Juno Above Jupiter (Artist's Concept)

Credit: NASA/JPL-Caltech

NASA's Juno Probe Is Far From Alone Up There

July 8, 2016

This week, after years of planning and a five-year journey through space, NASA’s Juno probe successfully entered into orbit around Jupiter, where it will spend the next two years studying the giant planet’s composition, atmosphere, and gravity field, and search for clues about how exactly it formed some 4.6 billion years ago. But NASA's latest darling isn't alone out there.

Certainly, the celebrations by the Juno team and the surge of attention they're getting now that the probe is successfully in Jupiter’s orbit are well deserved, says Jonathan McDowell, an astrophysicist at Harvard University's Smithsonian Center for Astrophysics.

"It’s a truism in our business: Space is hard," McDowell said. "I’m actually amazed that any of these missions work, because they’re so complex."

How complex? Like "a million tiny details" complex.

"So the challenge isn’t getting any one right, it’s not getting any one wrong when you’re doing a million of them," McDowell said.

But, oh, we humans are a fickle bunch. I mean, it was just this time last year that New Horizons was all the rage, with its Pluto flyby and stunning pictures. And the previous fall it was all, "Whoa, the Europeans soft-landed a little washing-machine-sized gadget called Philae on a moving comet."

And soon, just like we did with New Horizons and Philae, most of us will now move on—and probably never think about Juno again.

"Meanwhile the science teams are getting ready for years of data analysis," McDowell explained. "And one of the challenges is—even after a mission is over—the science hasn’t finished."

Indeed, Rosetta—the probe that carried Philae—is still with that comet, returning new science. And New Horizons has left Pluto in its cosmic dust and is on to the next.

"And now they’re targeting it to a little rock called 2014MU69, which is one of the Kuyper belt objects," said McDowell. "A whole new class of object that we’ve never visited, so New Horizons is going to give us a whole bunch of new science as it does that."

And these guys are far from alone out there. There are little robots scattered all across the solar system sending back heaps of data.

NASA’s Messenger probe circled Mercury for four years until it’s mission ended last year. Not to worry—the Europeans and Japanese have another probe about to head back there.

"The Chinese have an outpost on the moon, the Chang’e 3 lander and its rover, Yutu," McDowell said. "The Japanese have an orbiter around Venus. On Mars, we have a whole fleet of spacecraft from the United States and from Europe and form India. The Cassini probe [is] around Saturn and its many weird and wonderful moons."

Then there’s NASA’s Dawn probe exploring Ceres-–a former planet in the asteroid belt—and another NASA orbiter taking ridiculously high-resolution photos of the moon. In all, there’s a few dozen out there—measuring, mapping and snapping photos—including the grand duke and duchess of them all, Voyagers 1 and 2, launched in 1977, and still returning data from the edge of the solar system or beyond, depending who you ask. And while it might sound positively crowded up there, there are places in the solar system still waiting for their close-up.

"We flew past Neptune and Uranus once, with Voyager, in the 1980s and we haven’t been back," said McDowell.

The problem for poor Uranus and Neptune is that many of these probes keep turning up fascinating details about bodies closer to home; like Saturn’s moon Titan, with its methane oceans, and Europa, Jupiter’s icy moon thought to have an underground ocean that could harbor life, which NASA is targeting as its next high-profile destination.

"That will let us really do detailed studies of Europa and hopefully learn a little more about the ocean we think is underneath it," McDowell said.

McDowell does admit that as the years go by there is a point of diminishing return for these older probes. The really world-shaking results do usually come right at the start.

"But science isn't all about world-shaking results," he said. "A lot of it is about accumulating data so that slowly a pattern emerges or that your confidence in the initial flashy result increases."

So the next time a gleaming new probe gets its moment in the sun, take just a second to remember the dozens of others still out there, no longer in the spotlight, steadily churning out valuable data, that were once near-impossible, one-of-a-kind successes of their own. 

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