The very last images NASA’s Cassini spacecraft took before it crashed Friday are some of its most meaningful.
Here’s what the 20-year-old spacecraft saw just before it powered down its cameras for the last time and prepared for a final plunge into Saturn’s gauzy atmosphere. It’s of the icy moon Enceladus setting behind Saturn.
Many years earlier, Cassini discovered that Enceladus has a remarkable feature: Plumes of water vapor and gas shoot out of cracks in the surface. That water means there’s a liquid ocean beneath the ice-covered surface, which may have geothermal vents like those found at the bottom of our oceans. The discovery was immense: It shot Enceladus to the top of the list of places where we could possibly find life in our solar system. It could be the site of a second genesis — where life formed, evolved, and prospered undisturbed on another world. If even a few small microbes were found in its waters, it would be one of the greatest scientific findings of all time.
This image above says farewell to Enceladus, but it also beckons; we must, someday, go back to see if there’s life there.
These are what the very best photos from the Cassini mission do: They make us contemplate our place in the universe and help us imagine what’s potentially out there in the way-out-there. Since the Cassini mission began, scientists have discovered thousands of planets outside our own solar system. Investigating the moons of Saturn (and Jupiter) helps us gain an understanding of what planets might look like across the galaxy.
Here are some of the very best, most inspiring images from the mission.
A photograph of the entire Earth
This will probably be remembered as the most famous image from the Cassini mission. It’s a picture of Earth, as seen from the dark side of Saturn. We’re just a speck of dust.
Lakes on Titan
Saturn’s largest moon is Titan. It was discovered in 1655, but it wasn’t until Cassini and the Huygens lander that we knew how wonderful and complex a world it is. Titan is kind of like a bizarro version of Earth: It has a thick, nitrogen-dense atmosphere, where it rains down methane and other liquid hydrocarbons, which flow into amazing, earthlike features. There are rivers, lakes, mountains, and volcanoes. The following photo is shot in infrared, which cuts through the hazy upper atmosphere to reveal some surface features.
Landing on Titan
The European Space Agency–built Huygens lander hitched a ride on Cassini, detached, and actually touched down on the surface of Titan. This is what it saw: a rocky landscape about a billion miles from Earth.
Here’s Titan in orbit around Saturn.
Plumes on Enceladus
Here, water vapor escapes from vents on Enceladus.
One of the most beautiful features Cassini imaged: The clouds at Saturn’s north pole form a huge hexagonal storm.
And at the very center of that hexagon is a vortex that looks like a rose.
The glorious rings
Of course, Saturn’s defining characteristic is its gorgeous rings. But they’re not just pretty to look at. Scientists believe it’s in the swirling material of the rings that new moons can form. And it might be a model environment for how the planets formed around the sun.
Cassini has also spotted these “propeller” patterns in the rings. They’re made by little moonlets that form in the rings.
Here, Cassini takes a photo of Saturn backlit by the sun. The lighting exposes the gauzy texture of the rings, and even reveals the very faint, icy outermost F-ring.
Pan, the ravioli-shaped moon
Even small things are surprising in the Saturn system. Cassini discovered that the small moon Pan has an odd dumpling/pierogi/ravioli/empanada/name-your-favorite-stuffed-dough-treat-shaped moon. Astronomers hadn’t seen a moon with this odd shape before.
Over the past few days, NASA took a few final few shots of the planet. They’re beautiful but a bit sad. There’s no guarantee we’ll ever send a spacecraft back to Saturn.
Correction: An earlier version of this post stated the Cassini mission discovered the hexagonal storm at Saturn’s North Pole. It was discovered during the Voyager mission in the 1980s.