This morning, NASA’s Cassini spacecraft completed the first of three flybys of Saturn’s moon Enceladus. At 6:41 a.m. EDT, Cassini came within 1,142 miles of the moon’s surface. It’ll take a day or two to get the images back, but this flyby should give us our best views yet of Enceladus’ north polar regions.
Previous observations of these regions were not possible because the north pole was in darkness. Scientists are hoping to find indications of ancient geophysical activity.
“We’ve been following a trail of clues on Enceladus for 10 years now,” said Bonnie Buratti, a Cassini science team member and icy moons expert at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “The amount of activity on and beneath this moon’s surface has been a huge surprise to us. We’re still trying to figure out what its history has been, and how it came to be this way.”
Cassini helped propel Enceladus to one of the best places in the solar system to look for life. Using data gathered from the spacecraft, scientists have made several stunning announcements. We now know Enceladus features continually-erupting fountains of icy material. It may have hydrothermal activity on its seafloor. And the ocean beneath its frozen surface is global, not regional as was previously believed.
Jonathan Lunine, an interdisciplinary scientist on the Cassini mission, explains the significance of these discoveries.
“The global nature of Enceladus’ ocean and the inference that hydrothermal systems might exist at the ocean’s base strengthen the case that this small moon of Saturn may have environments similar to those at the bottom of our own ocean,” said Lunine. “It is therefore very tempting to imagine that life could exist in such a habitable realm, a billion miles from our home.”
Today’s flyby is just a small taste of what’s to come later this month. October 28th is the date you want to keep an eye on. This is when Cassini will cruise through Enceladus’ famous plumes at the south pole. The spacecraft will be just 30 miles above the surface when it flies through the icy material. It will gather the most precise measurements yet of what material is being jettisoned from the moon’s surface.
The Cassini mission team is timing the October 28th flyby for when the moon’s plumes are at maximum output.
Cassini scientists will also be on the lookout for any data that provides evidence for how much hydrothermal activity is occurring in the moon’s ocean. Knowing how much ocean floor activity there is could also give scientists an idea of the habitability of the moon’s ocean.
Cassini’s third and final flyby for many years to come will occur on December 19th. The spacecraft will back away from Enceladus to 3,106 miles from the surface. It will study the moon’s south polar terrain again to help improve measurements of heat flow from the interior to the surface. These measurements are vital if scientists hope to understand what processes are driving the geysers.
You can see a snapshot of this terrain dubbed ‘tiger stripes’ below.
The large fractures are where the jets of icy material and water vapor erupt from, and they are much warmer than the rest of the moon’s surface. This points to a subsurface source for the heat.
This time next year, Cassini will prepare for its final mission. A new set of orbits that will take it through Saturn’s rings and eventually the planet’s upper atmosphere. Data ranging from ring mass to sampling Saturn’s atmosphere and ionosphere will be gathered during this final phase.