Marciano tipped substitute Christy Manzinga strike on to the bar in the 79th minute.
Hibernian also hit the frame of the goal through Florian Kamberi but otherwise rarely threatened in a tight Ladbrokes Premiership encounter.
Ross MacIver was handed a first start in the central position, while Christian Ilic made his first start since the opening day of the league campaign.
Tom James was drafted in for his first game since Paul Heckingbottom was sacked and the right-back struggled in the opening stages, with James Scott getting the better of him several times. Scott curled just wide of the far post after cutting inside past the former Yeovil player.
Hibs were playing with two strikers in Christian Doidge and Kamberi and two wingers in Martin Boyle and Daryl Horgan and they occasionally looked dangerous on the break without carving out a shooting chance in the first half.
Despite the attack-minded players, Hibs got plenty of men behind the ball as Motherwell dominated possession.
The hosts' first-half shots generally fell from long range. Liam Polworth fired just over from 25 yards, Allan Campbell sliced wide from further in and Jake Carroll had a 20-yard free-kick beaten away by Marciano.
The game got ill-tempered towards half-time. Hibernian midfielder Stephane Omeonga escaped a second yellow card after sending Liam Donnelly crashing to the deck with a mid-air foul, and the Motherwell man was booked for a revenge tackle moments later.
Doidge was then let off with a yellow after catching the Northern Ireland international with an elbow.
Hibs created their best chance early in the second half after Motherwell lost possession just inside their own half. Horgan drove forward and had a shot palmed away and Boyle crossed for Kamberi to send a diving header against a post from close range.
Motherwell stepped it up. Scott had a shot saved from a tight angle and Donnelly had an effort deflected wide before Manzinga saw his shot tipped on to the bar by Marciano after Campbell had won the ball and put Hibs on the back foot.
Another substitute, Mikael Ndjoli, got in behind but his cross was kicked away by Marciano as Hibs survived late pressure.