How do you hunt for extraterrestrial life? You visit other planets, you find new planets, you study our own planet, or you listen.

All four methods came together last night at the World Science Festival when four speakers took part in a conversation called, simply, “The Search for Life in the Universe.” When you put four lively scientists with four different ways of thinking on a stage together, consensus isn’t the first thing to emerge. But the panel could agree on one thing: If you yearn to know whether we’re alone in the universe, it’s a hell of a time to be alive.

1. Mars

Steve Squyres of Cornell University is one of the project leads on the Mars rovers, those endurance robots Spirit and Opportunity that continue sending back Martian data. Spirit may be stuck, but in this week’s edition of the journal Science, Squyres’ team has published a new study based on information the rover found at a rock outcropping called Comanche about four years ago.

Spirit found evidence of carbonates that would have formed in the presence of water. The rover had done that before, but what’s exciting now, Squyres says, is that the chemistry of these new carbonate finds show they formed in water of a more neutral pH, rather than the more acidic circumstances that would have formed prior carbonate finds.

That water no longer flows on the martian surface, but “this points to more life-friendly conditions” billions of years ago, he said.

2. A Second Earth?

Humans have long imagined faraway planets around other stars, Harvard astronomer David Charbonneau said. “We are all alive at this magical moment when we have the technical ability to find those planets.”

The count of known exoplanets now stands at greater than 400, and astronomers have found most of those by one of two methods. There’s the wobble, in which astronomers spy a star jostled ever so slightly by its planet’s gravity. It’s like watching a dance, Charbonneau said, “it’s just that one of the dance partners is 1,000 times heavier than the other.” Secondly, there’s the transit method, in which a planet passes in front of its star and dims the star slightly, giving away its presence.

Charbonneau is also a member of the Kepler Space Telescope team. It launched last year with the express purpose of exoplanet hunting, and at the World Science Festival he predicted it would find a truly Earth-like world in two to three more years (he’s gotten close already). Plus, in 2014, exoplanet hunters will get another assist from this bad boy, the James Webb Space Telescope, a full-scale replica of which is currently on display in Battery Park.

3. Science Staycation

“This is my favorite planet, I have to say.”

Michael J. Russell is the most Earth-focused of the four panelists who spoke last night. And he might be the most convinced that Earth is not alone in harboring life. As someone who studies the emergence of life on our homeworld, especially the possibility that it emerged in the pressure cooker of deep-sea vents, Russell is impressed by the reach and expansion of life here. And that’s a good sign for life elsewhere in the universe.

What can Earth tell us about life on distant worlds? Life, Russell says, leaves evidence of itself in the waste it leaves behind. It accelerates chemical reactions—through photosynthesis, for example. Says Russell: “The question isn’t, ‘What is life?’ What we should ask is, ‘What does life do?’”

4. SETI

Zeta rays. Zeta rays are the key.

OK, I don’t know what zeta rays are, and neither does Jill Tarter, longtime member of the Search for Extraterrestrial Intelligence (SETI). The point is that we’re using technologies and weird physics that we didn’t know about a half-century ago when SETI was founded. Given our location in the galaxy, she says, any civilization that might like to contact us probably has had more time to mature. “We can be fairly confident that we are the youngest,” she said.

Thus, we use the methods we know—like optical and radio signals—to search for alien intelligences. But they might be trying to reach us with zeta rays, or some other crazy thing we haven’t discovered yet. That, plus the great vastness of the galaxy, tells Tarter that 50 years of nothing but silence doesn’t mean SETI is a failure. It means they’re just getting started.

[Read more about SETI's first 50 years in the feature "Call Waiting" in the July/August issue of DISCOVER, on newsstands soon.]

So what if it’s out there?

“First of all, I’m going to take a drink of champagne,” Tarter said.

In case you were worried, SETI does have a plan in place for its response to an alien signal. Tarter says the scientists won’t attempt to respond themselves, but would rather tell the world and try to reach a global consensus for our planet’s next move.

Right… “global consensus.” Tarter concedes that this sounds great on paper and is probably impossible to achieve. But in a socially connected world, maybe we can just take a vote on whether or not we want to tell E.T. we’re here.

That plan, of course, would apply only if we found intelligent life. But if we detected even “pond scum,” Squyers said, the achievement would be monumental. He’s willing to accept that habitable environments proliferate throughout the galaxy. Even in our own solar system, promising locales for life like the moons Europa and Titan lie outside what we would call the “Goldilocks Zone.” But finding that life independently arose twice just in our own tiny solar system would mean to him that the universe is “teeming with life.”

I hope it is.

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