The Philae lander, part of the Rosetta mission to investigate comet 67P/Churyumov-Gerasimenko, was delivered to the cometary surface in November 2014. Here we report the precise circumstances of the multiple landings of Philae, including the bouncing trajectory and rebound parameters, based on engineering data in conjunction with operational instrument data. These data also provide information on the mechanical properties (strength and layering) of the comet surface. The first touchdown site, Agilkia, appears to have a granular soft surface (with a compressive strength of 1 kilopascal) at least ~20 cm thick, possibly on top of a more rigid layer. The final landing site, Abydos, has a hard surface.

Abstract. We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low-activity state. Quasi-coherent, large-amplitude (δB/B ∼ 1), compressional magnetic field oscillations at ∼ 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied cometary interaction regions where waves at the cometary ion gyrofrequencies are the main feature. Thus classical pickup-iondriven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.

Knowledge of the magnetization of planetary bodies allows far--reaching conclusions on their formation processes, and the conditions in the solar nebular at that time. Based on magnetic field measurements during the descent and subsequent triple landing of the ROSETTA lander PHILAE on comet 67P/Churyumov--Gerasimenko, we show that no global magnetic field was detected within the limitations of analysis. The ROMAP suite of sensors measured an upper magnetic field magnitude of less than 2 nT at the cometary surface at multiple locations with the upper specific magnetic moment being < 3.1·•10 --5 Am 2 /kg for meter--size homogeneous magnetized boulders and the maximum dipole moment of 67P/Churyumov--Gerasimenko is 1.6·•10 8 Am 2 . We conclude that on this scale magnetic alignment in the pre--planetary nebular is of minor importance.One Sentence Summary: High--precision magnetic field measurements obtained during the triple landing of ROSETTA's lander PHILAE demonstrate that the Jupiter family comet 67P/Churyumov--Gerasimenko is unmagnetized (<3.1·•10 --5 A m 2 /kg).Main Text: Comets are believed to have been formed in the outer solar nebula beyond the snow line, where icy aggregates can grow in size to form larger bodies (1--3). Both the Kuiper belts as well as the Oort cloud are possible reservoirs of comets, with different processes leading to their formation (3). The dust--to--ice ratio of comets is of the order 1 (4, 5). Thus, a large fraction of cometary material is refractory material. Analysis of Stardust samples indicates a high contribution of Fe to this refractory material (6, 7). Up to 1% of the Fe content can be present as magnetite. Processes like accretional remanent magnetization (8) or detrital remanent magnetization (9) are possible candidates to form larger scale magnetic dust grains and cometesimals. These in turn allow the possibility for a comet to possess a larger scale remanent magnetic field.Detection of any cometary magnetization is difficult as a dipole field decreases with the cube of the distance from the object. Global magnetization of small solar system bodies can be detected either by spacecraft flybys or direct measurements on the surface. Whereas the flybys of the Galileo and Deep Space spacecraft at asteroids 951 Gaspra and 9969 Braille suggested the possibility of notable magnetization of these bodies (10,11), the distant flybys of the ROSETTA spacecraft (12) at asteroids 2867 Steins and 21 Lutetia provided an upper limit on the specific magnetic moment of 10 --6 Am 2 /kg (13, 14).Magnetic field measurements obtained during the flyby of the GIOTTO spacecraft at comet 1P/Halley offered an opportunity to estimate cometary magnetization as they revealed an almost magnetic field free (<50 pT) region around the nucleus (16,17). Taking into account the closest approach distance of 596 km to Halley's nucleus this corresponds to a formal dipole magnetic moment of < 5·•10 13 Am 2 or an upper specific magnetic moment of < 0.25 Am 2 /kg, an unreasonably large value indicating the l...

Abstract. The European Space Agency's spacecraft ROSETTA has reached its final destination, comet 67P/Churyumov-Gerasimenko. Whilst orbiting in the close vicinity of the nucleus the ROSETTA magnetometers detected a new type of low-frequency wave possibly generated by a cross-field current instability due to freshly ionized cometary water group particles. During separation, descent and landing of the lander PHILAE on comet 67P/Churyumov-Gerasimenko, we used the unique opportunity to perform combined measurements with the magnetometers onboard ROSETTA (RPCMAG) and its lander PHILAE (ROMAP). New details about the spatial distribution of wave properties along the connection line of the ROSETTA orbiter and the lander PHILAE are revealed. An estimation of the observed amplitude, phase and wavelength distribution will be presented as well as the measured dispersion relation, characterizing the new type of low-frequency waves. The propagation direction and polarization features will be discussed using the results of a minimum variance analysis. Thoughts about the size of the wave source will complete our study.

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