continental United States, is famous for its spectacular water-ice displays at dawn.

Cold nighttime air slides downslope, then flows back up the sunlit volcano flanks at sunrise; as it rises, the air expands and chills, and water vapor condenses into clouds.

When Mars reaches aphelion – its farthest point from the Sun – lower temperatures let these clouds thicken into a shimmering equatorial band called the aphelion cloud belt.

Arsia Mons, an ancient Martian volcano, was captured before dawn on May 2, 2025, by NASA’s 2001 Mars Odyssey orbiter while the spacecraft was studying the Red Planet’s atmosphere, which appears here as a greenish haze. come Credit: NASA/JPL-Caltech/ASU — Arsia Mons, an ancient Martian volcano, was captured before dawn on May 2, 2025, by NASA’s 2001 Mars Odyssey orbiter while the spacecraft was studying the Red Planet’s atmosphere, which appears here as a greenish haze. Click image to enlarge. Credit: NASA/JPL-Caltech/ASU

Odyssey’s new panorama catches that belt in full flourish, its bluish haze almost Earth-like against the orange surface below.

From orbit, the contrast is dramatic. Arsia Mons and its siblings Pavonis and Ascraeus Mons pierce the veil, looking like dark islands in a misty sea.

Water-ice clouds are crucial to the planet’s weather engine: they influence surface temperatures, control how dust is lofted, and may even seed local snowfalls.

Understanding their rhythm improves climate models and, eventually, the safety margins for landing future spacecraft.

Volcanic titans of Tharsis

Though dormant today, Arsia Mons on Mars once erupted with such ferocity that its caldera – the summit depression – could swallow a metropolitan city.

Its sheer size disturbs local winds, essentially steering the atmosphere around it. The new horizon image reveals how that topography interacts with water vapor.

“We picked Arsia Mons hoping we would see the summit poke above the early morning clouds. And it didn’t disappoint,” said Jonathon Hill of Arizona State University, who oversees THEMIS operations.

Seeing volcanoes from the side rather than from above helps scientists measure cloud altitudes more accurately. If the cloud layer intersects the mountain at six miles up, for instance, the intersection appears as a crisp boundary in profile.

Knowing that height refines calculations of temperature, humidity, and wind speed – data that feeds into global circulation models much like those used for Earth’s weather forecasts.

Old tech, new science

THEMIS was designed two decades ago to map minerals and sniff out water-ice reservoirs beneath the Martian dust.

Its infrared sensor can detect buried ice that future astronauts might mine for drinking water, oxygen, or rocket propellant.

At visible wavelengths, the camera has catalogued thousands of dust devils, monitored violent planet-wide dust storms, and even surveyed Mars’ moons, Phobos and Deimos, to reveal their patchy coatings of crustal debris.

Arsia Mons is the southernmost of the three volcanoes that make up Tharsis Montes, shown in the center of this cropped topographic map of Mars. Olympus Mons, the solar system’s largest volcano, is at upper left. The western end of Valles Marineris begins cutting its wide swath across the planet at lower right. Credit: NASA/JPL-Caltech — Arsia Mons is the southernmost of the three volcanoes that make up Tharsis Montes, shown in the center of this cropped topographic map of Mars. Olympus Mons, the solar system’s largest volcano, is at upper left. The western end of Valles Marineris begins cutting its wide swath across the planet at lower right. Click image to enlarge. Credit: NASA/JPL-Caltech

Yet the horizon campaign showcases the instrument’s flexibility. By capturing the edge of the planet, THEMIS turns into a low-cost weather satellite, watching how dust and ice swirl in layers tens of miles thick.

Such observations give engineers clues to the timing and intensity of dust storms – hazards that affect solar-panel performance, entry-descent-landing trajectories, and astronaut health.

Mars cloud details and humans

Detailed cloud measurements will help mission planners decide when to launch, where to land, and how robust life-support systems must be.

Water-ice clouds, in particular, can scatter sunlight and lower surface temperatures by several degrees. These small temperature drops matter greatly for battery life and thermal control of rovers, habitats, and ascent vehicles.

Moreover, the volcanoes themselves are intriguing for human explorers. Their gentle slopes – about five degrees on average – could be traversed by rovers to study ancient lava flows, search for volcanic caves that might shelter life, and harvest ice trapped in shaded craters.

The high elevations also provide commanding views and extended lines of sight for communications.

Targeting different seasons on Mars

Mars Odyssey’s next horizon sessions will target different latitudes and seasons, building a time-lapse of Martian atmospheric change.

Scientists hope to observe dust storm onsets, night-shining clouds near the poles, and perhaps the faint arc of Mars’ ozone layer, a tenuous shield that waxes and wanes with the planet’s seasons.

The spacecraft’s longevity demonstrates how even mature missions can pivot to fresh science with a twist of engineering ingenuity.

As it enters its third decade, Mars Odyssey continues to surprise – showing that a camera built to stare straight down can, with a little roll of the spacecraft, reveal an alien sunrise worthy of an astronaut’s window seat.

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