The valid theory of Martian berries must be consistent with their actual size distributions. What are they? The MARSOMETRY program  was used to measure berry sizes from Opportunity PANCAM images taken on Sols 45,50,126,140,162.
The images where selected because they show colonies of well formed spherical berries, all having similar blue tint, some of them attached to the rock - berries that are likely to have biological origin . Figure 1 shows the observed size distributions. A sample of berries from each site is provided with the graph.
Several points can be made about the distributions shown:
All the berries fit in the 0-8 mm interval.
The noticeable features of the distribution graphs are: a narrow maximum about 2.8 mm, and a wide maximum area approximately from 3 mm to 6 mm. Sols 50,126,140 have wide maximum only, the Sol 162 has both narrow and wide maximums, while Sol 45 distribution has only narrow maximum.
Berry size distributions from different Martian sites appear to be closely related. They are smoothly morphing one into another. Also, the more berries look to be growing, the more pronounced the wide distribution maximum is, and the less pronounced the narrow distribution maximum is.
It is appropriate to suggest then, that the berry communities have common underlying mechanism of their creation and development - which must be of the biological nature, if it holds true for some of them .
One might be tempted to associate narrow maximum with the dead or dormant berries, and wide maximum area with the alive and growing berries.
Any non-biological theory of Martian berries would have hard time explaining why their size is always less than 8 mm. If there are some scalable physical processes which growth them to this size on Mars, why would they do not ever grow them larger?
A fair effort was made to ensure precision of the measurements. The area coverage was pretty comprehensive with in most cases all the recognized berries measured, as seen on the measured berries map for Sol 162, Figure 2.
Thanks to the valuable service by Holdger Isenberg, we were able to use for the measurements color version of left eye images :
Sol 045: 1P132173973ESF05A6P2556L5M1_L4L5L5L5L6
Sol 050: 1P132626650ESF0602P2578L5M1_L4L5L5L5L6
Sol 126: 1P139377190EFF2831P2539L5M1_L2L5L5L7L7
Sol 140: 1P140611723ESF3182P2551L5M1_L2L5L5L7L7
Sol 162: 1P142561855ESF3221P2584L5M1_L4L5L5L5L6
Raw originals have been used for the right eye :
Sol 045: 1P132174096ESF05A6P2556R1M1
Sol 050: 1P132626768ESF0602P2578R1M1
Sol 126: 1P139377268EFF2831P2539R1M1
Sol 140: 1P140611791ESF3182P2551R1M1
Sol 162: 1P142561855ESF3221P2584R5M1
The color images from  were used to improve the form and object recognition. In order to improve pixel diameter measurement precision, the images were enlarged by a factor 3, reducing errors below 5 pct. The distance measurement error due to image granularity has been found, using digital experiments, to be less than 1 pct. The overall berry size measurement error consequently was about or less than 5 pct. This unbiased error should not be expected to noticeably alter the berry size distributions.
However, the berries of diameter less than 2 mm have likely been undercounted, as they are harder to spot, not fully formed yet, or might be hidden in dust - while the larger berries attract attention and get measured more often than not. This condition was properly mitigated by focusing discussion on the over 2 mm sizes area.
The berry size distributions, like other their properties, have to be properly explained. But before that, we must know them and how they vary. Hopefully, this work answers some of such need.
I am very grateful to Holdger Isenberg for his outstanding PANCAM color images service, which has contributed a lot to the quality of presented results. Deep gratitude goes to NASA for making this work and much more possible by taking the magnificent pictures of Mars surface, and generously providing full public access to them.
1. Zeltsman, A. (2005) Searching For the biological objects on Mars. Marsbugs, 18(26):10-11
2. Zeltsman, A. (2005) Berries suggest life on Mars. Marsbugs, 18(23):3-4
3. Isenberg, H. (2004-2005) PanCam true color images from Spirit and Opportunity Mars Exploration Rovers,
4. NASA image gallery, http://origin.mars5.jpl.nasa.gov/gallery/all