Mysterious Clouds in Mars’ Atmosphere Baffle Scientists

By Christian Schroeder, University of Stirling | February 17, 2015 12:29 pm
Mars with the plume circled, right, and augmented views at left. Credit: Grupo Ciencias Planetarias (GCP) - UPV/EHU

Mars with the plume circled, right, and zoomed in views of the region at left. Credit: Grupo Ciencias Planetarias (GCP) – UPV/EHU

This article was originally published on The Conversation

Enormous cloud-like plumes reaching 160 miles above the surface of Mars have left scientists baffled. This is way beyond Mars’ normal weather, reaching into the exosphere where the atmosphere merges with interplanetary space. None of the conventional explanations for such clouds make sense – neither water or carbon dioxide ice nor dust storms nor auroral light emissions usually hit such heights.

These “mystery clouds” came as a surprise, in particular when considering they were first spotted by a string of amateur astronomers in 2012. After all, an international fleet of five orbiters and two rovers is currently operating on and around Mars, and one may be excused thinking the red planet has little left to hide and its exploration has become routine.

A survey of images from the Hubble Space Telescope and amateur astronomers revealed massive clouds had been seen on Mars before, but none as prominent as the 2012 observations.

So what caused these clouds? An international team of scientists led by Agustin Sánchez-Lavega has now published an investigation in the journal Nature.

Martian Lights?

Perhaps these clouds could be aurorae – similar to the northern lights (aurora borealis) here on Earth, or their southern counterpart aurora australis. These displays happen when the Earth’s magnetic field channels charged particles emitted by the Sun towards the poles, where they interact with the atmosphere and emit light.

Mars does not have a global magnetic field, only pockets of magnetization. The mystery clouds were spotted over one of these so-called magnetic anomalies, and auroral lights have been observed there previously.

However, to explain the 2012 observations, an aurora would have had to be 1,000 times brighter than the northern lights. This would require an increased flow of charged particles from the sun, but its activity was not unusually high during the time.

Storms and Smashes

Could dust be the culprit? A volcanic eruption or an asteroid impact were among the earliest theories about these clouds’ origin.

New eruptions on Mars are plausible, though we’re yet to observe any active volcanoes on the planet. The youngest lava flows reported are a few million to tens of million years old, which is recent in geological terms.

Mars’ thin atmosphere offers little protection against asteroids, and its surface is pockmarked with impact craters. Cameras on board NASA’s Mars Reconnaissance Orbiter have documented the appearance of hundreds of new craters in the nine years since the spacecraft arrived at Mars.

However, both theories were quickly discarded because they were inconsistent with the behavior of the clouds. Continued observations showed that they disappeared during the Martian daytime, were not visible in the evening, and reappeared each morning for at least ten consecutive days.

This also rules out dust storms, which frequently engulf large areas of the planet’s surface. Furthermore, the wavelength profile of the light reflected by the mystery clouds is a poor match for Martian dust particles.

Not Cold Enough for Ice

That leaves water or carbon dioxide ice particles, which fit the wavelength profile of the reflected light. Both water and carbon dioxide molecules also occur naturally in the atmosphere at these heights.

However, to form these clouds both substances would need to condense into ice particles. This would require the atmospheric temperature at these heights to drop suddenly by up to 100˚C. We’ve no idea what would cause such a drop, and we’re yet to spot such a massive, localized cold snap.

Sánchez-Lavega and colleagues thus declare that their “explanations defy our current understanding of Mars’ upper atmosphere” and their investigation only partially lifts the shroud surrounding these mysterious clouds.

Other Martian Mysteries

High altitude clouds are not the only Martian mysteries keeping researchers on their toes. One question driving the exploration of the red planet is whether there has ever been life on Mars. Latest results by NASA’s Curiosity rover reaffirm that the planet provided habitable conditions in its past.

Water is the most important prerequisite for life. One explanation for the ongoing formation of gullies and related features, for example, is liquid water at or near the Martian surface even during the currently prevailing extreme dry and cold conditions. And while there are many possible explanations for the enigmatic whiffs of methane observed on Mars, one of the most exciting is the production by microorganisms living just below the surface.

Part of the fascination of Mars exploration is that it is very much about understanding our own origins and future. As the example of the mystery cloud observations shows, everybody has a chance to participate in unraveling the red planet’s mysteries.

The Conversation

CATEGORIZED UNDER: Space & Physics, top posts
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  • zlop

    Comets have CH4, NH3 and H2O — CH4 Hydride or similar combination?

  • Keith Campbell

    I think it’s spaceship exhaust from Martian ships fleeing their planet because of Earth’s ongoing invasion.

    • Jhollman

      That makes sense, oviously.

  • Shinypartsup

    Way outside my area, but what about aquifers close enough to the surface to explain some life causing methane, as well as occasional upwellings and runoff?

  • Snartfarfle

    “Baffles scientists” is the most overused and inaccurate news headline… scientists don’t get baffled, they know that eventually there will be a reasonable explanation. Stop blaming scientists for your own meager understanding of what science actually is.

  • Jamie Fry

    I kind of hope we find the ruins of a temple, or human remains on the planet.

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