On 28 September, a scientific paper was published in Nature, presenting a view on the formation scenario of Comet 67P/Churyumov-Gerasimenko, based on Rosetta OSIRIS images (read our news report here). The paper, led by Dr Matteo Massironi of the University of Padova, Italy, evaluated two possible models to explain the comet's curious shape: the merging of two cometesimals or the erosion of a single object. Observational data and thorough analysis of the comet's gravity field pointed towards the first of the two hypotheses: 67P/C-G seems to have originated from two separately formed comets that merged at low speed.
Today's CometWatch entry is an image from Rosetta’s NAVCAM taken on 1 October 2015, at a distance of 1323 km from the nucleus of Comet 67P/Churyumov-Gerasimenko.
Scientists from the European Space Agency's Rosetta mission are honoring their deceased colleague, Claudia Alexander of NASA's Jet Propulsion Laboratory in Pasadena, California, by naming a feature after her on the mission's target, comet 67P/Churyumov-Gerasimenko.
Today's CometWatch entry is an image taken by Rosetta’s NAVCAM on 30 September 2015, about 1488 km from the nucleus of Comet 67P/Churyumov-Gerasimenko. The image was taken a few hours after the spacecraft had reached the farthest point – 1500 km from the nucleus – on its far excursion to study the coma and plasma environment of 67P/C-G on a broader scale.
The mass spectrometer ROSINA on ESA’s comet probe Rosetta has for the first time detected the noble gas argon in the coma of 67P/Churyumov-Gerasimenko. This measurement adds to the debate about the role of comets in delivering various "ingredients," such as water, to Earth.
Using the Microwave Instrument for the Rosetta Orbiter (MIRO), scientists have studied the comets southern polar regions at the end of their long winter season. The data suggest that these dark, cold regions host ice within the first few tens of centimetres below the surface in much larger amounts than elsewhere on the comet.
Last week we reported on the daily water-ice cycle of Comet 67P/Churyumov-Gerasimenko that was observed in a specific region of the comet’s neck by Rosetta’s VIRTIS instrument, in September 2014.
Today's CometWatch entry was taken by Rosetta’s NAVCAM on 21 September 2015, about 330 km from the nucleus of Comet 67P/Churyumov-Gerasimenko.
Since arriving at Comet 67P/C-G in August 2014, Rosetta has been witnessing an increase in the activity of the comet, warmed by the ever-closer Sun. A general increase in the outflow of gas and dust has been punctuated by the emergence of jets and dramatic rapid outbursts in the weeks around perihelion, the closest point to the Sun on the comet’s orbit, which occurred on 13 August 2015.