So they came up with 102kg/m3 for the density? Really? That's like the density of very dry, loosely compacted snow. A block of ice has a density of about 1000kg/m3. Graphite is 2000kg/m3. I'm not saying it's wrong of course, but if they are close to correct, it' really is a dusty snowball with only a minimal amount of dust at that.
I was curious how the team of scientists would go about calculating the mass of the target object. This is very critical if you want to catch up to and orbit this object in any stable way.
reply to post by FireballStorm
You made me read a paper summarizing meteor science from the mid 1800's. That's when they were still debating that meteors were from extraterrestrial origin. pffft.
reply to post by FireballStorm
I don't know how you ended up with those totally unrelated comments from that. Try reading the paper I linked (and the one you linked) if you want to understand my OP.
Using a physical theory of meteors and on the basis of the results of double-station photographic observations of meteors in Dushanbe (Tajikistan), Kiev, and Odessa (Ukraine), the mean mineralogical and bulk densities of meteoroids belonging to nine meteoroid streams and sporadic background are determined. The mean mineralogical densities δm of meteoroids range from 2.2 g cm-3 (Perseids) to 3.4 g cm-3 (Quadrantids, δ-Aquarids, and α-Capricornids). The meteoroid bulk densities δ, which were determined according to the theory of quasi-continuous fragmentation of meteoroids in the Earth's atmosphere, vary from 0.4 g cm-3 (Leonids) to 2.9 g cm-3 (Geminids). Using the relation between bulk density and mineralogical density the porosity of meteoroids was estimated. The Geminid meteoroids are found to have the lowest porosity, while the Leonid and Draconid meteoroids have the most porous structure (83%). These results confirm the porous-structure nature of meteoroids' parent bodies i.e. comets and asteroids.
This paper is a review of the present knowledge on the structure of meteoroids. A summary of the evidence concerning the common occurrence of fragmentation among both photographic and radio meteors is given first. Then, an attempt is made to examine all the present observational, theoretical and laboratory data on the luminous and ionizing efficiencies of meteors, with the aim of establishing a mass scale. This allows the computation of the bulk density of meteoroids, which, on the average, turns out to be about 0.3 g/cm3. The paramount importance of progressive fragmentation, the behavior of abrupt-beginning meteors and the low density of nearly all meteoroids (even of those of relatively large sizes) support a porous and fragile structure for most of these particles. In turn, the crumbly structure and the cometary origin confirm Whipple's theory of comets and meteor production. A critical analysis of recent papers proposing different conclusions shows that the new theories always arrive at results which do not agree with well-established observational data.
The phenomenon of meteoroid fragmentation in the Earth's atmosphere was recorded repeatedly by means of different methods and especially using the photographic technique of instantaneous exposure. Among the four principal forms of fragmentation, the quasi-continuous fragmentation, i.e. a gradual release of the smallest fragments from the surface of a parent meteoroid and their subsequent evaporation, is most common. The analysis of photographic observations shows that a substantial fraction of meteoroids is exposed to this type of fragmentation. According to the theory of quasi-continuous fragmentation and on the basis of light curves of meteors photographed in Dushanbe (Tajikistan), the mean bulk densities of meteoroids belonging to six meteoroid streams and the sporadic background have been determined, which vary in the range from 0.4 g cm-3 (Leonids) to 2.9 g cm-3 (Geminids).
reply to post by wildespace
The comet's gravity is extremely small, so it's not like Rosetta will crash into it if there's not enough velocity.
originally posted by: Ross 54
I'm intrigued with the calculated low density of this comet, too. If it's mostly frozen water, as expected, it must be something like fresh snow, as noted in the original post. Comets are typically about six times as dense as this. I am wondering how something like snow could form on a small, airless body in space. On Earth, snow forms as large hexagonal crystals within, and influenced by Earth's atmosphere.