CH252 helmet

The CH252 Helmet is the standard issue helmet that the UNSC use for the Marines. It was most likely developed at the end of the year 2552 because it isn't shown in Halo: Combat Evolved.

In Halo 2, both regular Marines and ODST Helljumpers wear versions of the helmet - Marine helmets are painted green, while ODST helmets are painted black, like their combat suits, and feature a faceplate complete with HUD display. The standard helmet weighs about 3.3 pounds according to crates found in the game. Also, in Halo 2, you can shoot off their helmets. They will not pick them back up.

The Marine pilot helmet is a Version of this type of helmet. This was most likely manufactured around the end of 2552. It is not seen until Halo 3. This helmet is almost a replica of the ODST helmet. It does have a HUD and weighs about 4 pounds. It is not Black like the ODST helmet. Instead it has a Clear visor and is painted green.

Trivia
The helmet of the Johnson's pilot on the opening cinematic of the level "The Ark" has a Forerunner like symbol on it, like the plasma grenade of Halo CE