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Investigation of a Possible Source of a Persistent Elongated White Cloud
by Jim Melka ALPO assistant coordinator for the Mars Section of the Association of Lunar and Planetary Observers.
Abstract:
Abstract:
An elongated white cloud was imaged a number of times from Sep. 19, 2018 Ls 253 through Nov. 12, 2018 Ls 287. This particular white cloud, located over the Western flanks of Arsia Mons, has been imaged during apparitions going back to 1976. Images of the elongated white cloud were taken by amateur astronomers of the Association of Lunar & Planetary Observers (ALPO), the Mars Reconnaisance orbiter, the Viking Space Probe, ESA’s Mars Express, and by the Mars Global Surveyor. These clouds cannot be due to Volcanic gas since Arsia is believed to have been dormant for hundreds of millions of years. They do not have the characteristics of common orographic clouds. The elongated clouds in images appear to rise up vertically from Arsia's Western slopes and then tail away from the volcano. The author proposes that a shallow underground reservoir of glacial H2O ice exists under the lower Western slopes of Arsia Mons. With rising surface temperatures in late Southern Spring and Summer, the underground ice close to the surface sublimates H2O and is outgassed from the surface. Once airborne it freezes into ice grains that ascend vertically until high-altitude winds that can blow the cloud laterally up to more than a thousand kilometers.
An elongated white cloud was imaged a number of times from Sep. 19, 2018 Ls 253 through Nov. 12, 2018 Ls 287. This particular white cloud, located over the Western flanks of Arsia Mons, has been imaged during apparitions going back to 1976. Images of the elongated white cloud were taken by amateur astronomers of the Association of Lunar & Planetary Observers (ALPO), the Mars Reconnaisance orbiter, the Viking Space Probe, ESA’s Mars Express, and by the Mars Global Surveyor. These clouds cannot be due to Volcanic gas since Arsia is believed to have been dormant for hundreds of millions of years. They do not have the characteristics of common orographic clouds. The elongated clouds in images appear to rise up vertically from Arsia's Western slopes and then tail away from the volcano. The author proposes that a shallow underground reservoir of glacial H2O ice exists under the lower Western slopes of Arsia Mons. With rising surface temperatures in late Southern Spring and Summer, the underground ice close to the surface sublimates H2O and is outgassed from the surface. Once airborne it freezes into ice grains that ascend vertically until high-altitude winds that can blow the cloud laterally up to more than a thousand kilometers.
The author asked the science community for assistance to investigate this feature. Professor Marco Mastrogiuseppe* volunteered to analyze seven MRO-SHARAD (Shallow Radar) image scans in search of subsurface ice reflections . He used his algorithm to magnify the SHARAD images by a factor of three. The author examined five SHARAD scans of the high-western slopes of Arsia Mons. However, these twelve scans returned inconclusive results likely due to a proposed presence of a rocky regolith in the region where the suspected outgassing is occuring. It is suspected that sublimation of H2O ice is taking place through openings and cracks in the regolith.
The author asked the science community for assistance to investigate this feature. Professor Marco Mastrogiuseppe* volunteered to analyze seven MRO-SHARAD (Shallow Radar) image scans in search of subsurface ice reflections . He used his algorithm to magnify the SHARAD images by a factor of three. The author examined five SHARAD scans of the high-western slopes of Arsia Mons. However, these twelve scans returned inconclusive results likely due to a proposed presence of a rocky regolith in the region where the suspected outgassing is occuring. It is suspected that sublimation of H2O ice is taking place through openings and cracks in the regolith.
* The University of Link Campus, in collaboration with the DIET department at the University of Rome "La Sapienza
* The University of Link Campus, in collaboration with the DIET department at the University of Rome "La Sapienza
Establish the difference between Orographic Clouds and the Arsia Mons Cloud
Orographic Clouds:
H2O ice sublimates off the NPC during late Spring and Summer in the Northern hemisphere. During this period the H2O of the entire atmosphere increases. See heading DIFFERENCES BETWEEN THE ICE CAPS on page 399 of 'A Traveler's Guide to Mars' by William K. Hartmann. The Southern hemisphere is affected and orographic H2O clouds are imaged regularly over the Tharsis volcanoes. During the day-light hours, if there is an updraft of water vapor along the windward flank of a volcano, then as the water vapor rises and gets cold enough to reach the frost point, it will become a white cloud of ice grains and continue to rise and spill over the peak of a volcano. This action defines an orographic cloud. Figure 1 shows images of orographic clouds taken by members of the ALPO at Ls 71° and 85°. These clouds are irregularly shaped. Such clouds are recorded up to about an Ls of 210° early Fall in the Northern Hemisphere. After this much of the H2O content of the atmosphere is deposited as ice in the Northern polar regions. The temperature in the South polar regions during Southern Spring and Summer remains too cold for the H2O ice at the South Polar Cap to sublimate. Without the extra water vapor in the atmosphere orographic clouds do not form in these seasons.
Figure 1
More evidence against the cloud being orographic is captured by Clyde Foster's high resolution color image of Arsia Mons in Figure 2. The cloud and its long shadow are clearly recorded. The Ls is 260° that is very late Spring in the Southern Hemisphere. The cloud here rises vertically and then flows Westward away from Arsia. Clouds are not visible near Pavonis Mons or Ascraeus Mons.
Figure 2
Figure 2
Images by R. Iwmasa from Yokohama, Japan show the cloud and shadow on Oct. 22, 2018 Ls 274°.
See Figures 3a and 3b below.
Figure 3a Figure 3b
Figure 3a Figure 3b
Figure 4 below shows a blue-filtered image taken on Nov. 3, 2018 Ls 282° by Clyde Foster. It clearly shows a very long elongated cloud just West of Arsia Mons.
Figure 4
A mystery is solved for one of my 2005 images. A dark linear feature is visible between Phoenicis Lacus and Arsia Mons that is not shown on albedo maps of the surface of Mars. It is suspected to be the shadow of a elongated white cloud near Arsia Mons. See Figure 5 below.
Figure 5
Figure 6 shows a water-ice cloud near Arsia Mons. This composite of red and blue images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images was acquired on 6 July 2005 Ls 244°. This elongated cloud extends more than 30 kilometers above the Martian surface.
Figure 6 Image by NASA/JPL/Malin Space Science Systems
A Science Alert article on Oct 23, 2018 by McRae shows an image of Arsia Mons taken by a camera on the Mars Express on Sep. 21, 2018 Ls 255°. It shows a white elongated cloud originating from the lower slopes of the Western flank of Arsia Mons and extending far Westward. Once again this is not the typical behavior of an orographic cloud. The vertical rising cloud looks to be driven by an East to West wind. See Figure 7 below.
Figure 7
Figure 8 below is a Mars Reconaissance Observer context image showing part of the lower Western slopes of Arsia Mons. The two craters are the craters in Figure 7 above showing the outgassing. The verical-pointing-white arrow marks the proposed region where water vapor is being outgassed and to striations at the surface. Also note that the Northeast crater wall has been pushed inward.
Figure 8
Figure 9 below is a high resolution image showing some of the striations. The striations support glacier movement. Sublimation of glacier ice could be taking place through openings in the rubble. Note the striations on the surface that could have been caused by movement of a glacier.
Establish the probability that glaciers did form in the past on the Western slopes of Arsia Mons:
Please refer to Francois Forget's paper entitled "Formation of Glaciers on Mars by Atmospheric Precipitation at High Obliquity." See https://science.sciencemag.org/content/311/5759/368.full
He states the likelihood of glaciers being formed on the flanks of the Tharsis volcanoes. The last two sentences of his Abstract state, "The model predicts ice accumulation in regions where glacier landforms are observed, on the western flanks of the great volcanoes and in the eastern Hellas region. This agreement points to an atmospheric origin for the ice and reveals how precipitation could have formed glaciers on Mars."
Another paper pointing to glacier-sized ice deposits at Arsia Mons is entitled "Recent glaciation at high elevations on Arsia Mons, Mars: Implications for the formation and evolution of large tropical mountain glaciers" by David E. Shean, James W. Head III, James L. Fastook and David R. Marchant. See https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2006JE002761 .Paragraph [65] states "MOLA topography data suggest that ∼100–300 m of ice is still preserved at Arsia Mons beneath a debris cover within the large graben and in the surrounding smooth facies lobes. This observation suggests that in these locations, equatorial ice has been preserved for tens to potentially ∼100 Myr beneath a relatively thin debris cover. This stability has implications for sublimation processes on Mars and the importance of a debris cover for ice preservation on the surface [Helbert et al., 2005]. Initial results from the Berlin Mars Near‐Surface Thermal Model [Helbert et al., 2005] suggest that within the large graben, ice could survive beneath a debris cover that is only a few meters thick for at least 50 Myr [Helbert et al., 2006].
Another paper is also relevant to the origin of the cloud. The title is "TES spectroscopic identification of a region of persistent water ice clouds on the flanks of Arsia Mons Volcano, Mars" by E. Z. Noe Dobrea and J. F. Bell III in the Journal of Geophysical Research: Planets, published: 05 May 2005.
See https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2003JE002221
Paragraph 25 is copied below.
[25] "It is not clear, either, why these clouds are so closely associated with the distinct surface morphologic feature southwest of Arsia. Clouds are seen over this feature, for example, even when there is no sign of clouds over any of the other volcanoes. This leads to speculation that there may in fact be a unique surface/atmosphere relationship or interaction occurring at this specific location. For example, if there were enhanced porosity in the surface in this region there might also be enhanced vapor diffusion within the regolith, and a potentially larger local source (relative to the less porous surrounding regions) of atmospheric water vapor. As another perhaps extreme example, there may be enhanced subsurface sources of water vapor in this region associated with buried ice deposits." There are no geologic or thermophysical data to support such speculations, however, and so the reason for the occurrence of persistent clouds in this specific region remain uncertain and worthy of additional future investigation."
Author Robert Zimmerman wrote a feature article in April 2013 issue of Sky & Telescope "Exploring Caves on Other Worlds". A concluding paragraph of this article is presented below. He discussed caves on the Moon and then switches to Mars.
Research
Scans from the Mars Reconnaissance Orbiter's Shallow Subsurface Radar (SHARAD) were used to search for H2O ice underground on the western flank of Arsia Mons. Professor Marco Mastrogiuseppe* queried two SHARAD radar scans to focus solely on the suspected outgassing area in Figure 10. Both scans appeared very noisy, with suspected ground clutter making it difficult to observe sub-surface radar reflections. This ground clutter could represent a moraine. See Figure 11. It's ironic that the proposed rocky surface is where the cloud eminates and at the same time hinders observation of the source glacial ice under the rocks.
Scans from the Mars Reconnaissance Orbiter's Shallow Subsurface Radar (SHARAD) were used to search for H2O ice underground on the western flank of Arsia Mons. Professor Marco Mastrogiuseppe* queried two SHARAD radar scans to focus solely on the suspected outgassing area in Figure 10. Both scans appeared very noisy, with suspected ground clutter making it difficult to observe sub-surface radar reflections. This ground clutter could represent a moraine. See Figure 11. It's ironic that the proposed rocky surface is where the cloud eminates and at the same time hinders observation of the source glacial ice under the rocks.
Figure 10
Figure 11
At this time there are not any plans to resume this investigation.
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