Rising a mile high and up to 5 miles wide, the impact plume of the spent Centaur rocket was observed by the NASA LCROSS shepherding probe before it travelled through the cloud of dust and crashed 4 minutes later.
The lack of an observed dust plume has been the cause of much confusion to people who watched the events unfold in the early hours of October 9th. NASA publicised the impact event as if it was going to be an explosion of dust (and possibly ice), observable from telescopes on Earth. To say the mission finale was a disappointment is an understatement.
Following the impact, NASA responded by saying that although infrared images proved the Centaur crashed on target (and a 20 meter-wide crater was created), the lack of an accompanying plume could mean that the mass hit the side of a crater (therefore blasting debris at an angle), or it hit a region devoid of dust and water ice, or the plume was simply less obvious than expected. Now that NASA has released new images of the impact, it would appear the latter may be the case; the plume was just less spectacular than the promo videos depicted.
Nine instruments on board LCROSS captured impact sequence, but until now it was unknown whether an impact plume occurred. Now NASA has confirmed that an impact flash, plume and crater were all generated.
“There is a clear indication of a plume of vapor and fine debris,” said Anthony Colaprete, LCROSS principal investigator. “Within the range of model predictions we made, the ejecta brightness appears to be at the low end of our predictions and this may be a clue to the properties of the material the Centaur impacted.”
So the number-crunching continues as we wait to find out whether water was contained within that plume. However, judging by the faint cloud of ejecta, I’m thinking dreams of a H2O reservoir in Cabeus crater might be short lived.