With Europe still in the grip of winter, Martin Ahr from Munich, Germany, has sent us a beautiful animation of weather on another planet - in this case pre-dawn clouds on Mars. These clouds were captured during the 5 November 2009 VMC observation and are in the Southern Hemisphere of Mars, where summer had just ended and autumn was starting. At this time the temperature was far below 0°C, probably closer to -50 or -60°C -- makes our European winter seem a little less chilly!
 
Anyone on Mars around the time of these images would have woken up to a cloudy dawn, with Martin Ahr's assesment being, "There are clouds which appear to move also in a direction transverse to the direction of rotation of Mars, and some seem to disappear as the sun starts shining on them."
 
Martin has done a fantastic job of enhancing the clarity of these images and has sent us a detailed description of what he did to achieve this (click "Full Story" for his description). Click on the image for the full-size version. Thanks for your submission Martin! --Thomas

 
Martin wrote this to us about his processing work on the images:
I have created an animation from a VMC image series that was made on November 5, 2009. It shows what I believe to be clouds onto which the sun starts shining as the rotation of Mars brings them towards the sunlit side. There are clouds which appear to move also in a direction transverse to the direction of rotation of Mars, and some seem to disappear as the sun starts shining on them.

For each frame of the animation, I combined three images from one of the exposure bracketing series into one HDR image. I tried to also use the fourth image having the shortest exposure time. However, the HDR program I used could not combine this image with the other three images, probably because the difference in brightness between the image and the other three images is very large. Since the sunlit side of Mars is overexposed in all three images used, it remains overexposed. However, the dynamic range of the HDR image is sufficient to cover the entire brightness range of the clouds.

I then took the logarithm of the brightness values of the pixels in each HDR image to obtain images that can be displayed on a monitor while still showing the full dynamic range of the HDR images.

Thereafter, I shifted the images such that Mars it at substantially the same position in each image, combined the images into an animation and rotated the animation such that the sunlight shines from the right. I tried several orientations, and, in my opinion, this one looks most natural.

Unfortunately, Mars is moving out of the camera's field of view at the end of the series. Since the clouds are not shown any more in images No. 30 and later, I omitted these images. In the remaining images, I made the cut off portions transparent (which can be seen in the animation at the upper right part of Mars).

GIF images can comprise only 256 different colors. Therefore, I converted the images to grayscale. This does not make much difference, since the color saturation in the original images is so low that colors are almost invisible.

I used three computer programs for the processing:
  • Fitswork for reading the raw data, extracting color information from Bayer patterns, shifting images and calculating logarithms of brightness values
  • FDRTools Basic for creating HDR images and
  • Gimp for combining the images into an animation, minor adjustment of the brightness of individual images and rotating the animation.
This is a list of the VMC images used for the animation:

Frame 1:
09-309_19.02.06_VMC_Img_No_3.raw
09-309_19.02.59_VMC_Img_No_4.raw
09-309_19.03.53_VMC_Img_No_5.raw

Frame 2:
09-309_19.05.39_VMC_Img_No_7.raw
09-309_19.06.33_VMC_Img_No_8.raw
09-309_19.07.26_VMC_Img_No_9.raw

Frame 3:
09-309_19.09.13_VMC_Img_No_11.raw
09-309_19.10.06_VMC_Img_No_12.raw
09-309_19.10.59_VMC_Img_No_13.raw

Frame 4:
09-309_19.12.46_VMC_Img_No_15.raw
09-309_19.13.39_VMC_Img_No_16.raw
09-309_19.14.33_VMC_Img_No_17.raw

Frame 5:
09-309_19.16.19_VMC_Img_No_19.raw
09-309_19.17.13_VMC_Img_No_20.raw
09-309_19.18.06_VMC_Img_No_21.raw

Frame 6:
09-309_19.19.53_VMC_Img_No_23.raw
09-309_19.20.46_VMC_Img_No_24.raw
09-309_19.21.39_VMC_Img_No_25.raw

Frame 7:
09-309_19.23.26_VMC_Img_No_27.raw
09-309_19.24.19_VMC_Img_No_28.raw
09-309_19.25.13_VMC_Img_No_29.raw
Martin Ahr, February 2010   

If you would like to do something similar to Martin, or send us any work you've done with VMC images then check out our "Help us with VMC" pages.