The year 2016 was a dynamic time for spaceflight and space science, marked by major technological achievements in rocketry and scientific discoveries that will completely alter our understanding of the Universe for decades to come. Scientists announced the first detection of gravitational waves and rockets landed after launching to space. New missions took off to learn more about the history of our Solar System and we’ve inched ever closer to answering that ultimate question: are we alone in the Universe?

This was a dynamic year for spaceflight and space science

Of course, the space community experienced its own share of failures this year, too. A few missions didn’t go according to plan, while major milestones that were supposed to be met got delayed instead. And yeah, a few things exploded that weren’t supposed to. But overall, this year was filled with achievement in space. Below, relive the biggest wins and losses for space in 2016, as well as everything in between.

The biggest wins for space

The evidence grew for Planet Nine

In January, “Pluto Killer” Mike Brown and Konstantin Batygin at Caltech took everyone by surprise when they announced that a mysterious ninth planet is probably lurking at the outer edges of the Solar System. Although they hadn’t actually seen the planet, their argument was based on the movements of six objects in the Kuiper Belt — the large cloud of icy bodies beyond Neptune. The orbits of these objects seem to indicate that they’ve been pushed around by a larger planet, roughly 10 times the mass of Earth. And this planet orbits super far out from our star — between 200 and 1,200 times the distance between the Earth and the Sun.

Since then, even more evidence has come to light that strengthens the Planet Nine or “Planet X” theory. Additional Kuiper Belt objects have been found with orbits that indicate the planet’s presence. And a study published in October found that Planet Nine may explain why the Sun is tilted on its axis somewhat. But until we actually see this stranger, the case isn’t fully closed just yet.

Blue Origin relaunched its reusable rocket

Private spaceflight company Blue Origin had a good end to last year. In November 2015, the company successfully landed its New Shepard suborbital rocket after flying it to the edge of space — the first time such a feat had been performed. Of course, the whole point of landing such a reusable rocket is to actually reuse it. So that’s what Blue Origin did at the end of January, when it launched and landed the same New Shepard vehicle for the second time. The New Shepard rocket wasn’t so “new” anymore.

Blue Origin continued to conduct test launches and landings of the New Shepard throughout the year. And the normally secretive company even started live-streaming the events, too — an effort to be more transparent with the public. However, the New Shepard vehicle that went through testing all year has since been retired, after surviving a test flight that was supposed to destroy the rocket. More versions of the vehicle should be flying soon.

Scientists announced the discovery of gravitational waves... twice

At the end of 2015, rumors started to percolate online that scientists at the LIGO collaboration had detected gravitational waves for the first time. These ripples in the fabric of space-time were predicted a century ago by Albert Einstein, but had yet to be proven through scientific observation. Gravitational waves were also the last part of Einstein’s theory of general relativity that had yet to be proven, so the scientific community was eager to hear that this phenomenon had been confirmed.

“Ladies and gentlemen, we have detected gravitational waves.”

Buzz about the discovery eventually died off only to pick up again with fervor in early February, when the National Science Foundation held a press conference to announce a new discovery by LIGO. It turned out the rumors were true: “Ladies and gentlemen, we have detected gravitational waves,” David Reitze, the LIGO executive director, triumphantly told journalists at the start of the conference. “We did it.” LIGO’s two observatories in Louisiana and Washington state had made the detection on September 14th, 2015, measuring the waves of two black holes merging 1.3 billion light years away.

But LIGO didn’t stop there. In June, the collaboration’s scientists announced that they had detected gravitational waves for the second time in December 2015, also from the merger of two black holes. And now, LIGO is poised to announce even more discoveries in 2017. The collaboration has spent the past year upgrading the LIGO observatories, making them 15 to 20 percent more sensitive to wave detection. The observatories have been up and running again since the end of November, so it’s possible we have new discoveries to look forward to next year.

Virgin Galactic unveiled its new spaceplane

In February, private spaceflight company Virgin Galactic unveiled its new SpaceShipTwo spaceplane. Dubbed the VSS Unity by famed scientist Stephen Hawking, the vehicle ultimately takes the place of Virgin Galactic’s previous SpaceShipTwo, which crashed during a test flight in 2014. CEO Richard Branson showed off the VSS Unity during a flashy ceremony at the Mojave Air and Space Port in California, where the company conducts its test flights. Branson’s granddaughter even christened the ship by breaking a bottle of milk over the spaceplane’s nose.

After many months of ground tests and a few captive carry flights, the VSS Unity finally glided on its own for the first time this December. The spaceplane has yet to fire its rocket engine, but Virgin Galactic plans to continue tests throughout next year.

Scott Kelly returned to Earth after a year in space

Scott Kelly became the internet’s favorite NASA astronaut this year, as he wrapped up a nearly year-long stay aboard the International Space Station. His extended visit to the ISS was part of a NASA study called the One-Year Mission — an experiment to see how long-duration spaceflight affects the human body. Humans have evolved to live on Earth — with all the gravity that implies — so living in microgravity for lengthy periods of time can wreak havoc on the body’s systems. Kelly served as the perfect subject for this experiment since he has an identical twin, Mark Kelly, who is a retired NASA astronaut. Mark stayed on Earth during his brother’s trip, serving as the study’s control subject.

After 340 days in orbit, Kelly finally came back to the planet in a Russian Soyuz capsule on March 1st. Upon his return, he quickly threw himself into his pool in Houston and then announced his retirement from NASA a week and a half later. Still, NASA has continued to study the Kelly twins and plans to announce the first results of the year-long experiment sometime next year.

SpaceX finally landed at sea — and then landed a bunch more

SpaceX came into this year at the top of its game. In December 2015, the company successfully returned to flight following a six-month hiatus from launches and pulled off its first ever rocket landing. Fresh from that success, SpaceX wasted very little time forging ahead with its Falcon 9 missions in 2016 — as well as its experimental rocket landings. But instead of landing its rockets on solid ground, as the company demonstrated in December, SpaceX went back to ocean landings again. Those entail landing the Falcon 9 on a drone ship at sea after the vehicles launch to space. Of course, SpaceX hadn’t yet mastered its drone ship landings in 2015, so the first two attempts this year were a little... rough.

Following SpaceX’s second explosive rocket landing in March, CEO Elon Musk tweeted that there was a “good chance” that the next Falcon 9 ocean landing would finally work. And sure enough, the odds were in SpaceX’s favor. On April 8th, a Falcon 9 landed intact on one of SpaceX’s drone ships in the Atlantic Ocean, after launching cargo to space for NASA. It was the first time the company had pulled off an ocean landing, and it proved that SpaceX was capable of landing its rockets both on land and at sea. After that, SpaceX went on to land three more Falcon 9 rockets in the ocean and even did another successful land landing in July.

NASA sent the first bouncy castle inflatable habitat to space

The Falcon 9 that SpaceX landed in April was also responsible for sending the first-ever inflatable habitat into orbit. The habitat, called BEAM, was manufactured by private company Bigelow Aerospace, which has a dream of one day filling Earth orbit and beyond with space hotels. Bigelow focuses on an inflatable design because it’s easy for space travel. The habitat launches deflated and compact, saving room on the rocket; once in space, it expands to provide more room for astronauts to move around in.

The BEAM was attached to the Tranquility module on the International Space Station in April, and it took two tries to fully inflate it. But since then, ISS astronauts have entered the BEAM a couple times, and all signs seem to indicate that the module is holding up well in space. Perhaps inflatable space hotels are in our future after all.

Stephen Hawking and Yuri Milner announced Starshot

Some just don’t have the patience for conventional interstellar travel — including Stephen Hawking and Russian venture capitalist Yuri Milner. That’s why the two teamed up to announce a new initiative called Starshot, an ambitious way of sending a spacecraft to another star within our lifetime. Specifically, the goal is to use a giant laser array to propel a micro-satellite to Alpha Centauri, the next closest star system to our Sun. The laser light would “push” on a thin sail connected to the satellite, propelling it up to one-fifth the speed of light. And with Alpha Centauri just over four light years away, the spacecraft would be able to reach the star system in just 20 years. The only problem? Well there are a lot of problems, but one recent study found that a large enough collision with interstellar dust could destroy the tiny satellite on its journey.

SpaceX announced its Red Dragon missions

It’s no secret that Elon Musk wants to start a colony on Mars, and in April his company SpaceX announced its first plans to send spacecraft to the Red Planet as early as 2018. The goal of this inaugural mission: see if SpaceX can land one of its Dragon capsules intact on the Martian surface. Starting a colony is going to require landing a lot of heavy hardware and supplies on Mars. But landing on the Red Planet can be tricky; its atmosphere is too thin to provide substantial cushion for incoming spacecraft, so parachutes alone aren’t enough to slow vehicles falling from space. So far, the heaviest thing that’s ever successfully touched down on Mars is the Curiosity Rover at a little less than 2,000 pounds.

That’s why SpaceX wants to test out a type of landing technique called supersonic retropropulsion — a method of using rocket engines to lower a vehicle down to the ground from space. It’s similar to how SpaceX lands its rockets after launch. For the Mars missions, engines embedded in the hull of the Dragon will help lower the vehicle all the way down to the surface, no parachutes required. It’s a type of landing that’s never been fully tried on Mars before, but if it works, the Dragon will be the heaviest thing that’s ever landed on the planet.

SpaceX says it will send Dragons to Mars every two years

NASA is helping SpaceX out with the “Red Dragon” mission, in exchange for data the company receives from its landing. And SpaceX doesn’t plan to stop after this first trip. The company says it will send Dragons to Mars every two years — when Earth and Mars are closest together on their orbits — in order to establish a cargo route that future colonists can rely on.

First private mission to the Moon approved by the FAA

In August, private spaceflight company Moon Express announced that it had received approval from the Federal Aviation Administration for its mission to send a lander to the Moon. A contender for the Google Lunar X Prize, Moon Express is aiming to send its MX-1 lander to the lunar surface before the end of 2017. However, there is no regulatory framework in place just yet that will allow the US government to oversee a private mission to the Moon and ensure that such a trip doesn’t violate international law. That’s why Moon Express came up with its own “regulatory patch” for the FAA, giving the government enough comfort that the company would adhere to the Outer Space Treaty — an international agreement on how to explore space. The patch worked, and Moon Express received the first ever regulatory approval for a private mission to the Moon.

An international docking adapter was installed on the ISS

This year, NASA took a big step toward making it possible for private spaceflight companies to dock with the International Space Station when astronauts installed the International Docking Adapter, or IDA. Until now, SpaceX and Orbital ATK weren’t actually docking their spaceships. Instead, these companies had to park just next to the space station and wait for the crew to pluck their craft from the void — a process that took up a lot of the ISS astronauts’ time. The IDA will change all of that. It allows for automatic docking with the space station, and it’s also built on an open standard — meaning in the future other companies will be able to build spacecraft that can dock with this port, too. The IDA will also come in handy when SpaceX and Boeing start sending astronauts to the ISS with their new crew-capable spacecraft — though those launches have been pushed to 2018.

It’s going to be a while before the ISS becomes any sort of truck stop in space. NASA originally tried to send the first IDA to space in 2015, but it was lost when SpaceX’s Falcon 9 rocket exploded mid-flight. That means there will only be one IDA-equipped docking station for the foreseeable future, and it’s why this year’s installation was crucial. — Sean O’Kane

Potentially habitable planet found around closest star to Earth

Perhaps the most exciting exoplanet ever discovered was found this year. It turns out there’s a potentially rocky world orbiting around Proxima Centauri — the closest star to our Sun — and to make matters even sweeter, the planet is in the habitable zone. That’s the region around a star where temperatures are just right for water to pool on a planet’s surface. That makes this exoplanet, called Proxima b, the closest place for life to exist outside our Solar System.

We have yet to actually see Proxima b directly, though; astronomers only inferred the planet’s existence based on the movements of Proxima Centauri. And Proxima b is a little too close to its host star for comfort, so it probably gets doused with a lot of solar flares and radiation. That’s not very conducive to life. But despite these problems, astronomers will probably continue to search for answers about this little exoplanet for years to come.

NASA’s OSIRIS-REx mission launched

In September, NASA launched its OSIRIS-REx spacecraft on top of an Atlas V rocket, sending the vehicle on a round trip mission to the asteroid Bennu. OSIRIS-REx is tasked with grabbing a sample of rocks off the asteroid and bringing them back to Earth. Such a sample could provide a unique snapshot of what the Solar System was like when it first formed, since asteroids are thought to be relatively unchanged since that time period. Also, scientists believe that asteroids may have brought life’s building blocks to Earth, and studying Bennu’s samples may help solidify that theory. But it’s going to be awhile before we get those answers. OSIRIS-REx won’t grab a sample from Bennu until 2020, and the spacecraft’s return to Earth is slated for 2023.

Jeff Bezos unveiled the design for the New Glenn

Right now, Blue Origin’s New Shepard is only capable of going to suborbital space, but the company has dreams of building a rocket that can achieve orbit. In September, CEO Jeff Bezos revealed what that vehicle will look like. Called the New Glenn, the rocket looks like it’ll be a monster, towering over SpaceX’s Falcon Heavy and the United Launch Alliance’s Delta IV Heavy. And just like the New Shepard, the New Glenn will be reusable. Bezos says the rocket will fly by the end of the decade, but first it needs to be built at Blue Origin’s future rocket factory in Cape Canaveral, Florida, which is currently under development.

Elon Musk revealed SpaceX’s Mars colonization plans

Missed our coverage on Elon Musk’s Mars talk at IAC? Check out all of our updates from the event here.

After years of teasing, Musk finally revealed the details of how he plans to colonize Mars. The SpaceX CEO gave a highly publicized lecture at the International Astronautical Congress in Mexico, where he outlined the rocket and interplanetary spacecraft he hopes to build to start a permanent human settlement on the Red Planet. The lecture hall where he gave his speech was filled to capacity with people eager to hear Musk’s vision. As ambitious as his plan was, though, there are still quite a few things left to figure out before Musk’s plan can be turned into a reality.

China launched its longest human spaceflight mission yet

China has been pouring copious money, time, and effort into its space program over the last decade, and in 2016 we saw the country’s longest human spaceflight mission. Chinese astronauts (or Taikonauts) Jing Haipeng and Chen Dong spent one month aboard the brand-new Tiangong-2 space station — twice the length of the country’s previous spaceflight record.

China has been pouring copious money, time, and effort into its space program

Despite China’s budding space program, it remains absent from the International Space Station thanks to a contentious law passed by Congress in 2011. Taikonauts aren’t allowed aboard the ISS because they are considered a threat to national security. It doesn’t stop there — Chinese citizens aren’t even allowed to attend NASA conferences. While US relations with China have been contentious — especially recently — the ISS is typically seen as a project that exists above politics. To date, the space station has hosted astronauts from 15 different countries, and major collaborators include Russia, Japan, the European Space Agency. — SO

Orbital ATK flew its Antares rocket again

In October 2014, spaceflight company Orbital ATK lost its Antares rocket when the vehicle exploded in a spectacular fireball during a launch at NASA’s flight facility in Virginia. The source of the explosion was traced to the rocket’s engines, so Orbital decided to replace them with ones made by a Russian manufacturer. The hard work paid off. Nearly two years after the accident, the refurbished Antares flew again, sending cargo to the International Space Station for NASA.

The telescope portion of the James Webb Telescope was completed

In November, NASA finally finished the telescope portion of its James Webb Space Telescope — the successor to the Hubble Telescope that will soon be the most powerful space observatory in the world. The telescope consists of 18 hexagonal mirrors coated in gold, which together form the spacecraft’s primary mirror. JWST will sit a million miles out from Earth and use these mirrors to observe light from the earliest stars and galaxies that formed in the Universe. While the telescope’s main optics are complete, JWST still has to undergo a lot of testing before its ready for launch in 2018. But after spending two decades in development, this space telescope is nearing the end of its Earth life.

The biggest losses for space

Japan’s Hitomi satellite breaks apart in space

In March, the Japanese Aerospace Exploration Agency lost contact with its Hitomi satellite — an X-ray astronomy probe that had recently launched into orbit. Soon, video surfaced showing the satellite tumbling through space. Engineers later learned that a glitch had ultimately caused Hitomi to spin rapidly, which then caused the spacecraft to break apart. JAXA eventually gave up trying to get in contact with the satellite, and the Hitomi mission was lost. But this story doesn’t have an entirely bad ending. Hitomi was able to do a little bit of science before it died: it measured the movements of interstellar gas within a galaxy cluster 250 million light years away.

SpaceX’s Falcon 9 rocket exploded on a Florida launchpad

On the morning of September 1st, those near Kennedy Space Center in Florida heard the sound of a loud explosion and later witnessed a thick trail of smoke rising into the sky. The source was one of SpaceX’s Falcon 9 rockets, which had been getting fueled for a routine engine test. During that process, the rocket exploded in a giant fireball, destroying the entire vehicle and the satellite it was supposed to carry into space.

The explosion forced SpaceX to halt the rest of its launches for 2016

The explosion forced SpaceX to halt the rest of its launches for 2016 as it investigated the accident. The company also had to delay the first flight of its Falcon Heavy — a larger variant of the Falcon 9 that has yet to launch. Musk said the explosion was “the most difficult and complex failure” SpaceX has had in 14 years, but he eventually announced that the company had figured out what caused the incident. However, the accident investigation has yet to be finalized, causing SpaceX to postpone its return-to-flight mission from December to January 2017. An official date for that flight hasn’t been announced.

The Rosetta mission ended

The Rosetta spacecraft spent 786 days orbiting Comet 67P/Churyumov-Gerasimenko. On that final day — September 30th, 2016 — it softly crash-landed on the comet at just two miles per hour.

The spacecraft was launched by the European Space Agency in 2004, and it spent a decade traversing hundreds of millions of miles in order to meet up with Comet 67P. When it arrived in 2014, Rosetta deployed the Philae lander, which became the first spacecraft to land on a comet. There was a problem with that landing, though — Philae’s harpoons, which were supposed to help anchor the craft to the comet, didn’t fire. As a result, Philae skipped across the comet’s surface. The subsequent two years were full of drama as the ESA tried numerous times to establish contact with Philae. The agency finally found the long lost lander, just one month before the mission ended.

Despite the difficulties, Rosetta (and Philae) helped scientists learn a lot about comets, which in turn help us learn about our Solar System’s earliest years. And so it was with many teary eyes and hashtag campaigns that the Earth said goodbye to both Rosetta and Philae this year. — SO

A Russian cargo ship failed to get into orbit

One of the few space catastrophes of the year happened when Russia’s Progress spacecraft burned up in the Earth’s atmosphere. Progress accidentally separated from the Soyuz rocket that was powering the cargo ship to Lower Earth Orbit, and the spacecraft tumbled back toward Earth as a result. It was mostly destroyed in the atmosphere, but debris was found scattered around the remote Tuva region.

Debris was found scattered around the remote Tuva region

The Progress ship was about six minutes into a mission to deliver supplies to the International Space Station when the accident occurred. NASA makes sure the ISS is always more than stocked with supplies in case of situations like this, so the astronauts on board were never at risk — in fact, a previously scheduled cargo run by Japan’s space agency went off without a hitch one week later. For Russia, however, the Progress failure was just the latest in a line of similar mishaps. Roscomos, Russia’s space agency, hasn’t gone one full year without losing a spacecraft since 2009–2010. — SO

Mixed results

The first phase of the ExoMars mission reached the Red Planet

In March, the launch of a Russian Proton rocket put two vehicles on the course to Mars, kicking off the first phase of the ExoMars mission. The venture — a partnership between the European Space Agency and Roscosmos — is aimed at figuring out if life has ever existed on the Red Planet. To do this, the first phase included an orbiter and a lander. The orbiter’s job? Get itself into orbit around Mars, where it can sniff out gases in the Martian atmosphere that could indicate the presence of life on the surface. Meanwhile, the lander was just designed to land, in order to demonstrate that ESA and Roscosmos have the right technology for the next phase of the ExoMars mission: putting a rover on the Martian surface.

A typical trip to Mars takes about six months, though, so the ExoMars spacecraft didn’t reach the Red Planet until October. When the two vehicles arrived, the orbiter successfully inserted itself into Mars orbit — but the lander didn’t fare so well. A problem with one of the lander’s instruments made the vehicle think it was below ground while it was still falling. As a result, the lander deployed its parachute too early and slammed into the Martian surface, creating a new crater.

NASA extended the New Horizons mission, but kept Dawn at Ceres

A year and a half has passed since NASA’s New Horizons spacecraft made its historic flyby of Pluto, but the engineers behind the mission aren’t done with their little space bot just yet. They plan to have New Horizons fly by another object at the edge of the Solar System — an icy body called 2014 MU69. The spacecraft has already made the necessary course correction maneuvers to reach the space rock on January 1st, 2019. All that was needed was the official approval — and funding — from NASA to conduct this extended mission, which the team got in July.

While NASA gave the New Horizons team the go ahead, the team behind the Dawn mission was told to keep their spacecraft where it is. The Dawn probe has been in orbit around the dwarf planet Ceres in the asteroid belt since 2014, and its mission officially ended in June of this year. The mission team had hoped to send Dawn from Ceres to an asteroid called Adeona. However, the space agency decided that it would be better if Dawn stayed put.

Juno got into orbit around Jupiter — and then had a bumpy ride

After five years of traveling through space, NASA’s Juno spacecraft finally reached its intended destination of Jupiter this year and successfully inserted itself into the gas giant’s orbit on July 4th. Since then, the vehicle has encountered a few hiccups. In October, NASA revealed that Juno’s main engine wasn’t behaving as expected, which prevented the space agency from putting the probe into a shorter orbit around Jupiter as was originally planned. And just a few days after that, the mission team announced that the spacecraft had gone into safety mode just before one of its close passes of Jupiter, meaning the vehicle didn’t get any science done during that flyby. NASA has since recovered Juno from safety mode, but the engine problems have yet to be resolved. So for now, Juno is staying in a much longer orbit around Jupiter, meaning its mission could last years longer than expected.

Sean O’Kane contributed to this report. Photo-illustration by James Bareham and Amelia Holowaty Krales.