Only Friday's relegation vote can save Motherwell now after a ninth defeat in ten matches confirmed that they will finish the season at the bottom of the SPL.
Having fallen 3-1 behind not even a late penalty from top scorer James McFadden could alter the result and when substitute Richard Offiong headed wide with four minutes left Motherwell's last hope had gone.
Well started the game as strongly as they finished it and carved out a chance in the opening minute when a Steven Hammell free-kick was headed wide by McFadden.
The home side deservedly took the lead in the 16th minute as McFadden raced to the byline and cut the ball back for David Clarkson to sidefoot home from close range.
But Motherwell stayed in front for only three minutes with Leigh Hinds following up his equaliser against Partick Thistle the previous week by thumping a low angled shot passed Francois Dubourdeau and into the far corner of the net.
The French goalkeeper could not be blamed for that but he was found wanting nine minutes later when former Motherwell defender Eric Deloumeaux embarrassed him with an audacious chip from well over 30 yards.
Aberdeen sensed more goals and soon grabbed their third as another piledriver from Hinds was parried one handed by Dubourdeau allowing Paul Sheerin to tuck away the rebound.
Motherwell gritted their teeth again at the start of the second half but it was obvious that luck was not on their side when Hammell's goalbound deflection was cleared off the line by Steve Payne.
More solid defending denied McFadden at the end of a brilliant solo run and even when the Scotland star finally managed to find an opening, defender David Partridge sent a free header over the top.
With 18 minutes left Aberdeen keeper Peter Kjaer dived full length to push away a stinging drive from Keith Lasley as Motherwell battled to launch a grandstand finish.