Cassini spacecraft plummets into Saturn's atmosphere

Credit: Courtesy of  NASA/JPL-Caltech via Wikimedia Commons Credit: Courtesy of NASA/JPL-Caltech via Wikimedia Commons

assini, the probe whose 20-year mission to Saturn transformed scientific understanding of the bodies in our solar system, has finished its journey. Early Friday morning, the probe dived into Saturn’s atmosphere, where it rapidly disintegrated due extreme heat and pressure.

The end of the mission was a bittersweet moment for the team of scientists who made it happen. “It was a perfect spacecraft,” said spacecraft operations chief Julie Webster. She continued, “Right to the end, it did everything we asked it to. It’s perfect, it’s perfect.”

While it’s sad to see Cassini go, the team knew the mission had to end sometime; the research segment of the probe’s tour was originally supposed to last four years, but it was extended in 2008 and again in 2010. Eventually, the hardy probe started to run out of fuel. Thus, the mission’s “Grand Finale” was conceived: Cassini would end its journey with a fatal plunge into Saturn’s atmosphere.

“This is the final chapter of an amazing mission, but it’s also a new beginning,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at NASA Headquarters in Washington. Cassini’s plunge not only ensures that Saturn’s moons will not be contaminated with Earth materials. It also supplies us with the first data transmitted from within Saturn’s atmosphere.

Scientific firsts are nothing new for Cassini. Well-armed with various instruments — described by science writer Maggie Koerth-Baker as “a Swiss Army Knife in the sky” — Cassini orbited Saturn for 13 Earth years, or almost half a Saturn year. During that time, it made nearly 300 orbits around the planet, and completed 127 close flybys of Titan and 23 flybys of Enceladus, both moons of Saturn.

Before Cassini, the only things known about Titan were its size and the fact that its atmosphere is dense. There was no way to tell what lay below its thick nitrogen clouds. When Cassini arrived there in 2005, it sent a smaller probe named Huygens to investigate Titan’s surface. Through stunning photographs and atmospheric data, Huygens revealed a world NASA described as “surprisingly Earth-like.” We discovered that Titan has lakes, rivers, deserts, seasonal weather like Earth’s, and an underground ocean. These discoveries led many scientists to believe that Titan could be a hospitable environment for life.

Cassini discovered another underground ocean on Enceladus, hidden under a thick crust of ice. Scientists were intrigued by unusual magnetic data collected near the moon, and directed Cassini to take a closer look. The magnetic activity turned out to be caused by a geyserlike phenomenon — jets at Enceladus’ south pole shoot out material at 800 miles per hour through cracks in the ice, creating a gigantic spray of salt water, ice, and chemicals. Data from Cassini’s examination of the jets determined that Saturn’s outermost ring is composed of material ejected from Enceladus. Cassini also demonstrated that the interior of Enceladus was much warmer than previously thought, sparking further discussions about life on Saturn’s moons.

Cassini also brought us greater understanding of Saturn’s rings — perhaps the most iconic feature of any planet in our solar system. By studying shadows of particles in the rings, Cassini supplied data on the rings’ size and composition. They’re mostly made of chunks of ice and are flat, not warped. Some of the rings’ ice chunks are gigantic, so the rings aren’t perfectly smooth.

Cassini eventually transmitted amazing data on the planet itself: photos of the peculiar six-sided jet stream known as the Hexagon, observations of a 300,000-kilometer megastorm that encircled an entire hemisphere, the first images of lightning on a planet other than Earth. Cassini’s breathtaking photographs of Saturn are one of its most widely-celebrated accomplishments.

Cassini continued to transmit data even as it was breaking apart in Saturn’s atmosphere. Scientists are already beginning to study this final transmission and the information it contains. Even during its demise, Cassini carried on providing revolutionary insight about Saturn.