Rosetta mission lets scientists learn comet’s life cycle

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Comet 67P/Churyumov-Gerasimenko aka C-G is shedding its dusty coat and as it does so, scientists have managed to garner a never-before look at a comet’s life cycle thanks to ESA’s Rosetta mission.

On board the Rosetta spacecraft is the COmetary Secondary Ion Mass Analyzer, or COSIMA, which is one of Rosetta’s three dust analysis experiments. COSIMA started collecting, imaging and measuring the composition of dust particles shortly after the spacecraft arrived at the comet in August 2014.

ESA revealed that the study of dust particles collected during the period between August and October [inclusive] when the comet C-G was moving along its between about 535 million kilometers to 450 million kilometers from the Sun. Rosetta was in the comet’s orbit at distances of 30 km or less.

Scientists analysed how large dust grains broke apart when they were collected on COSIMA’s plate, typically at low speeds of 1-10 m/s. The grains, which were originally at least 0.05 mm across, fragmented or shattered upon collection.

Scientists reveal that as the dust grains broke apart, it meant that they were not well bound together and that there was no ice in them. If there was any ice, they would not have broke apart on impact, but instead the icy components would have evaporated off the grain leaving voids in what remained. Scientists further add that if a pure water-ice grain had struck the detector, then only a dark patch would have been seen.

The analysis further revealed that the dust particles were rich in sodium – a characteristic that is common in ‘interplanetary dust particles’.

“We found that the dust particles released first when the comet started to become active again are ‘fluffy’. They don’t contain ice, but they do contain a lot of sodium. We have found the parent material of interplanetary dust particles,” said lead author Rita Schulz of ESA’s Scientific Support Office.

Currently C-G is on a 6.5-year circuit around the Sun and will be closest in August 2015. At that point, Rosetta and the comet will be 186 million kilometers from the Sun, between the orbits of Earth and Mars.

“Rosetta`s dust observations close to the comet nucleus have been crucial in linking together what was happening at the very small scale with what was visible at much larger scales, as dust was lost into the comet`s coma and tail,” said Matt Taylor, ESA`s Rosetta project scientist.

“For these observations, it really is a case of `watch this space` as we continue to watch in real time how the comet evolves as it approaches the Sun along its orbit over the coming months.”

Results from the first analysis of data are reported in the journal Nature.