While the Rosetta and Philae teams are busy planning the next activities for the spacecraft and lander, CometWatch continues with a new view of Comet 67P/Churyumov-Gerasimenko captured on 7 June 2015, several days before Philae’s wake-up call was received. This single frame NAVCAM image, taken at a distance of 203 km from the comet, has a resolution of 17.3 m/pixel and measures 17.8 km across.
Single frame NAVCAM image of Comet 67P/C-G taken on 7 June 2015 from a distance of 203 km to the comet centre. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
The comet appears with the larger lobe up, its ‘underside’ gloriously illuminated. Familiar features of the Imhotep region are visible at the centre, as well as parts of Ash towards the top left. The elongated depression of Aten is partly cast in shadow and lies to to the lower left, with parts of Khepry to its right.
The image was processed to bring out the comet’s activity, showing a multitude of jets – especially in the upper part of the image – but also the overall glow around the nucleus. Below the larger lobe, a beautifully delineated silhouette of the comet’s neck and smaller lobe stands out against the diffuse material in the coma of 67P/C-G.
Another NAVCAM image of the comet, taken by Rosetta shortly before receiving Philae’s signal on 13 June 2015, was published on Monday, alongside a status update on the operational aspects after the lander’s historic wake-up. A press briefing with members of the Rosetta and Philae team took place this morning at 09:30 CEST at the International Paris Air and Space Show, Le Bourget, and the replay is available here.
The original 1024 x 1024 image of today’s CometWatch is provided below:
Discussion: 8 comments
As 67P/C-G “rotates” on its axis, where is that axis pointed to in terms of Decl and RA (on the forward side of its movement in its elliptical path)? I suppose it precesses as well and will wobble much more as increased venting goes on and its morphology changes drastically, but for the most part you must be working off of some value. Thanks.
Sorry, back to the jets, here’s my question:
Looking at the jet column at roughly 11 o’clock, there are clearly two large jets rising from the comet surface. Each of these jets must be quite large at the base, many many meters across at least, and yet, they are both perfectly parallel until they merge into the larger column far above the comet. The directional accuracy required to maintain a parallel trajectory to distances far above the comet is mind blowing, especially when you consider their surface area at their base. So, how is this possible? Two perfectly aligned, many meters-wide jets originating from two separate surface areas, each one also many meters across, maintaining a perfectly parallel course?
Sovereign Slave, the best I can give you from mere visual impression and some general basics are sources of a mix of gas (by sublimation) and dust. The gas expands roughly concentrically away from the comet with a speed of several hundreds of m/s. It drags the dust. So the dust may be seen as a marker for the direction of the expansion of the gas into space.
The main sources of the jets seem to be the pits, according to the latest press briefing.
That’s of course not perfectly accurate, since the gas is rather dilute, therefore the inertia of the floating dust needs to be considered, too.
This wind tunel testing may give some idea:
https://www.youtube.com/watch?v=IIHFkp1aAOI
Thanks Gerald for the presentation of the sublimation basics. As I mentioned in the water ice detected post, would be great if before leaving the lab, the guys that were conducting the ice/dust/sublimation experiments also tossed in experiments related to the pressurization and jetting of the dust. Since the dust jets are such a prominent feature of the comet activity, seems some experiments would be in order.
Hi Claudia,
A beautifully haunting image, thank you!
Here again, no intrinsic visible light glow from any jets in the entire dark regions.
On another note, maybe to the right dept.:
Can someone impress upon the webmasters that the search button does not work except for only thread titles? I search Ramcomet and nothing turns up to see comments, even while on a thread I am in. Just look at the length of the tread ” Rosetta Lander Philae Wakes Up…” and try to ffind nd your own comment, LOL!
If this could be fixed, since I read EVERYTHING (rabidly, I might add… (Forever thank you ESA, from an ever lovin ESA NASA USA Space Coast Boy)… and only comment occasionally, it is very difficult to find recent answers to my few comments, in all the threads!
Thanks so much, I am in awe that you include us in this adventure to begin with! I hope to contribute some tiny thoughts outside of the box.
Another interesting image Claudia with as you say the jets strongly evident as well as the more diffuse glow you observe which silhouettes the lower part of the nucleus. We see a two dimensional image which makes the jets appear as a circular radial array and the brightness of the upper surface of the nucleus creates the illusion that they all originate behind the nucleus. In reality however we are looking at a three dimensional object and the jets we see are indeed a radial array but an approximately spherical one originating at places scattered over the bright surface as well as from behind it.
I would like to draw your attention to one jet in particular which has some very interesting features. It is in an upper left position of between 10 and 11 o’clock. It is distinctly separate with a darker zone on either side of it and with clearly delineated edges. Parallel edges too, at least to a distance of more than a kilometre. I would estimate it to be around 100 metres in width. If a jet with such a delineated edge had emerged as gas under pressure from
beneath the surface you would expect at its origin to find a similarly sharply defined surface feature. A hole into the interior. A hole 100 metres in diameter in fact, or perhaps a slot 100 metres long.
Rather than just surmising about this however Claudia perhaps we should start looking for these holes. You and Emily and probably Holger too, seem familiar with the surface regions by name and you comment here on the recognisable
features in this image. It should be possible to associate individual sustained jets with exact features on the surface. Perhaps your team has already been doing this.
In that context might I make the following observation. It is my impression on studying this image that the distinct jet I refer to above originates from a point on the bright surface that we can see. It is a clearly defined circular
crater with a bright interior and a darker raised rim. It lines up exactly with the jet in question, is somewhat isolated and has the appearance of a searchlight with a parallel beam. The impression is that the jet originates at the surface. I am sure you would recognise this crater and perhaps you have a name for it. I am sure also that you would be able to examine many views of it closely in your archive. Very valuable if you could look at it as a potential jet source. I would be interested first of all if you agree with my observation and then on any other comments you have, about this jet as well as about the general possibility of relating particular long term jets to particular surface features.
South pole structure looks crowned. On playing contrast and brightness, jetting extends up to crown’s tips. Jet density seem to suggest a surface, not a volume phenomena [like auroras].
That ‘crowns’ and ‘chimneys’ are electrically relevant.
This is absolute fiction: On consulting the photo library of first days of arrival could see that some ‘plateau’ concave structures were emitting some ‘blobs’.
When jetting start by ‘drops’? Or a different, unrelated phenomena?
That were the cold days of a timid Sun approaching to the after-party.