Last Friday, one of NASA’s most successful planetary exploration missions to date, Cassini, plunged into Saturn’s atmosphere at speeds in excess of 70,000 miles per hour, before ultimately succumbing to the heat and pressure of the gas giant, and powering down forever. Before the spacecraft’s 20-year mission came to a fiery end, however, NASA transmitted the final set of orders: to use the remaining power in the craft’s maneuvering thrusters to angle its antennae back toward Earth, and transmit as much of its historic descent as possible.
Cassini’s final glimpse of the ringed planet didn’t reach Earth until more than an hour after Cassini was no more. With such vast distances to cover, even the speed of light isn’t fast enough to grant NASA’s team of scientists and researchers with a live feed of the demise of a project that, for many, represents the breadth of a long and storied career. Just shy of 20 years in the making, this is the final glimpse of Saturn that Cassini was able to transmit back.
A superb machine in an amazing place doing everything possible to reveal the mysteries and secrets of our solar system,” Cassini program manager Earl Maize said. “This morning, a lone explorer, a machine made by humankind, finished its mission 900 million miles away. To the very end, the spacecraft did everything we asked. We believe we got every last second of data. We have indeed accomplished everything we set out to do.”
As Cassini descended into Saturn’s upper atmosphere, it once again traveled between the gas giant and its characteristic rings – a feat only ever accomplished by Cassini itself, and sent back a series of photographs of the planet below, its moons, and the ring system itself.
These images are unlike anything ever before taken by a man-made object, and although we have grown somewhat accustomed to seeing computer rendered images of stars and planets in films and TV shows like Star Trek, what makes these images so dramatic is the reality that human beings were able to snap these photographs in orbit around another world, using nothing more than human ingenuity and the resources we had available on our comparably tiny, little blue dot of a planet, set somewhere far off in the distance.
As Cassini plummeted to its demise, it peered up for one last glimpse at Saturn’s moon Enceladus. In an ironic twist of fate, it was Cassini’s discovery of water plumes escaping the icy crust of Enceladus that confirmed NASA’s concerns that led to the decision to send the spacecraft on a trajectory that would destroy it in Saturn’s atmosphere.
Scientists believe Enceladus could potentially have the right ingredients to harbor life in the massive liquid water ocean believed to lie just beneath its frozen exterior, and NASA was not willing to potentially compromise such an environment with Cassini’s carcass. Had the spacecraft been permitted to operate until it completely depleted its nuclear energy stores, there would have been no way to avoid a collision with one of Saturn’s moons if Cassini’s degrading orbit intersected with one’s path.
Instead of risking such an event, NASA chose to doom one of its most successful missions in history, but not before it added these incredible images to the vast library of content it has already beamed back to Earth over the years.
The Cassini operations team did an absolutely stellar job guiding the spacecraft to its noble end,” said Maize. “From designing the trajectory seven years ago, to navigating through the 22 nail-biting plunges between Saturn and its rings, this is a crack shot group of scientists and engineers that scripted a fitting end to a great mission. What a way to go. Truly a blaze of glory.”
The Cassini mission may be over, but the effect it will have on the future of space exploration remains profound.
“It was a perfect spacecraft,” said Julie Webster, spacecraft operations chief. “Right to the end, it did everything we asked it to. It’s perfect, it’s perfect.”
Images courtesy of NASA