2015: A year that was out of this world

FROM Pluto probes to potentially habitable worlds, 2015 was an incredible year in space exploration. Here’s six of the most significant moments.

FROM Pluto probes to potentially habitable worlds, 2015 has been an incredible year in space exploration. Here’s six of the most significant moments:

PLUTO UNMASKED

For almost a century Pluto has been little more than a pinprick of light. Even the Hubble Space Telescope couldn’t show us more than a blotchy little orb. Then, after a 4.9 billion kilometre, nine-year journey, the New Horizons space probe finally arrived in July.

What it saw sent shivers through the spines of the world’s astronomical community.

“Far from a frozen, geologically ‘dead’ world it surprised us by revealing an active geology — revealed by smooth resurfaced ice, free of meteorite impacts,” says Swinburne University astrophysicist Dr Alan Duffy.

“It has mountains and valleys like those that form on Earth through tectonic plates moving. But what powers this on such a cold world? Then it was seen to have an atmosphere that’s blue like Earth, but with ice that’s stained red by organic gunk called tholins that we still don’t understand. What a year ...”

An artist impression of the surface of Kepler 452b. Pic: SETI Institute/Danielle Futselaar

EARTH’S DISTANT COUSIN

There’s nowhere like home. Well, perhaps there is.

Kepler 452b. It’s the first out of more than 1900 worlds found orbiting distant stars that looks a whole lot like our own.

“This world, Kepler 452b, is in the goldilocks zone around its Sun-like star, meaning the surface temperature isn’t too hot or too cold for liquid water to exist,” Dr Duffy says. “It’s the closest in size to Earth too, only 60 per cent wider. This means it’s probably got a thicker atmosphere so might be closer to Venus with a hellish landscape. For now we’ll have to wait for new telescopes to launch to learn more.”

We also won’t be visiting any time soon. It’s some 1400 light years away.

“Based on this rapidly increasing number of new worlds, we’re much more confident in statements like ‘every star probably has some kind of planetary system in orbit around it’,” says Dr Charley Lineweaver from the Planetary Sciences Institute at Mt. Stromlo Observatory.

“More specifically, estimates for the number of planets in the habitable zone have also increased significantly. This is ongoing research, but this year has given us thousands of new planets to think about.”

Dr Duffy agrees: “What it does prove is that Earth isn’t unique and that there are other rocky worlds around Sun-like stars that might be habitable.”

Planet J1407b which has rings that are 200 times larger than those Saturn.

ALL THINGS WEIRD AND WONDERFUL

While Kepler 452b had significant implications for the existence of life out there, other discoveries helped prove how amazing the universe we live in really is.

“Dozens of new planets are being found each year, and some are truly bizarre,” says Associate Professor Michael Brown of Monash University.

Take Planet J1407b.

“This planet has rings that are 200 times larger than those Saturn,” he says. “As J1407b orbits its Sun-like star, the rings block a detectable fraction of the star’s light, which astronomers can detect from Earth.”

The ringed planet is the first of its kind seen outside our solar system. But its scale is truly amazing.

Analysis of the planet shows its has a series of 30 rings, each tens of millions of kilometres in diameter.

And then there’s the strange, stuttering star KIC 8462852.

Is it caused by an ‘alien megastructure’? Or some strange, previously unknown natural phenomena.?

Ongoing analysis of the star since attention was first directed at its unusual blinking seems increasingly to support the idea of large masses of comets having been kicked up by a passing wanderer, sending them down towards the star in erratic clouds.

Comet 67P Churyumov-Gerasimenko.

ROSETTA — UP CLOSE AND PERSONAL

Catching and orbiting a fast-moving comet may seem complex enough. But what about landing a probe the size of a refrigerator on its surface?

The Rosetta space mission achieved this in late 2014, with the first streams of data beginning to flood through early this year.

“We’ve been able to make incredible science from this fossil of the earliest days of our Solar System,” Dr Duffy says.

“The theory of Earth’s seas and oceans being filled by comets like 67P crashing into us over billions of years no longer holds water (sorry) as the isotope ratio simply doesn’t match.”

What wasn’t found on Comet 67P is equally significant. For example, there was little trace of a magnetic field. This puts astrophysicists back to the drawing board when it comes to understanding the mechanics behind our solar system’s formation.

“By finding molecular oxygen in the comet we’ve learnt that it formed in a solar system twice as warm, but much less violent, than our understanding previously suggested,” he says.

“That’s why we undertake incredible technological breakthroughs necessary to explore space,” Dr Duffy says.

Dark, recurring streaks on the walls of Garni Crater called "recurring slope lineae," are hypothesised to be formed by the flow of briny liquid water on Mars.

WATER ON MARS

After decades of speculation, we now have definitive proof: Liquid water still flows on Mars.

Just.

“The only other place we know of in the universe where this happens is Earth and, at least on our world, where there’s water there’s life,” Dr Duffy says.

The giveaway was a series of recurring streaks on the edges of some craters. Water had been flowing down the walls, leaving behind darkened patches of ground where the liquid had mixed with salts.

And it was these salts which had prevented the water from freezing in the first place.

Are there underground reservoirs? Or is it some form of precipitation?

We don’t know. Yet.

Nor can we determine if this water supports microbial life.

“Unfortunately Earth bacteria are so hardy that we can’t properly sterilise our spacecraft to prevent contamination of these sites so landing there isn’t on the cards just yet. We couldn’t be sure any life we find is not just something we’ve brought with us …” Dr Duffy says.

What’s next?

“2015 brought more questions than answers on Mars but fortunately a new fleet of probes are heading there in the next few years to investigate further,” Dr Duffy says.

Associate Professor Michael Brown takes the notion one step further: He says the movie “The Martian” — a story where key parts of the plot are driven by science — was itself a significant event for astronomy.

“Millions of people have gone to see the Martian, where transfer orbits and escape velocities were central to the plot. Astrophysics doesn’t have to be purely explanatory, but can be part of the human story too,” he says.

Streaks on steep Martian slopes, such as the walls of craters, could be formed by salty water. Pic: NASA

SEARCH FOR INTELLIGENCE POWERS UP

One of astronomy’s most significant events hasn’t produced any results yet.

But it’s a whole lot more likely to do so because of it.

It is the gift of $US100 million to the Search for Extraterrestrial Intelligence — SETI — by Russian billionaire Yuri Milner.

“This is why the search for extraterrestrial intelligence is so exciting in 2015, and will only become more so in 2016,” Dr Duffy says.

“Project Breakthrough Listen will tune into any potential radio signals from a million of the closest stars as well as from 100 of the closest galaxies. The search is 50 times more sensitive of 10 times more of the sky of 5 times more of the signal, all 100 times faster than has ever been attempted than before. “