Strange radio activity picked up from the outer reaches of the universe proved the latest false alarm of finding extra-terrestrial life. Ahead of a public talk by visiting top experts on Great Barrier Island this weekend, science reporter Jamie Morton asked: are we alone in space?
"It's probably just a piece of cosmic spam, the astrophysical equivalent of butt dialling," New York Times science writer Dennis Overbye mused in a column last week.
Overbye was referring to a weird radio spike detected by Russian astronomers more than 15 months ago, yet only revealed at a recent lecture.
The activity, captured by an ATAN-600 telescope, appeared to have come from a sun-like star some 95 light-years away from Earth in the constellation Hercules.
While the news triggered a flurry of excited headlines - see the Sun's especially giddy "ALIEN COVER-UP: Extraterrestrial hunters launch bid to solve mystery of 'alien signal' that's been kept secret for a YEAR" - astronomers soon dismissed the would-be encounter as "noise" that probably came from our own planet.
A spokesperson from the SETI Institute (search for extraterrestrial intelligence) told Overbye: "We covered the frequencies observed by the Russians and more ... No dice."
Although we might not think it, given the explosion of media coverage that often accompanies them, these anomalous radio signals are nothing new.
The most famous came in 1977, the same year Steven Spielberg released Close Encounters of The Third Kind, when SETI astronomer Jerry Ehman was left so ebullient by a 72-second signal from the constellation Sagittarius that he scribbled "Wow!" next to it on the computer print-out.
Researchers have most recently hypothesised the gesture came from a pair of comets.
The big problem with such signals was that they were often not acquired for a long enough time to make any conclusions about them - and were almost certainly not from an advanced alien civilisation.
They might be the result of faults in the detection equipment, local electronic interference, or signals from Earth satellites.
But that's just local sources: all sorts of natural physical phenomena on stars, such as flares, can produce strange and unexpected signals that are completely natural.
At Australia's Parkes Radio Observatory, astronomers detected a burst that came, went and defied explanation - until it was finally traced to an emission from the cafeteria microwave.
When studied closely, none of these "false alarm" signals looked convincing, University of Auckland cosmologist Professor Richard Easther told the Herald.
They typically involved radio astronomy: unlike optical images, taken as a single long exposure, radio signals were easy to record as a continuous stream, so it was easier to find signals that changed quickly with time in radio frequencies.
Sometimes, though, these interesting signals led to big astronomical discoveries.
Pulsars, for example, were originally detected through their periodic radio signals, and were half-jokingly proposed to be something like an alien lighthouse.
The first one, found in the 1960s, was informally dubbed LGM-1 - an acronym for "Little Green Man-1".
"We now know that pulsars are actually formed in supernova explosions," Easther said, "and are objects more massive than the sun that are only tens of kilometres across, and spin up to 1000 times a second - which makes them remarkable objects in their own right, and their discovery was recognised with a Nobel Prize."
Is there life out there?
Meanwhile, the hunt for extra-terrestrial life goes on, and SETI continues to monitor radio waves from space for signs they were created by an intelligent alien culture.
While radio telescopes have become more powerful and numerous across the planet - Auckland University of Technology (AUT) runs a 12-metre device at Warkworth - the challenge isn't with the technology itself, but with the tricky nature of what's actually being captured.
In relative terms, radio waves don't really travel that fast - so our radio and television emissions into space have created a bubble of noise stretching only around 200 light years across.
"A more advanced civilisation might have a longer timeframe for its broadcasts, but there is strong evidence that after travelling about 100 light years any signal would become so attenuated by other background radio 'noise' in space that it would be virtually undetectable," said AUT astrobiologist Professor Steve Pointing.
"The big advances in the search for life on other planets have, for me, been through understanding the history of water on planetary bodies in our solar system and how this has led to the concept of habitable zones around a star, coupled with the discovery of thousands of potential Earth-like planets orbiting other stars, with a significant number of them in this habitable zone."
If we were to find life on another planet, scientists expect this will be first achieved somewhere within our own backyard: perhaps with traces of life on Mars, which may have had liquid water on its surface in the past, or on one of Jupiter's intriguing moons.
Read more: Island event poses cosmic queries
Its sixth closest, Europa, also might have extensive liquid water oceans under a solid crust of ice.
Given discoveries that life on Earth could exist in extreme conditions - consider the microscopic, ultra-hardy extremophiles that happily live around sub-ocean thermal vents - it could be speculated that there may exist similar species there.
But proving they were from another planetary body would demand irrefutable evidence that the origin was indeed extra-terrestrial; one only had to look to recent false positive claims such as those of fossilised Martian microbes in the Antarctic meteorite ALH 84001.
Those holding out for something we might consider intelligent would probably have to wait for space telescopes such as the new tennis court-sized James Webb telescope to detect a planet with spectral signatures that indicated civilisation.
Conventional optical astronomy was considered a great tool for finding planets, because stars and the planets that orbited them emitted most of their energy as visible light.
"A planet like the Earth orbiting another star might be detectable via its oxygen-rich atmosphere, but current telescopes are not big enough to sense this directly - however one of the design goals for the coming generation of big telescopes is to be able to better explore the solar systems we are now discovering," Easther said.
His colleague at the University of Auckland's Physics Department, Dr Nick Rattenbury, felt that receiving a bona fide radio communication from an alien species would be enough evidence for life other than that on Earth.
Striking up a conversation with E.T. would be even better.
"Such a conversation would be rather different to those we're used to, as we'd have to wait for ages for a response to any of our questions owing to the finite speed of light of any transmissions we - or they - make," Rattenbury said.
"For this reason, I expect that our first convincing evidence of an alien species will be through the receipt of a radio signal from their civilisation."
Aliens "wouldn't look like us"
What would such a species look like?
The answer remains sketchy, because we're still only beginning to understand life on Earth.
Could there be a life form on Saturn's moon Titan, or floating high in the atmospheres of worlds like Jupiter or Venus?
A Google search of the "Panspermia Theory" offers up another mind-blowing concept; that there may be some lifeforms which can survive in outer space and can travel between planets.
"What life might look like on alien worlds has been the subject of some fascinating science-fiction, some of which is well motivated by our understanding of life in all the environments in which it is found here on Earth," Rattenbury said.
"Certainly when we look at the number of living organisms on Earth, complex life forms are far outnumbered by smaller, simpler organisms."
Assuming a similar process for the emergence of life occurs elsewhere, we might well expect that on an alien world, simpler life forms such as bacteria or microbes are more prevalent and would evolve first, before more complex organisms like our own.
But Pointing wasn't even sure why popular culture tended to colour aliens green, let alone represent them as bipedal beings like ourselves.
"Any large animal is unlikely to have evolved to gain energy via photosynthesis using a green pigment like chlorophyll," he said.
"To me an alien would be much more likely to have dark skin that may have evolved through exposure to UV light."
More to the point, it was "highly unlikely", for energetic reasons, that a reptile or insect could evolve to become large and sentient like us humans - which is perhaps a relief for people picturing the terrifying beasts from the 2002 film Signs.
Unsurprisingly, whether aliens exist was a common question among visitors to Auckland's Stardome Observatory - and most people had quite strong opinions on the issue, resident astronomer Dr Grant Christie said.
"A minority think we have already been visited by alien craft."
For his part, Christie believed the evolution of life into a technological civilisation such as ours may be very rare - perhaps just one case per galaxy.
However, he added, extrapolation from a sample of one was always going to be highly debatable.
"Our own civilisation is young and we are already placing our planet in peril through destabilisation of Earth's climate and ecosystem," Christie said.
"Therefore based on the evidence of our own civilisation - the only one we know of - the ability to send and receive signals may be restricted to a very narrow window in time before the civilisation fades."
But, if we weren't too late, the discovery that life had formed independently from that on Earth would clearly be one of the greatest discoveries of all time, something that would touch every aspect of faith, society, philosophy and science.
As efforts on Mars and other exploration missions planned for Europa were all aimed at answering the questions related to the formation of life, there was no shortage of appetite from governments or the science community for tackling it.
Indeed, understanding how life happens was near the top of any list of big questions for science - and not just to know whether life exists elsewhere, but to help us understand how life begins.
The Kiwi connection
In New Zealand, there's a sprinkle of research going on that's loosely linked to the topic.
One connection is the strong collaboration between the Nasa Ames Research Centre and AUT, looking at how microscopic life in Antarctic rocks might be a good model for how life may have persisted on Mars until relatively recently.
Kiwi researchers from several institutes are contributing to the building of the gigantic Square Kilometre Array radio telescope, which will have a much higher sensitivity and resolution than anything in the world today.
And since the early 2000s, the Japan-New Zealand Microlensing Observations in Astrophysics (MOA) collaboration has been discovering extra-solar planets using a technique called gravitational microlensing.
"The technique we use is more sensitive to the detection of cold planets, however, rather unlike those orbiting in the habitable zone," said Rattenbury, an MOA member who contributed to the first discovery of a planet using the method.
"However, the discoveries made by the microlensing groups, both here in New Zealand and around the world, have advanced our understanding of what type of planetary systems exist in our galaxy, and challenges our current understanding of how planetary systems form."
Still, there were relatively few people making direct searches for alien life, Easther said.
"On the other hand, searching for simple life provides a huge impetus for exploring our own solar system with robotic spacecraft.
"Likewise, understanding the sorts of planetary systems that can exist around other stars is one of the biggest topics in astronomy right now, and part of the reason it is exciting is that it will let us understand the possible homes for life that might exist throughout the universe."
Easther noted how his own field, cosmology, had progressed over the last 25 years from being seen by many scientists as an almost hopelessly speculative area to the point where rigorous tests of theories of the evolving universe could be made.
"My sense is that searches for life elsewhere are likely undergoing a similar transition - the big questions have always been there, but we are developing the tools we need to tackle them directly."
Similarly, the study of astrobiology had grown remarkably over the last decade.
Thousands of exoplanets have been discovered, and our understanding of planetary formation and of the exoplanets found to date suggests that the galaxy is teeming with planets.
Rattenbury pointed out that a certain fraction of those orbited their host star in the habitable zone.
"The question then of whether life could arise on planets other than our own Earth has been advanced considerably," he said.
"There appears to be strong reasons to accept that there will be planets around stars other than our own sun on which conditions are similar to those on Earth, and therefore the question of whether life could, or does, exist on such planets is much less academic than it was previously."
Could we be alone?
Was there a chance that we actually are alone in the universe?
It's possible - but with more planets out there than there are grains of sand on Earth, probability suggests we have company somewhere.
Christie figured it was certainly possible we're the only technological life form in the Milky Way, a galaxy about 13 billion years old.
"If a technological civilisation only lasted for 10,000 years and they were rare, then there may be almost no chance that two ever co-existed in our galaxy - but of course, that assumption may be wrong."
Many features of the formation and evolution of our own planet were arguably flukes, but, presently, there was no way to calculate the chances.
Much depended on the forms that life can take, Christie said, and we'd only had a chance to study one planet so far.
"We've found amino acids in space and in meteorites so it looks like they are common and therefore likely that those molecules could have assembled into life given a favourable environment."
But how far, really, are we down the track?
Countless blips like the Russians' spike have yielded a result of zero for SETI.
Easther believed that while we have better technologies for making a search, it was hard to measure our progress, simply because we have no idea about how hard it will be to find anything.
"We may be hunting unicorns."
The free public talk, Is There Life Out There, will be held this Saturday at the Great Barrier Island Sports and Social Club from 2.30pm to 5.30pm.
Panellists include AUT astrobiologist Professor Steve Pointing, US planetary scientist Dr Faith Vilas, Weta Digital creative arts director Gino Acevedo and Vatican Observatory director Brother Guy Consolmagno. Registration is essential, and people can book by emailing firstname.lastname@example.org or via the event's Facebook page.