Earth’s oceans may hold the key to finding life beyond our planet

A new book by NASA astrobiologist Kevin Hand argues the first step to finding aliens should be exploring the depths our own planet’s oceans.

Last fall, astrobiologist Kevin Hand and I were aboard the Norwegian icebreaker Kronprins Haakon for a month, crashing through the frozen ocean off the northeast coast of Greenland. Around us, Earth looked alien—a world where the normally shifting seas were a solid mass of glowing ice.

The otherworldly environment was fitting for the expedition, which had been dispatched to this frigid place to hunt for signs of life in the deep that might resemble organisms on other worlds, including the icy moons of the outer solar system. Some of these moons—particularly Europa, Titan, and Enceladus—are considered the best places to look for life beyond Earth.

In the mid-2020s, NASA plans to launch a spacecraft to Europa, one of Jupiter’s large moons, to search for signs of life. The space agency is also planning a mission to land on Saturn’s moon Titan, and in the future, scientists hope to design a mission to land on Europa that could tunnel through the ice and explore the watery depths with an autonomous submarine.

Hand, director of the ocean worlds lab at NASA’s Jet Propulsion Laboratory (JPL) and a National Geographic emerging explorer, has spent his career studying these watery moons and the technologies we’d need to explore them. His recently published book, Alien Oceans: The Search for Life in the Depths of Space, describes why studying Earth’s own ocean is a crucial chapter in the quest to explore the shores of extraterrestrial seas. Hand spoke with National Geographic about that link, and why failure has to be an option when sending spacecraft to the solar system’s frozen nooks.

(This interview has been edited for length and clarity.)

First things first: Is there life beyond Earth?

That’s the first question?! Well, if the conditions needed for the origin of life are found on worlds beyond Earth, then yes, I think there is life beyond Earth, and that we live in a biological universe.

Why do you think alien oceans are among the best places to look for alien life?

If we’ve learned anything from life on Earth, it’s that where you find liquid water, you generally find life. And these oceans beyond Earth potentially harbor a tremendous amount of liquid water. They are incredibly compelling places to search for life that is alive today—extant life—rather than fossils of extinct life.

What I want to understand is the underlying biochemistry of life. Is there a periodic table of life? Is there another biochemistry, different from the DNA, RNA, and protein paradigm that drives all life on Earth? To answer these questions about the fundamentals of how life works, we really need to find living life with much of its biochemistry still intact. That’s why ocean worlds are so compelling.

How does this compare to looking for life on Mars?

Mars is an amazing place to search for signs of life. But on Mars, for the most part, we’re searching for ancient life. The Curiosity rover could see a stromatolite—a rock of fossilized microbes—in Gale Crater tomorrow, and that would be amazing, but we wouldn’t be able to extract any DNA or large molecules from that rock. The large molecules of life do not survive for long periods of time in the rock record. They do not fossilize well; they decay rapidly. This is why we don’t have the DNA of dinosaurs, for example. So, as profound as that discovery would be, it would leave us asking many more questions.

Do you have a favorite target in the search for life beyond Earth?

That’s like asking a parent to choose a favorite child! But, at the end of the day, I would love to continue the search at Europa, and we’re currently planning a mission, called Europa Clipper, to fly by the moon some 45 times. That mission is also hopefully setting the stage for another mission to land on the surface sometime in the not-too-distant future.

What makes Europa such a great place to search for life?

First, we have good reason to predict that Europa’s ocean has been around for a very long time—it’s basically been around for the history of the solar system. And that’s important. A stable ocean that’s been around for a long time might be critical both for the origin of life and for the long-term survival of anything living in that ocean.

Second, we have good evidence and models indicating that Europa’s ocean is a global ocean, and that it likely has a rocky seafloor. That rocky seafloor may contain hydrothermal vents that could be exhaling fluids and gasses that microbes love to eat. We also know that Europa’s ice shell contains compounds that could help feed life in the ocean below.

You write about how exploring our ocean and exploring alien oceans are technologically intertwined. What sorts of earthly ocean exploration projects are you working on now?

Two that I’ll highlight. One is the Buoyant Rover for Under Ice Exploration, which is a JPL-developed robot that focuses on the ice-water interface and studying the chemistry and biology of that interface.

The second vehicle is our Orpheus vehicle, and this is a partnership between JPL and the Woods Hole Oceanographic Institution. Orpheus is a small submersible that will eventually go down to the deepest depths of our ocean—the Mariana Trench, New Britain trench, Puerto Rico trench—these places where very little exploration has been done.

Part of our goal with the buoyant rover and with Orpheus is to leverage a lot of the lessons that we’ve learned in the space community about making robotic systems that are smaller, lighter, lower power, autonomous, capable of doing science on-site. All of those are attributes of how we explore worlds beyond Earth, and we’re trying to leverage some of those capabilities to advance the exploration of our ocean.

What will it take to get a similar robotic explorer into an ocean in the outer solar system?

Here’s the thing: None of those technologies requires a magic wand. We don’t have to break the laws of physics, or come up with some crazy new invention, to make it possible. That said, these are incredibly technically challenging and complicated mission concepts. In theory, we can get through the ice and get directly into these oceans. There’s nothing analogous to warp drive or some other magic that would need to be invented. The key limitation is sustaining a dedicated program that can get us there over the course of the next few decades.

Now, long before we get into an alien ocean beyond Earth, we’ll have to do all sorts of development and testing of new technologies in our ocean. Part of what’s great about that is the win-win of developing the tools needed to explore beyond Earth while also getting exploration done—and making discoveries—here on Earth.

In your new book, you write that, “Failure has to be an option when you are trying to do new things and push the frontier.” How do you think space agencies can be convinced to support these risky missions?

There are many different types of risk that one has to weigh when engaging in exploration, be it on Earth or beyond. Examples are science risk—what’s the likelihood that you’re going to succeed at doing the science you want to get done? Cost risk—what’s the risk that you’re going to blow your budget? And the technological risk of actually building the robot or instrument needed to explore the region and make the measurements.

If you’re trying to do civilization-scale science—science that is meritorious of significant investment because it targets one of humanity’s oldest and most profound questions, in this case whether or not we are alone—I think the value of that question warrants taking some risk. But the upside is that if we succeed, we may well transform the universe as we know it. We may ignite a revolution in our understanding of the science of biology.

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