Flying Through the Plume on Saturn's Moon Enceladus

• Download the Student Worksheet from the materials list and make copies of the full problem set or individual problems to hand out to students.

UPDATE – April 13, 2017: Scientists for NASA's Cassini mission have released the results from the spacecraft's flyby through the geyser plume at Enceladus in October 2015. By analyzing the material sampled during the flyby, as well as previous measurements made, scientists discovered that the ocean under Enceladus’ ice shell contains hydrogen. This hydrogen is being pumped into the ocean by hydrothermal vents on the seafloor. If microbes exist in Enceladus’ ocean, they could use hydrogen combined with CO₂ as a source of energy. This process, called methanogenesis, could have played an important role in the origin of life on Earth.

For more, read the news release "NASA's Missions Provide New Insights Into 'Ocean Worlds' in Our Solar System" from April 13, 2017.

In the News

Saturn’s icy moon Enceladus has been making news lately, and it could make even bigger news soon! In September 2015, scientists confirmed that there was a global ocean underneath Enceladus’ thick icy shell. That was just the latest in a long history of exciting finds dating back to the beginning of NASA’s Cassini-Huygens Mission to Saturn in 2004 that have helped scientists to better understand this fascinating world!

Even while Cassini was still on its way to Saturn, its Cosmic Dust Analyzer detected microscopic grains of silica (tiny grains of sand). On Earth, grains of silica similar in size to those detected near Saturn form when hydrothermal activity -- the processes involving heated water beneath Earth’s surface or ocean -- causes salty water to chemically interact with rocky material to form silica. But where were these grains coming from in the space around Saturn?

In 2005, scientists were surprised to find out that Enceladus’ south pole is both warmer than expected and warmer than the surrounding areas, suggesting there is a heat source inside Enceladus. Not only that, but they also discovered long parallel cracks in the ice on Enceladus’ south pole. The young age of these cracks, nicknamed Tiger Stripes, meant that Saturn’s icy moon is a geologically active place.

Another piece of this puzzle was put in place with the discovery of jets of material spraying out of the Tiger Stripes. Studies have shown these jets are composed of mostly of water vapor, tiny ice particles and small amounts of other material (for example, microscopic silica grains). Together, over 100 jets make up a feature called a plume. Investigating further, scientists have hypothesized that these silica grains are the result of hydrothermal activity on the ocean floor below Enceladus’ icy crust.

On October 28, 2015, Cassini will fly right through the plume jetting out of Enceladus’ south pole at an altitude of only 49 kilometers (30 miles) – closer than any previous passes directly through the plume! This is an exciting moment in the mission -- one that allows science teams to use a combination of tools on board the spacecraft to strengthen previous findings and potentially make new discoveries.

Why It's Important

Cassini will use its Cosmic Dust Analyzer to study the solid plume particles and an instrument called the Ion and Neutral Mass Spectrometer to “sniff” the gas vapor in order to determine the composition of the jets. Specifically, the latter instrument is looking for H₂, or molecular hydrogen. Finding H₂ in the plume will strengthen the evidence that hydrothermal activity is occurring on Enceladus’ ocean floor. And the amount of H₂ in the plume, will tell scientists just how much activity is happening.

In addition to indicating that hydrothermal activity is taking place, figuring out the amount of hydrothermal activity will give scientists a good indication of how much internal energy there is deep inside Enceladus.

That Cassini is making a pass through the plume at such a low, 49-kilometer-high altitude is also important. Organic compounds -- substances formed when carbon bonds with hydrogen, nitrogen, oxygen, phosphorus or sulfur -- tend to be heavy and would fall out of the plume before reaching the heights of Cassini’s previous, higher altitude flybys and be undetected. Organic compounds are the building blocks of life on Earth. Without them, life as we know it wouldn’t exist. If they are present in Enceladus’ oceans, they could be detected when Cassini passes through the plume on this encounter.

Perhaps more important, though, are the implications of finding hydrothermal activity somewhere other than Earth. It was once believed that all forms of life needed sunlight as a source of energy, but in 1977, the first hydrothermal vent -- essentially an underwater geyser of hot, mineral-rich water -- was discovered and it was teeming with life. The organisms were using the heat and minerals as a source of energy! Some scientists have hypothesized that hydrothermal vents could be where life on our planet first took hold and could represent environments in the solar system with the necessary ingredients to support life.

Use it in the Classroom

Use the lessons and resources below to teach key concepts related to the October 28, 2015, Enceladus flyby and engage your students in science at Saturn.

Student ability to solve the various math problems will vary with grade level and exposure to mathematics, but consider allowing students to examine and discuss more difficult problems and suggest how they might go about solving the problem if they had the appropriate mathematical tools (formulas, etc.). This will give you, the teacher, insight into students' problem solving ability beyond computational skills.

• Enceladus flyby information page
• Slideshow and poster: 8 Real World Science Facts About Saturn's Moon Enceladus
• Enceladus facts and figures
• Enceladus images
• Eyes on the Solar System: Enceladus flyby simulation
• Cassini mission overview
• Teachable Moments Blog