|Jupiter animation 8-March-2014 - possible impact??? by (Editting ALPO-Japan-homeapge:Oprator),Michel.J,mike wong,Glenn Orton,John H.Rogers|
------ Michel.J Report ----- This dark spot at about B"=32 is visible since February 16th on the my images and those I received for the JUPOS project.
It is retrograding at +0.8/d (see attached plate and graph). ------ Michel.J Report ----- ------ John H. Rogers Report ----- Thatfs indeed a notable and interesting dark spot: thanks to Dave Tyler for spotting it, and to Anthony and Michel for assembling those sets of images, and to everyone else who has observed it. Anthony and Michel have shown that it is a meteorological feature which developed over several weeks, although it was certainly worth investigating a possible impact origin for such a notable dark spot. From it's latitude of 32 deg.N, it's an anticyclonic dark spot. Attached is a more extensive set of images, with the feature(s) of interest marked. In deference to the people who provided the great majority of these images, and to professional interest in this, north is up in this set! But I can send a version with south up, or a version without labels, if required. This seems to be another example where small-scale but intense turbulence in the cyclonic belt gives rise to retrograding disturbance which feeds dark material into the adjacent anticyclonic zone. This is happening at other longitudes in the N. Temperate domain at present, in the aftermath of the 2012 NTB revival, as small cyclonic rifted regions produce dark material which comprises a eNorth Temperate Disturbancef in the NTZ [refs. 1 & 2]. It also sometimes happens in the S. Temperate domain, in the eSf. tailf of a dark STB segment, generating an anticyclonic dark spot [ref.3]. In the present case, the best images show a small turbulent outbreak developing in the NTB in early Feb., then the very dark spot developing f. it, initially on Feb.16 when you can see tiny dark spots enveloping a tiny white spot, which I suggest was an anticyclonic vortex. The small black arrowheads are suggested identifications of subsequent tiny dark spots which I think were arising from the turbulent outbreak (so small-scale that it is barely visible in some images) and retrograding to merge with the very dark spot, making it especially dark on Feb.21 and Feb.28 and thereafter. best regards, John ------------------------------- References to our recent bulletins:  2013/14 Report no.4 (http://www.britastro.org/jupiter/2013_14report04.htm)  Set of images sent out last month, showing the bright new outbreak in NTB (Ifll post an updated version soon).  eJupiterfs South Temperate domain: Behaviour of long-lived features and jets, 2001-2012f (http://www.britastro.org/jupiter/stemp2013.htm) ------------------------------- ------ John H. Rogers Report ----- ------ mike wong Report ----- here is a screenshot of the IRTF/CSHELL data viewer. gordy bjoraker is PI of our time at IRTF, and tilak hewagama the other observer. on the left you see a 5-micron image, on the right a 1.60-micron continuum image. we were imaging through clouds, and the instrument is designed for spectroscopy, so these are not the prettiest of images. the location of the feature is 33 +/- 3 deg N (planetographic) and 220 +/- 6 deg W (sys III). we do have some methane images at 1.64 microns, but we are still analyzing calibration issues with that. but combined with the pic du midi result, it seems pretty clear that this is not an impact. these were taken last night, UT march 8 at about 08:33. ------ mike wong Report ----- ------ Glenn Orton Comment ----- I've not seen Mike Wong's CSHELL images,
but it will be instructive to see the relative brightness temperature of the dark features.
We normally see dark-albedo regions as relatively bright at 5 microns, although not as bright as genuine 5-micron 'hot spots'.
But there were plenty of dark regions, as I recall, in the SEB revival sequence where this was not at all the case.
------ Glenn Orton Comment ----- [Michel Jacquesson : Sevigny-Waleppe (Ardennes) France]
ALPO-Japan Latest Jupiter Section