General Science

Juno vs. Cassini: Battle of the Planetary Probes

posted: 06/23/17
by: Jason Ginsburg

Two of NASA's most sophisticated probes are circling two of the solar system's most fascinating planets. Juno arrived at Jupiter in 2016 and will study the giant planet until February 2018. Meanwhile, Cassini has been monitoring Saturn since 2004 and will end its mission on September 15.

Video: Juno 101

Both of these spacecraft have immensely expanded our knowledge of the gas giants and some of their moons. But which probe is bigger, smarter, and faster? Which had the more perilous journey? And which has taken the best pictures and videos? Let's take a look.

Which is Faster?
Cassini was plenty fast: Its top speed on the journey to Saturn was 42, 561 miles per hour relative to Earth, or about 27 miles per second. That's far faster than an SR-71 Blackbird aircraft (2,200 mph) or even the Space Shuttle (17,000 mph). Juno, though, had the massive gravity of Jupiter on its side. As the probe approached the giant planet, it was accelerated to 160,000 miles per hour, almost four times the speed of Cassini. According to Guinness World Records, Juno might be the fastest spacecraft in history, if measured by speed relative to Earth (instead of the sun).

Winner: Juno

Which is Bigger?

Both probes might be able to claim victory here. Juno measures about 132 square feet by itself, along with three solar panels each 30 feet long. That gives it a total area that dwarfs Cassini, which is too far from the sun to have solar panels -- it's powered by radioisotope thermoelectric generators instead. However, Cassini's main body is 288 square feet, more than twice as large as Juno's body. So we'll call this a tie.

Winner: (Tie)

Video: Cassini Sends Back Images from Its Descent

Which Traveled Farther?
Saturn is simply farther away from us than Jupiter is, so Cassini wins this one easily. With its looping journey and gravity assists from other planets, the probe traveled a total of 2.2 billion miles. Juno only had to log about 1.7 billion miles.

Winner: Cassini

Which Conducted the Better "Bonus" Mission?
We forget that Cassini is actually the Cassini-Huygens mission; the spacecraft carried a second probe with it to Saturn. It dropped Huygens off at Titan, Saturn's hazy moon, at the end of 2004. The actual footage from Huygens's descent is incredible, featuring highlands, peaks, and boulders of ice covered by methane. The plucky lander even broadcast for about 90 minutes from the surface. It's the farthest world we've ever landed on. Juno, on the other hand, has mostly ignored Jupiter's dozens of moons and completely on its target planet. However, on its way to Jupiter, it did turn around and film this beautiful "pirouette" of Earth and its moon.

Winner: Cassini

Which Took the Better Photo?
Most of Cassini's photography has been in black and white, giving the images a quietly artful quality. One of my favorites is this
picture of Saturn's rings dwarfing the moon Mimas. It conveys just how massive the planet and its rings are:

Saturn and Mimas

Juno has taken lots of color photos, showing off Jupiter's range of swirling clouds. I'd have to pick this image of Jupiter's south pole. We're so used to seeing the giant planet with its famous Great Red Spot; this image shows us how much we can learn about Jupiter (and everything else) with a simple change of perspective.

Winner: Juno

Which Shot the Better Video?
NASA released this video taken by Cassini over a four-day span of watching Saturn. The ringed planet fills the frame, and you can actually watch it spin -- something we often don't consider about the outer planets. The video shows storms, faint inner rings, and a strange hexagonal weather system on Saturn's north pole.

As for Juno, I'm charmed by this "ballet" of Jupiter's moons, taken as the probe first approached the planet. Seeing the moons orbit the planet gives the impression that Jupiter is really the center of its own mini-solar system. Both videos are fascinating, but I have to give the edge to Cassini.

Winner: Cassini

Adding It All Up
Cassini wins in three categories, Juno wins in two, and there's one tie. Clearly the probes are almost equally impressive. Though Cassini has had more than a decade to earn its victories; Juno's mission only really began a year ago. As we bid goodbye to Cassini, I'm sure we'll see more stunning images and videos from the Jupiter probe.

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