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Jonathan Lunine is the David C. Duncan Professor in the Physical Sciences, Chair, Department of Astronomy at Cornell University. His work investigates how planets form and evolve, what processes maintain and establish habitability, and what kinds of exotic environments (methane lakes, etc.) might host a kind of chemistry sophisticated enough to be called “life”.

What is the biggest question facing your field?

I’m an astronomer, planetary scientist, and astrobiologist. Let me pick the Big Question from the last of these, astrobiology. The Big Question is where, if anywhere, will we find life that had an independent origin from life on Earth. Could be intelligent, self-aware life, or microbes. Either would be a tremendous discovery. And for those who think the caveat “if anywhere” is unnecessary, let me say the until we discover life elsewhere, we cannot know if it exists. To say it’s likely, or certain, in the absence of evidence, is to offer an opinion; we’d like to actually know.

Why is it significant?

Carl Sagan in 1966 quoted the American physicist Philip Morrison as saying that the discovery of life on one other planet can “transform the origin of life from a miracle to a statistic”. Now, I’m not saying that life’s beginning on Earth was a miracle…nor was he. But the point of the statement is that a singular event is difficult or impossible to study scientifically. One supernova… and only one… doesn’t tell you about the systematics of such explosions and hence how they occur.

And, for the origin of life, the number of steps and our ignorance of the environment in which it occurred are daunting problems. Finding a second origin, where natural processes “did it again” would be hugely informative.

And, life forms different from Earthly, but not too different, might give us a whole new set of tools for various kinds of biotechnologies on Earth.

Where is the answer likely to come from?

One of three ways: (1) Are you feeling lucky? Use radio telescopes to search for signals from distant civilizations, and hope they are transmitting. (2) Look at nearby exoplanets with space telescopes, determine if they are habitable and search for atmospheric signatures of life (microbial or otherwise). And, (3) go to promising worlds in our solar system, the “ocean worlds” like Europa, Enceladus, Titan, where there are liquids on or under the surface, and look directly for microbes.

I’m solidly in the number-3 camp. Saturn’s moon Enceladus has a liquid water ocean spewing into space from fractures at the south pole, and Cassini found salty water, organic molecules, and tiny silica grains that are the signpost of hydrothermal systems beneath the surface. It’s the easiest place to go search for life. And go to Europa with Europa Clipper to determine the ocean habitability then follow up with a lander. At Titan, start with the Dragonfly quadcopter and go hunting for complex organic molecules on the surface.

Who knows what kinds of gardens of unearthly microbial delights exist in the solar system beyond Mars? We know how to find out. Let’s go!

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IMAGE SOURCE: Joseph Lunine; NASA/Creative Commons