  The Rosetta lander Philae successfully landed on the nucleus of comet
67P/Churyumov-Gerasimenko on 12 November 2014. Philae is equipped with two gas
analyzers: The Cometary Sampling and Composition experiment (COSAC) and the gas
chromatograph and mass spectrometer Ptolemy. On 12 to 14 November 2014 both
instruments measured the organic composition of the comet nucleus material
through seven measurements in sniffing mode during Philae's hopping and at its
final landing site Abydos. We compare the temporal evolution of intensities of
several ion species identified by both mass spectrometers. For COSAC this is
the first analysis of the temporal behaviour of the measured ion species. All
ion species showed the highest intensities in the first spectra measured by
both instruments about 20 to 30 minutes after Philae's first touchdown at
Agilkia, and a decay during the six consecutive measurements at Abydos. Both
instruments measured a nearly identical decay of the water peak (m/z 18), and
also CO (m/z 28) behaved similarly. In the COSAC measurements the peak at m/z
44 decays much slower than all the other ion species, including the water peak.
In particular, the m/z 44 peak decays much slower in the COSAC measurements
than in the Ptolemy data. This supports our earlier interpretation that COSAC
for the first time analyzed a regolith sample from a cometary nucleus in situ,
while Ptolemy measured cometary gas from the ambient coma. The m/z 44 peak
measured by COSAC was likely dominated by organic species, whereas the peak
measured by Ptolemy was interpreted to be mostly due to $CO_2$. Ion species
heavier than m/z 30 tend to decay somewhat slower in the COSAC measurements
than in the Ptolemy data, which may be related to differences in the exhaust
designs between both instruments.
