With the recent discovery by NASA’s Cassini spacecraft of promising conditions beneath the icy surface of Saturn’s moon Enceladus, the search for extraterrestrial life in our solar system is heating up. Following last year’s discovery of a six-mile deep ocean beneath Enceladus comes news of hydrothermal vents spewing hot water into a warm ocean at its southern pole. Conditions there are thought to be similar to those at vents in our own oceans that may have first spawned life here on Earth.
With a diameter of only 310 miles, Enceladus is very small, only a tenth the size of Saturn’s largest moon, Titan. As it receives very little heat from the distant sun and has a reflective icy crust, why would its interior be hot enough to harbor a warm ocean with hydrothermal vents? The most likely cause is tidal heating. This occurs as Saturn’s immense gravity pulls with varying strengths on either side of Enceladus, with more force exerted on the side closest to Saturn. The tidal flexing that results exerts a squeezing force, causing friction, which generates heat within the moon.
The new research, published in the journal Nature, focused on analyzing the dust in Saturn’s outermost E ring. Enceladus lies in the densest part of that ring, and has been known for some time as the source of the material found in the E ring. How this material got there wasn’t known until the 2005 discovery of geysers spewing large jets of ice particles, water vapor, other gases and dust into space.
By analyzing minute dust particles in the E ring, Hsiang-Wen Hsu of the University of Colorado and his international team were able to estimate the temperature, salinity and pH (acidity level) of Enceladus’s ocean. Using Cassini’s mass spectrometer tool, an instrument that measures the masses and relative concentrations of atoms and molecules, they found that the dust particles were made mostly of silica, a building block of quartz, and were the remains of evaporated saltwater ejected into space by the geysers on Enceladus. From the size and composition of the silica particles the researchers were able to tell that the salt content of Enceladus’s ocean is less than 4% (Earth’s oceans are about 3.5%) and that it is alkaline, with a pH level of between 8.5 and 10.5 (Earth’s oceans are currently about 8.07). They could also tell that the hot springs at the bottom of the ocean were at least 200 degrees Fahrenheit.
As the only known way the tiny silica particles found could form is through hydrothermal activity, the findings imply that the particles form from interactions in the hot water spewing from vents in the rock surrounding Enceladus’s core. If confirmed, this would be the only place apart from Earth where such chemical reactions between water and rock are known to be happening today.
From analyzing gases from the geysers on Enceladus we know that its ocean contains nitrogen and carbon dioxide, as well as hydrocarbons, which can, in the presence of nitrogen, form complex structures such as amino acids which form the building blocks of life. Detecting a warm ocean with chemicals associated with life is not the same as finding life itself, but it does raise the stakes for Enceladus as a prime spot in the search for extraterrestrial life.
Ever since Cassini first arrived at Saturn in 2004 it has been returning remarkable data and photos of the ringed planet and its moons. However, given that it was first launched back in 1997, its technology is now outdated, so there are plans afoot to update the Cassini mission with a new spacecraft, using state of the art technology to search for signs of life. According to Jonathan Lunine, a planetary scientist at Cornell University who works on the Cassini mission but was not involved in the recent research, “If we go back to Enceladus and build upon the Cassini results with the instruments of today, the short answer is, we know that we’ll be able to look for life frozen in the (geyser) particles, and really nail this habitability question.”
Join the Springfield Stars Club on Tuesday, April 28th at 7pm at the Springfield Science Museum for a talk by Jack Megas on “The Twenty Brightest Stars.” Megas is an astronomy educator at the Springfield Science Museum’s Seymour Planetarium, and a retired laboratory hematologist at Baystate Medical Center. He is a past president of the Springfield Stars Club and the Naturalist Club. Refreshments will be served and the public is welcome. The meeting is free of charge for members, with a suggested donation of $2 per non-member. For more information please visit the Stars Club – Massachusetts page on Facebook at https://www.facebook.com/groups/929125583765113/ or the Stars website, reflector.org.
Also, on Friday, May 1st at 7:30pm, the Stars Club and the Springfield Science Museum will host “Stars Over Springfield.” Richard Sanderson, Jack Megas and Dave Gallup will talk on “A Dipper full of Stars – Astronomy through the Four Seasons.” A fee of $3 for adults and $2 for children under 18 will be charged.
Copyright © Amanda Jermyn