The coma of Comet 103P/Hartley 2 has a significant population of large particles observed as point sources in images taken by the Deep Impact spacecraft .
We measure their spatial and flux distributions , and attempt to constrain their composition .
The flux distribution of these particles implies a very steep size distribution with power-law slopes ranging from -6.6 to -4.7 .
The radii of the particles extend up to 20 cm , and perhaps up to 2 m , but their exact sizes depend on their unknown light scattering properties .
We consider two cases : bright icy material , and dark dusty material .
The icy case better describes the particles if water sublimation from the particles causes a significant rocket force , which we propose as the best method to account for the observed spatial distribution .
Solar radiation is a plausible alternative , but only if the particles are very low density aggregates .
If we treat the particles as mini-nuclei , we estimate they account for < 16 - 80 % of the comet ’ s total water production rate ( within 20.6 km ) .
Dark dusty particles , however , are not favored based on mass arguments .
The water production rate from bright icy particles is constrained with an upper limit of 0.1 to 0.5 % of the total water production rate of the comet .
If indeed icy with a high albedo , these particles do not appear to account for the comet ’ s large water production rate .