Couloir des Cosmiques

From the top of the Aiguille du Midi tram, descend the well-marked ridge (east) well, used for access to Vallée Blanche. This first part is done carrying your skis, crampons may be useful. Descend a first slope (east), then via not very steep slopes (southwest), you reach the base of the southeastern wall of Aiguille du Midi and skirt it without losing too much altitude. The go up to Col 3593 located between the Simond shelter and Cosmiques refuge.

From the pass, move towards the west between rocks to approach Couloir des Cosmiques as best as you can. Depending on the snow conditions, a small rappel may be necessary to enter the corridor. Descend it while remaining on the right bank until a small ridge where the corridor is divided into two branches. Take the right branch and follow it until the bergschrund which can be crossed fairly well depending on the year. Take foot on the Bossons glacier. Notes: it is also possible to descend the left branch which is less direct to reach Bossons glacier.

Return to Plan de l’Aiguille: depending on the year and snow conditions the descent of Bossons Glacier can be more or less difficult. - If the glacier is closed, descend the right bank directly (large crevasses). -Otherwise, return in its centre (west) while possibly climbing and descending as best as you can between the crevasses (N). Around 2600 meters, return towards the right bank of the glacier. Leave it around 2530 meters to head (NE) under the north face of Aiguille du Midi (do not to remain too near the wall, stone falls and possible avalanches). Go up between fifty and one hundred meters (seal skins useful) then continue the traverse under Aiguille du Midi to take foot on Pélerins glacier that you traverse (N) towards the Plan de l’Aiguille tram station (2310 m).