The time is coming when we will all say goodbye to Cassini, the spacecraft exploring Saturn since it first turned its cameras to stare at the planet in 2002. It began its Grand Finale activities some months ago with final orbits, final images, and other “last” looks at the Saturn system. The last pass around the moon Titan is done. The spacecraft got a gravitational kick from that loop that sends it right into Saturn’s northern hemisphere clouds on Friday. The last command sequences are sent. All controllers can do now is wait, monitor transmissions coming back from Cassini, and make any last-minute changes as necessary.
Cassini Opened New Windows on Saturn
As I look over the many, many images and other data reports from the mission, it’s hard to select a “favorite” result. It continues to show us way more than simply a ringed planet with a bunch of moons and some gorgeous rings. Granted, we are used to seeing great images of the system from the Voyager spacecraft in the 1980s. But, Cassini did it in high-res for years.
One of the great truisms about planetary science tells us that while it’s good to take snapshots of a target, it’s even better to study how that target changes over time. It’s the difference between taking a baby picture of someone and having a series of pictures taken during their lifetimes. You get to see how they grow and change. Cassini opened windows of opportunity to watch the Saturn system change over time — from its storms and cloud belts and zones to activities on some of its moons and within its rings.
Encountering Enceladus
A 14-hour image sequence of Enceladus made by Cassini shows plumes spewing ice crystals out to space. Courtesy NASA/Cassini Mission.
Still, if I had to select just one result that’s really important, I’d go with the discovery and long-term study of the moon Enceladus and its jets. Those geysers spew out to space and create the E ring. Their ice particles told scientists about the ocean hidden beneath the icy crust of that little moon. The fact that there’s an ocean there at all is a major surprise. The finding that it’s salty and “warm” (i.e. not frozen) indicates conditions could be hospitable to life.
Now, to be clear, life hasn’t been discovered there. But, the conditions exist. For a world that far from the Sun’s heat, that’s a tantalizing finding. It rewrites what we know about frozen worlds in the outer solar system.
After Cassini, What Happens?
A “propeller” of ring material swirling around a tiny moonlet near the Encke Gap in Saturn’s rings. This one is named “Earhart” after Amelia Earhart, a famous aviator in the early 20th century. Courtesy Cassini mission.
The Enceladus discoveries are enough to start people looking at future missions to Saturn. Those will follow up on Cassini’s accomplishments. While we’re thinking about sending more spacecraft to Saturn, it wouldn’t be a bad idea to check out Titan again. That world was another surprise, with its frigidly weird landscapes and lakes. The rings could use some more study, too. Those tiny little ‘propellers’ that interact with ring particles in an intricate dance are intriguing.
Both worlds merit closer looks and in-depth surveys, if not landers. It may be many years before those missions happen. NASA might not be leading those missions. Perhaps other countries will see what the international Cassini team has achieved and will launch probes to these worlds. However we get back to this system (and who ever does it next), Cassini made it possible.
Follow the final few days of Cassini’s historic mission as it sails into the clouds. NASA’s Cassini link is your best source of info.
It has been two days since I stood in the shadow of totality and wow! I’m still processing the mental images I gathered while watching this amazing event. It was completely overwhelming and spectacular. This eclipse was also a reminder that the solar system hands us some mind-blowing events to experience.
Mind you, it wasn’t my first eclipse “rodeo”. We’ve been chasing totality (when we can) since our first in 1979. I estimated last night that we’ve experienced 24 minutes and 33 seconds of eclipse darkness over seven eclipses. For two of them, we had to put up with some cloudiness during at least part of the time. It’s a respectable amount of “umbral” experience. And, that doesn’t count all the partials and annulars and lunar events we’ve watched.
Building Up to Totality in Casper
John Bally sharing astronomy insights during AstroCon in Casper, WY.
We experienced the August 21, 2017, eclipse from the centerline cutting through Casper, Wyoming. The town celebrated it with festivals, concerts, great food, and a true western welcome. We attended the Astronomy League’s annual meeting, called AstroCon. I joined a stellar crew of speakers there. My talk was about professional-amateur cooperation in astronomy research. Mr. Eclipse himself, Fred Espenak, was the keynote speaker, sharing his thoughts about eclipses and photography. Scientists from the University of Colorado (Fran Bagenal and John Bally), Stacy Palen (professor of physics from Weber State University in Utah), Alan MacRobert of Sky & Telescope (one of my former colleagues), my friends Martin Ratcliffe and Mike Murray (of Sky-Skan, Inc and Delta College planetarium, respectively) plus many others, shared their knowledge of photography and observing with the more than 900 attendees! It was an amazing meeting and set us all up nicely for the eclipse. We also visited the planetarium in Casper, and got together with friends from Denver who also drove up for the events. It was like a big astronomy family reunion.
The Big Event
TheSpacewriter watching the partial phases of the eclipse. Photo by Mark C. Petersen.
All too soon, it was time to get ready for Monday morning’s big event. It didn’t take long after we set up our chairs for the action to start. At 10:22 a.m. (MDT) the Moon started “taking a bite” out of the Sun and we were on our way to umbra! We watched as the leaf shadows changed and the atmosphere darkened and cooled over the next hour and 20 minutes. In fact, the temperature dropped more than 20 degrees between the start of the eclipse and second contact (when the Sun is completely covered).
The view of the partial phase through a shielded iPhone, by Carolyn Collins Petersen.
I took pictures of the tree leaves, tried some filtered images through the iPhone, and did a Google street view of our viewing area.
As you can see by the partial image, we didn’t bring along our “big rig” camera, filters, etc. We decided to simply enjoy this one. We’ve photographed all the other eclipses, and figured there would be a jillion great images on the Web and social media. So, we simply watched and waited as the sky grew darker, the temps dropped, the birds went to roost, and the people around us exclaimed in awe as this event unfolded inexorably above and around us. (Many were first-timers — eclipse virgins.)
Totality!
Nothing can prepare you for totality. For a few brief seconds just before the Sun disappears behind the Moon, there’s a hush as everybody awaits the moment of second contact. Then: totality! It seems to come on so fast. Even before you can process what’s happening, the Sun is gone, replaced by a dark hole in the sky, ringed by the corona. That “black hole” apparition is what stays in my memory from eclipse to eclipse. It never fails to amaze me with its awesome look. Words cannot describe it.
Leaf shadows show the shape of the partially eclipsed Sun before totality. Photo by Carolyn Collins Petersen.
This one seemed larger for some reason. I remarked to myself that the corona looked very pearly white. I also looked around to see the sunset surrounding us on the horizon. Always, I kept coming back to the main event: the darkened Sun, surrounded by corona and magnetic streamers stretching out away from it.
Totality during the August 21, 2017 solar eclipse Image by NASA/Aubrey Gemignani. Public domain, Wikimedia Commons.
As time went by, we looked around us to see the sunset surrounding us on the horizon. We looked at the corona and magnetic streamers stretching out away from the Sun. Eventually, we saw the prominences and then, suddenly, the second diamond ring appeared! And, then, in 2 minutes and 40 seconds, it was over!Eventually, we saw the prominences and then, suddenly, the second diamond ring appeared! And, then, in 2 minutes and 40 seconds, it was over!
Mark C. Petersen joins me in celebrating the corona with a tasty brew after totality! Photograph by Carolyn Collins Petersen.
I was elated and amazed. And, sad that it was over. The people standing with us, who had never seen totality before, turned to me and said, “Now we see why you can get hooked on these!” And, it’s true. You can never get enough totality. And, of course, when you do get totality, it’s worthy of celebration! People celebrated with Corona beers, champagne, Moon pies, and all kinds of other foods and drinks.
Facebooking Totality
The International Space Station tracked the eclipse shadow on August 21, 2017, including the path of totality. Courtesy NASA.
One thing that was different about this eclipse from the many others I’ve seen was our ability to track it via social media as people got online to share their experiences. My FB news stream lit up with exclamations of “First contact in Madras!” and “Diamond ring!” and “wowowowowowowowow!” comments as the event progressed across the country. The folks who were experiencing a partial eclipse also got in on the act, posting pics of their sky and the crowds watching in their regions.
It was something that really drew attention across the country. And, from space, too. Not too long after totality, we started to see an image taken by the space station crew, who watched as the shadow tracked across North America. What really blew my mind was an image of the space station as it crossed in front of the Sun, taken from the ground!
Staying in Contact
The International Space Station crosses the face of the Sun during its orbit during the solar eclipse on August 21, 2017. Courtesy NASA/Bill Ingalls
Not long before totality, I got an email from a teacher in Boston whose principal was concerned that the eclipse glasses they bought weren’t going to be safe. I talked them through a couple of simple tests to check the glasses. Thanks to quick emails, we were able to get their students a good experience.
Social media played a huge role in getting the word out about the eclipse around the world, and I hope that the next one will garner the same attention. It was an amazing, awesome event for everyone who stood in the shadow of the Sun!
For all the folks who can’t enough of eclipses, there’s another one crossing the United States in 2024. If you want to see one sooner, totality will swoop over the South Pacific, Chile, and Argentina on July 2, 2019. (There’s a complete guide to future eclipses on MrEclipse.com.)
