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A member of Spartan Gray Team wearing the Mark IV.
"You're the only ones who can use them, Petty Officer. Who else could we give them to?"
Dr. Halsey

The MJOLNIR Powered Assault Armor/Mark IV was the fourth version of the MJOLNIR Powered Assault Armor. The suit was issued to SPARTAN-II commandos on November 27th, 2525,[1] and was in service until August 29th, 2552, when it was replaced by the Mark V.



Created parallel to the SPARTAN-II Program, the MJOLNIR Mark IV Armor was a radical redesign to previous powered exoskeletons, streamlining their design into a practical purpose for use in the field. The brainchild of Dr. Catherine Halsey, the Mark IV represented her vision of creating a powered exoskeleton capable of taking full advantage of the physical capabilities of a SPARTAN-II. The MJOLNIR battlesuit is constructed in overlapping layers. It is a sealed system, capable of extravehicular activity or operations in toxic atmosphere. It is hardened against EMP and radiation, and has filters that are completely effective at removing toxins and bacteria from local atmosphere.

The armor's shell is composed of a multilayer alloy of remarkable strength and has been augmented with a refractive coating capable of dispersing a limited amount of Covenant energy weapon strikes. The suit contains a gel-filled layer underneath a thick black armored bodysuit. The gel layer regulates temperature and can reactively change its density. The inner skinsuit is made of a moisture-absorbing synthetic material linked to an environment control computer and the occupant's UNSC-issue neural interface. An upgrade to the standard Neural Interface is issued to all high ranking officers; another modified version of the neural lace is issued to all SPARTAN-IIs in the UNSC. This network translates electrochemical signals to digital code and routes them through an interface connection at the rear of the skull. Through this interface, the user's thoughts command the armor's movement and weapons; and input from the on board sensors comes directly to the user's mind. The synthesis of machine and mind is so fast that it is almost impossible to chart reaction time. Unfortunately the system is so reactive that normal human beings cannot use the suit without injuring themselves.[2] Only humans who have carbide ceramic ossification, a skeletal augmentation, given to a SPARTAN-II, can safely wear the suit.

Sandwiched between the external armor and the internal padding is the most devastating weapon the suit carries: a layer of reactive metal liquid crystal. Woven by molecular tools into a superdense layer, this layer is amorphous, yet it amplifies force, doubling lifting capability and increases reaction time by a factor of five.[3] Such technology did not exist when work began on the Mark I prototypes.

Because of these advancements, the design is more akin to an actual suit of armor, as opposed to a powered exoskeleton; the user moves the suit, and in return the suit moves the user. This allows for an incredibly compact design when compared to other combat systems. The armor contains numerous features including an integrated computer system which continuously monitors weapons, biological functions, and an intelligent motion-sensing radar. The suit also contains a built-in oxygen re-breather system that can provide air for up to 90 minutes. The suit's helmet also features imaging and video recording, and thermal sensors among other features.

In its final phase the MJOLNIR battle suit weighs half a ton, or 1000 LBs and when in use, is a fully neural-linked system and is currently the most advanced piece of tactical military hardware in human hands at that time.

Armor Variants

Throughout the Human-Covenant War, the Mark IV became a testing bed for new technologies and hardware to help improve the integrity of both the system and the efficiency of it in certain combat conditions. While some of these variants of the Mark IV MJOLNIR armor are rumors and have never been witnessed in the field, some have become common knowledge.


Mark IV MJOLNIR Powered Assault Armor/Advanced Hardware Prototype

The MJOLNIR advanced hardware prototype refers to a series of hardware and technologies developed for testing and incorporation into later versions of the MJOLNIR Armor. The advanced prototype is a single variant, that changes in appearance for research and development of future MJOLNIR components.[4]

Mark IV MJOLNIR Powered Assault Armor/C Variant

Main article: MJOLNIR Powered Assault Armor/C variant
The MJOLNIR Mark IV Close Quarters variant was developed to help improve survivability in close combat situations, specifically by looking at alternate methods of K dispersal and improving joint mobility. In addition to providing increased mobility, the suit offers additional capabilities including storage, and a dedicated port for attaching a close combat weapon.

Mark IV MJOLNIR Powered Assault Armor/V variant

Main article: MJOLNIR Powered Assault Armor/V variant
The MJOLNIR Mark IV Extra Vehicular Activity variant was developed to focus on increasing exo-atmospheric endurance and improving mobility in zero gravity. The movement could be controlled with the use of a T-PACK, or Thruster Pack, attached to the armor. This was not without dangers however; in case the T-PACK would malfunction, the wearer would be propelled into deep space where a rescue would be nearly impossible. The V variant of the MJOLNIR armor contains a reverse-angle camera on the helmet to allow for better view of anything behind the wearer. The helmet also contains a single-beam laser TEAMCOM system for communications. The only limitation of this variant is the mobility of the wearer is a fraction of normal movement.[5] Technologies developed for the Mark IV EVA variant were later applied for the V Variant of the Mark VI armor. However, this version was able to maneuver in vacuum without the original use of thruster packs.

Armor Components

  • Helmet: The MJOLNIR Helmet is one of the most vital aspects to the MJOLNIR system. It is made of Titanium and contains key features like a Heads Up Display that links to the brain and hands, and can identify equipment and display information about it when it is picked up by the wearer. Another feature is the direct neural interface system which connects to a SPARTAN-IIs neural implants. Two core processor chips are implanted into the subjects skull in the rear of the head. This is essentially comparable to an on board computer using parts of the human brain for processing - when the connector at the rear of the subjects head and receptors in the brain link to the helmets on board sensors it creates the neural link needed to move the MJOLNIR suit. The helmet also contains other equipment to protect and aid the user in hostile conditions. This includes: filters to remove toxins from the atmosphere, a supply to provide air to the wearer during EVA, thermal and motion sensors, communications, solar-powered lighting, and imaging and video gear.
  • Titanium Alloy Outer Shell: The outer shell of the MJOLNIR armor is comprised of a fairly thick titanium alloy. This plating covers the chest, arms, hip, legs, calf's, feet and hands. This alloy is very resilient, can take significant punishment, and is nearly impervious to small arms fire. While enough shots from armor piercing rounds will breach the outer shell, the suit can take a few glancing blows from them without compromising the armor. The outer shell of the all MJOLNIR suits is covered with a refractive coating to help disperse the heat experienced from Covenant energy weapons. However one or two direct hits from any Plasma weapon will compromise the armor plating.
  • Titanium Nanocomposite Bodysuit: Sandwiched between the external armor and the internal padding is a thick black armored bodysuit. This suit has numerous functions, small but vital to the safety and survival of the wearer. The bodysuit is made of a titanium-based material, making it very strong and yet very flexible. It also serves as another layer of protection against ballistics attacks and is coated with a heat resistant material to disperse heat from plasma weapons.
  • Hydrostatic Gel: Underneath the armored bodysuit is a gel-filled layer, this gel layer regulates the temperature of the suit and can re actively change its density to conform to the wearer's shape - the temperature inside the suit is controlled by the moisture absorbing cloth suit underneath the hydrostatic layer. The hydrostatic gel layer can also be pressurized to various levels to potentially save the wearers life should the wearer be subjected to high G forces or a high velocity impact; however, over pressurizing this layer can cause nitrogen embolisms.[6]
  • Reactive Metal Liquid Crystal Layer: Liquid crystal forms the inner structure of the suit. This reactive metal increases the strength, reaction time, mobility, speed, and all around physical performance of the SPARTAN-II. This layer of crystal, knitted together at a molecular level and fitted in between the outer plates and the inner padding. This type of crystalline improves reaction time, strength and durability; as such this layer accounts for over eighty percent of the MJOLNIR armors cost of construction and materials.
  • Magnetic Weapon Holder Strips: The suit contains a magnet system on the boots of the MJOLNIR suit that allow its wearer to stay attached to a metal surface in Zero G environments and can be toggled on or off by the wearer.
  • Pressure Seal: The Pressure Seal is a vital component to the MJOLNIR system, it keeps the system airtight, underwater or in space. The seal is very strong but will only break under extreme pressure, such as in a high velocity impact or when the Hydrostatic Gel has been over pressurized.
  • Automatic Biofoam Injectors: The biofoam injectors on the Mark IV is a port where a direct supply of biofoam or other medicines, must be administered from a standard military first aid kit when the wearer is injured, as the suit does not hold or generate its own supply inside the suit.
  • Fusion Reactor: The fusion reactor is the most essential part of the MJOLNIR System, as it provides power to all equipment on the MJOLNIR armor, the reactor is built into the suit and allows for nearly unlimited movement. The fusion reactor in all versions of the MJOLNIR armor are half the size of a normal fusion pack that conventional marines carry around[7]


The visual appearance of the MJOLNIR Mark IV has changed considerably every time it has appeared in fiction, this has led to confusion of whether these are separate variants or if the differences are simply aesthetic in nature.[note 1]


Halo: The Cole Protocol

The Cole Protocol cover design of the Mark IV depicts it as a very rough, yet familiar in recognition to later incarnations of the MJOLNIR armor. Its chest plate is more angular than that of the other versions, somewhat reminiscent of the Mark V. The helmet of the Mark IV shows hints in design to both the Mark V and Mark VI helmet. The shoulder pauldrons consist of a semi-circular plate of metal to allow more freedom of movement in the shoulder area. The back shoulder plates also appear to be removable to attach additional equipment.

Halo Wars/Legends

In Halo Wars the Mark IV resembles a combination of the Mark V and VI. The armor plating for the body, arms and legs are more akin to the Mark VI, with a sculpted chest plate and large shoulder pauldrons. The helmet in terms of design is almost exactly like the Mark V's. The armor also appears to contain magnetic holders for clips and weapons. In the Halo Legends episode The Babysitter, Cal-141 wears an armor similar to the version in Halo Wars though slightly less detailed. In Origins more Spartans are seen wearing this variation of the armor. This variation has appeared in more Halo media than the other variations leading to the conclusion that this is the standard Mark IV.[note 2]
Package MK IV.

The Package

In The Package, the Mark IV armor is almost visually identical to the Mark VI, despite some differences in the proportions and the details, such as having larger rougher shoulder pauldrons. There are slight differences in the helmets as well. Each Spartan's number is also printed on the chest plate of the armor along with other markings such as white stripes in the chest and the shoulders. This version also appears to have magnetic holders for weapons. Halo Waypoint states that The Package Mark IV is a specialized MJOLNIR armor, meaning that this variation could have been made for the mission to retrieve Dr. Halsey.[note 3]



  1. This section is here in part to bring together a difference of opinions pertaining to the design of the MJOLNIR Mark IV, using what information is available and combining them into a single as factual as can be entry. No official source has defined if the Halo Wars or Cole Protocol version is the standard variant. Please refer to the talk page for questions or issues.
  2. Halo Wars portrays the Mark IV with energy shields. This is a non-canonical artistic liberty intended to enhance gameplay, much like the stamina mechanic of Halo 3: ODST.
  3. In Halo: Legends many of the designs for characters, armor and so forth are portrayed with considerable artistic license and may or may not be embraced as canon. For example, The Fall of Reach states in that the MJOLNIR armor does not bear any rank insignia. The reason the SPARTAN-IIs' service tags appear on the chest plate in The Package is essentially to inform the viewer who is who. Halo Wars and The Babysitter show the Spartans with personalized insignia painted on their armor; this artistic liberty is partially explained in an interview with Graeme Devine, the lead designer of Halo Wars.


  1. Halo: The Fall of Reach, Page 113
  2. Halo: The Fall of Reach Chapter 13, page 115
  3. Halo PC Strategy Guide Page 5
  4. Halo Encyclopedia Page 88-89
  5. Halo: Ghosts of Onyx Chapter 3, page 49 and 50. Chapter 4, page 57.
  6. Halo: First Strike Chapter 2, page 13 Halo: Ghosts of Onyx Chapter 1, page 36
  7. Halo: The Fall of Reach Chapter 13, page 114; chapter 27, page 248
Types of Armor
UNSC Marine BDU (Vest | Helmet | Boots)ODST ArmorMarine Vacuum SuitBlack Body Suit
MJOLNIR Armor (Mark I | Mark II | Mark III | Mark IV | Mark V | Mark VI | Armor Permutations)
SPI Armor (Mark I | Mark II)Hayabusa Armor
Covenant Sangheili Combat HarnessJiralhanae Power ArmorUnggoy Combat Harness
Forerunner Combat Skin

This article uses material from the "MJOLNIR Powered Assault Armor/Mark IV" article on the Halo wiki at Wikia and is licensed under the Creative Commons Attribution-Share Alike License.


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