Scientists have found caves

MOSCOW, 6 Feb – RIA Novosti. The “dumbbell” of comet 67P/Churyumov-Gerasimenko, despite its extremely low mass, does not contain large voids, which suggests that primary matter of the Solar system was unusually loose and porous, according to ESA.

Current estimates of scientists, the mass of the comet is about 10 billion tons, which is 20 million times heavier than the largest man-made object in space, the ISS. This is a rather small figure for a celestial body the size of comet Churyumov-Gerasimenko. The secret of lightness is to a very high degree of porosity of the comet — about 70-80% of its total volume occupied by voids, and its density is about the same as tubes, wood, or aerogel.

Therefore, as says Martin Petzold (Martin Patzold) from the University of Cologne (Germany), the astronomers came the question of distribution of these voids on the interior of the comet evenly, or low density of this celestial body due to the fact that within it, there are large “caves” and networks of large voids.

Scientists have been able to answer this question comprehensively studied the gravitational field of comet Churyumov-Gerasimenko using ingenious methods of observation used on the probe Rosetta, studying the comet  and a number of radiotelex on Earth.

Petzold and his colleagues took advantage of the fact that the attraction of the comet’s influence, as “Rosetta” communicated with the Earth, affecting the frequency of the radio signal traveled from the transmitter to ground station communications.

When the probe approached the comet, fluctuations in the force of gravity, which arose as a result of inhomogeneities in the density of the subsoil, in a special way affect the signal, making it wave slightly shorter when driving over very dense areas, and slightly longer – when passing over voids.

These fluctuations in the frequency of the radio signal helped the authors to make fairly accurate gravitational map of the comet Churyumov-Gerasimenko, to find all the major voids and to re-measure its mass and calculate the average density. It was almost the same as was shown by the previous measurements – the mass of the comet was almost the same 10 trillion tons, and a population density of about 530 kg per cubic meter.

In turn, the bowels of the comet, judging from its gravitational map, do not contain any major “caves”, whose dimensions exceed a few hundred meters. This means that matter is 67P is extremely friable in nature – it is about 72-74% consists of pores and other microscopic voids, occupying the space between the grains of dust and ice.

Most of the subsurface of the comet is dust – its in the rocks of 67P is about four times larger than ice crystals that survived inside this “hairy monster” since the birth of the Sun, Earth and other planets. Accordingly, the high open porosity and porosity of the subsurface of the comet suggests that primary matter of the Solar system had similar properties.

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