The Waters of Mars (TV story)

The Waters of Mars was the first Doctor Who special not tied to a particular holiday. Mostly a character piece, it showed the extremes to which the Doctor would go when unregulated by either other Time Lords or companions. It continued the "He will knock four times" story arc begun in the previous episode.

It won a 2010 Hugo Award for writers Russell T Davies and Phil Ford. After years of stability at the producer's office, The Waters Of Mars was the fourth episode in a row to be produced by a different person.

Synopsis
Mars, 2059, Bowie Base One. Last recorded message: "Don't drink the water. Don't even touch it. Not one drop."

Plot
The TARDIS arrives on Mars and the Tenth Doctor steps out in his spacesuit, seemingly just to relax and enjoy the landscape. Stumbling across a base inhabited by a team from Earth, he is detained by a remote-controlled robot called "Gadget" and taken inside. The base commander, Adelaide Brooke, is at first suspicious of the Doctor, but after a tense interrogation, decides to trust him. The Doctor learns that the date is 21 November 2059, and this is Bowie Base One, the first human outpost on Mars. History has it that on this date, the base was destroyed in a mysterious explosion and Brooke and her crew were all killed. Unwilling to break the laws of time and interfere with a "fixed point" in history, the Doctor decides to leave. However, a crisis is developing: a crew member, Andy Stone, has been infected by a mysterious life form which takes over his body and causes him to gush copious amounts of water. Maggie Cain, another crew member, screams as Andy growls and attacks her, leaving her unconscious in the biodome corridor. After Ed Gold attempts to establish contact with Andy and Maggie over the comlink and they hear Andy's guttural snarls over the comlink, Adelaide confiscates the Doctor's spacesuit, thinking he may be responsible for the infection in some way, and orders him to come with her and another crew member, Tarak Ital, to investigate.

As the Doctor, Adelaide and Tarak walk down the corridor with Gadget, operated by Roman Groom from the central dome, the Doctor asks the famous Adelaide Brooke if the Bowie Base One mission was worth everything she sacrificed, to which the Captain replied that Earth was reaching the point of uninhabitability with all the smog and pollution, all of which pushed humanity to the brink of extinction, and that to walk on another planet without any smoke but just infinite sky... yes, it's worth it. The Doctor is greatly impressed, and tells Adelaide that she was the woman with starlight in her soul. Adelaide says nothing, but her expression is thoughtful.

As they walk down the corridor, Adelaide's torch picks out Maggie's unconscious form, and they race to her. She is still alive and breathing, but has a nasty gash on her head. Tarak calls Yuri Kerenski over the comlink, who arrives with a medi-pack for Maggie and a stretcher. Ed also arrives, after realising that only one other person was in the biodome — officer Andrew Stone. Ed tells Maggie that the only way this couldn't have been an accident was that Andy has gone berserk. Adelaide dismisses him using rank and security protocol.

Meanwhile, Steffi Ehrlich checks the growling noise on the diagnostics unit of the computer, and is shocked to discover that the growling was the voice of Andy Stone. She calls Adelaide on the comlink to warn her that it seems Andy has gone wild. Adelaide, Tarak and the Doctor step into the dormant biodome, and using his sonic screwdriver, the Doctor restores the lights, all of which had been shorted out by the infected Andy. Tarak goes to the left to check the biodome airlock doors, while Adelaide and the Doctor go to the right. Maggie awakens as they walk down the biodome, unwittingly carrying the mysterious virus which is hiding in her body, but she has amnesia of the previous occurrences. Slightly groggy, she tries to get Yuri to open the door for her to come out, but Yuri refuses, saying a little rest won't hurt. As he turns his back, however, Maggie's features crease into a disapproving frown, indicating that she is not herself anymore...

Tarak is the first to find Andy, who swings round onto him and infects him with the virus by pouring water over his head, causing Tarak to acquire the same zombie-like characteristics that Andy has. At that point, in a conversation with Yuri, Maggie's virus finally becomes active. The organism occupying her body reveals its desire to reach Earth, a planet rich in water. Yuri is first alerted to her transformation when she speaks in a deep voice distorted by the internal fission, "We should like that world", while gazing at planet Earth on a monitor, and Yuri, stammering in horror, briefly describes what has happened to their comrade: the skin around her mouth has become horrifically cracked and broken, her teeth have blackened and she is emitting water in an overwhelming torrent from her mouth, as if she is drowning.

Adelaide, realising the biodome is unsafe, tries and fails to establish contact with Tarak over the comlink, and then she and the Doctor run back through the dome in time to see Tarak transform. While Adelaide points her gun at her infected crew member, the Doctor tries to encourage Andy to take his dripping hand away from Tarak's head. Amazingly, Andy seems to obey, and yanks his hand away from Tarak, who collapses as his mutation is completed. The Doctor then acts friendly and introduces himself to the infected man, but then Tarak flicks his head up and turns to face them, and they are horrified to see that Tarak now looks just like Andy — the skin of his mouth has cracked, his eyes are a dead, white-blue, his teeth have gone black and copious water pours from his mouth. The Doctor, realising they have to get away, runs with Adelaide hot on his heels, but then Andy and Tarak run after them back through the dome to the door, whose seals are set at maximum, just as Andy fires a thick stream of viral water from his hand onto the door. Not a single drop gets inside, but Andy then steps closer to the door and slams himself against it.

Ed reaches the medical dome to see Maggie for himself. He is shocked by her appearance, and his face shows his fear. Steffi, Mia Bennett and Roman look through the medical dome camera at Maggie, and Steffi wonders what she has become. She calls Adelaide over the comlink, begging her to come back, but Adelaide orders Ed to make sure that Maggie is contained. Ed confirms it, then Adelaide orders all the water supplies to be closed down, and also orders the others: "Don't drink the water, don't even touch it, not one drop". The Doctor examines Andy, who looks at him with his dead white eyes, and suddenly grins. The Doctor fails to get a response from the zombie or his friend standing behind him. Andy then starts examining the door, and the Doctor realises that humans are 60% water, so they are the perfect host for something like a mutating water virus. The Doctor says he has to go, and that he can't stay to see what happens, leaving Adelaide confused.

Suddenly, Andy slams his whole body against the door, making both the Doctor and Adelaide jump. Andy growls at Tarak, who then attacks the door by firing water from his mouth into the side, fusing the systems and causing the tortured door to open. The Doctor and Adelaide escape and start running down the corridor back to the central dome, but Andy and Tarak then break out of the biodome doors and race after them. Realising that the infected men can run faster than them, the Doctor sonics Gadget, making him able to move considerably faster, and he and Adelaide hitch a ride on the robot, which causes agony to Roman Groom, the robot's operator. Andy and Tarak, still infected, chase the Doctor, Adelaide and Gadget back to the central dome, but are unable to pursue them any further due to the hardinger seals in the central dome airlocks and are contained in the base's "bio-sphere" section while Maggie is secured in the medical wing. The Doctor, however, is worried about the doors and whether they can protect them from creatures with such power, making a chilling statement, "Water is patient, Adelaide, water just waits. It wears down the clifftops, the mountains, the whole of the world. Water always wins!"

In the medical dome, the Doctor and Adelaide meet the infected Maggie, who just stares at them all, but she suddenly takes an interest in the Doctor when he speaks ancient North Martian to her, Maggie appearing to understand it. The Doctor realises that, looking at Maggie's blackened mouth and cracked skin, that whatever the infection is, it doesn't just live as water, it can produce immense amounts of it. The crew plan to evacuate in an escape shuttle, and the Doctor grimly tells the news to Adelaide that they could be carrying the infection, as they discovered, from Maggie's transformation, that the infection could hide in a human and mutate it at any moment. As the Doctor and Adelaide go to inspect the glacier from which the virus came from, Maggie breaks out of confinement by seeping water into the door and alerts Andy and Tarak in the biodome corridor to the humans' plans by emitting a terrifying alien scream that is heard by the two men over a hundred metres away. The infected men slowly lower their heads and then look towards the medical dome from which the scream is coming from, then they slowly walk away. In the dome containing the glacier, the Doctor hypothesises that the virus may have been preserved and imprisoned in the glacier by the Ice Warriors to prevent its spread. However, before they can get to work, Adelaide queries the Doctor on how he knows so much about them. Reluctantly, the Doctor comments that she may have a story to tell, and Adelaide agrees. She says that when she was 10 years old, the sky had changed, as it was the moment when the Earth was snatched by the Daleks, and Adelaide says that she saw a Dalek float down to her window, and it saw her and just stared at her, then flew away. Adelaide says that she knew, someday, she would follow it into the stars.

The Doctor and Adelaide work out, through a last message from Andy, that the water was fine to drink until the filter broke and the virus could get into the water supplies. Since the water won't yet have been drunk by the rest of the crew, they are free to leave. The crew plan to evacuate in an escape shuttle, and the Doctor breaks the news to Adelaide that she must die today, on Mars, if events are to unfold as they should. Adelaide begs him to help but the Doctor insists he cannot interfere, so Adelaide allows him to leave, saying two last words: "Damn you". However, as the crew prepare to leave, Andy and Tarak climb the maintenance shafts in the main dome, walk to the centre of the roof of the control centre, fall to their knees and exude more water from their hands and mouths through the girders in the roof. The water quickly pours into the room and claims a distraught Steffi Ehrlich, even as she watches a tape left by her two daughters. Shortly afterward, Roman is infected when a single drop of viral water falls on his cheek. However, he warns the others to run just before he changes. Mia screams and sobs as he is infected, but Yuri restrains her, and so they all make for the shuttle.

As Ed prepares the shuttle for take-off, Maggie infiltrates the shuttle and blasts water up the shaft into the pilot room, which cascades over Ed's arm, infecting him with the virus. However, just as the infection consumes him, and his eyes turn white-blue, Ed bids Adelaide, Yuri and Mia a final farewell, "See you later", and triggers the shuttle's self-destruct system, which traps the Flood on Mars but leaves the rest of the crew stranded with no means of escape. The Doctor narrowly avoids being caught in the blast, but nevertheless can hear the cries of the doomed and their desperation as escape seems hopeless. Tortured by their suffering, he thinks about how the Time Lords used to enforce the laws of time, but they are all dead and gone now. He is the last Time Lord; he can make his own rules. With fierce determination on his face, he returns to the base to save the crew.

Finding the base falling apart, the Doctor rallies Adelaide, Mia and Yuri, and tries to assess the situation. Adelaide insists that the Flood cannot be stopped and the Doctor should save himself, but the Doctor tells of the prophecy regarding his death and states, "It doesn't mean right here, right now, 'cause I don't hear anyone knocking, do you?!". In response, the infected Andy slams his fist against the door three times; the Doctor shouts back, "Three knocks is all you're getting!" and electrifies the door, causing Andy to conduct the electricity, scream with pain, and let go of the door. The Doctor realises that, coming from Mars, the Flood creatures would be very sensitive to heat. He reasons that if heat worked against the Ice Warriors, it would work against the Flood. He plans to activate the environment controls and boil them. Adelaide reminds him of his assertion that they must die to ensure history unfolds correctly, but the Doctor replies that as the last of the Time Lords, "The laws of time are mine, and they will obey me!" Suddenly, an explosion rocks the base, destroying its environmental controls. The Doctor states he will reactivate them from outside, only to find his spacesuit destroyed. Refusing to admit defeat, he plans to get a spacesuit from the storage section of Bowie Base, only to find the entire section flooded. At the same time, Maggie heads to the glacier and lets out a deafening shriek that begins to crack the very ice. As the glacier cracks under Maggie's screams, the base's stability begins to collapse; sensing that history will follow its inevitable course, Adelaide activates Action 5 — a nuclear device placed at the heart of the base. It will destroy the Flood, but also kill everyone else, infected or not. The Doctor, realising they have one chance, uses Gadget to roll across the Mars landscape and bring the TARDIS to the base. As time runs out, Maggie continues to wail at the glacier, causing even more ice to crack, and the other infected personnel, Andy, Tarak, Roman and Steffi begin to scream as well, adding their efforts to the Flood's release. Just as the Flood begins to escape the glacier, the TARDIS materialises in the control room, and the survivors get inside. The nuclear device explodes, destroying the base and wiping out all the Flood creatures, the explosion unnoticeable from Mars' atmosphere.

The TARDIS materialises outside Adelaide's house on Earth. Mia and Yuri are shocked by their experiences on Mars and by the Doctor's power and depart, bewildered. In a conversation with Adelaide, the Doctor reflects on why he ultimately decided to save her and the others. He argues that the rules of the Time Lords were only valid while their civilisation existed, and that since he is the last of his race he has total authority over time. He proudly declares himself the "Time Lord Victorious" and remarks that with this power he will now be able to save influential figures such as Adelaide as well as "little people": the likes of Yuri and Mia. Horrified by the Doctor's newfound arrogance, Adelaide says: "Who decides how important they are!? I don't care who you are, the Time Lord Victorious is wrong!".

After that, an adamant Adelaide returns home. The Doctor begins to walk away from her door, thinking all is well. He is grievously wrong. The windows of her house erupt with blue light as a single laser blast rings out. Adelaide has committed suicide, reverting the changes that the Doctor has made to the timeline. The Doctor feels the course of history being re-written in his mind. His fond memories of reading about the Bowie Base One article are painted over and exchanged with the morbid amendments he engraved on history. Captain Adelaide Brooke has been robbed of her noble death on Mars, now a martyr who left her remains on Earth in the most disgraceful fashion. The two crew members he rescued will be spared an early demise and live fruitful lives, but they are somewhat emotionally damaged from their ordeal. And though Adelaide's granddaughter will still travel into space, she will bear more sorrow for her grandmother's senseless demise. The Doctor's spirit breaks.

Only now understanding the full impact of his actions, the Doctor is overcome with horror, and realises that there will be a price to pay for his interference. Ood Sigma inexplicably appears in the street, prompting the Doctor to ask him whether he has finally gone too far — whether the time has come for him to die. The fear in his voice is incredibly potent.

Unresponsive, Sigma vanishes, and the Doctor staggers back into the TARDIS to the ominous sound of the Cloister Bell. With a defiant "No!", he begins to work the machine's controls, staring down with the most forlorn, serious glance he can possibly make. The Doctor resolves to keep travelling on, finding adventures anew, in a desperate plight to delay his impending death as long as he possibly can.

Cast

 * The Doctor - David Tennant
 * Adelaide Brooke - Lindsay Duncan
 * Ed Gold - Peter O'Brien
 * Tarak Ital - Chook Sibtain
 * Andy Stone - Alan Ruscoe
 * Margaret Cain - Sharon Duncan-Brewster
 * Mia Bennett - Gemma Chan
 * Yuri Kerenski - Aleksander Mikic
 * Steffi Ehrlich - Cosima Shaw
 * Roman Groom - Michael Goldsmith
 * Emily Brooke - Lily Bevan
 * Mikhail Kerenski - Max Bollinger
 * Ulrika Ehrlich - Anouska Strahnz
 * Lisette Ehrlich - Zofia Strahnz
 * Adelaide's Father - Charlie De'Ath
 * Ood Sigma - Paul Kasey
 * Young Adelaide - Rachel Fewell

Individuals

 * Adelaide was 10 years old when the Earth was stolen by the Daleks, and she witnessed one herself.
 * Susie Fontana Brooke entered the Space Agency at an early age.
 * Tarak Ital attended Aga Khan University.
 * Steffi Ehrlich trained in Bundeswehr.

Earth history

 * Adelaide Brooke says that the last forty years on Earth have been chaos, with massive climate change, ozone degradation, and "the oil apocalypse"; humanity "almost reached extinction" during this period. Andy's obituary mentions "appalling storm conditions" in 2040, and climate change affecting agriculture in 2045.
 * Maggie believes the Doctor may be a Filipino or Spanish astronaut, as the Philippines are rumoured to be building a Mars rocket and Spain have a "space link" that they managed to keep secret. Andy Stone's sister worked for the Spanish space programme. Ed Gold believes the Doctor is from a non-state independent group, referring to the "Branson Inheritance", likely a reference to, a British industrialist who uses his vast wealth to fund commercial space flight.
 * Various lunar missions have been carried out, including ten German missions and Project Pit Stop, establishing a refuelling station on the moon. Mars was landed on in 2041, with Adelaide Brooke as part of the crew. Thirty years after 2059, Brooke's granddaughter Susan will pilot the first lightspeed ship.
 * At least one of the webpages (the one showing Brooke's granddaughter) dates from the 2080s or later, suggesting the Internet still exists in some form in the late 21st century.
 * On Adelaide's web page, there is a line of text at the top that states the page was updated on Thursday, 22 November 2059.
 * In 2059, flares emanating from the Sun are preventing clear communications between Earth and Mars.
 * One of the web pages indicates that the name of the spacecraft that brought Brooke's crew to Mars, and that of the vessel Ed Gold is forced to destroy, is Apollo 34.
 * NASA sent the space probe Phoenix to Mars, where it discovered liquid water.

Locations

 * Bowie Base One is Earth's first off-world colony.
 * Bowie Base One is located on Mars in the Gusev Crater.
 * The Republic of Dagestan exists by the Caspian Sea, apparently a reference to the part of Russian Federation.
 * Mars is one of the few planets where the Doctor needs a spacesuit. This implies that most other planets that the Doctor visits contain atmospheric elements that he can breathe.
 * The Celestial Belt of the Winter Queen was discovered by one of Adelaide's descendants.

Species

 * The Doctor mentions the Ice Warriors and suggests that they may have frozen the Flood.

Robots

 * The Doctor said that he hates "funny robots" but notes that he'd be okay with a robot dog.
 * Gadget was built by Roman Groom using parts from the drones that constructed Bowie Base One.

TARDIS

 * Whilst on Earth, the Cloister Bell is audible while the Doctor stands alone in the TARDIS.

Story notes

 * This story was initially envisaged as a Christmas special. Several festive references remain, such as the crew on Mars preparing for Christmas dinner, and the snowing when the Doctor arrives back on Earth as he exclaims how he likes snow.
 * This story was originally entitled Red Christmas.
 * Lindsay Duncan became the oldest actress, and briefly the oldest individual, to be cast in the companion role (although like several before her, her official status as a companion will remain debatable). As Bernard Cribbins took on the companion role in TV: The End of Time, he became the oldest male actor and oldest individual in this role.
 * The episode ends with a dedication to Barry Letts. The former Doctor Who producer and writer had died several weeks before the broadcast.
 * Phil Ford's original draft was called A Midwinter's Tale, and was a sword and sorcery tale about an alien princess coming to Earth to be married. It ended with a long chase sequence in secret tunnels beneath Buckingham Palace.
 * When initially sketching out the story, Davies considered as a potential actress to play the character that eventually became Adelaide. In an early draft, the character that became Adelaide was Russian, but this was changed when, still thinking of Mirren as a potential guest star, Davies felt it would have been too close to the character played by Mirren in the film 2010: The Year We Make Contact. (REF: Doctor Who: The Writer's Tale - The Final Chapter)
 * In a deleted scene, the Doctor suggested that the Ice Warriors were unable to fully defeat the Flood and fled the planet as a result, explaining their absence.
 * This story won the 2010 Hugo Award in the category of Best Dramatic Presentation, Short Form.
 * The Waters of Mars is the last Doctor Who story released on DVD to include a "Next Time..." trail for a following episode, and one of only two Blu-ray releases, along with TV: Planet of the Dead, to include a "Next Time..." trail. The End of Time did not include such trailers even at broadcast, and while most episodes from series 5 were broadcast with a "Next Time..." trail, they were excised from the DVD and Blu-ray release.
 * "Bowie Base One" has a layout similar to the Moonbase from Gerry Anderson's TV series "UFO".
 * "What the hell is that noise?" The sound is a proximity alarm, used in the movie 2001, a Space Odyssey.
 * "Bowie Base One" is a reference to David Bowie's song "Life on Mars".
 * Chronologically, The Waters of Mars was the last live-action story to feature David Tennant dressed in the Tenth Doctor's blue suit. TV: Dreamland would be the last of the Tenth Doctor's broadcast stories to depict him in the blue suit. He would appear in his more commonly worn brown suit for his ultimate serial.
 * This story was intended to be transmitted on 21 November 2009, exactly 50 years before the events of this story, but had to be moved back. As such it is the only new episode of a show that is not a Christmas special transmitted on a Sunday.
 * The original draft of this script had Adelaide surviving, with the Doctor realising upon seeing Ood Sigma (who arrived straight after he'd declared himself the 'Time Lord Victorious') that he had gone too far. Russell T Davies later decided that Adelaide would need to commit suicide in order to stop the Doctor from going down a destructive path, a decision Julie Gardner agreed with. (REF: Doctor Who: The Writer's Tale - The Final Chapter)

Ratings

 * 15th November 2009 - 10.32 million
 * 33.9% of TV share

Filming locations

 * Victoria Place, Newport
 * National Botanic Gardens of Wales, Carmarthenshire
 * Taff's Well quarry, Cardiff, Wales

Production errors

 * The first of the web pages brought up in the episode claims that Adelaide had a seven-strong crew with her, though there were 9 people on-site not counting the Doctor.
 * In Yuri Kerenski's profile near the beginning of the episode, Tarak Ital's name is incorrectly spelled as "Tarek". Secondly, by pausing the image of his profile, it becomes apparent that the first paragraph is repeated at the bottom simply to fill what would be white space, in hopes it went unnoticed in general broadcast.
 * Steffi Erlich's profile lacks a full stop between two sentences, causing it to read "After finishing secondary school there and two years in the Bundeswehr, she studied physics at the RWTH Aachen University In 2042, she was awarded a diploma..."
 * When it is revealed that Maggie is one of the creatures, the outer shot shows her hair back while in the closer shot, it is around her face.
 * When the Doctor opens Adelaide's door, the door unlocks and is opened till it is ajar. When Adelaide approaches the door however, it is closed over.
 * While Yuri is watching a video of his brother, during the close up of Yuri, in the background, Maggie's mouth seems to be grey and cracked the same as the Flood. When the scene returns to a shot of Maggie, her mouth is normal. This is repeated twice until it shows Maggie throwing her head back.
 * When Susie Fontana Brooke's website is brought up, it shows her crew as identical as that of Bowie Base One. This is likely a typographical error, saying "Brooke's team consists of" when it should have read "Brooke's team consisted of", meaning the article referred to Adelaide's team, not Susan's.
 * One of the webpages shown said that the Dalek invasion (TV: The Stolen Earth / Journey's End) happened in 2008, but it actually happened in 2009.

Continuity

 * The Doctor refers to his visit to Pompeii in August 79 in the company of Donna Noble. (TV: The Fires of Pompeii)
 * Adelaide recalls seeing a Dalek during her childhood, which occurred when Earth was relocated to the Medusa Cascade. (TV: The Stolen Earth / Journey's End)
 * The Doctor wears the spacesuit he picked up on Krop Tor. (TV: The Impossible Planet / The Satan Pit, 42)
 * Carmen's prophecy, "He will knock four times", is mentioned. (TV: Planet of the Dead)
 * The Doctor reflects on his own relatively recent statements about the Time Lords and the Time War.(TV: Rise of the Cybermen, Doomsday, Gridlock, Utopia, The Sound of Drums, Last of the Time Lords)
 * The Doctor references a race known as the Ice Warriors that had lived on Mars. (TV: The Ice Warriors)
 * The Doctor says that heat worked against the Ice Warriors. (TV: The Seeds of Death, The Monster of Peladon)
 * The Doctor previously used the tactic of electrifying bulkhead doors. (TV: The Ark in Space)
 * Adelaide mentions the oil apocalypse that hit Earth during her lifetime. (TV: The Infinite Quest)
 * After the Doctor sees Ood Sigma (TV: Planet of the Ood) and enters the TARDIS, the Cloister Bell sounds. (TV: Logopolis, et. al.)
 * The Doctor realises that his "summons" by Ood Sigma precedes what could be his death. He delays, beginning a series of travels before encountering him again. (TV: Dreamland, TV: The Day of the Doctor, The End of Time)
 * The Eighth Doctor once changed a fixed point in time by saving Charlotte Pollard's life. She was supposed to die in the crash of the British airship R101 on 5 October 1930. (AUDIO: Storm Warning)
 * An alternate version of the Tenth Doctor would dub himself the Time Lord Victorious and rule over the universe as a tyrant, until being killed by a Raxacoricofallapatorian. (COMIC: Four Doctors)

International broadcasts

 * - New Zealand: 29 November 2009
 * ABC1 - Australia: 6 December 2009
 * BBC America: 19 December 2009
 * Space - Canada: 19 December 2009 ; rebroadcasts on 20 December 2009 and 2 January 2010.
 * Virtually no major edits were made to The Waters on Mars for any of its broadcasts on Space on 19 and 20 December, except that the preview for The End of Time was omitted (the dedication to Barry Letts, however, remained intact).
 * France - 30 October 2010

Home video releases
The four specials along with The Next Doctor were released in North America on both DVD and Blu-Ray in a box set on 2nd February 2010.

The Waters of Mars was released with The End of Time in a 'Winter Specials' DVD and Blu-Ray Box Set.

The US Netflix lists this as episode 17 of Series 4.