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The seasonal cloud over Arsia Mons on Mars

Water-ice cloud over Arsia Mons
The cloud as seen in 2018.

Scientists have now documented the seasonal nature of the strangely elongated cloud that was first spotted in 2018 above the giant volcano Arsia Mons (the southernmost volcano of the three volcanoes east of Olympus Mons).

From their abstract:

We find that the AMEC [Arsia Mons Elongated Cloud] repeated regularly each morning for a number of months, and that it is an annually‐repeating phenomenon that takes place every Martian Year around the southern hemisphere spring and summer. The AMEC follows a rapid daily cycle: it starts to expand from Arsia Mons at dawn at an altitude of about ∼45 km, and for ∼2.5 hours it expands westward as fast as 170 m/s (around 600 km/h). The cloud then detaches from Arsia Mons and evaporates before noon. In previous Martian Years, few observations of this phenomenon are available because most cameras orbiting Mars are placed in orbits where they can only observe during the afternoon, whereas this cloud takes place in the early morning, when observational coverage is much lower.

They also state that they will outline their theories as to the cause of the cloud in a follow-up paper.

I can’t help wondering if it is related to other evidence that suggested past glacial activity on the western flanks of Arsia Mons. There are many pits surrounding this volcano, and many might contain residue ice. One wonders if, during the warm spring and summer months at dawn the arrival of the sun might cause this cloud to form, and then vanish as the day passes, just like the dew does on Earth.

That is my uneducated guess, and likely wrong. We shall have to wait for their theoretical paper for a more educated guess.

Conscious Choice cover

Now available in hardback and paperback as well as ebook!


From the press release: In this ground-breaking new history of early America, historian Robert Zimmerman not only exposes the lie behind The New York Times 1619 Project that falsely claims slavery is central to the history of the United States, he also provides profound lessons about the nature of human societies, lessons important for Americans today as well as for all future settlers on Mars and elsewhere in space.

Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
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  • David Telford

    I am reminded of a presentation by Dr Michael Malin long ago where he remarked on observations from the Mars Global Surveyor where dust devils would appear on mars at the same place and in the same time as they had a martian year before. It hints of a peculiarly stable system of weather activity.

  • David Telford: Speaking of dust devils returning to the same spot, you might find this BtB article of interest: The dark splotches on Mars: Magnets for dust devils.

  • David Telford

    Thank you Bob, an interesting phenomenon around Olympus Mons. I could wonder if there are prevailing and steady winds that hit the Mons and maybe there are large wavelength resonances that cause the dust devils to concentrate, and subsequently expose the darker stuff underneath. I recall years ago crossing eastern Washington in the early summer. Stopped to see some dust devils going, and noticed there were dozens formed in a large grid slowly moving across the open plane. Would be nice to know that science has this figured out. Or maybe not yet?

  • pzatchok

    I wonder if its simple uplift like we have in mountain rangers on Earth.

    Water laden air hits a mountain and its pushed up till it gets cold enough to condense into clouds and eventual rain.
    On Earth its normally a mountain range and the rain falls on the same side of the mountains that the wind hits,
    But since Olympus Mons is singular wouldn’t the clouds travel around it and re-converge on the other side?
    And because of the unique Mars atmosphere and the hight of the mountain the rain would be coming from way to high to ever actually hit the ground and show up as a wet spot.
    It goes from super high ice crystal clouds to low level falling clouds and right into sublimated water vapor to thin to see.

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