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Adventure Science Center Blog

Science Educators and guest authors exploring our world and the science and technology that connects us.

 

 

ENCELADUS: THE FROZEN GIANT by Jason Moeller, Science Educator

Despite recent Mars discoveries, an icy moon circling Saturn may hold the secret to extraterrestrial life! 

In 1960, a young astronomer named Frank Drake aimed the National Radio Astronomy Observatory’s 85-foot radio telescope towards two nearby, sun-like stars. The goal of Frank’s project, named Ozma after the fictional ruler of Oz, was to search for life using a radio frequency that Frank thought an interstellar civilization might use. Although the stars failed to answer, Drake’s project marked the beginning of the Search for Extraterrestrial Intelligence (SETI) and humankind’s hunt for life beyond Earth.

This past July, the newest chapter in the hunt for life off Earth opened when a group of scientists working for the Italian Space Agency published a study stating they had detected a stable body of liquid water located underneath the southern ice cap of Mars. That study used an advanced radar known as the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) to send pulses through the surface of the ice caps to analyze how the pulses were bounced back to the radar.

An area of twelve and a half miles reflected brightly back in the same manner that water reflects back from under ice pools on Earth. If confirmed by other experts, this is a tremendous find that might – just might – be able to harbor life.

Life has proven to be extremely resilient on Earth, with organisms known as extremophiles being able to survive in some of our planet’s most inhospitable environments. Extremophiles have been found in deep ocean volcanic vents, acidic volcanic springs, briny seas, and yes, even ice. Tardigrades, also known as water bears, can even survive exposure in the vacuum of space!

Despite life’s ability to survive, the newly discovered Martian environment poses some serious challenges, including extremely cold temperatures and high levels of salt. In other words, finding life on Mars is far from assured, and maybe even unlikely. Fortunately, for those of us who are interested in the hunt for life in our solar system, another candidate is also showing great promise.

Enceladus is the sixth largest moon of Saturn, measuring 310 miles in diameter (roughly the size of Arizona), which was discovered by William Herschel in 1789 and named for the giant king whom the Ancient Greeks believed caused fiery volcanic eruptions. Covered by fresh, clean ice, Enceladus is one of the most reflective bodies in the solar system, rejecting heat energy and maintaining a frigid noon surface temperature of -324 degrees Fahrenheit.

In looking at its frozen cover, Enceladus seems to be the last place anyone would judge suitable for a living organism… but it’s all changing with Cassini. This collaboration between NASA, the European Space Agency and the Italian Space Agency, focused on learning more about Saturn and its moons. Although Cassini purposely crashed into Saturn in September of 2017, scientists are still analyzing the data, which is quickly proving that this icy moon is a leading contender in the hunt for interstellar life. But how can we be sure?

First, by measuring Enceladus’s “wobble” as it orbits Saturn (known as libration), scientists determined that Enceladus’s icy crust does not rest on its rocky core, but instead covers a moonwide liquid ocean. The data implies that the ocean is between 26 and 31 kilometers deep… nearly 10 times the average depth of our oceans!

Second, Cassini observed water-rich geysers erupting from the moon’s southern pole, shooting water, water vapor, ice, molecular hydrogen, and other solid materials such as salt crystals into space. This “soup” helped form a large portion of Saturn’s outer ring structures and also gave scientists insights into what Enceladus’s hidden ocean is like. Using tools on the Cassini spacecraft, scientists determined the water has a salinity and PH that are comparable to our oceans.

What's really interesting, though, is these geysers are spouting their contents at a temperature of 200 degrees Fahrenheit. Not negative, positive. The ocean’s hot springs are just that – hot!

Finally, and perhaps most critically, scientists announced earlier this June that Cassini had found complex organic molecules originating from Enceladus. Although previous excursions had only found small, common organic compounds, the ones discovered in June were significantly larger.

Christopher Glein, a Southwest Research Institute space scientist specializing in extraterrestrial chemical oceanography, said in a statement reprinted on CNN, "Previously we'd only identified the simplest organic molecules containing a few carbon atoms, but even that was very intriguing. Now we've found organic molecules with masses above 200 atomic mass units."

Why are these complex molecules important? They show that the ocean has the chemical energy needed for microbes to produce methane in a process known as methanogensis.  In this process, microbes get energy by breaking down molecules such as carbon dioxide and molecular hydrogen into methane. In short, these molecules prove that Enceladus’s ocean has food that can sustain microbes similar to those seen here on Earth!

Cassini’s data paints the picture of a habitat surprisingly similar to Earth’s deep-sea volcanic vents that teems with life despite the harsh conditions. With its deep ocean, warm water and available energy sources, Enceladus may just be the answer to Frank Drake’s question of whether life exists away from Earth – even if Mars can’t.

Want to learn more about Enceladus and our other celestial neighbors?
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Posted by Anna Leigh Goolsby at 11:23 AM
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