The first photographs of a new and ominous crack in Greenland's enormous Petermann Glacier were captured by a Nasa airborne mission at the weekend.
Nasa's Operation IceBridge, which has been flying over northwest Greenland for the past several days, took the photos after being provided coordinates by Stef Lhermitte, a professor at Delft University of Technology in the Netherlands, who had spotted the oddly located chasm by examining satellite images.
The Nasa pictures make clear that a significant new rift has opened near the centre of the glacier's floating ice shelf - an unusual location that raises questions about how it formed. Moreover, this crack is not so distant from another much wider and longer crack that has been slowly extending toward the shelf's centre from its eastern side wall.
Nasa also noted another feature in the ice that it termed a "medial flow line" that, it said, "may exert a stagnating effect on the propagation of the new rift toward the older one". So it remains to be seen just how much, and how rapidly, the new rift - which has only just been discovered - could undermine the floating ice shelf.
Two prior ice islands broke off the glacier in 2010 and 2012.