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We present an attempt to extract information about the comet 9P/Tempel 1nucleus from the characteristics of the ejecta cloud produced by the impactorof the Deep Impact mission. For this purpose we use two techniques. We firststudy the shadow cast on the nucleus surface by the ejecta cloud andinvestigate how areas of different brightness are related to the varyingoptical thickness or albedo of the ejecta cloud. The shadow was seen during thefirst 2.0 seconds after the impact (afterward it became obscured by the ejectacloud). We have found that all brightness variations in the shadow are theresult of the surface inhomogeneities, indicating that during first 2.0 secondsthe ejecta cloud was homogeneous within the MRI spatial resolution. Our secondtechnique is to study the obscuration of the nucleus limb by the ejecta. Thisstudy covers the period 0.76- 68.8 seconds after impact and is based oncomparison of the ejecta cloud brightness on the limb and just beyond the limb.At this stage we do see inhomogeneities in the ejecta cloud that relate to thealbedo and optical thickness variations in the ejected dust. Specifically, wehave found two distinct bands of low optical thickness and one band of a highoptical thickness. Based on crater formation ideas we estimate the depth ofexcavation of the ejected material for the found inhomogeneities and, thus,define a potential layering structure for the comet nucleus, Our estimatessuggest that the low-optical thickness material was excavated from a depth of15-18 and 30-32 meters in the case the porous nucleus material and 37-46 and87-93 meters in the case of a non-porous nucleus material, and a layer of highoptical thickness originated from the depth 9-11 m for porous material or 20-23m for non-porous material. Based on the crater diameter estimates, we expectthat the real depth of the layers is between these two cases.

Studying the nucleus of comet 9P/Tempel 1 using the structure of the Deep Impact ejecta cloud at the early stages of its development