Seasonal changes of the volatile density in the coma and on the surface of comet 67P/Churyumov–Gerasimenko

Abstract

Starting from several monthly data sets of Rosetta's COmetary Pressure Sensor we reconstruct the gas density in the coma around comet 67P/Churyumov-Gerasimenko. The underlying inverse gas model is constructed by fitting ten thousands of measurements to thousands of potential gas sources distributed across the entire nucleus surface. The ensuing self-consistent solution for the entire coma density and surface activity reproduces the temporal and spatial variations seen in the data for monthly periods with Pearson correlation coefficients of 0.93 and higher. For different seasonal illumination conditions before and after perihelion we observe a systematic shift of gas sources on the nucleus.

Local Manifestations of Cometary Activity

“…This asymmetry can also be found in the overall production rate (Hansen et al, 2016) and the number of jets seen by the cameras on board Rosetta Kramer et al, 2017). It is compatible with our understanding of the thermal processes involved .…”

Surface localization of gas sources on comet 67P/Churyumov-Gerasimenko based on DFMS/COPS data

“…The localization of the most active emitting areas in Sect. 5 is in good agreement to Hoang et al (2017) and Kramer et al (2017). This activity pattern shows a high correlation (0.7) to active gas emitters with short living dust locations derived from OSIRIS and NAVCAM images by Vincent et al (2016).…”

“…The global reconstruction of the entire three-dimensional coma around 67P/C-G proceeds as a two-step process from the time-series of COPS and DFMS measurements along the trajectory of Rosetta and is based on the assignment of surface emission rates as described by Kramer et al (2017). First we run a forward model on a surface shape to build a global coma model by assuming equally strong emitting gas sources on each of the surface elements.…”

“…These local inhomogeneities define the inner boundary condition of their DSMC model. Kramer et al (2017) introduce a different simplified gas model and fit surface production rates on 10 4 surface elements to COPS density data.…”

Revisiting the science case for near-UV spectroscopy with the VLT

“…This severely limits studies of water production in comets around their orbits and we miss the seasonal effects that the Rosetta mission has recently revealed to be important (e.g. Kramer et al 2017). It also prevents study of the vast majority of comets which are simply too faint.…”