Seveneves

At some unspecified date in the near future, an unknown agent causes the Moon to shatter into seven pieces. As the pieces begin to collide with one another, astronomer and science popularizer "Doc" Dubois Harris calculates that the number of collisions will increase exponentially. A large number of Moon fragments will begin entering Earth's atmosphere, forming a white sky and blanketing the Earth within two years with what he calls a "Hard Rain" of bolides, causing the atmosphere to heat to incandescence and the oceans to boil away, rendering Earth uninhabitable for thousands of years. The world's leaders decide to evacuate as many people and resources as possible to a "Cloud Ark" in orbit, including a swarm of "arklet" habitats that can avoid the debris from the Moon, both to attempt to preserve the human race and to prevent civil disorder from breaking out before the Hard Rain. Each nation is invited to choose a group of young people, dubbed "Arkies," for training to join the Cloud Ark.

The Cloud Ark is to be based around the International Space Station (ISS), currently commanded by American astronaut Ivy Xiao. The ISS is already bolted onto an iron Arjuna asteroid called Amalthea, which provides some protection against Moon debris. Robots are used to excavate Amalthea to provide more protection in a project that is run by mining and robotics engineer Dinah MacQuarie. Technicians and specialists, including Doc Dubois, are sent to the ISS in advance of the Hard Rain to prepare it to become the headquarters of the Cloud Ark.

The plan is that the Cloud Ark must be self-sufficient for 5000 years and capable of repopulating Earth once the Hard Rain ends. A Human Genetic Archive is sent to the Cloud Ark, with the intention that it will be used to rebuild the human population. Approximately 1500 people are launched into space in the two years before the Hard Rain begins.

Some suspect that the architects of the Cloud Ark are interested only in pacifying Earth's inhabitants with a false hope, rather than creating an environment that will actually survive in the long term, including billionaire Sean Probst, who realizes that the Cloud Ark will need a large supply of water to create propellant for the space station to keep from eventually falling into the Earth's atmosphere. He embarks on a two-year expedition to extract ice from a comet nicknamed Greg's Skeleton by using a nuclear reactor to provide power to bring it back towards Earth.

The Hard Rain begins 701 days after the destruction of the Moon, as predicted. Human civilization as well as nearly all life on Earth is obliterated although some try to take shelter underground (such as Dinah's father) or in the deep ocean (such as Ivy's fiancé). Markus Leuker, appointed leader of the Cloud Ark, declares all nations of Earth to be dissolved, and imposes martial law under the Cloud Ark Constitution. Despite a worldwide agreement that members of government will not be launched into space, US President Julia Bliss Flaherty manages to get herself sent to the Cloud Ark at the last minute. Soon, most of the physical Human Genetic Archive is ruined in an Arklet accident, leaving only samples that had been distributed among the arks.

There is disagreement on the Cloud Ark about the best way to organize its society and avoid the debris of the Moon. Some Arkies want to convert the Cloud Ark into a decentralized swarm of small space vessels at a higher orbit out of range of debris, rather than to maintain the central authority of the ISS. Doc Dubois wants to shelter in the "Cleft", a Grand Canyon–sized crevasse on the now-exposed iron core of the Moon. Others want to go to Mars. Julia Flaherty, marginalized by the ISS crew, instead fosters the Arkies' swarm and Mars plans and so becomes their de facto spokesperson and leader.

Sean Probst's expedition succeeds and returns a comet ice fragment to Earth orbit. However, he and his party die of radiation sickness caused by nuclear fallout from their reactor before the expedition is complete. Markus Leuker and Dinah take a small crew to the comet to take control of it and bring it back to the Cloud Ark to provide sufficient propellant to reach the Cleft. Just before Dinah returns with the ice comet as the sole survivor of the mission, Julia Flaherty persuades the majority of the Arklets to abandon the ISS and to move to higher orbit in a decentralized swarm, and she sends a preliminary expedition to Mars. Her faction hacks the ISS's early warning system to mask its unauthorized departure, which causes the ISS to be struck by a bolide and suffer catastrophic damage, killing 300. The surviving portions of the Human Genetic Archive are carried along with Flaherty's Swarm, but the Arkies' ignorance causes the surviving portions are discarded or ignored. Only the digital version of the Human Genetic Archive survives aboard the ISS. The ISS, the ice comet, and remaining third of the Cloud Ark combine into a new ship rechristened Endurance, named after Ernest Shackleton's 1912 ship which pioneered exploration to Antarctica.

It takes three years for Endurance to reach the Cleft, and most of its population had died of cancer, accidents, and suicide, leaving only about 30 survivors. Meanwhile, Julia Flaherty's Swarm is even more decimated by coronal mass ejections from which they are much less shielded than Endurance and by a collapse in food production. The Swarm resorts to cannibalism and even self-cannibalism before Flaherty's faction is overthrown. By the end of three years, only 11 survive, including Flaherty and the leader of the opposing faction, Aïda. The survivors among both the Endurance and the Swarm are predominantly female, a result of the Cloud Ark being seeded with a three-to-one female-to-male sex ratio and of women's better resistance to the space environment. Aïda negotiates reuniting the Swarm with Endurance before it reaches the Cleft but, fearing that it will be ostracized by the crew, starts a battle for control of the ship, which ultimately fails but diminishes the population even further.

When Endurance reaches the safety of the Cleft, there are only eight surviving Homo sapiens in space, all of whom are women. One, the sociologist Luisa, has reached menopause, and the remaining seven (Dinah, Ivy, Aïda, Tekla, Camila, Moira, and Julia) come to be known as the Seven Eves. The Human Genetic Archive has been destroyed, but there are sufficient resources for Moira to use the surviving genetics laboratory to rebuild the human race by automictic parthenogenesis. The first generation of babies must be female, but Moira will reconstruct the Y chromosome in the second generation to re-enable natural reproduction without the aid of technology. They agree that each of the Seven Eves gets to choose how her offspring will be genetically modified or enhanced. Aïda predicts that hundreds of years thereafter, the project shall result in seven new races.

There are now three billion humans living in a man-made ring of different "habitats" circling the Earth 5000 years later. Consisting of seven races, each of which was descended from and named after the Seven Eves who survived the events of Part 2, humanity now has quite distinct racial characteristics. For instance, Moirans can undergo epigenetic shifts, radically changing their bodies in response to new environments. Most of the iron core of the Moon has been used to build space habitats along the ring, but Cleft itself has been turned into the "Cradle," an exclusive piece of real estate attached to a tether that occasionally "docks" with Earth along the equator.

Humanity has divided mostly along racial lines into two distinct camps, Red and Blue, which are engaged in a form of Cold War that is characterized by cultural isolation, espionage and border skirmishes, mediated by treaty agreements that are more occasionally breached than observed.

The orbiting races, or Spacers, terraform Earth by crashing ice comets into it to replenish the oceans and seed the planet with genetically-created organisms based upon re-sequenced DNA data that was saved before the Hard Rain. Once Earth's biosphere is restored, some Spacers resettle the planet in violation of treaty agreements and are eventually dubbed "Sooners."

A "Seven," a group of seven people with one member from each race, is recruited by "Doc" Hu Noah to investigate mysterious people who have been sighted on Earth. As the story unfolds, they discover that some humans ("Diggers") indeed survived the Hard Rain on the planet by living in deep mines, and others survived in ocean trenches using submarines ("Pingers"). Although the survivors have also evolved socially and biologically to form two additional races, the survival of "root stock" humanity separate from the Seven Eves causes turmoil in Spacer high politics. Ground conflict eventually occurs because each of the orbiting camps (Red and Blue) wishes to establish a preferential or exclusive relationship with the Earthbound races: the Diggers, although descendants of Dinah's family, interpret the Blue's presence on their territory as an act of aggression and develop an alliance with Red, prompting Blue to seek out an alliance with the Pingers on the strength of Ivy's connection with one of their founders. Matters are further complicated because the Diggers claim all of the Earth's land surface as their own and initially hold the Spacers in disdain for having fled the planet eons ago.

In an epilogue, it is revealed that a separate, secret underwater ark had been created concurrently with the Cloud Ark, leading to the development of the Pingers, based on analysis of the "selfies" that Ivy's fiance had sent her revealing clues in diagrams and sketches in each photo's background. Ty invites the surviving Seven (along with Sonar and Deep, representatives of the Diggers and the Pingers, respectively) back to apartments at his bar in the Cleft with the intent of forming the first "Nine."

• Dinah MacQuarie: A roboticist working for Arjuna expeditions (a private asteroid mining company). She decides to focus her descendants' genetics on leadership and "heroic" qualities.
• Ivy Xiao: Born in Los Angeles, California, Xiao graduated from the United States Naval Academy before obtaining a PhD in applied physics from Princeton University. At the start of Seveneves, Xiao is the Commander of the International Space Station. She is demoted after allowing Sean Probst to utilize ISS resources but becomes commander again after the death of her successor, Markus Leuker. Her descendants have attributes more focused on intelligence and academic study.
• Julia Bliss Flaherty: Frequently referred to as "JBF," Flaherty is President of the United States during the events of Part 1. In violation of an international accord, Flaherty saves herself by fleeing to the ISS aboard a Boeing X-37, along with Pete Starling, her science advisor. Flaherty attempts to reassert her leadership and persuades a large number of cloud ark inhabitants to abandon the ISS. Disaster and internal dissent lead to her eventual replacement by Aïda Ferrari. Her descendants are more attuned to and adept at social and psychological manipulation.
• Moira Crewe: A geneticist sent aboard to ensure humanity's heterozygosity, Crewe was raised in London and obtained degrees from Oxford and Harvard, and previously worked on the de-extinction of the woolly mammoth. The loss of the physical Human Genetic Archive makes Crewe's talents extremely valuable. Being the only person who understands the genetic endowments that Aïda requests for her own descendants, she responds after successive failures by giving her only surviving child the ability to undergo epigenetic shifts to counter the changes that Aïda makes in her offspring.
• Tekla Alekseyevna Ilushina: A Russian cosmonaut, Tekla was a former Olympic heptathlete and was sent in the initial wave of suicide workers called "Scouts" to retrofit the ISS for its role as the cloud ark hub. Rescued by Dinah when her suit life support system malfunctions, Tekla became the head of security aboard ISS. Her descendants have increased discipline and physical ability.
• Camila: A student and activist, who is implied to be from Afghanistan or Pakistan. She had survived an assassination attempt that necessitated extensive reconstructive surgery, and was granted asylum in the Netherlands. Camila was chosen as an arkie as a rebuke to conservative Muslim countries that refused to nominate women in the Casting of Lots. While initially a close friend of Flaherty, Camila grows disillusioned with her during the events of the novel, ultimately preventing Flaherty from murdering Tekla. Camila has Moira imbue her descendants with nonaggressive traits to be better suited to living in the close confines of space for generations.
• Aïda Ferrari: An Italian arkie," Aïda first appears after having led a revolt against Julia's control of the arklets who rebelled against the ISS. Deciding that future humans will look down upon her descendants for the cannibalism that she participated in while the ark cloud was cut off from the ISS, she gives each of her children markedly different qualities to best counter the attributes that are selected by the other Eves.

• Luisa Soter: A sociologist and the eighth surviving female of Endurance's journey to Cleft, Luisa is post-menopausal and thus incapable of becoming an "Eve." Luisa was born in New York City and educated at the Ethical Culture School, instilling in her a philosophy some of the Eves' descendants would carry forward. Luisa had previously worked with refugees and economic migrants, making her the first psychologist and social worker of the ISS population.
• "Doc" Dubois Jerome Xavier Harris: An astronomer and television personality, "Doob" informs Flaherty of the forthcoming Hard Rain and is eventually sent up to the ISS as a leader and scientific advisor. Doob pushes for the resettlement of the cloud ark on a canyon on "Cleft," a remnant of the moon's iron core that would protect them from radiation and meteorite strikes. He dies of multiple forms of cancer and metastases, probably obtained from radiation exposure, shortly after his arrival on Cleft, but is content in the guaranteed safety to humanity provided by their new home.
• Tavistock Prowse: A blogger and journalist and primary source of information for the arkies in the Cloud Ark, he sides with Flaherty and disseminates her propaganda advocating for secession from ISS. He initiates cannibalism among the arkies by eating his own leg because of their relative uselessness in space. He unintentionally creates a religion among the secessionist arkies, with the swarm being viewed as a supernatural being. He is later eaten by Aïda and her followers shortly before their battle for Endurance to give them energy. The future human races view his siding with Flaherty and his willingness to write her propaganda as caused by his reliance on distractive social media and thus scorn advanced "soft" forms of microcomputing technologies intended for personal use.
• Sean Probst: A mining magnate and commander of the comet-mining spacecraft Ymir. He launches an expedition to retrieve a comet after a political battle over aerospace resources. He brings an ice comet into near Earth orbit but succumbs with the rest of his crew to radiation sickness from the fallout of the nuclear reactor that they used to power their spacecraft.
• Cal Blankenship: United States Navy commander of a nuclear ballistic missile submarine. He nukes the Venezuelan Navy and an army of protesters to protect rocket launches to the ISS under orders by the President. He and Ivy amicably end their engagement during the Hard Rain before he submerges to avoid the devastation. He is revealed in the epilogue to have been part of an underwater ark project as extensive as the Cloud Ark, with his descendants recognizing the last photograph that he had sent to Ivy.
• Rufus MacQuarie: Dinah's father and operator of a mine in the Brooks Range, in northern Alaska. He establishes a bunker with his friends, family, and associates to survive the Hard Rain, and his descendants become known as the Diggers. Of all the races, the Diggers remain closest to "root stock" humanity, simply by having enacted population control, instead of using genetic engineering, as the Spacers or selective breeding, as the Pingers.
• Pete Starling: Flaherty's science advisor oversees the development of the Cloud Ark and attempts to seize the resources that Sean Probst is acquiring for his asteroid mission. It is implied that he viewed the Cloud Ark as a palliative for maintaining social order in the face of extinction and not necessarily a viable plan. Unconcerned in the actual success of the project, he is later killed by a micrometeorite within a space capsule that had been launched into orbit in an X-37 at the last minute with the President. His gun is eventually displayed as a relic in a museum by the future human races, allowing visitors to see how different their armaments are from old Earth.
• Ulrika Ek: A Swedish project manager of the construction of Cloud Ark. She refused to provide separate religious worship pods, earning the ire of every religious group, and limited it to an interfaith pod. She dies from a stroke during the journey to cleft.
• Markus Leuker: A former Swiss Air Force pilot and ISS veteran, he is appointed as a politically-neutral commander of the cloud ark after Ivy's demotion by the fallout from her refusal to stop Sean Probst. He and Dinah quickly form a relationship. Markus dies during the expedition to continue Sean Probst's mission of bringing Ymir to the ISS.
• Rhys Aitken: A British engineer specializing in unusual constructs, Rhys is initially sent to the ISS to integrate a torus for space tourists. He inspires several upgrades and uses for Dinah's robots, and they have a brief relationship which she breaks off because of his depressive moods following the conclusion of any of his projects. He assists in the creation of Endurance, slips into a depressive mood, and commits suicide a month into the journey.
• Vyacheslav Dubsky: A Russian cosmonaut who is launched to the ISS along with Rhys.

• Kath Amalthova Two: Moiran Surveyor for Blue who takes the name Kath Amalthova Three after undergoing post-traumatic epigenetic shift. She is a descendant of Eve Moira.
• Beled Tomov: Teklan Surveyor for Blue with an extensive military background. His is the most physically capable of humanity's seven races. He is a descendant of Eve Tekla.
• "Doc" Hu Noah: An elderly Ivyn geneticist leading the expedition to the surface and the most prominent head of the new Earth terraforming project. His race is the most intelligent one. He is a descendant of Eve Ivy.
• Ariane Casablancova: Julian quarantine agent. Julians, the most suspicious of the races, dominate intelligence and statecraft work. She is secretly a mole for Red and ensures the creation of a Red-Digger treaty. She is a descendant of Eve Julia.
• Remembrance "Memmie": Hu's Camite aide/nurse. Camites tend to be non-confrontational and compassionate. Remembrance killed on first contact with the Diggers. She is a descendant of Eve Camila.
• Tyuratam "Ty" Lake: Dinan bartender/manager, Indigen ("Sooner"), and military veteran. Dinans are natural leaders. He is employed by a secretive society serving the "Purpose" and recruited by Doc for his seven. He is a descendant of Eve Dinah.
• Langobard: Aïdan Neoander and Indigen. Neoanders are one of the seven subraces of Aïdans, most of which were initially designed to counter the strengths of the other races. Neoanders posess both the physical prowess and intellectual cunning of several of the other human races. Neoander DNA was sequenced with remnants of [Neanderthal] DNA from Aïda and a preserved Neanderthalian toe.
• Einstein: Ivyn Indigen. His race colonized the surface as soon as it was habitable, a know violation of pre-existing treaties. He discovered a buried truck from Old Earth, and his efforts to show it to the seven lead to their first contact with the Diggers, who highly value the truck's metal.
• Sonar Taxlaw: Digger encyclopedist. Her race descended from Dinah's father and his family and associates who survived the Hard Rain in underground shelters. A specialist of the 17th volume of the Encyclopedia Brittanitca, she joins the seven to flee her repressive society and explains to them how to contact the Pingers.
• Deep: Pinger envoy. Pingers are the descendants of those who survived the Hard Rain in underwater caverns aboard submarines. Initially selectively breeding for confined spaces, they started selectively breeding to survive underwater after the "spacers" had restored water on Earth via bombardment by comets.