Oct 21

What’s Up in the Sky

What’s Up in the Sky – October, 2017

An Historic Mission Comes to an End

On September 15, the Cassini spacecraft became part of Saturn when it melted into its atmosphere upon its final descent from orbit. NASA sent out a tweet that said, “Earth received Cassini’s final signal at 7:55 a.m., ET. Cassini is now part of the planet it studied.” The “Grand Finale” orbit that sent it plunging into oblivion was chosen as “moon protection”. Saturn has several moons on which conditions may be favorable for some life, and we didn’t want to contaminate it with any of our microbes.

Many readers know that the Cassini mission uncovered a number of mysteries through its extensive study of the planet’s rings, moons, atmosphere, magnetic field, and more. More than half a dozen previously unknown moons of Saturn were discovered by Cassini. It studied the planet’s seasons and spin. It also delivered a photo of Earth from Saturn that builds on the legacy of Carl Sagan’s pale blue dot.

The loss of Cassini marks the end of an era of “great missions” that used large, expensive, complex spacecraft such as Voyager and Galileo to accomplish their goals. Of course, these programs were tremendously successful and continued far past their designed time frames (Voyagers 1 and 2 are still sending back data!)

Cassini was launched in 1997 and reached Saturn in July, 2004, after flybys of Venus and Jupiter. It orbited the planet for the next 13 years, collecting data, taking magnificent photos and studying mysteries such as oceans of frozen methane on Titan, and salt water geysers on Enceladus, two of the planet’s moons.

Some of the scientists working on this project have been together since the planning and design stage, almost thirty years. For many, Cassini represents an entire career’s worth of work. The scientists became like family, watching each other’s kids grow up. They even formed a singing group.

For many of the 1000 people gathered at JPL (Jet Propulsion Lab) for the spacecraft’s final moments, the end of the mission was a bittersweet experience filled with mixed emotions. When asked about the moment contact with Cassini is lost, one scientist at mission control said, “Do we cheer or go into silence?”

But when you work on a project for 20 or 30 years with the same people, sharing important discoveries and contributing to an historic mission, it makes a lasting impression. One researcher described making discoveries with her colleagues as, “. . . a beautiful feeling; nothing like it in the world.”

Many of these project scientists will continue their work on other programs and some will retire. But the data collected during the entire mission will keep planetary scientists busy for a long time. The Cassini spacecraft has given us a great appreciation for the splendor of what’s up in the sky.