Gliese 581d Gliese 581d was the destination of a colony ship that the Fourth Doctor , Romana II and K9 Mark II encountered . ( PROSE : " All Snug in Their Beds " ) Gliese 581 D was one of the first human colonies settled after Earth ' s population had been evacuated . The planet that supported the colony was 20 light - year s from Earth and had twin suns . When Bill asked the Twelfth Doctor travel to the future with her , he took Bill to Gliese . ( TV : " Smile " ) Astronomical data . Gliese 581 D was the fourth planet of the Gliese system and was located twenty million light year s from Earth , in orbit around twin sun s . Following the terraforming of the planet by Vardies , the composition of the atmosphere became identical to Earth ’ s . It also had fertile soil and vast sea s , rendering it suitable for human colonization . ( TV : " Smile " ) Landscape . Gliese ' s sky was blue , and it had two sun s . The city that would serve as the home of the colonist s was surrounded by vast fields of wheat on one side and was located at the edge of a sea on the other side . The architecture of the city was made up of futuristic and smoothly designed building s with many window s , open spaces and an overall white colour . It had numerous plant s , bridge s and bodies of water flowing through the street s . ( TV : " Smile " ) History . At some point in the far future , Earth was devastated and the human population was evacuated on spaceship s . One of these was the starship " Erehwon " that contained millions of people in stasis . The ship landed on the planet Gliese 581 D . Once it landed , a small number of the crew were awakened and deployed swarms of Vardies , " the worker bee s of the third industrial revolution " . The Vardies successfully terraformed the atmosphere and ground of Gliese in order to make it habitable for humans . They then built an entire city out of Vardies , which would serve as the colonist s ' home . However , the Vardy were programmed to keep the colonists happy at all times . When one of the colonists died of natural causes , her friend s and family began to grieve . The Vardies , reading grief as the opposite of happiness , treated it like a virus and began killing the colonists as to them , eliminating sadness meant eliminating sad people . In just one morning , the entire set - up team was slaughtered for displaying negative emotion s . Some time later , the Twelfth Doctor and Bill Potts visited Gliese , only to find the city empty . They eventually discovered the remains of the set - up team who had been turned into fertilizer for the botanical garden s . The Doctor , assuming the colonists had not arrived yet , decided to blow up the city . They ventured into the starship " Erehwon " and the Doctor sabotaged the engine . However , Bill discovered the remaining population in stasis and quickly warned the Doctor , who undid his sabotage . As the colonists began to awaken , the Doctor briefed them on what had happened and why . But the humans , believing the Vardies simply wanted to kill them , took up arms and an open conflict erupted between the humans and the Vardy , who had begun showing the first signs of sentience . The Doctor ended the battle by erasing the Vardies ' memory up until the moment they made the error of perceiving grief as a virus to be eliminated . Though the Vardy thought the city belonged to them , they welcomed the humans onto their new world and the Doctor made sure they would not make the same mistake . ( TV : " Smile " ) Technology . The colonist s that populated Gliese had made a number of technological advancements that participated in the functioning of the colony . The entire city was made up of Vardy , microrobot s that interlocked in order to create solid and complete structures such as the building s and the machines . They could easily break apart into swarms and attack anyone they perceived as a threat . They would envelop the target and could strip them of clothing and flesh in seconds , leaving nothing but bone s behind . The Vardy also carried out daily tasks , such as scanning new arrivals or pollinating the wheat fields that surrounded the city . The city was also equipped with Emojibot s , an interface between the human colonists and the Vardy that carried out maintenance . Humans communicated over long distances through a wireless network that was implanted directly into their ear s and used their nervous systems as circuitry . Mood badges were handed out by Emojibots to the human residents and automatically put themselves on the humans ' back . They monitored their emotion s and communicated the data directly to the Emojibots . ( TV : " Smile " )