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The Exchange

The Sky Guys: Juno, Jupiter and the Milky Way

We're checking in with the Sky Guys this week for the latest news on the Juno mission to Jupiter, why eighty percent of Americans can no longer see the Milky Way, and gravitational ripples confirmed for a second time.   Plus, what to look for in the stars for summer nights ahead.



  • John Gianforte – co-founder of the "Astronomical Society" of northern New England and astronomy instructor for Granite State College and UNH
  • Mal Cameron - former astronomy and space educator at the McAuliffe Shepard Discovery Center and coordinator of its NASA Educator Resource Center

Link to Information on the New England Fall Astronomy Festival.

Here's a video on gravitational waves:



Juno’s journey: A fingers-crossed kind of mission.   

Mal Cameron:  The first sweep around the planet is the most important one.  Juno will get as close as 3100 miles above the surface of Jupiter and will use massive solar panels rather than a radiation system to run it.  The radiation zone around Jupiter would appear to be as large as the full moon. It’s massive and dangerous to travel in. 

Just how gigantic is Jupiter?

John Gianforte:  It has more mass, more stuff inside of it than all the rest of the planets in the solar system combined. Its magnetic field  extends some 600 million miles into space beyond Jupiter,  almost to the orbit of Saturn.   The plan is for Juno to make 33 orbits around Jupiter.

Juno will transmit photos of Jupiter back to earth. But will the spacecraft ever return?

John: They’re going to crash the Juno mission into Jupiter’s atmosphere so it burns up like a meteor would burn up in earth’s atmosphere. This will protect some of the moons of Jupiter that we now know could be habitable and could be damaged if Juno were to crash into one of them.  

Despite the dangers, there’s plenty of solid science backing up this mission:

John:  We know the mass of Jupiter and the mass of the Juno spacecraft. And we’re pretty good at knowing Newton’s Universal  Law of Gravity, which dictates how close we can fly to Jupiter and what trajectory we have to fly. 

Still… plenty can go wrong (hence, the crossed fingers):

John:  Bad things happen in space. Let’s say the engine doesn’t act or fire as long as it should, and it doesn’t slow down enough for Jupiter’s gravity to capture the spacecraft into orbit. Then we fly by the target and the mission is over. If the engine fires too long, which is unlikely, then it crashes into the planet.  Space is a nasty place and this is a very hazardous environment.

Meanwhile, on Mars… Curiosity still roams.

John:  It’s proven that Mars once provided a habitable environment for life. There are organic compounds on Mars.  So, now we know there’s lots of water on Mars. There are no flowing rivers or open lakes but just beneath the surface we believe there’s lots of water.

Listener Richard from Portsmouth: Enough of Mars already! There’s too much emphasis on planets you can actually land on and walk around on, like the moon.  (He calls it “surfacism.")

Why not look at Venus and the idea of floating cities on Venus?   If you live in the cloud top, the temperatures are not a whole lot hotter than they get on earth and clouds keep out almost all the radiation, so it solves a lot of the biological problems.  Not to mention Venus is almost half the distance of Mars.  It has a tremendous amount of solar energy…  A win-win if we can get over not having to walk on the surface.

Mal and John ponder this notion:

Mal: I wouldn’t want to go there.  Those clouds on Venus are just pure carbon dioxide and that would not be good for us. It’s an extremely acidic environment in the atmosphere. Sulfuric Acid is raining on the planet all the time. On the surface, the temp is roughly 900 degrees F. 

John: You can find temperatures and pressure in Venusian atmosphere  similar to the earth’s. But I'm not sure how you’d stay elevated; you’d constantly need to fire rockets, unless you have some very, very durable balloon.

Mal: It would be dangerous and difficult.

John: But so was going to the moon!