The object, called MU69, is nicknamed Arrokoth, which means sky in the Powhatan/Algonquian language (it was previously nicknamed Ultima Thule). It's the most distant object humanity has ever visited. The New Horizons probe took hundreds of photographs as it flew by the space rock at 32,200 miles per hour. Images revealed that Arrokoth is flat like a pancake, rather than spherical in shape. The unprecedented data will likely reveal new clues about the solar system's evolution and how planets like Earth formed, though scientists are still receiving and processing the information from the distant probe.Before Chang'e-4's success, no country or space agency had ever touched the far side of the moon. The name Chang'e is that of a mythical lunar goddess, and the 4 indicates that this is the fourth robotic mission in China's decade-long lunar exploration program. The rover landed in the moon's South Pole-Aitken Basin, which is the site of a cataclysmic collision that occurred about 3.9 billion years ago. The celestial smash-up left a 1,550-mile-wide impact site that likely punched all the way through the moon's crust. Landing the spacecraft in this crater could therefore enable scientists to study some of the moon's most ancient rocks.NASA's InSight lander, which touched down on Mars in November 2018, has given scientists the unprecedented ability to detect and monitor Mars quakes. The lander's built-in seismometer detected its first Mars quake in April. Since then, researchers have recorded more than 100 seismic events, about 21 of which were likely quakes. Reading the seismic waves on Mars, scientists hope, will reveal clues about what the planet's inside looks like. The Japan Aerospace Exploration Agency (JAXA) launched its Hayabusa-2 probe in December 2014. Hayabusa-2 arrived at Ryugu in June 2018, but didn't land on the asteroid's surface until this year. In order to collect samples from deep within the space rock, Hayabusa-2 blasted a hole in the asteroid before landing. The mission plan calls for it to bring those samples back to Earth. By studying Ryugu's innermost rocks and debris — which have been sheltered from the wear and tear of space — scientists hope to learn how asteroids like this may have seeded Earth with key ingredients for life billions of years ago.The probe beamed back unprecedented data about previously unknown boundary layers at the far edge of our solar system — an area known as the heliopause. The discovery of these boundary layers suggests there are stages in the transition from our solar bubble to the interstellar space beyond that scientists did not know about until now.In September, scientists announced they'd detected water vapor on a potentially habitable planet for the first time. The planet, named K2-18b, is a super-Earth that orbits a red dwarf star 110 light-years away. K2-18b is the only known planet outside our solar system with water, an atmosphere, and a temperature range that could support liquid water on its surface. That makes it our best candidate for habitability, one researcher said.The unprecedented photo shows the supermassive black hole at the center of the Messier 87 galaxy, which is about 54 million light-years away from Earth. The black hole's mass is equivalent to 6.5 billion suns. Though the image is somewhat fuzzy, it showed that, as predicted, black holes look like dark spheres surrounded by a glowing ring of light. Scientists struggled for decades to capture a black hole on camera, since black holes distort space-time, ensuring that nothing can break free of their gravitational pull — even light. That's why the image shows a unique shadow in the form of a perfect circle at the center. In August, astrophysicists detected the aftermath of a collision between a black hole and a neutron star (the super-dense remnant of a dead star). The catastrophic collision nearly a billion years ago created ripples in space-time, also known as gravitational waves. They passed through Earth this year. This was the third event scientists observed using gravitational-wave detectors. In 2015, researchers detected waves from the collision of two black holes, and in 2017 they observed two neutron stars merging. Einstein predicted the existence of gravitational waves in 1915, but thought they'd be too weak to ever pick up on Earth. New tools have proved otherwise.The maiden flight of Crew Dragon marked the first time that a commercial spaceship designed for humans has left Earth. It was also the first time in eight years that any American spaceship made for people launched into orbit. Crew Dragon's successful test flight was a critical milestone for the US. Since NASA retired its fleet of space shuttles in 2011, the US has relied on Russian rockets and ships to taxi astronauts to and from the ISS.This summer, the Planetary Society — led by science communicator Bill Nye — launched a satellite called LightSail 2 into orbit, where it then unfurled a 344-square-foot solar sail. As light particles reflect off that sail, they transfers momentum to the spacecraft. A spacecraft that utilizes a solar sail in this way has an almost unlimited supply of energy. Advancing this type of propulsion technology could one day help spacecraft reach nearby star systems that aren't currently accessible due to the finite amounts of fuel we can launch off the planet.In April, a study revealed that the Greenland ice sheet is sloughing off an average of 286 billion tons of ice per year. Two decades ago, the annual average was just 50 billion. In 2012, Greenland lost more than 400 billion tons of ice. Antarctica, meanwhile, lost an average of 252 billion tons of ice per year in the last decade. In the 1980s, by comparison, Antarctica lost 40 billion tons of ice annually. What's more, parts of Thwaites Glacier in western Antarctica are retreating by up to 2,625 feet per year, contributing to 4% of sea-level rise worldwide. A study published in July suggested that Thwaites' melting is a time bomb that is likely approaching an irreversible point after which the entire glacier could collapse into the ocean. If that happened, global sea levels would rise by more than 1.5 feet.A September report from the United Nations Intergovernmental Panel on Climate Change projected that sea levels could rise by more than 3 feet by the end of the century. The rising water could affect hundreds of millions of people who live on small islands and in coastal regions. Another study suggested that the number of people displaced by sea-level rise could reach 630 million if greenhouse-gas emissions continue to rise through 2100.The report, published in April, estimated that 40% of amphibian species, more than 33% of all marine mammals and reef-forming corals, and at least 10% of insect species are threatened, largely as a result of human actions. Researchers also found that more than 500,000 land species already don't have enough natural habitat left to ensure their long-term survival. This finding contributes to a rapidly growing body of evidence that suggests Earth is the midst of a sixth mass extinction — the sixth time in the planet's history that species are experiencing a major global collapse in numbers.The giant squid, which inspired the legend of the Kraken monster, has only been caught on video one other time. The creatures almost never leave the icy depths of their habitat, up to 3,300 feet (about 1,000 meters) beneath the waves. In 2012, scientists from Japan's National Museum of Nature and Science filmed a giant squid in its natural habitat in the Ogasawara archipelago.Hundreds of millions of years ago, Earth had one giant supercontinent named Pangea, which eventually broke up into our modern-day continents. A recent study showed that in that process, an eighth continent slid under what is now southern Europe about 120 million years ago. It's still hidden deep within the Earth. The researchers named this continent Greater Adria. Its uppermost regions formed mountain ranges across Europe, like the Alps.The skull, which belonged to the species Australopithecus anamensis, is 3.8 million years old. The fossil, nicknamed MRD, revealed that these ancient people had protruding faces with prominent foreheads and cheek bones, much like other australopithecus species in the fossil record. MRD's age also suggested that these human ancestors coexisted with another species of human ancestor, Australopithecus afarensis, for at least 100,000 years. The nearly complete skeleton Lucy was a member of that latter group, which roamed Africa between 3.9 million and 3 million years ago. The new species, named Homo luzonensis after the Philippine island on which it was discovered, lived between 50,000 and 67,000 years ago. A study described how this human ancestor shared traits with older human ancestors like Australopithecus and Homo erectus, as well as with modern-day humans. An October study suggested that every person alive today descended from a woman who lived in an area of modern-day Botswana south of the Zambezi River about 200,000 years ago. Researchers narrowed in on that area using genetic analysis of DNA that gets passed down the female line. This finding supports the theory that modern human ancestors migrated out of Africa then populated the world, rather than evolving in different pockets around the globe simultaneously.At a site in Egypt's Asasif necropolis, where the ancient city of Thebes once stood, diggers uncovered 30 ancient wooden sarcophagi with perfectly preserved mummies inside. The coffins are about 3,000 years old and were probably for priests and children. According to quantum mechanics, two particles can be paired and separated, yet remain intimately and instantly connected across vast distances. One particle will affect the other no matter how far apart they are. This is quantum entanglement, and the strange phenomenon rattled Albert Einstein so much that he died disbelieving it could exist.In July 2019, the World Health Organization declared the Ebola outbreak in Africa a global health emergency. Fortunately, two experimental treatments proved to dramatically boost survival rates. The two treatments, called REGN-EB3 and mAb-114, are cocktails of antibodies injected into people's bloodstreams. These therapies saved about 90% of new infected patients in the Congo. From now on, we will no longer say that Ebola is incurable, Jean-Jacques Muyembe, director general of the Institut National de Recherche Biomedicale in Republic of Congo, told Wired.Babies who are born with X-linked severe combined immunodeficiency (XSCID) don't have disease-fighting immune cells. For them, the outside world is an intensely dangerous place. XSCID was nicknamed bubble-boy disease because of a young boy named David Vetter, who famously lived his entire life in a protective plastic bubble. Vetter died more than 30 years ago at age 12 after a failed treatment. In April, St. Jude scientists announced that they had successfully cured babies with XSCID using a new experimental gene therapy.