The search for life on one of Saturn's moons

By JAEMIE BENNETT | February 22, 2018

The eighth planet from the sun, Saturn, with its giant rings, is thought to be the most dazzling to picture. However, perhaps it is not the gas giant that should intrigue us but rather the rocky moons that orbit it. 

Recent data from NASA’s Cassini mission shows that Enceladus, the moon sitting in Saturn’s E ring, may have the ingredients perfect for life, right here in our solar system.

Enceladus always presented itself as an intriguing heavenly body, being the brightest object in our solar system and forging an odd pathway through Saturn’s ring.

The dust particles of the rings give Enceladus a wide berth, larger than its diameter of 504 kilometers, as if Enceladus was somehow pushing them away.

The exploration of Enceladus started with NASA’s Cassini mission, launched in 1997, which was meant to get up close and personal with Saturn. 

Cassini first visited Venus in 2002 with two flybys before returning to Earth and Earth’s moon. It then made its way through the asteroid belt and to Jupiter before finally taking its first photograph of Saturn. 

Cassini finally entered Saturn’s orbit in 2004, and it made its final descent into Saturn’s atmosphere in September 2017, just short of the 20th anniversary of its first launch.

Enceladus was not initially a point of interest for the Cassini mission, but, after noting a strange pressure on Saturn’s magnetic field, Cassini was scheduled to further explore Enceladus. 

Plumes from the surface of Enceladus were photographed in 2005, indicating that the moon had active geology and that it created giant geysers.

Enceladus was also found to have a liquid ocean surrounding its entire core. Originally it was thought to be small, but now it is believed to cover the entire moon just below a sheet of ice. The proof for this was long in the making: Nearly seven years of photos were analyzed, tracking the “wobble” of Enceladus as it orbited Saturn. 

The magnitude of this wobble was too great for Enceladus to be completely solid. If the ice were in direct contact with the rocky core, Enceladus would be much more stationary. 

Therefore there had to be some sort of liquid beneath the entire sphere of ice. Although the subsurface ocean evidently exists, why it isn’t frozen as well is unknown. 

But, on Oct. 18, 2015, Cassini recorded data even more fascinating. Cassini flew within 30 meters of the surface of Enceladus, flying through a plume fueled by the ocean, and it recorded the presence of hydrogen. 

The Ion and Neutral Mass Spectrometer (INMS) used to detect the composition of the plumes was calibrated to block out “background” hydrogen, the hydrogen naturally existing in that area of space. 

In these plumes, the INMS found 98 percent water, one percent hydrogen, and one percent carbon dioxide, methane and ammonia.

The implication of hydrogen in Enceladus’ plume is enormous. Hydrogen is created by reactions in underwater thermal vents, where warm water reacts with mineral rich compounds on the ocean floor. 

This reaction is essential to life on Earth, allowing for the process of methanogenesis, where carbon dioxide and hydrogen are used to produce energy for an organism, creating a byproduct of methane. 

Methanogenesis powers the food chain near Earth’s own thermal vents, providing energy for tiny organisms that larger organisms eat, passing the energy up the food chain. Theoretically, this could be what’s happening in Enceladus’ ocean.

“Although we can’t detect life, we’ve found that there’s a food source there for it. It would be like a candy store for microbes,” said Hunter Waite, lead author of the Cassini study, according to an article by NASA.

Enceladus seems to check off all the boxes necessary for life. Water? Check. Energy for metabolism? Check. Hydrogen? Check. Carbon, oxygen and nitrogen? Check, check and check. The only things missing are sulfur and phosphorus, but it is hypothesized that Enceladus’ core is similar to asteroids that contain both sulfur and phosphorous.

It’s worth noting that Enceladus is far outside the Goldilocks zone, which is the area of warmth from a star that is theoretically the best place for liquid water and for life. In fact, many researchers are skeptical about the idea of life near a gas giant such as Saturn, due to its stormy atmospheres and little to no solid surfaces. 

The only three planets in the habitable Goldilocks zone for our solar system are Earth, Jupiter and Mars. 

Many places in the solar system, noticeably far from the Sun, have shown possible signs of water. For example, three of Jupiter’s moons — Europa, Ganymede and Callisto — and even Pluto have shown these signs.

With so many heavenly bodies in our own solar system containing one of the most important criteria for life, there’s a question that must be considered: Is extraterrestrial life closer than we thought?

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