The year of milestones in space

In this handout provided by the National Aeronautics and Space Administration (NASA), SpaceXs Falcon 9 rocket and Dragon spacecraft lift off from Launch Complex 40 at the Cape Canaveral Air Force Station for their eighth official Commercial Resupply (CRS) mission on April 8, 2016 in Cape Canaveral, Florida.
NASA | Getty Images

Whatever you think of life on Earth in 2016, it was a year of milestones for space.

Space travel companies made technical leaps, NASA reached Jupiter, and great discoveries were made. There were also high-profile failures and sad moments, as great scientists and astronauts left Earth forever.

Here are a few of the highlights:

Gravitational waves detected...twice!

A black hole in the milky way.
Universal History Archive | UIG | Getty Images

On Feb. 11, scientists announced they had detected gravitational waves rippling through space. Gravitational waves are echoes from the collision of two black holes billions of years ago.

The discovery confirmed the existence of the phenomena articulated by Albert Einstein about 100 years earlier. Four months later, that same group of scientists detected the waves again.

"Gravitational waves are a different kind of information, and it is a kind of information we have never had before, these two detections," Dave Reitze, a professor of physics at the University of Florida, and the executive director of the Laser Interferometer Gravitational-Wave Observatory, told CNBC in June.

"This is a new kind of astronomy, this is a new frontier for high-energy astrophysics," he said. "It will let us look at these events in ways that nobody else can look at them."

Return from longest stay on the ISS

Russian cosmonauts Mikhail Kornienko, left, Sergey Volkov of Roscosmos, center, and Expedition 46 Commander Scott Kelly of NASA, rest in
Bill Ingalls | NASA | Getty Images

American astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko returned from the One-Year Mission March 2, ending the longest stay on the International Space Station.

The mission was designed to study the long-term effects of human habitation in space. Already, being in weightlessness for so long lengthened Kelly's body by 2 inches.

Kelly's twin brother, Mark, who is also an astronaut, served as a control subject on Earth. The two are so close genetically, it will be easier for scientists to determine which changes to Scott's body may be the result of his time at the ISS.

SpaceX nails landing of a Falcon 9 on a drone ship

SpaceX's Falcon 9 rocket stands after making its first successful upright landing on the 'Of Course I Still Love You' droneship on April 8, 2016 some 200 miles off shore in the Atlantic Ocean after launching from Cape Canaveral, Florida.
NASA | Getty Images

After several failed attempts, SpaceX accomplished a major feat April 8: landing one of its reusable Falcon 9 rockets on a drone ship in the water. It was the first time the company landed a rocket on water, and the second time it landed one at all. SpaceX's four previous attempts to land on water had failed.

SpaceX has built its business strategy, in part, around cleverly cutting costs. Perhaps the best example of this is its plan to reuse rockets, which could save millions of dollars per launch — though that requires landing them first. SpaceX already has plans to relaunch the rocket it landed.

A new kind of space habitat hooked onto ISS

Inflated BEAM module (balloon structure at top center) berthed to the Tranquility node of ISS.

The successful water landing was not the only major accomplishment of SpaceX's April launch. It also ferried the Bigelow Expandable Activity Module (BEAM) to the International Space Station, taking the concept of low-cost prefab housing to outer space.

The BEAM represents a new approach to quickly building lightweight, easily transportable habitats and structures off planet. If successful, these structures could rapidly accelerate human space travel.

BEAM foregoes the use of rigid (and often heavy) building materials for a collapsible manufactured structure that is expanded once in place. This saves a tremendous amount of weight and space in cargo holds. Once in place, the BEAM can be used either as a living or working area, and can be outfitted with whatever equipment astronauts need. Single pods can be strung together to make larger structures.

The BEAM is currently undergoing testing at the International Space Station.

NASA's Juno mission reaches Jupiter

(From L) Geoff Yoder, acting administrator for NASA's Science Mission Directorate, Diane Brown, NASA Juno program executive, Scott Bolton, Juno principal investigator, Juno Project manager Rick Nybakken, Guy Beutelschies,and Lockheed Martin director of space exploration, celebrate at a press conference after the Juno spacecraft was successfully placed into Jupiter's orbit, at the Jet Propulsion Laboratory in Pasadena, California on July 4, 2016.
Robyn Beck | AFP | Getty Images

After five years of flying through space, NASA's unmanned Juno spacecraft in July finally reached its destination: Jupiter.

Launched in 2011, Juno is the second craft launched as part of NASA's New Frontiers program. The mission's purpose, according to NASA, is to peer into Jupiter's atmosphere to measure water levels, temperature, and the movement of atmospheric clouds. It is also measuring the planet's massive magnetic field.

"Juno is very special because it is one of those rare missions where it is entirely focused on looking inside Jupiter," Curt Niebur, lead program scientist for New Frontiers, told CNBC in July. Being covered with and largely composed of gaseous elements, Jupiter does not have the kind of same kind of rocky surface a planet like Mars or Earth has.

"With the instruments and techniques we are using, we can unzip the planet and really peer inside it and understand what its deepest internal structure is," Niebur said.

SpaceX Falcon 9 rocket explodes on launchpad

Musk: SpaceX explosion toughest puzzle we've ever had to solve

SpaceX watched a Falcon rocket carrying a multimillion-dollar satellite go up in flames during a pre-launch test at Cape Canaveral, Fla., just days before it was set to launch at the beginning of September. The company spent the next two months attempting to tease out the cause of the fire, at one point investigating the possibility of sabotage.

The rocket was supposed to carry a satellite commissioned by Facebook CEO Mark Zuckerberg's initiative to bring wireless internet to Africa. In an interview with CNBC, SpaceX CEO Elon Musk said figuring out the cause of the explosion was "the toughest problem we have ever had to solve."

"It was a really surprising problem," Musk said. "It's never been encountered before in the history of rocketry."

Musk said the explosion's cause "basically involves a combination of liquid helium, advanced carbon fiber composites, and solid oxygen, oxygen so cold it actually enters solid phase."

SpaceX had to delay launches scheduled for the end of the year, but recently has been gearing up for another launch.

Elon Musk announces plan to colonize Mars

Elon Musk
Brendan Hoffman | Bloomberg | Getty Images

Undaunted by the loss of the rocket, SpaceX's Musk took the stage at the International Astronautical Congress in Guadalajara, Mexico, on Sept. 27, to lay out the technical and financial details of how he plans to put human settlements on the Red Planet. The long-term goal is turning the human race into a "multi-planetary species," enabling humans to evade catastrophes on Earth.

During his remarks, Musk said a crewed mission to Mars could happen in 10 years "if things go super well," and said funding the mission is the primary reason he is accumulating wealth.

ExoMars mission loses Schiaparelli lander

Mars as seen by the webcam on ESA’s Mars Express orbiter on 16 October 2016, as another mission, ExoMars, is about to reach the Red Planet.

The European Space Agency lost its Schiaparelli lander Oct. 19, during its ExoMars mission to the Red Planet. But the Mars Express orbiter that deployed it will still be able to execute the major pieces of the mission's goals.

The Schiaparelli probe was part of a larger mission to determine whether there could be life on Mars. Despite the setback, the Mars Express continues to orbit the planet, collecting data and delivering some stunning images.

Pioneering astronaut John Glenn dies

US astronaut and senator John Glenn waves as he leaves the Operations and Check out building at the Kennedy Space Center, FL, 29 October in route to board the US space shuttle Discovery.
Roberto Schmidt | AFP | Getty Images

The first American astronaut to orbit the earth, John Glenn died at age 95 on Dec. 8. Glenn, a former Marine, had been hospitalized just before his death.

The icon was most famous for flying around the earth in the the Friendship 7 space capsule back in 1962. The accomplishment allowed the United States to match Russia's accomplishment, in one of the earliest events in the ongoing "Space Race" between the Soviets and the United States.

Glenn was later elected to the United States Senate, serving from 1974 until 1998. But he was perhaps always best known as an astronaut. While still serving in Senate, Glenn became a crew member of the Discovery space shuttle in 1998, making him the oldest person to fly in space.

Dark matter researcher Vera Rubin dies

World famous astronomer Vera Rubin, 82, in her office at Carnegie Institution of Washington in Washington, DC on January 14, 2010.
Linda Davidson | The Washington Post | Getty Images

Dark matter makes up much of the material in space, and yet we know so little about it. Vera Rubin was one of the scientists who shed a bit more light on it.

Rubin, who died at age 88 on Dec. 25, figured out that galaxies don't spin exactly as physicists had once thought. The discovery suggested there must be other forces acting upon them in the universe.

Enter dark matter, the mysterious substance that makes up more than a quarter of all of the matter in the universe. As NASA's Science Directorate quips, "We are much more certain what dark matter is not than we are what it is."

While there is still much to be learned, Rubin's discovery showed scientists something was there. President Bill Clinton presented Rubin the National Medal of Science in 1993.