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UNSC WARNING: This document, Ares IV, is property of the UNSC and is Classified [NOVEMBER BLACK], protected under Office of Naval Intelligence Security Protocol 1A. Disclosure of its contents to, or access or alteration by, personnel with a clearance level lower than GAMMA THREE is an offense punishable by court(s) martial and imprisonment or execution for treasonous acts. Failure to disclose confirmed or suspected breaches of security will be treated as complicity, and is punishable by dishonourable discharge and/or imprisonment.
Lieutenant Commander Michael Pomare, Office of Naval Intelligence, UNSCDF Navy
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Ares IV (Mu Arae d)
General Information



Mu Arae System

  • Mu Arae
Orbital Characteristics

1.35356 AU


1.38644 AU

Orbital Circumference

4.303 AU (643866534.44506629858 km)



Orbital Period


Satellite of

Mu Arae

  • Siren
  • Hydra
Physical Characteristics
Equatorial Radius

3390 kilometers

Polar Radius

3370 kilometers

Mean Circumference

40,041.47 km

Surface Area

510064471.32 km2

Land Area


Water Area



1.1 Earths

Mean Density

6068 kgm-3

Equatorial Surface Gravity


Sidereal Rotation Period

25 hours

Spectral Type


Apparent Magnitude


Surface Pressure

1 Atm


101.3 kPa (MSL)

  • Oxygen
  • Carbon Dioxide
  • Nitrogen
  • Hydrogen
  • Water vapour

Ares IV (also known as Mu Arae d or Tolatuih) was a Unified Earth colony in the Mu Arae System approximately 50.592 lightyears from Sol. Founded in 2433 by Earth-backed European colonial corporations, Mu Arae would become the UNSC's largest supplier of Iridium and Osmium, rare-Earth elements necessary in the construction of Shaw-Fujikawa Translight Engines, and a launch site for UNSC Navy, Marine and Army counter-insurgency operations among the Outer Colonies and later the Covenant incursion. Contact with the planet was lost in 2536, presumed to be an indication of a Covenant invasion of Ares IV and its subsequent glassing. Engagements among the Inner Colonies prevented an investigation into the planets fate, and Ares IV has remained somewhat of a mystery since then.

Physical Characteristics


Orbit and Rotation



Although Ares IV was deemed uninhabited during the initial surveys, this belief has since been conclusively disproven among the scientific community. Certainly no large multicellular organisms are extant, either floral or faunal, but the planet maintains a delicate biosphere of microscopic organisms of varying complexity, mostly unicellular although a small number of multicellular organisms are present. Many of these organisms appear to be more primitive than bacteria, and may represent an evolutionary leap between viruses and bacteria - the implications of this theory on the origins of life are tremendous, and was the reason for the establishment of the Kukulkan University of Biological Sciences, but it is their applications to terraforming methods that brought them the interest of the UNSC - one species in particular, C. errera, is capable of using methane gas in respiration, converting it into oxygen - the method it does this by still remains a mystery; Another, K. paulus, is commonly used by medical centers as a temporary secondary immune system, programming the organisms to attack specific viruses and bacteria that have eluded the best attempts of even modern medicine - the AIDS virus was wiped out by inoculations of cultured K. paulus. Some researchers use this to claim that the organisms are far more complex than their structure and behaviour would deem - various fringe scientific and religious groups claim that they are bioengineered terraforming agents used by an ancient alien species, though no strong evidence has ever been put forward.

The oceans of Ares IV are teeming with microscopic lifeforms, ranging from plankton-like photosynthesising multicellulars that use Mu Arae's light, to predatory multicellular or unicellular creatures, some of which have been observed working in unison to attack larger prey, or living symbiotically. Further down, near Ares' underwater geothermal hotspots, entire self-contained biospheres have evolved around specific vents, isolated from each other sometimes by only a few meters, but nevertheless have remained isolated for hundreds or thousands of years. The most fascinating aspect of Ares' underwater ecosystem is not that it is so immense, but that it is there at all. The majority of the planet's impact craters are found on the oceanbeds, and are calculated to have each released the energy equivalent of seven Hiroshima-class nuclear warheads. That the planet's microscopic biosphere has recovered to such a stunning degree is nothing short of astonishing.

Unfortunately, the same cannot be said of other species among Ares IV's prehistoric ecosystem. Fossil beds along the equator indicate a thriving biosphere with reptillian, mammalian, insectile and avian species all similar to Terran lifeforms, sometimes to an astonishing degree. These linneages appear 65.5 MYA to the end of Earth's Cretaceous period, before which no trace of life is found on Ares, and appears similar to the Minorcan fossil record, a phenomenon that has led many to conclude that the two planets were "Ark worlds" for an ancient civilisation, featuring the transplantation of desired Earth species to Ares and Minorca. Whatever species was extant then, with the resources to perform such a feat on such a scale, has not been discovered. Recent information indicates that the Forerunners performed a similar practice with Terran species, but Ares and Minorca predate the rise of the Forerunners by millions of years..




The 23rd Century presented unprecedented challenges to humanity. Overpopulation and the threat of famine on a global scale forced the newly-formed Unified Earth Government to sponsor a number of projects intended to alleviate this, ranging from genetic modification, to agricultural pods orbiting the planet, and more. The only option that ever received serious support from the UEG, however, was a colonisation effort intended to transfer some of the strain into nearby star-systems with possibly inhabitable planets.

Though certainly not the first colony, Ares would become one of the most important “frontier worlds.” Located in the Mu Arae star system, approximately 50 light-years from Earth, initial colonisation efforts were funded by members of the European Union, especially the Iberian Peninsula Union, and the Unified South American Republics, forming a strong link to the later colonist’s South American and Spanish heritage. As unmanned terraformer drones enhanced the planets already nearly ideal suitability to human occupation, the first colony ship, the UNSC Tanngrisner, carried approximately 1000 colonists intent on starting a new life there. First landing was made in 2487, where the planets first settlement was established, named Tlatelolco, and for a time became the planet’s capital city and only major port.


Over the next fifty years, colonisation of the world proceeded at an aggressive pace, fuelled by an extensive promotion campaign by Terran funding organisations eager to put forward their interests. For the large part, most colonists originated from South and Central America, as well as the United Spanish and Portuguese Peninsula, with the colony's dominant language a mixture of Spanish, Mexican and Portuguese, with elements of Nahuatl added to the concoction, creating a unique dialect. Many places on Ares IV are named after Incan, Mayan or Aztec figures or places, and the dominant architecture style is based upon the imagery of ancient Aztec temples, though excluding the images of debauchery and human sacrifice, mixed with popular Spanish tastes.

The second city would also eventually become the colony's capitol, formed on an island in the middle of one of Ares IV's many crater lakes. Named for the ancient Aztec capitol city, Tenochtitlan became a thriving harbour for river barges ferrying materials from the southern latitudes upwards, and eventually one of the planet's three space elevators was built in the city to facilitate the loading of these materials aboard orbital freighters. For more than forty years, Tenochtitlan was the largest and most prosperous city on the colony, with various districts breaking off into the smaller cities of Tlacopan and Cakchuah.


The rich fossil records of the planet were only discovered in 2390, and the planet immediately became of immediate concern to the scientific community. The possibility of extraterrestrial life "seeding" other systems with Earth life was tantalising evidence of our own "superiority." The interest sparked curiosity of the planets odd ecosystem, leading to the discoveries of dozens, then hundreds, then billions of unique species. A permanent scientific presence was set up, based in the city of Tenochtitlan Science Centre. The University of Tolatuih became a prominent centre of biological research and study.

The discovery of alien ruins in 2491 changed that.

The first ruins were discovered on the edge of the farming community of Tepeu. Uncovered by a Series 5 Jotun agricultural drone, the land was assessed by UNSC scientific advisors and deemed an area of military interest. The protection of the site from potential URF vandalism was the initial concern, but with the discovery of several working artefacts, specifically relics capable of creating artificial gravitational and magnetic fields efficiently, though mysterious, were promptly confiscated by the Office of Naval Intelligence for research. A military protection was set up to protect the site in the southern hemisphere, but no new technological discoveries were made. Eventually, the UNSC Firebase "Sarrissa" evolved into a staging ground for Naval and Marine response to URF threats in the nearby Outer Colonies.

In 2519, another excavation site was discovered, this time in the northern hemisphere. Another military outpost was set up to provide protection for the area, and to prevent curious colonists and rebels from making their own investigations. ONI Section III researchers supplemented civilian scientist personnel, and excavation of a large structure was begun in 2534. By 2537, approximately 7% of the structure was uncovered. Its status after that is unknown.

Lost Contact

The planets unusual electromagnetic field meant that periodically, every four years, electrical storms would play havoc with equipment, creating a communications blackout. These were tolerated because of the enormous potential the colony possessed to be a new Earth, but interfered with many colonial functions, such as the extra-planetary wide web and civilian and military communications.

In 2537, one of these storms began a year early, an unusual event. More unusual was its assumed duration. Weeks passed without contact being restored. Eventually, it was decided to send a reconnaissance Prowler to investigate. The UNSC Prowler Hunters Arrow returned with telemetry indicating several nuclear detonations had destroyed the major population centres, with the nuclear fallout already settling, and that no human or alien life signs had been detected. CENTCOM marked the colonist's fate down to a Covenant invasion, believing it had fallen to the enemy’s warships, using the nuclear weapons to take as many of the invaders with them, before the Covenant had moved on. The fact that the planet hadn't been glassed was a secondary concern, and enemy movements in the Inner Colonies shunted attention to saving the colonies that were left.

Current Status

Ares IV is famous in society as the only defeated colony world not glassed by the Covenant. As such, conspiracy theories circulate that it was a UNSC coverup for a secret military program. Others hold that it was defeated by aliens, just not by the Covenant. More put it down to a remnant of the URF, zealously striking any way they can, destroying the colony out of sheer spite. Currently, the Mu Arae System has a reputation similar to the Bermuda Triangle of Earth: Its dangerously close proximity to conquered Covenant territory makes it a tempting site for daredevil civilians with personal yachts to "joyride," risking attack by Covenant patrols. No civilian has ever landed on the planet - or, at least, no living civilian has ever done so. Military personnel are forbidden to enter the system, as it is designated a Class 7 Restricted Area.

The UNSC Aeneas, carrying Marine and ODST battalions and a Naval Air Wing, was caught in the slipspace wake of a fleeing Covenant Assault Carrier during the First Battle of Earth. Office of Naval Intelligence analysts estimate that their trajectory will take them at least through the system, though no inhabited UNSC or Covenant worlds lie in that trajectory. A joint Sangheili-UNSC Taskforce has been dispatched to ascertain the situation of the personnel.


  • "A lot of people would have dismissed Ares as a backwater colony. They would be mistaken. It used to be at the end of the Mu Arae-Epsilon Eridani trade route, a hub of activity shuttling rare-earth elements to the Inner Colonies - now, it sits silent in space, waiting for someone to figure out what the hell happened to it."
  • "My grandfather was born on Ares. He'd tell me stories of tremendous beauty - of flowing rivers abundant with introduced fish, of sprawling forests and of towering mountain peaks. From what he said it was paradise - now, alas, Paradise Lost."
  • "Terraforming can take a while. Back in the 2200's, it took humanity a hundred years to fully terraform Mars until it was like Earth. Even then, people had to adapt. We never had any of those problems with Ares - earth-like gravity and atmosphere, existing ecosystems, stable climatic cycle, shielded from the suns radiation - it was almost like it was made for us."