2015 was a great year for space exploration

NASA announced this week that it will be canceling the planned March 2016 launch of the InSight mission to Mars, which is designed to study the Red Planet's geology and seismic activity.

The cancellation was necessary, given concerns over the functionality of on-board instruments crucial to the mission, and there is hope the craft will be able to launch again in just over two years if the problems can be corrected. Nevertheless, it was a disappointing day for fans of planetary science, and NASA's space programs, and it made it a bit too easy to forget that 2015 was a huge year for space exploration, planetary science and astronomy.

Here are just some of the discoveries and developments brought by space agencies, researchers and the burgeoning commercial space industry this year.

—By CNBC's Robert Ferris
Published 24 December 2015

Boeing and Space X have been awarded three of four guaranteed contracts to fly commercially supplied crewed missions to the International Space Station. NASA announced this week it has ordered its second commercial crew mission from Boeing — the company received its first order in May. Space X was also awarded a contract in November to build a spacecraft capable of carrying astronauts and cargo to the ISS. NASA hopes the program will send astronauts into space as early as 2017.

Both Elon Musk's company Space X and Jeff Bezos' company Blue Origin successfully landed booster rockets intact after launching them — an unprecedented feat in space technology. Until now, rockets have typically been damaged or destroyed after launches. Reusing them could save a lot of money — a single Falcon 9 rocket costs $60 million to build, according to NBC News.

In late October, NASA's Cassini spacecraft completed the closest ever flyby of Saturn's icy moon Enceladus, which is still geologically active. Saturn has 62 moons.

NASA mission New Horizons became the first-ever to fly past Pluto, gathering data and the clearest images ever seen of the dwarf planet.

Because Pluto has essentially been in "deep freeze for the last 4.5 billion years," the mission could provide scientists with more insight into how the Earth was formed than many of the nearer, more geologically active planets, astronomer Mike Brown told CNBC.

Though perhaps overshadowed by Pluto, the dwarf planet Ceres should not be forgotten. NASA's Dawn spacecraft in March became the first in history to orbit Ceres, after traveling 3.1 billion miles.

Researchers found the strongest evidence yet that there may be (or may have been) flowing liquid water on the surface of Mars, according to a paper published in Nature Geoscience in late September.

"The most exciting thing about the announcement today is that it would be possible to have life on Mars," said NASA's John Grunsfeld.

NASA scientists identified a planet outside our solar system that exists in a "habitable zone," meaning it is located at a distance from its star that might make it hospitable to life.

"It's awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth," said research team leader Jon Jenkins, of NASA's Ames Research Center. "That's substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet."

The famous telescope has been capturing stunning images and furthering knowledge of space for a quarter of a century.