Credit: WORLD BOOK photo

April 23 is World Book Day, a celebration of the special role that books play in our lives. To celebrate, we at World Book (get it?) invited author William D. Adams to talk about his experience creating a special set of books, Out of This World 2.

I’m Will Adams, a content creator at World Book. I’ve had the privilege of working on many books during my career at World Book, most recently by writing the second series of Out of This World.

When I was a kid, I loved going to the local library and browsing the science and science fiction sections. But as I got older, I got frustrated by the technological leaps required in science fiction. Why couldn’t we live in space and travel among the stars already?

Out of This World is World Book’s collaboration with a branch of the United States National Aeronautics and Space Administration (NASA) called the NASA Innovative and Advanced Concepts program (NIAC). NASA is world-famous, but you may never have heard of NIAC before. NIAC is working to bring some of that technology from science fiction into existence.

NIAC is a bit like a startup incubator for space exploration projects. Scientists, engineers, entrepreneurs, or anyone else from across the United States may submit a proposal to NIAC about an idea that could revolutionize the way we reach, explore, or live in space. The idea has to be revolutionary and largely unstudied: no small plans are allowed. A committee reviews the proposals and awards small grants to the most deserving projects.

The NIAC inventors use the money to test their ideas and to work out details of their designs. The hope is that the best ideas become part of NASA missions or get picked up by the private space industry.

One of the most prominent ideas to “graduate” NIAC is the starshade. A starshade is a spacecraft with a giant, unfolding shade, a bit like a giant umbrella. The shade can block out a distant star’s light, enabling a space telescope to directly image any exoplanets (distant planets) orbiting around it. It’s the same principle as using your hand to block the sun’s light when trying to see something in the bright sky. Engineers hope to launch a starshade in the next 5 to 10 years.

I had so much fun interviewing the scientists and engineers for this series. They’re all incredibly smart people, of course, but also down to earth and from a wide variety of backgrounds. And—no surprise here—many of them were inspired by books growing up, both fiction and nonfiction.

Out of This World reads like a blueprint for the future. It shows how we can study other planets, how we can get to those planets faster, how we can live in space or on other planets, and even what to wear when we get there!

Amazingly, Out of This World 1 & 2 only scratch the surface of the innovative concepts that NIAC has funded. And, NIAC’s blueprint for the future grows every year. Just a couple of weeks ago, on April 8, they released their 2021 Phase II and III grants. These awards are for projects that are proven to work but need more research and development before they can be incorporated into mission designs.

One 2021 Phase II grant is to further study plans for a huge radio telescope. Remember the Arecibo telescope that collapsed last year? Think of this as an extra-large replacement—but located on the far side of the moon! NASA engineer Saptarshi Bandyopadhyay proposes sending a robotic probe to construct a giant radio dish in a lunar crater. Shielded from the noisy radio-wave emissions of human technology on Earth, such a telescope could study the early history of the universe. I can’t wait to write about it in series 3!

I hope you celebrate World Book Day by picking up a book and getting inspired, just as many of the NIAC inventors did. Maybe you’ll be inspired to think about things a different way, to write your own story, or even to explore the stars.

NASA’s Mars 2020 rover Perseverance
Credit: NASA/JPL-Caltech

Mars is one of the most difficult destinations to arrive safely at in the solar system, but you might not know it if you have been paying attention to the news lately. Earthlings are a perfect three-for-three on Mars missions this February. Two countries saw their first missions ever arrive at the Red Planet last week. Then yesterday, the United States National Aeronautics and Space Administration (NASA) landed the Mars 2020 rover Perseverance on the surface of Mars. This flotilla of missions to the Red Planet was facilitated by a favorable alignment in the middle of 2020 that brought the planet close to Earth.

On February 9, a spacecraft from the United Arab Emirates (UAE) arrived in orbit around Mars. The orbiter, called Hope or Amal, will map Martian weather on a planet-wide scale. Such mapping has never been attempted before. UAE became just the fifth country to reach the planet. All systems look good at the moment, but Hope is due to enter the orbit from which it will conduct its mapping in May. At that point, engineers will know for sure if the probe will be able to accomplish its mission.

Hot on Hope’s heels was an ambitious mission sent by the China National Space Administration (CNSA). The mission, called Tianwen-1, went into orbit around Mars the next day. The mission consists of an orbiter, a lander, and a rover. The lander and rover will attempt a landing in a few months. If CNSA successfully deploys Tianwen-1, China will become the third country to land a spacecraft on Mars and just the second to land a rover on Mars.

The last—but certainly not least—to arrive was Perseverance. The rocket carrying the beefy rover blasted off from Cape Canaveral in Florida on July, 30, 2020. Perseverance is the largest rover ever sent to Mars. It’s the size of a small automobile and weighs over 2,200 pounds (1,000 kilograms) on Earth.

Unlike China and the UAE, the United States is a Mars veteran. NASA has landed several successful missions there, including the still-operational sibling craft of Perseverance, the Mars Science Laboratory (MSL) rover Curiosity.

The design of Perseverance is based on that of Curiosity, which has been exploring Mars since 2012. Engineers used many extra components that were originally created as backups for Curiosity in case of manufacturing defects in the originals. But Perseverance is more than just a pile of spare parts. Jet Propulsion Laboratory (JPL) scientists and engineers modified—and beefed up—the design to fit Perseverance’s mission. Perseverance is about 5 inches (13 centimeters) longer and 278 pounds (126 kilograms) heavier than Curiosity.

No matter how many successful missions are under a space agency’s belt, getting a spacecraft to Mars is a heart-pounding ordeal. Landing on the Red Planet is especially challenging. Mars is a large planet, so its gravity pulls spacecraft towards it at high speed. It lacks a thick atmosphere like that of Earth, however, that spacecraft could use to slow down. Furthermore, retrorockets placed on the rover would scour the ground near the landing site and contaminate it with rocket exhaust.

JPL has developed a complex of system to land a large rover on the Martian surface, which was first used with MSL. A parachute slowed the craft after it entered the Martian atmosphere. A set of rockets then fired to hover the craft above the surface. Then, Perseverance was lowered to the ground on a tether. Mission planners call this complicated ride through the atmosphere, filled with opportunities for mission-ending disaster, “the seven minutes of terror.”

Perseverance touched down in Jezero Crater. Billions of years ago, the crater held a lake that was fed by a river system. Perseverance will explore this ancient river delta and search for signs of past life there.

Perseverance carries many sophisticated scientific instruments that will enable it study the geology and climate of the region. The rover is equipped with a special drill and sample vials. After studying the rock samples it has drilled, it will place them in sealed vials and cache (stow) them on the surface. Scientists hope to recover the cached vials and send them to Earth in an ambitious sample return mission in a decade or so.

Other special features included an upgraded autonomous driving package, which will enable Perseverance to pick its way through obstacles on its own to reach a target, and a small helicopter drone called Ingenuity that will look to demonstrate the first powered flight on a solar system body other than Earth. Expect to hear about more exciting discoveries—and see more stunning pictures of Mars—in the months and years ahead.

November 25, 2019

This month, scientists at the United States National Aeronautics and Space Administration (NASA) released their latest findings from decoded transmissions sent from the space probe Voyager 2 in interstellar space (the space between the stars). About a year ago, Voyager 2 became the second spacecraft (following its twin, Voyager 1) to enter interstellar space, exiting the heliosphere, a vast, teardrop-shaped region of space containing electrically charged particles given off by the sun.

Voyager 2, seen here passing Neptune in 1989, entered interstellar space in late 2018. Credit: © Mark Garlick, Science Source

The sun and all the planets are inside the heliosphere. Scientists estimate that the nose (blunt end) of the heliosphere is about 9 billion to 15 billion miles (15 billion to 24 billion kilometers) from the sun. Voyager 1, launched in September 1977, crossed the boundary from heliosphere to interstellar space in 2012. The crossing was marked by a steady drop in temperature and an increase in the density of charged particles known as plasma. Voyager 1 also detected an abundance of cosmic rays (particles accelerated by exploding stars) in interstellar space and provided evidence that the heliosphere protects Earth and the other planets from much interstellar space radiation.

This artist’s depiction shows the approximate locations of the two Voyager spacecraft relative to the sun, the bright spot in the center, in the mid-2010′s. In 2012, Voyager 1, shown as the upper probe in the image, sailed beyond the heliopause and into interstellar space. Voyager 2, the lower probe in the image, crossed the heliopause in 2018. Credit: NASA/JPL-Caltech

Voyager 2 was launched a month before Voyager 1 in August 1977. Slightly slower than its twin craft and following a different course, Voyager 2 reached the heliopause (the edge of the heliosphere) in November 2018. Voyager 2 also detected changes in temperature and plasma and cosmic ray density, but the heliosphere at Voyager 2′s crossing point appeared to be sharper and thinner. This could be explained by Voyager 2 crossing the heliopause at a different location or at a less angled trajectory or by crossing during a period of lower solar activity than that experienced by Voyager 1 in 2012. The sun goes through a roughly 11-year cycle of high and low activity, theoretically causing the heliosphere to expand and contract or thicken and thin. Both spacecraft found that particles from the sun are trickling through the somewhat porous heliopause into interstellar space. Voyager 2 also confirmed Voyager 1′s detection of similar magnetic fields on both sides of the distant boundary.

This artist’s impression shows Voyager 1 passing through the heliopause in 2012. Credit: NASA/JPL-Caltech

Both Voyager space craft are powered by slowly decaying plutonium. In 1977, scientists did not know exactly how long the space probes would continue to operate, nor did they know if, when, or where they would reach interstellar space. Now that the probes are there, scientists hope to learn more about the distant realm before the Voyagers power down sometime in the next few years. Voyager 1 is currently more than 13.6 billion miles (22 billion kilometers) from the sun, and Voyager 2 is about 11.3 billion miles (18.2 billion kilometers) away. After they lose power, scientists expect both to continue sailing through space for billions of years.

Click to view larger image
The path of  Voyager 2 is shown in red. Voyager 2 flew past Jupiter in 1979, Saturn in 1981, Uranus in 1986, and Neptune in 1989. Credit: WORLD BOOK illustration by Ken Tiessen, Koralik Associates

October 23, 2019

Last week, on Friday, October 18, the United States astronauts Christina Koch and Jessica Meir made history by performing the first spacewalk in which all the participants were women. Before then, all spacewalks had involved at least one man. That includes the first spacewalk by a woman, which was performed in July 1984 by the Soviet cosmonaut Svetlana Savitskaya, who was accompanied by Vladimir Dzhanibekov. In October 1984, Kathryn D. Sullivan became the first U.S. woman astronaut to conduct a spacewalk (with the mission specialist David Leestma).

NASA astronaut Christina Koch. Credit: NASA

The National Space and Aeronautics Administration (NASA) did not intentionally plan the first all-woman spacewalk. Rather, it was the natural result of an increasing number of women astronauts in the space program. Last Friday, Koch and Meir worked outside the International Space Station (ISS) for more than seven hours, replacing a crucial battery charger. The batteries power the ISS during the night portions of its orbits, which occur about every 45 minutes.

NASA Astronaut Jessica Meir. Credit: NASA

NASA had planned for Koch and another U.S. woman astronaut, Anne McClain, to conduct a spacewalk in March. But NASA did not have two appropriately sized spacesuits, and McClain was replaced by a male astronaut who “fit the suit.” In the following months, NASA delivered more varied spacesuit pieces to the ISS to reduce the likelihood of future sizing conflicts.

Koch and Meir’s spacewalk represents an important move toward gender parity in the U.S. space program. In privately-funded tests conducted in the early 1960’s, several women passed the same rigorous physical examinations that the male Mercury astronauts had passed. But NASA had no interest in selecting female astronauts at the time. No women were selected for the Mercury, Gemini, or Apollo missions. It was not until 1983 that the first woman U.S. astronaut, Sally Ride, reached space.

NASA has made strides to correct the gender imbalance in recent years. The 2013 astronaut class that produced Koch and Meir was the first class to have as many women as men (four each). The space agency is working towards returning astronauts to the moon in 2024 through the new Artemis program. NASA stated that at least one woman will walk on the moon.

Koch and Meir have stellar resumes that compelled NASA to select them for the astronaut training program. Both had done scientific work in Antarctica. Koch is an electrical engineer and helped develop a scientific instrument on the Juno mission to Jupiter. Meir has a Ph.D. in marine biology and has studied how penguins and other animals conserve oxygen in extreme environments. She raised a group of bar-headed geese from hatchlings so they would be comfortable with her during experiments. Even the two women’s hobbies prepared them for the spacewalk. Koch is an avid rock climber, having developed the climbing and tether safety skills similar to those needed for working outside a spacecraft. Meir enjoys underwater diving, where conditions are somewhat similar to those experienced during a spacewalk.

July 19, 2019

On July 20, 1969, 50 years ago tomorrow, the United States astronauts Neil Armstrong and Buzz Aldrin did what had seemed impossible not that long before: they landed on the moon. Watched by millions of people over a live television broadcast worldwide, Armstrong and Aldrin’s lunar first was the crowning moment of the National Aeronautics and Space Administration’s (NASA) Apollo space program.

Astronaut Buzz Aldrin took this photo of Neil Armstrong working on a storage assembly on the lunar module, Eagle, on the surface of the moon in July 1969. Credit: NASA

In May 1961, President John F. Kennedy proposed landing astronauts on the moon by the end of the decade. This goal seemed out of the realm of possibility at the time. The United States was trailing the Soviet Union in the space race, a period of intense competition between the two countries to achieve supremacy in space exploration. The Soviet Union had already launched the first satellite (Sputnik in October 1957) and the first person (cosmonaut Yuri Gagarin in April 1961) into orbit around Earth. American efforts had been riddled with launch failures, and the greatest success at that time had been a brief suborbital flight (astronaut Alan Shepard spent a few minutes in space) shortly before Kennedy’s announcement. From the looks of things in 1961, if anyone was going to land on the moon before 1970, it would be a cosmonaut.

A NASA Saturn 5 rocket launches from Florida’s Kennedy Space Center on July 16, 1969, carrying the Apollo 11 astronauts who would land on the moon days later. Credit: NASA

NASA, however, accepted the challenge with intensity and enthusiasm. It wound down the initial Mercury space project and began the Gemini program. Gemini helped develop the technology and skills to travel to the moon. Astronauts were launched in pairs, and they practiced docking with other spacecraft—an important part of Apollo’s novel mission design. The astronauts also practiced more precise ocean landings, to gain skill for lunar touchdowns. Gemini ended in 1966 and was succeeded by Apollo.

The Apollo program started with disaster. In January 1967, a fire during a pre-launch test took the lives of astronauts Roger B. Chaffee, Virgil I. (Gus) Grissom, and Edward H. White II. After the accident, NASA engineers redoubled their focus on crew safety.

Apollo 11 astronaut Buzz Aldrin stands on the surface of the moon in July 1969. Credit: NASA

After several crewed and uncrewed Apollo test flights, NASA was ready to land the first people on the moon. On July 16, 1969, a Saturn 5 rocket, the most powerful rocket ever built, launched from Kennedy Space Center carrying the three astronauts of Apollo 11. After three days in transit, the mission entered into orbit around the moon. On July 20, Armstrong and Aldrin landed on the surface in the lunar lander module, named Eagle. Fellow astronaut Michael Collins stayed aboard a command module orbiting the moon.

This photo taken during the Apollo 11 mission shows Earth rising above the surface of the moon. Credit: NASA

As the mission commander, Armstrong was the first person to leave the lunar module and set foot on the surface. Upon taking his first step onto the moon, he famously said: “That’s one small step for [a] man, one giant leap for mankind.” (The word “a” was lost in radio transmission.) Aldrin joined him on the surface about 20 minutes later. They explored the lunar surface for more than two hours, performing experiments, setting up scientific equipment, and collecting samples of the lunar surface. Then, they blasted off in the lunar module, reunited with Collins in orbit around the moon, and safely returned to Earth.

Armstrong, Aldrin, and Collins were greeted with honors and awards upon returning home, including the Presidential Medal of Freedom, one of the two highest civilian honors awarded by the U.S. government. (They were awarded the second highest honor, the Congressional Gold Medal, in 2011.) The lunar astronauts received huge parades in New York City, Chicago, and Los Angeles. They were celebrated in their home towns as well as at state dinners around the world.

Astronaut Buzz Aldrin stands next to a seismograph on the lunar surface in July 1969. The lunar module, Eagle, stands in the background. Credit: NASA

Armstrong never became fully comfortable with the fame associated with being the first person to walk on the moon, refusing most interview requests until his death in 2012. Aldrin, however, enjoyed the spotlight and continues to be a prominent spokesperson for the advancement of human space exploration. Collins would have likely been selected to finally walk on the moon as the commander of Apollo 17—the last moon mission. But he retired from NASA after Apollo 11, happy to have been a vital—albeit relatively invisible—part of the first moon mission.

After six successful moon landings, Apollo was cancelled and NASA turned its attention to the development of the space shuttle. Humans have not left Earth’s orbit since since Apollo 17 in December 1972. That could change soon, however, as the United States and many countries and private companies are seeking to return to the moon in the near future. The American spacecraft company SpaceX is developing a rocket and lander intended to orbit and land on the moon. Another company, Blue Origin, is also developing rockets and landers with the ultimate goal of building a permanent settlement on the moon.

April 8, 2019

After nearly 15 years on the surface of Mars, the Opportunity rover died as it lived: studying its adopted home planet. The United States National Aeronautics and Space Administration (NASA) officially ended the rover’s mission in February 2019, months after the craft was silenced by a dust storm.

The NASA Mars rover Opportunity studied the red planet from January 2004 until the summer of 2018. Credit: NASA/JPL/Cornell University, Maas Digital LLC

Opportunity and its twin vehicle, Spirit, together made up the Mars Exploration Rover Mission. They were launched in 2003 to study the history of water on the red planet. The golf-cart-sized rovers carried scientific instruments created by teams of scientists and engineers from the United States and Europe.

Spirit and Opportunity were each designed for just 90-day missions. But both continued to gather information on the surface of Mars without any major setbacks for more than five years. In early 2009, Spirit became permanently trapped in a bed of loose Martian soil, ending that rover’s exploring career. Finally accepting its loss, NASA officially ended Spirit’s mission in 2011.

Opportunity landed in January 2004 in Meridiani Planum, a broad plain on the surface of Mars. Planners chose the site because it was known to contain hematite. Hematite is an iron-bearing mineral. On Earth, hematite generally forms in the presence of water. In 2013, Opportunity detected certain clay minerals that form only in the presence of water. This discovery was proof that liquid water once existed on the surface of Mars. This finding was confirmed by other Mars missions, such as NASA’s larger Curiosity rover, sent to Mars in 2011. Opportunity went on to learn that the water was similar to bodies of water on Earth, allowing for the possibility of life on Mars.

Huge dust storms occasionally blanket the surface of Mars. A particularly intense storm occurred in mid-2018, causing NASA to lose contact with Opportunity. The dust blocked out the sun and covered the rover’s solar panels, making it impossible for Opportunity to keep its core systems warm. Even after the skies cleared, there was no response from the rover. The bitterly cold temperatures on Mars—about -80 °F (-60 °C) on average—can damage and destroy electronics.

The end of Opportunity is not the end of humankind’s robotic presence on Mars. Curiosity continues to roll along. InSight, a non-mobile lander also launched by NASA, is currently studying the interior structure of Mars. And in 2021, two new rovers will launch: NASA’s Mars 2020 rover and Rosalind Franklin, a rover developed by the European Space Agency (ESA) and Russia’s state space agency, Roscosmos. (Rosalind Franklin was a British chemist famous for her studies of molecules and crystals.) The new rovers will try to find out if Mars held life at some point in its distant past. Thanks to the hard work of Opportunity and the mission’s engineers and scientists, we know it is a possibility.

March 20, 2019

In honor of Women’s History Month in the United States, World Book looks at the American mathematician Katherine Goble Johnson. For many years, Johnson worked for the National Aeronautics and Space Administration (NASA), where she performed notable spaceflight calculations. She calculated the trajectory (path) for Apollo 11, which made the first landing on the moon. As a black woman in a racially segregated United States, Johnson broke many racial and gender barriers to excel as a mathematician.

Katherine Johnson at her desk at NASA’s Langley Research Center in Virginia. Credit: NASA/LRC

Johnson was born on Aug. 26, 1918, in White Sulphur Springs, West Virginia. She was fascinated by numbers from a young age, and she excelled in her studies. In 1937, she received a bachelor’s degree in mathematics and French from West Virginia State College. She then took a job teaching mathematics at a grade school in Marion, West Virginia. In 1939, Johnson was selected to join West Virginia University’s graduate mathematics program. She enrolled, becoming the first black woman to attend the university.

In 1953, Johnson learned that the National Advisory Committee for Aeronautics (NACA) Langley Research Laboratory in Hampton, Virginia, was hiring women mathematicians. That summer, she was assigned to Langley’s West Area Computing unit, a group of black women mathematicians headed by Dorothy Vaughan. Johnson was soon reassigned to the Flight Research Division, where she analyzed data from flight tests. In 1958, NACA transitioned into NASA.

At NASA, Johnson and other Flight Research Division members were directly involved in the budding spaceflight program. In 1961, Johnson performed trajectory analysis for the Freedom 7 mission, investigating the route that was planned for the first U.S. human spaceflight. She also calculated the trajectory for astronaut John Glenn in his pioneering orbital flight around Earth in 1962. NASA’s new electronic computers had performed these calculations, but Glenn requested that Johnson personally check and approve them before the launch.

Johnson also calculated the exit and entry trajectories for the Apollo 11 mission, which landed the first two people on the moon in 1969. She authored or coauthored many research reports throughout her career. Johnson continued to make important contributions to NASA’s spaceflight program until her retirement in 1986. She has received multiple honors and awards. In 2015, President Barack Obama awarded her the Presidential Medal of Freedom. NASA’s Katherine G. Johnson Computational Research Facility—a data center at the Langley campus—was named in her honor in 2016. In 2019, NASA renamed its Independent Verification and Validation (IV&V) Facility the Katherine Johnson IV&V Facility.

American author Margot Lee Shetterly’s book Hidden Figures: The American Dream and the Untold Story of the Black Women Mathematicians Who Helped Win the Space Race (2016) chronicles Johnson’s life and career, along with those of other members of the West Area Computing unit. American actress Taraji P. Henson depicted Johnson in the 2016 film Hidden Figures, based on Shetterly’s book.

January 16, 2019

On January 1, the United States National Aeronautics and Space Administration (NASA) probe New Horizons flew by a 21-mile- (34-kilometer-) long rock at the outer reaches of our solar system. The probe took the rock’s first “close-up” photos, revealing details of the snowman-shaped space object, called 2014 MU69 or “Ultima Thule.” The term Thule was used by ancient European cartographers to describe the farthest northern lands of Earth. Ultima Thule (farthermost Thule) once described areas beyond the known world. Ultima Thule, then, is a fitting name for the distant object: it is 4 billion miles (6.5 billion kilometers) from Earth.

The New Horizons spacecraft took this photo of Ultima Thule on Jan. 1, 2019, from a distance of some 18,000 miles (28,000 kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

New Horizons is the first spacecraft to study Pluto and the Kuiper belt, a band of icy bodies largely beyond the orbit of the planet Neptune. New Horizons flew past Pluto in July 2015, revealing a surprisingly varied and geologically active world. Despite its distance from the sun, Pluto has been molded and shaped by many of the same forces that created the eight planets of our solar system.

With the flyby of Ultima Thule, New Horizons became the first spacecraft to visit an object discovered after the spacecraft was launched. The craft blasted off from Cape Canaveral Air Force Station in Florida in 2006. Astronomers discovered Ultima Thule in 2014.

This NASA illustration shows New Horizons encountering 2014 MU69–“Ultima Thule.” Credit: NASA/JHUAPL/SwRI

What’s so special about Ultima Thule? It may look like just another space rock, but it is far different from the asteroids and comets found closer to the sun. The solar system’s planets and other inner objects have been transformed by the sun’s extreme heat, by catastrophic collisions, and by immense gravitational pressures. Ultima Thule and other Kuiper belt objects (KBO’s) are like frozen time capsules that show how things looked as the solar system was forming. The first grainy photographs of Ultima Thule show an object made up of two lobes that likely came together in a walking-speed “collision”—a rather serene birth in an otherwise violent universe.

New Horizons has completed its study of Ultima Thule, but NASA expects to learn more about the distant object over the next 20 months or so as information continues to trickle in. It takes a while for data to be transmitted across the immense distance to Earth. And this may not be the last distant flyby for New Horizons. NASA is searching for other space objects to visit before New Horizons runs out of power in the mid-2030’s.

December 26, 2018

On Dec. 26, 1968, 50 years ago today, United States astronauts of the Apollo 8 mission prepared to reenter Earth’s atmosphere after becoming the first humans to orbit the moon. Apollo 8 was part of the Apollo space program that eventually landed people on the moon. The program lasted from 1961 to 1975. It was conducted by the National Aeronautics and Space Administration (NASA). Live telecasts by the Apollo 8 astronauts were shown around the world, including a famous Christmas Eve broadcast that, at that time, was the most watched television program in history.

The Apollo 8 crew–astronauts Frank Borman, James A. Lovell Jr., and William A. Anders–prepare to board a van which will transfer them to the launch pad at Florida’s Kennedy Space Center on Dec. 21, 1968. The crew orbited the moon and returned safely to Earth on December 27. Credit: JSC/NASA

Apollo 8 launched on Dec. 21, 1968, with astronauts William Anders, Frank Borman, and James Lovell, Jr. It was the second piloted Apollo mission, following Apollo 7 that had tested equipment in low orbit two months earlier. After separating from the carrying Saturn V rocket, the Apollo 8 astronauts guided the command and service module, or CSM, through trans-lunar injection, a maneuver sending the spacecraft toward the moon. The CSM entered lunar orbit and then passed to the dark side of the moon. People on Earth held their breath as communications were lost—as expected—for several minutes. Contact then resumed and was lost and resumed again as the CSM orbited the moon 10 times over 20 hours.

Apollo 8 astronaut William Anders took this famous photograph–known as Earthrise–on Christmas Eve, Dec. 24, 1968. The lunar surface can be seen in the foreground. Credit: NASA

The NASA telecasts took place just before, during, and after these orbits, and the astronauts took a series of remarkable photographs—including the famous “Earthrise” and other photos that showed humans what our planet looks like from space. On December 27, Apollo 8 returned to Earth, splashing down in the Pacific Ocean near the recovery ship Yorktown, 147 hours after launch and precisely on time.

This official emblem of the Apollo 8 lunar orbit mission featured the names of the crew: Frank Borman, commander; James A. Lovell, Jr., command module pilot; and William A. Anders, lunar module pilot. Credit: NASA

Apollo 9 and 10 carried out further tests before Apollo 11 landed humans on the moon for the first time in July 1969. Five more Apollo missions landed astronauts safely on the moon through December 1972.