Thank you all the observers who have been contributing to the project of late. You have done well.
Having lots of contributions enables us to confirm even very weak outbursts as can be seen with the March 6th event.
Here's a close-up of the last 4 out of 5 mini-outbursts:
MISSION 29P has been going 11 years to date during which we have witnessed 254 outbursts, 57% of which have been of the mini-outburst variety.
On average we cover 82% of each apparition, losing 18% to solar conjunctions.
That means that on average 29P has exhibited 28 outbursts per annum - FOUR times the number that are claimed to take place according to Wikipedia!
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We have detailed observations of the rise in brightness after about 10 of these and in all cases it appears that the active ejection stage only lasts a matter of minutes (max. ~10 min) after which we see the expanding optically opaque ejecta cloud increasing in size and brightness for up to 20-30 minutes. Then further expansion renders it optically transparent after several hours when maximum brightness is reached.?
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In NO case out of >250 outbursts do we see jets develop, so when a fissure does appear it promptly empties its ejecta into the vacuum of space in one short process before resealing. This behaviour is characteristic of a classic cryovolcanic eruption in which a fluid cryomagma exists at a positive pressure beneath a consolidated crust. The rapid expansion of gas and boiling of the liquid fraction during the ejection phase extracts large amounts of heat energy from the remaining cryomagma, which quickly cools and solidifies bringing the eruption to a halt. We have also seen that strong outbursts tend to trigger further strong outbursts within a day or two, suggestive of debris falling back and fracturing the crust, or precipitating low-albedo dust that causes sealing material to warm up, soften and melt provoking the triggered event.
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29P appears to be entering a new phase in its behaviour when we start to see strong outbursts only coming from one side / hemisphere of the nucleus. This phase may last another 3 years. If so, we will have a good opportunity to verify the previous 57.7-day rotation period that used the 2010-2014 observations. Maybe the retro effect of eruptions will have slowed it down slightly?
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Do keep up the good work everyone,
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Richard?
Richard Miles