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Mars Express observes curious cloud near Red Planet volcano

Artist's impression of the European Space Agency's (ESA) Mars Express spacecraft orbiting Mars. Image Credit: ESA

Artist’s impression of the European Space Agency’s (ESA) Mars Express spacecraft orbiting the Red Planet. Image Credit: ESA

With the skies above Mars finally clearing after the massive dust storm that engulfed the whole planet in June and July of this year (2018), an unusual visitor appeared in the thin skies above the Red Planet.

The European Space Agency’s (ESA) Mars Express spacecraft is studying an elongated cloud formation that has been seen near the 12 mile-high (20 kilometer) Arsia Mons volcano. mars Express first imaged this feature by using the spacecraft’s Visual Monitoring Camera (VCM) on Sept. 13.

Elongated cloud on Mars. Image Credit:ESA

Elongated cloud on Mars. Image Credit: : ESA/GCP/UPV/EHU Bilbao

While it might seem like the cloud is originating from Arsia Mons itself, it is not the result of volcanic activity. It is believed that the wispy trail is an ice cloud formed as a result of the influence of the mountain’a leeward slope on the air flow above it.

Researchers refer to it as an orographic or lee cloud, and it is a reoccurring  phenomenon in this region of Mars. The long, white cloud extends about 930 miles (approximately 1,500 kilometer) westward from Arisa Mons, which has a diameter of about 155 miles (250 kilometers).

The summit of Arsia Mons is  usually covered with clouds throughout most of the Martian year. These clouds disappear in the months in the months leading up to the winter solstice, which occurred on October 16.

A seasonally reoccurring water ice cloud is known to form along Arsia Mons’ southwestern flank. Mars Express and other spacecraft have observed such clouds in 2009, 2012 and 2015.  The cloud changes its appearance throughout the Martian day. During the morning, it grows in length downwind of the volcano, reaching such a massive size that it may become visible to Earth-based telescopes.

The formation of water ice clouds is effected by the amount of dust in the Martian atmosphere. 

In addition to the VMC, Mars Express is using the visible and near-infrared mapping spectrometer (OMEGA) and the High Resolution Stereo Camera (HRSC) to observe the elongated cloud. Data collected by Mars Express will help further our knowledge of the Martian atmosphere and how these reoccurring water ice clouds form near volcanoes like Arsia Mons.

Mars Express was launched from the Baikonur Cosmodrome in Kazakhstan, atop a Russian Soyuz/Fregat rocket on June 2, 2003.  The spacecraft successfully entered orbit around Mars on Christmas Day of that year. Initially it maneuvered into a highly elliptical  orbit before making its way into its operational near-polar orbit in January 2004.

Annotated image of elongated cloud formation near Arsia Mons. This image was taken on October 10 by Mars Express' Visual Monitoring Camera (VMC). Image Credit: ESA/GCP/UPV/EHU Bilbao

Annotated image of elongated cloud formation near Arsia Mons. This image was taken on October 10 by Mars Express’ Visual Monitoring Camera (VMC). Image Credit: ESA/GCP/UPV/EHU Bilbao





Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.

Reader Comments

What I find curious though:

1) Arsia Mons is the 3rd highest in the Tharsis 4 volcano system – so if it was caused by moisture in the air being raised – why are no clouds forming in the vicinity of the two higher volcanoes in the more than a month that this “cloud” has been observed.

2) The very pronounced shadow cast from the origin point from below the cloud at sunrise/set over the volcano.

3) Despite claiming that similar clouds have been observed – no “cloud” of this nature – in terms of shape, density, spread and duration – has ever been seen before at that volcano – or anywhere else on Mars.

4) The density and persistence of the ball like “cloud” at the origin point is not consistent with ice cloud formation.

5) The presence of curious dark regular shadows within the cloud maintain their orientation and shape across hours or days.

6) The published high resolution image of the cloud by ESA on its website in late October was taken more than a month earlier and bears no relationship to how it has been developing.

7) … the oddness goes on, but let’s stop there.

Ref: ESA’s VMC Mars webcam images

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