On the "Halo" level of Halo 3, what is that glowing orb inside of the...

[halo 3]

...construct. It has fragments of speech. I found it after you leave the Pelican to find 343 Guilty Spark in side the construct to destroy the halo. Before you jump off the first ledge when you turn aroun their is a small crevice in the ice. Once inside you find the glowing orb with the fragments of speech.

 

[VileHazerd]

They're called terminals and unlike the skulls, are located on just three levels: 'The Ark', 'The Covenant' and 'Halo'. The terminals tell a back story of Halo. Each with their own story to tell about that mysterious race and their fight against the flood. There are 7 in total.

 

[FOXY]

I dont really remember where the terminal is on that level... but, It sounds like the terminal on that level, from your description