Picture a winter morning where everything glistens in white. The morning frost serves as a testament to Earth’s water cycle, with dew forming from the chilled air overnight. A similar phenomenon occurs on Mars, situated 63 million miles (or 102 million kilometers) away, presenting scientists with a unique opportunity to understand how water behaves on the red planet.

A group of researchers led by Dr. Valantinus from the University of Bern has uncovered evidence suggesting that morning frost may indeed exist on Mars. They identified this potential frost in bowl-shaped formations known as Calderas at the summit of the Tharsis Volcano. Among these volcanoes, Olympus Mons stands out as it towers over Mount Everest—more than double its height—reaching 21 km (approximately 13 miles) above sea level, making it the tallest volcano in the solar system.

Earlier studies estimated that around 1 trillion kilograms (approximately 2.2 trillion pounds) of water vapor cycles through Mars’ atmosphere annually between its northern and southern hemispheres. The massive Tharsis volcano disrupts this water flow due to its significant elevation, creating areas with lower pressure and wind speed referred to as Microclimates. The Valantinus team concentrated on this region, which produces optimal conditions for frost development in the microclimate above the volcano, increasing the likelihood of water vapor condensing to form frost.

To search for potential frost, the team analyzed thousands of spectral images captured by a color and stereo surface imaging system called Cassis, part of the European Space Agency’s Trace Gas Orbiter satellite orbiting Mars. They noted that the bright bluish tint in the area might indicate frost. By focusing on images with cooler tones, they set out to gather more evidence supporting the presence of frost.

To accomplish this, the team utilized a tool capable of detecting the composition of materials based on light wavelengths, known as a Spectrometer. A spectrometer onboard the Trace Gas Orbiter, named NOMAD, yielded ice readings concurrent with Cassis images. By combining Cassis imagery with NOMAD spectrometer data and additional high-resolution stereo camera images, the researchers pinpointed frosts in 13 distinct locations related to Mars’ volcanoes.

The Valantinus team anticipated that observations would reveal frost, but they needed to identify its type. Mars possesses a carbon dioxide atmosphere, which means carbon dioxide frost can naturally appear on the planet’s surface. To differentiate between carbon dioxide and water frost, researchers analyzed the surface temperatures on Mars.

They noted that the temperature at which carbon dioxide frost forms on Mars is around -130°C (-200°F), resulting in the conversion of solid carbon dioxide to gas as temperatures rise. Conversely, water frost appears at about -90°C (-140°F). Using a general circulation model, the team estimated that the average surface temperature in the areas where frost was discovered is roughly -110°C (-170°F), a temperature too warm for carbon dioxide frost but sufficiently cool for water frost.

Observations revealed frost deposits along the floors and edges of the volcanic calderas, while bright, warm areas inside the caldera lacked these deposits. The team also observed that some frost partially rested on dust-like particles on the ground, which cool down more at night and warm gradually in the morning, providing an ideal surface for frost. Additionally, frost was only evident during the early mornings on Mars, likely due to the daily warming cycle of the planet’s surface, similar to Earth.

The Valantinus team utilized imaging and chemical measurements on Mars to track the exchange of water between the planet’s surface and atmosphere. They recommend that future researchers continue to monitor Cassis images in these regions to deepen understanding of how morning frosts develop on Mars.

For alternative perspectives on this article, please see summary by Paige Lebman, a University of Delaware student.

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