Subject: Rosetta Mission: 67P Photo Using NAVCAM
From: Alex Kemp
Date: Wednesday, 19 November 2014 00:04:25 +0000
To: Oliver Kemp, Micaela Kemp, Liisa Kemp, Davin Kemp

NAVCAM image of part of 67P (November 2014)

You are getting this photo just because I thought that it looked great.

It was taken by the NAVCAM camera (I believe that this is the same one as took the photos in my last email) at 18:08 GMT on 26 October 2014. This is a part of the larger lobe of 67P (Philae has possibly ended up on that lobe). The camera is about 7.8 km from the surface, and the whole area pictured is 857 x 857 m. The photo is 1024 x 1024 pixels, and each pixel therefore shows an area 83.7 cm square.

he rocks & dust that you are looking at are reckoned to be as old as this solar system:- 14.5 billion years (that is one of the big reasons for wanting to go to a comet in the first place, as current theories of the formation of this solar system reckon that they are amongst the bits left over after the sun & the planets were made - but mostly unchanged). However, it is more likely to be frozen water-ice with sprinkles of angel dust than rock...

Earlier measurements have shown that the overall density of 67P is 0.4g/cc (grams / cubic cm). That is much too light to be rock, although it is possible that the lower layers are much more porous (and therefore less dense) than the sintered surface (due to exposure to the Sun). Early results from MUPUS--before the hammer broke--suggested a layer of dust 10-20cm thick on the surface with very hard water-ice underneath; indeed, a tensile strength similar to sandstone. It was much harder than expected, although still within the known spectrum for ice.

The very clear layering in the photo above needs to be explained. Unfortunately, the COSAC+SD2 combo failed. The sample-drills worked fine (the drills went to full extension + returned), but the latest info is that nothing got delivered to the ovens. APXS (the Alpha Particle X-ray Spectrometer) which is designed to provide information on the elemental composition of the surface, also seems to have partially seen a signal from its own lens cover - which could have dropped off at a strange angle because Philae was not lying flat.

In the face of all these glitches, COSAC found organic molecules (molecules that contain carbon) within the thin atmosphere. That also leads to the last comment in this post:- in the background at the top of the photo you can see a faint stream of gas and dust. As each moment passes the comet gets closer to the Sun & it gets a little hotter. There are circular spouts on the comet’s surface which are the source for these streams and, clearly, an active region is nearby.

Alex Kemp