Rosetta, Philae and Comet 67P/Churyumov-Gerasimenko.

[lajoswinkler]

Who says the thing did not actually look like that back then? It seems unlikely, but we don't know what happened.

It couldn't. All that mass would have to escape, and we know, by observation, that such carving releases of ices didn't happen.

[Camacha]

It couldn't. All that mass would have to escape, and we know, by observation, that such carving releases of ices didn't happen.

It couldn't what? And, remember, the same mass could make different shapes too.

[Aningaaq]

Well my question went unanswered on reddit but you all may find some interesting new information here: http://www.reddit.com/r/space/comments/2mofoz/im_emily_lakdawalla_planetary_evangelist_for_the/

[Camacha]

Ah, too bad. I am really pretty curious now.

Edited November 19, 2014 by Camacha

[Aningaaq]

Ah, too bad. I am really pretty curious now.

It will be a long time before we see any radargrams or other CONSERT data (too much to ask for the general public to understand it). Hopefully some word on it soon though. I'll keep my eye out...

[lajoswinkler]

It couldn't what? And, remember, the same mass could make different shapes too.

It couldn't look much different. Why would it make different shapes? It's not near anyone's Roche limit. It's a lump of ices and rocks. It goes around the Sun and it's slowly erroded by sublimation over the eons. 10 years is nothing. It's a ridiculously small amount of time for comets in such orbits.

[Aningaaq]

Here is another chance for some of us to ask questions to the Mission Engineers:

Engineers from ESOC and the Lander Control Centre will take part in a reddit AMA (Ask me Anything!) on Thursday, 20 November 19:00CET start. More details here shortly.

I suggest preparing your question in advance and posting it as soon as the thread begins. I'm guessing there will be a lot of replies like the last Rosetta related AMA. Good luck! I will be asking about CONSERT (lander orientation and a few other data related things).

[Camacha]

It couldn't look much different. Why would it make different shapes? It's not near anyone's Roche limit. It's a lump of ices and rocks. It goes around the Sun and it's slowly erroded by sublimation over the eons. 10 years is nothing. It's a ridiculously small amount of time for comets in such orbits.

I assume it was obvious that I am just having a little fun with it, though you dismiss it a little too easily. Who says comets are not so fragile and unstable that Jupiter shifts it around, or the sun at perihelion. Don't forget that this comet has a very short orbit time and that its orbit has been shifted around a couple of times in recent history.

Good luck! I will be asking about CONSERT (lander orientation and a few other data related things).

Yes please. I need this now.

[hzigy]

A little something that a friend of mine made for fun: http://vimeo.com/112319984

[Aningaaq]

A little something that a friend of mine made for fun: http://vimeo.com/112319984

That was unexpected and hilarious! Good stuff!

[lajoswinkler]

I assume it was obvious that I am just having a little fun with it, though you dismiss it a little too easily. Who says comets are not so fragile and unstable that Jupiter shifts it around, or the sun at perihelion. Don't forget that this comet has a very short orbit time and that its orbit has been shifted around a couple of times in recent history.

People are so serious around here so I thought you were, too.

Comets are fragile, but there's no evidence it was pulled around in the last 10 years. It was discovered in September 1969 and we know very well its orbit and the changes it has experienced during all these decades. It was never close to anyone's Roche limit so there is absolutely no reason to think that it has significantly changed its shape - probably in the last few millenia, and certainly not in the last decade.

[Aningaaq]

People are so serious around here so I thought you were, too.

Comets are fragile, but there's no evidence it was pulled around in the last 10 years. It was discovered in September 1969 and we know very well its orbit and the changes it has experienced during all these decades. It was never close to anyone's Roche limit so there is absolutely no reason to think that it has significantly changed its shape - probably in the last few millenia, and certainly not in the last decade.

Well, we may have some new insight about the solar effects on a comet eventually with this mission.

By the way, I read in an article that Philae will officially be dead when the comet is about 2 AU away from the Sun. The Rosetta tracker says that will occur at the end of March 2015. Does that sound right? Is it possible that Philae could recharge before then for some more science?

[KerbMav]

Is it possible that Philae could recharge before then for some more science?

That is what they are hoping for.

[lajoswinkler]

Well, we may have some new insight about the solar effects on a comet eventually with this mission.

We will, but it's impossible for a comet to change its shape so dramatically in 10 years. I honestly don't know why we're discussing this, it's dumb.

By the way, I read in an article that Philae will officially be dead when the comet is about 2 AU away from the Sun. The Rosetta tracker says that will occur at the end of March 2015. Does that sound right? Is it possible that Philae could recharge before then for some more science?

ESA did reposition Philae a bit, so it's very much possible it will receive enough energy to do more experiments.

[Camacha]

We will, but it's impossible for a comet to change its shape so dramatically in 10 years. I honestly don't know why we're discussing this, it's dumb.

Who knows what is possible? Don't forget the gravitational pull is almost negligible, which means it goes for the material of the comet too, which in turn makes shifting around material easier. We also still have little clue what exactly the outgassing of a comet means when it comes closer - we only have seen it at distances that resulted in that clueless approximation that started this discussion. Even a slight push from the gas - which we know changed its orbit recently - could push large amounts of mass around.

Don't forget that the gravity is several hundred thousand times weaker than on Earth, which means even a human should be able to lift millions of kilos of material on 67P.

[Kryten]

That's a comparison of comet Tempel 1 during the 2005 Deep Impact flyby and the 2011 Stardust/NEXT flyby; it's in a roughly similar orbit to 67/P. Does it look like it'd be unrecognisable after twice that time to you?

[Camacha]

Does it look like it'd be unrecognisable after twice that time to you?

That rather depends on whether it is a similar comet in other areas too Again, I am not all too seriously claiming that the comet changed dramatically (because I don't think so), but I do feel you should be careful not to jump to conclusions.

[SuperFastJellyfish]

We will, but it's impossible for a comet to change its shape so dramatically in 10 years. I honestly don't know why we're discussing this, it's dumb.

I know that English isn't your first language and that you're knowledgeable, but you throw absolutes(e.g. impossible, never, always, etc.) around on this forum as if you were some omnipotent being. You don't know every possible scenario that could happen so don't suppose you know impossibility. If you want to be taken seriously, you should find another dismissive tool. Just friendly advice from an avid science forum lurker.

[Aningaaq]

That rather depends on whether it is a similar comet in other areas too Again, I am not all too seriously claiming that the comet changed dramatically (because I don't think so), but I do feel you should be careful not to jump to conclusions.

You are right though. If we knew everything about comets and their change over time then why would we be studying them? I suppose a hypothesis claiming that comets cannot change dramatically over 10 years is a bold one that requires quite a significant amount of data to back up. I don't think anyone can make any definitive conclusions so far so I think Camacha has a point here that we should be open minded about the possibilities...let us not close any doors just yet!

By the way, my questions once again went unanswered. Here is what I asked about CONSERT "A maximum of 20 complete acquisition sequences were hoped for under optimal conditions (Herique, Lasue, Rogez, Zine, Kofman 2012). It was known that less optimal conditions (not enough solar light for recharging batteries) would limit the total acquisition sequences. My first question is: Did the limited amount of power severely limit the total acquisition sequences? If so, about how many occurred? If not all have occurred yet, are acquisition sequences planned for when there is more information about the Long-Term Science Mission and power availability? My last question is if the orientation of Philae is an issue for an instrument like CONSERT?"

I guess that 1) the engineers didn't have time to answer and or 2) they don't have a clue or are not allowed to disclose such information. I am probably asking the wrong people. I could shoot off an email the principal scientist investigators about this but I don't know French and I doubt they have time.

Regardless, I'm willing to bet that 20 CONSERT acquisition sequences was very optimistic. But...then I read an article saying that the majority of CONSERT data would occur during the "Long-Term Science" mission. This is when Philae would be relying on solar energy to conduct science. Since a complete acquisition sequence could be perhaps equated to a complete orbit by Rosetta then it might be safe to say that CONSERT won't have much data to work unless Philae gets more sunlight... The principle scientists behind CONSERT said that it is a "one shot" instrument and I'm beginning to wonder if that shot was a miss.

[KerbMav]

Hmm... how difficult would it be to tell Rosetta to keep 67P between itself and the sun ... ?

[Laie]

By the way, I read in an article that Philae will officially be dead when the comet is about 2 AU away from the Sun.

That was the original plan: even with Philae sitting in a well-lit spot, the sunlight wouldn't suffice anymore when the distance is greater than 2AU.

With where it's actually sitting, it should have enough sunlight to operate once it gets closer to the sun. However, for this to work the battery has to become warm enough; and without electrical heating, this, too, has to happen by sunlight. As I understand it, there's little doubt about having enough light for electricity generation in a few weeks' time; the question is whether the lander becomes warm enough so that the electricity may be used. If that happens, the probe can be powered up and will remain powered up until (duration of sunlight per day * intensity) falls below the threshold again.

If they can't find a way of shifting it's position, the final poweroff will happen a lot sooner than at 2AU.

[lajoswinkler]

Who knows what is possible? Don't forget the gravitational pull is almost negligible, which means it goes for the material of the comet too, which in turn makes shifting around material easier. We also still have little clue what exactly the outgassing of a comet means when it comes closer - we only have seen it at distances that resulted in that clueless approximation that started this discussion. Even a slight push from the gas - which we know changed its orbit recently - could push large amounts of mass around.

Don't forget that the gravity is several hundred thousand times weaker than on Earth, which means even a human should be able to lift millions of kilos of material on 67P.

I know it's impossible for a 4 km lump of icy rocks to look completely different in 10 years as in "now it looks like a lump, and now it looks like two lumps connected by a neck".

I don't really think you understand the work (in physical sense, W) needed for something like that to occur. The comet was never close to any body in 10 years. The only thing affecting its shape was sublimation, and we know it wasn't serious because it was discovered in 1969 and it never expelled much gas. It takes very little icy matter (compared to the mass and volume of the comet) to make even a spectacular coma and tail. This comet is a local one, with aphelion at around Jupiter's distance, and perihelion at around Mars' distance. For as long as it has been observed, it was very quiet. The amount of matter released from the surface is very small, which is expected. This comet was spinning around the Sun since the nebula has collapsed into a protostar. If it was so active, it wouldn't survive this day as any icy body. All the volatiles would be long gone.

There is no concieveable mechanism in the realm of physical laws that would turn its shape from Hubble's approximation into the observed comet we're seeing today.

I know that English isn't your first language and that you're knowledgeable, but you throw absolutes(e.g. impossible, never, always, etc.) around on this forum as if you were some omnipotent being. You don't know every possible scenario that could happen so don't suppose you know impossibility. If you want to be taken seriously, you should find another dismissive tool. Just friendly advice from an avid science forum lurker.

On the contrary, I pay a lot of atention to the style of my writing. When I use absolutes, which is rarely, there's a very good reason behind it. I'm not really sure most people reading this thread and commenting understand what I'm arguing against. I'm saying that the comet such as 67P can not change its shape from what Hubble telescope data analysis predicted into the duck-shaped 4 km double bulge we're seeing today using Rosetta. That's all. Nothing else.

[Athlonic]

How about bringing it down here for more science ?

[Streetwind]

That would take a loooot of claws with parachutes!

[Camacha]

Regardless, I'm willing to bet that 20 CONSERT acquisition sequences was very optimistic. But...then I read an article saying that the majority of CONSERT data would occur during the "Long-Term Science" mission. This is when Philae would be relying on solar energy to conduct science. Since a complete acquisition sequence could be perhaps equated to a complete orbit by Rosetta then it might be safe to say that CONSERT won't have much data to work unless Philae gets more sunlight... The principle scientists behind CONSERT said that it is a "one shot" instrument and I'm beginning to wonder if that shot was a miss.

I think I heard talk of three measurements (what you call acquisitions I think) were done and that this was a good result. I don't have any sources that confirm this at the moment, it was again part of that torrent of information the past couple of weeks and I might be mistaken.

I know it's impossible for a 4 km lump of icy rocks to look completely different in 10 years as in "now it looks like a lump, and now it looks like two lumps connected by a neck".

I am having a hard time taking you serious when you make these kinds of strong stances without much definitive evidence. We know so little about comets, how they work and how they vary from one comet to the next. This is the very reason we went there.

I don't really think you understand the work (in physical sense, W) needed for something like that to occur. The comet was never close to any body in 10 years. The only thing affecting its shape was sublimation, and we know it wasn't serious because it was discovered in 1969 and it never expelled much gas.

You don't call the fact that they think 67P's rotational period was changed by this phenomena relevant? Maybe it changed shape from a ball into the current form through that process and the larger shape slowed the rotation down through the conservation of angular momentum. I doubt that might be the case, but I don't have enough evidence to dismiss it and it is somewhat plausible. The energy could be provided by either gravitational perturbation or the sun.

I'm saying that the comet such as 67P can not change its shape from what Hubble telescope data analysis predicted into the duck-shaped 4 km double bulge we're seeing today using Rosetta. That's all. Nothing else.

I think you understand what we are arguing against - science is all about evidence and unless you have enough data to disprove a hypothesis, you cannot be this adamant about it. Well, you can, but you'd be wrong.

Again, I am just having a little bit of fun with it.

Edited November 21, 2014 by Camacha