Cassini's demise

After two decades of circling Saturn while also exploring the gas giant's famed rings and fascinating moons, NASA's Cassini spacecraft ended its mission in a blaze of glory in September.

The probe discovered that both Titan and Enceladus are ocean worlds. It even flew through the spray of the huge geyser at the latter's south pole, picking up hints of the moon's potential habitability. Along the way it also proved to be one of humanity's greatest photographers ever.

Asteroid 2012 TC4

Asteroids are whizzing about the inner solar system all the time, but astronomers are now tracking and discovering more so-called near-earth objects than ever before. 

2017 saw a number of newly-spotted space rocks whizzing closer by the Earth than the distance to the moon, including a return visit from Near Earth Asteroid 2012 TC4, which is surrounded by a blue circle in this ESO image.

All the asteroids that made headlines passed safely by us in 2017, but an impact can't yet be ruled out for the 2079 visit by 2012 TC4.

SpaceX gets Xtra serious

After suffering a major setback in 2016, SpaceX not only resumed launching its reusable Falcon 9 rockets, it also picked up the pace, doubling the amount of completed missions over the prior year. Those missions included satellite and secretive space plane launches as well as resupplying the International Space Station.

Elon Musk's rocket company now plans even more launches for 2018, including the debut of its massive Falcon Heavy rocket.

Musk to Mars 2.0

Elon Musk debuted his grand scheme to colonize Mars in 2016 and returned in September to double down on the plan, saying that SpaceX has found ways to make it cheaper to pull off and that unmanned rockets could start making the Red Planet voyage as soon as 2022.

The project comes with a possible side benefit that stole the show this year: Musk's Mars rocket could also be used to transport passengers from one side of the Earth to the other in under an hour.

Blue Origin builds up

Not to be outdone by Elon Musk and SpaceX, Jeff Bezos and his Blue Origin continued to test and develop rival reusable rockets. It was also revealed that Bezos has designs on colonizing the moon, perhaps with help from extra-planetary Amazon shipments.

Asgardia alights

The first "space kingdom" claimed its territory in November when the cubesat Asgardia-1 left Earth. The tiny satellite is basically an orbiting server for the many "citizens" of the virtual nation Asgardia and makes up the entirety of its territory.

Founder Dr. Igor Ashurbeyli hopes to eventually expand the country to include stations and "arks" in space where humans can actually live one day.

The first interstellar visitor

For the first time ever, astronomers detected an object thought to be passing by from beyond our solar system when the oddball asteroid (or maybe comet? or alien craft?) now called 'Oumuamua was first spotted in October.

The space rock has a very unusual shape for an asteroid, leading some SETI researchers to check it for signs of extraterrestrial intelligence.

The black hole that shouldn't be

In December, astronomers discovered a supermassive black hole so large that it shouldn't exist. The black hole dates to when the universe was very young, but is so huge (at 800 million times the mass of the sun) that astronomers can't figure out how it grew so big so fast.

Stay tuned for updates on this one in 2018.

Life on the (other) moon?

Space plumes were a big deal in 2017. NASA revealed that Cassini data suggests the building blocks of life are present in the spray from Enceladus' south pole that originates from the moon's subsurface ocean. The moon of Saturn and Jovian satellite Europa are now among the most exciting prospects in the search for life beyond Earth.

Phoning E.T.

We are definitely not hiding from the aliens any longer, if we ever were. In November, a group of artists and scientists sent a message designed to be received by alien intelligence in the direction of a nearby star system with a potentially habitable exoplanet. 

The message features music and math, and if anyone is out there to receive it, we could conceivably get a response as soon as 2042.

Gravitational wavy gravy

Gravitational waves continued to be a big deal in 2017 with a Nobel Prize going to the collaboration that discovered them. Meanwhile, detections of the ripples in the fabric of space-time continued to be made, including the first detection of the waves from colliding neutron stars that was seen by astronomers as well as "felt."

This a particularly important first, ushering in a new era of what's called "multi-messenger astronomy" that could help unravel some of the universe's mysteries.

Earth-like exoplanets abound

Astronomers once again discovered a multitude of new exoplanets in 2017, including some similar to Earth such as Ross 128 b, only 11 light years  away, and perhaps the best exoplanet to check for signs of life.

By Jovian, it's Juno!

NASA's Juno spacecraft arrived at Jupiter in late 2016 and began sending back all kinds of trippy photos, sounds and fascinating data about the gas giant and its iconic red spot this year.

Searching for life on Ceres

Huge asteroid belt dwarf planet Ceres has thrilled us with its mysterious bright spots in past years, but in 2017 it joined the growing list of spots in the solar system that might be worth checking closer for signs of life or at least habitability. Research shows the building blocks of life may be hiding on the mega asteroid.

The space president?

President Trump signaled during his first year in office that space is part of his agenda. He set a target date of 2033 for sending astronauts to Mars, revived the National Space Council and directed NASA to return to the moon.

Beyond Pluto

Pluto is no longer a planet, but in 2017 the search for other solar system planets even further out in space grew more intriguing. The gravitational influence of a hidden ninth planet could explain the strange movements of some Kuiper Belt objects and this year the effort to spot such a large, distant object ramped up.

This year also saw the debut of new theories, including the existence not just of an unseen ninth planet, but of a 10th planet as well.

Listening for E.T.

The effort to scan the skies for signals from across the cosmos got a boost in 2017 from initiatives like the Stephen Hawking-backed Breakthrough Listen, new telescopes in Australia and elsewhere.

Some weird signals have already been picked up, including the especially mysterious phenomenon of "fast radio bursts."

No definitive signs of E.T. have been heard just yet, but some false positives were ruled out and plenty of new data was collected to analyze over the past 12 months.

The weirdest star abides

KIC 8462852, also known as "Tabby's Star," "Boyajian's Star," the "alien megastructures star" or just the weirdest star in the universe, continued to confound astronomers two years after first making news with its odd, unpredictable habit of dimming.

Telescopes trained on the star in May when it started doing weird things again and new theories posit that lots of space dust, and not alien structures may be responsible for the star's odd behavior.

Still Wowing us

Forty years after first wowing astronomers, the so-called "Wow! Signal" was a point of discussion again in 2017. When one scientist proposed that comets could explain the inexplicable signal picked up by a radio telescope in 1977, Aliens could still explain the "Wow signal," scientists say, keeping alive the possibility that some sort of extra-terrestrial intelligence could be behind the exciting signal.

Proxima b, close to home

The nearest planet beyond our solar system, Proxima b, continued to be a source of excitement for astronomers in 2017. Scientists see evidence of an atmosphere on the earth-sized planet and models of the potential climate there show it just might be able to host life.

Space youth?

New findings in January from NASA's study of twin astronauts Scott and Mark Kelly surprised researchers. Scott was the first person to spend a year in space on board the International Space Station while Mark remained on Earth.

Preliminary results on the changes Scott's trip included the intriguing observation that sections of his DNA associated with longevity grew longer. More study is needed, but the finding has scientists wondering if space could be a counterintuitive fountain of youth.

Super supernovas

Space watchers spotted a number of high profile and unique supernovas in 2017. Dying stars often collapse in a spectacular explosion or "go supernova" at the end of their lives.

In February, astronomers spotted the very early stages of a supernova explosion for the first time. In November, another supernova that appears to have exploded multiple times over decades, was identified to the bafflement of scientists.

Traversing the Trappist-1 system

Of the many distant stars hosting exoplanets, Trappist-1 is one of the most enticing. First announced in February, the system boasts no less than seven planets, including three that could be in the habitable zone.

Fast Radio Bursts hit repeat

The odd phenomenon of "fast radio bursts," quick, bright bits of radio signal from across the cosmos, became weirder in 2017 when one of the bursts from a distant galaxy was observed to repeat. No other FRBs have ever been picked up more than once. More data should be forthcoming in 2018.

Fake News in spaaace

Finally, even with the abundance of fascinating space news in 2017, a number of false, exaggerated or misrepresented stories also grabbed headlines, continuing the fake news trend that went mainstream in 2016. 

So just for the record, Earth was never seriously threatened by a killer asteroid or a hidden planet at any point in 2017. And no, there is no child slave colony on Mars. I don't anticipate any of these things happening in 2018 either, but there should be plenty more exciting space news to come during our next trip around the sun.