ExoMars Observes Water Frost On The Caldera Floor of the Ceraunius Tholus Volcano
Researchers have discovered frost atop volcanoes near Mars’s equator for the first time – a part of the planet where it was thought impossible for frost to form. The finding used observations from two ESA ExoMars Trace Gas Orbiter (TGO) instruments – CaSSIS and NOMAD – with additional imaging by ESA’s Mars Express.
This image shows frost on the caldera floor of the Ceraunius Tholus volcano. The frost is shown in blue. This blue colour is due to the way in which CaSSIS constructs its images, using both near-infrared and visible channels – a so-called ‘NPB’ image, as opposed to a typical RGB (red-green-blue) image.
This combines the instrument’s near-infrared (N), panchromatic (P) and blue (B) filters. This provides more information on a feature’s spectral diversity in a large range of wavelengths invisible to the human eye. Read more on how CaSSIS constructs its blue-hued images, and how this allows us to explore the Red Planet.
These four frames show (A) a wide-angle contextual view of Ceraunius Tholus from NASA’s Mars Reconnaissance Orbiter’s Context Camera, with early morning observations made by CaSSIS overlaid within the blue-toned rectangle. This rectangle is shown close-up in frame (B), with an additional white rectangle marking out an even more zoomed-in image, shown in frame (C). (C) shows ubiquitous frost on the caldera floor, but none on the caldera rim. (D) shows a CaSSIS image of the same region acquired at a different time of day, when there is no frost present.
Both the CaSSIS images shown in (B) and (D) were acquired using a similar observing setup, suggesting that the apparent presence of frost is unlikely to be due to any photometric effects. Image (B) was acquired in early northern spring, and (D) in late northern winter.
This image shows frost on the caldera floor of the Ceraunius Tholus volcano. — ESA (Larger Image)
North is up in all frames, and image scales are indicated in the bottom-right of each frame. The Local Solar Time (LST) is shown for the two frames on the right, as is ‘incidence angle’ (i) and ‘solar longitude’ (Ls). Incidence angle indicates where the Sun is in the sky; it is 0° when the Sun is directly overhead, and 90° at the horizon. Solar longitude marks the position of Mars in its orbit relative to the Sun, reflecting the martian seasons through the year for each hemisphere (0° when northern spring begins, 270° at winter solstice).
Related Links
Water Frost Detected On The Tharsis Volcanoes On Mars, Brown University
Newfound Frost Atop The Martian Volcano Olympus Mons, ESA
According to the study, the frost is present for only a few hours after sunrise before it evaporates in sunlight. The frost is also incredibly thin — likely only one-hundredth of a millimeter thick or about the width of a human hair. Still, it’s quite vast. The researchers calculate the frost constitutes at least 150,000 tons of water that swaps between the surface and atmosphere each day during the cold seasons. That’s the equivalent of roughly 60 Olympic-size swimming pools.
Tharsis, the region of Mars where the frost was found, hosts numerous volcanoes. They tower above the surrounding plains at heights ranging from one to two times that of Earth’s Mount Everest. Olympus Mons, for instance, is as wide as France.
The frost sits in the calderas of the volcanoes, which are large hollows at their summits created during past eruptions. The researchers propose that the way the air circulates above these mountains creates a unique microclimate that allows the thin patches of frost to form.
Astrobiology
