The Martian terminator “plumes” in Nature magazine


During the 2012 and 2014 apparitions of mars, we talked a lot about a very curious detail imaged by several amateurs: an object projected beyond the terminator, that could only be at a very high altitude. Seven scientists and six amateurs co-sign this month a paper about it in the famous magazine Nature!

 An extremely high-altitude plume seen at Mars’ morning terminator is a study written by A. Sánchez-Lavega, A. García Muñoz, E. García-Melendo, S. Pérez-Hoyos, J. M. Gómez-Forrellad, C. Pellier, M. Delcroix, M. A. López-Valverde, F. González-Galindo, W. Jaeschke, D. Parker, J. Phillips and D. Peach.

First it presents the result of our measures of the altitude of such “plumes” : they reach at least 200 kilometers above the surface, and probably more (up to 280 km), which is much higher than any known Martian cloud. Both dust storms and white clouds are not observed past an altitude of only 100 km!

Second we studied two hypothesis to try to find a plausible explanation. However, none of them looks completely satisfactory and the mystery is not solved!

  1. A cloud made either of water or carbon dioxide. This idea looks to be the more solid, but we would still have to explain how they can form so high. It’s coherent with the photometric behavior of the objects, being similar to that of the usual white clouds of the planet (brighter in blue). In any case the dust storm hypothesis can be ruled out because they are, to the contrary, brighter in red.
  2. Auroras. This hypothesis is backed by the fact that many occurrences have been observed above Mare Cimmerium, a region of the Martian ground that presents the strongest magnetic anomaly. However, they would then be much brighter than the terrestrial auroras, and this looks hard to justify…

If you don’t have access to the article I recommend the reading of two on-line materials:

Martian mystery cloud defies explanation, on Nature’s web site that describes briefly the main study, by Alexandra Witze

Martian Terminator Projections Observed by the HST , an amateur article in Communications in Mars Observations (I’m the author), quoted in the main study and that describes the plumes as they can be seen in HST images. I did not made any altitude estimations at the time but there are some interesting developments about the hourly and seasonal behavior of such “clouds”, their geographic repartition and photometric behavior. My feeling at the time was that of a cloud, although certainly a bit different than usual (I have been striked by how fast their shape evolve in a matter of minutes).


Image Wayne Jaeschke, 19 mars 2012

What conclusion for amateurs?

Once again, amateur observations do have a scientific interest. Image the planets, you can always meet surprises :).

In 2016, Mars will be observable again from Earth. However the configuration will not be very favorable to my eyes. Such plumes are mostly observed above and beyond the morning terminator during Martian southern winter. But the morning terminator can only be observed after opposition, and the Martian season will then reach late southern winter and if they are clouds, they should not form as easily. Let’s see!


Some better conditions on Jupiter, why ?


In my last article Jupiter under the jet-stream, what’s the result? I described the effect of one the worst meteorological conditions for the seeing. During my last observing night of January 17th, images were noticeably better (although still not really good…). It is possible to find explanations?

Here are some Jupiter images […] Continue Reading…


Jupiter under the jet-stream, what’s the result?


Last year I made a summary on the best conditions for a good seeing. Unfortunately there are as well other conditions that damage it. Here is a “good” example on Jupiter: the influence of the jet-stream.

What is the jetstream?

The jet-stream is a very narrow, but very fast, stream of […] Continue Reading…


Prepare for the elongations of Venus in 2015: talk at RCE


Last week-end I gave a talk at the Rencontres du Ciel et de l’Espace (RCE) at Cité des sciences et de l’industrie in Paris, about Venus. The planet will be easily observable for northern amateurs in 2015, do not miss it!
In 2015, we will see two nice venusian elongations […] Continue Reading…


Different ways of using colors for imaging planets


The concept of color is often discussed among observers. The purpose of this article is not to debate about the concept of realism, but to describe and discuss the use of three ways to use color for planetary images : “true” colors, “false” colors, and colorized monochrome images…

The three […] Continue Reading…


The reference article about pro/am cooperation in planetary astronomy


Participating to scientific work when you’re an amateur observer, is that possible? Answer is yes! I have talked about it on several occasions on this blog, and here is a must-read on the topic if you’d like to get into that.

The adventure started two years ago during the “4th pro-am […] Continue Reading…


A possible new “high altitude cloud” observed


The most noticeable observation of Mars in the last 2012 season has been the imagery of what is generally interpretated as a cloud of very high altitude, because it was projecting well beyond the terminator into the night. Those phenomena look to happen regularly and many have been found […] Continue Reading…


Planetary mission at the Pic du Midi, 8-9th March 2014


On March 8/9th, I had the honor and pleasure to participate to a planetary mission at the 1-meter telescope of the Pic du Midi (T1M) lead by Marc Delcroix, President of the SAF planetary observations commission. Here is a summary!

The T1M of the Pic du Midi observatory is […] Continue Reading…


Observing Mars: some technical advices


After the article, “What can we see on Mars this year” let’s now review some technical advices.

Make images in true colors
The Martian details are quite unequals, between the sharp and contrasted surface details seen in red, and the faint, low-contrast clouds observed in blue light. As the most interesting […] Continue Reading…


What can we see on Mars this year?


Mars will be at opposition again on April 8th, 2014. Here are some phenomena you must look for!

Mars will be at opposition in one month and a half and is already finely observable since its apparent diameter has now passed 10″. It will reach a maximum of 15,2″ […] Continue Reading…

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