NASA’s Cassini Begins Its Grand Finale with a Grand Discovery

Cassini flies near Saturn

Illustration of the Cassini spacecraft above Saturn’s northern hemisphere. NASA/JPL-Caltech

Beginning this month, NASA’s Cassini spacecraft will begin its final journey, fatefully dubbed its Grand Finale. On April 26, Cassini will make the first of what should be several intrepid new orbits around Saturn that will ultimately result in 22 dives within the 2,400-kilometer gap between the planet and its innermost rings. Throughout these final orbits, the spacecraft will gather new pieces of information that will ideally reveal the inner composition of the sixth planet as well as the material make up of its enigmatic rings.

Launched on October 15, 1997, Cassini—NASA’s largest and most complex interplanetary spacecraft—made a seven-year voyage to the ringed planet, arriving in orbit in June of 2004. Since then, it has given us countless discoveries, including rain, rivers, lakes and seas on Titan (Saturn’s largest moon), and information from the rings that helps us understand how planets and moons form. Now, Cassini’s latest discovery, which scientists anticipate to be the first of many throughout the Grand Finale, shows evidence for what could be the ingredients for life on Saturn’s icy moon Enceladus. As described in a paper from Cassini researchers published in the journal Science, the spacecraft transmitted data indicating evidence of hydrogen gas, which has the potential to serve as a source of chemical energy for life.

According to a NASA release on April 13, “The presence of ample hydrogen in the moon’s ocean means that microbes—if any exist there—could use it to obtain energy by combining the hydrogen with carbon dioxide dissolved in the water. This chemical reaction, known as ‘methanogenesis’ because it produces methane as a byproduct, is at the root of the tree of life on Earth, and could even have been critical to the origin of life on our planet.” The hydrogen has been found in water that erupts in plumes from the moon’s surface, which could be an indicator of hot spots hidden within the oceans beneath the icy surface. These hot spots, similar to hydrothermal vents found here on Earth, are ripe for potential microbial life.

So, what does this all mean?

These findings do indeed tell us that, for a certain kinds of small organisms, Enceladus could potentially be habitable. However, that does not mean that the moon necessarily contains life. What it does mean is that Enceladus warrants further investigation. This is undoubtedly an important discovery, and Cassini is not entirely equipped to do the detection and research needed to dig deeper into the moon’s oceans to look for life. As Scott Eddington, deputy project scientist for Cassini, explained to the Verge, what scientists need is a spacecraft specifically created to look for life within the cracks on Enceladus’s surface: “a lander that could land in one of those tiger stripes at the south pole and sample that ice as it’s coming out of those cracks.”

In the meantime, Cassini continues along its final treks through the moons and rings of the sixth planet. Running low on fuel after its 20-year mission—13 of those spent in orbit—Cassini will ultimately end its endeavors and 22 dives, completing its Grand Finale with a final, fateful plunge to Saturn’s surface.

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