What are dark streaks on the wings of the aircraft near the engine?

[RandomGuy88]

My question is referring to the first picture of the SR-71 on wikipedia.

http://en.wikipedia.org/wiki/Sr-71

What are those dark streaks on the wings of the aircraft near the engine?

 

[Antiphon]

That's jet fuel leaking out of the seams. The SR-71 was designed to "seal up" at full speed through thermal expansion at Mach 3+. It has no fuel tanks in those sections of the wings. The fuel is stored directly in the bulkhead to save weight.

 

[Cyrus]

Keen observation!

 

[Phrak]

That's jet fuel leaking out of the seams. The SR-71 was designed to "seal up" at full speed through thermal expansion at Mach 3+. It has no fuel tanks in those sections of the wings. The fuel is stored directly in the bulkhead to save weight.

You sparked my interest. I know the fuel is rather thick. It turns out to be JP-7. But check out this Wikipedia quote: "SR-71 development began using a coal slurry powerplant,"! I never would have guessed that one.