[X] My Assistant

[Guest_Richard Trigaux_*]

Hello all


This spectrum,, obtained by Cassini's ion and neutral mass spectrometer, shows a lithium ray (ordinate= 7)

and also this figure, a mass spectrogram from the same instrument, also show lithium (abscissa=7)

First of all, I wonder if these rays are real, or if they are intrument defects or artifacts. Otherwise only lithium could have a mass of 7 daltons.

The presence of lithium is not really astonishing by itself (there was sodium in Io's atmosphere) but it implies that Titan's atmosphere would be much more reducing than with hydrogen alone. Also there are no traces of oxygen or water in these spectrograms (oxygen and water are linked through oxydation and photo-dissociation)

In a medium where there is an excess of hydrogen, all the available oxygen is reduced, so that this medium becomes reducing. But lithium is much more reducing than hydrogen, so it would take the oxygen in priority. So the presence of lithium implies that there is a source of lithium in excess over Titan's atmospheric oxygen, and that Titan's atmosphere is much more reducing than with only the presence of hydrogen and hydrocarbons...

Where could this lithium come from? It looks as if Titan's hydrogen would be formed directly from an interstellar cloud, and thus would contain some lithium. But if so, it would also contain helium... which is nearby absent! Right on the countrary the mainstream hypothesis is that this hydrogen comes from the photo-dissociation of methane. Maybe there would be some volcanism, releasing together methane and lithium. But this is incompatible with the presence of an ice surface or underground ocean, as lithium and water react violently.

So, if these rays are not instrument artifacts, they are a complete mystery. As far as I know, there was no comment on this.

Anybody have some idea?

Richard

[volcanopele]

Be very careful interpreting INMS data below 10 daltons. Much of the spectrum below that point is dominated by instrument noise (as you can see in the first graph). The numbers in the second graph are too low to really be meaningful, again, probably just noise.

[Guest_Richard Trigaux_*]

Yes volcanopele, you may be true, and in this case there would be no lithium, or at least no evidence of it. But I would prefer to hear such a statement from persons knowing the instrument, manufacturer or owner. However the first graph also shows a clear hydrogen ray at 2 daltons, which, as far as I know, was considered meaningful in further comments.

The only thing I see is that a ray of similar magnitude, marked "diacetylene", is spread between 50 and 55 daltons, while a ray marked "background" is not. (this "background" ray being very likely an instrument defect or calibration system). Like the "background" ray, and unlike the "diacetylene" ray, the "lithium" ray is not spread, leading to think that it may be too an instrument defect. But its intensity over time follows the general law, while the "background" ray is constant...

So I think it is difficult to guess the instrument limitations from the figures. Our only hope here is that somebody knowing it could reply to this thread. If anybody have some info, please...

[volcanopele]

Yes volcanopele, you may be true, and in this case there would be no lithium, or at least no evidence of it. But I would prefer to hear such a statement from persons knowing the instrument, manufacturer or owner. However the first graph also shows a clear hydrogen ray at 2 daltons, which, as far as I know, was considered meaningful in further comments.

The only thing I see is that a ray of similar magnitude, marked "diacetylene", is spread between 50 and 55 daltons, while a ray marked "background" is not. (this "background" ray being very likely an instrument defect or calibration system). Like the "background" ray, and unlike the "diacetylene" ray, the "lithium" ray is not spread, leading to think that it may be too an instrument defect. But its intensity over time follows the general law, while the "background" ray is constant...

So I think it is difficult to guess the instrument limitations from the figures. Our only hope here is that somebody knowing it could reply to this thread. If anybody have some info, please...

The instrument issue I mentioned is my recollection of a conversation I had with the INMS PI a few months ago. I can ask Roger again about it but I think he is in Crete for the Titan meeting (why can't I go to the cool places )