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Forty years ago this coming Tuesday, a car-sized piece of equipment launched from Cape Canaveral in Florida. Thirty five years later, it became the first and only man-made object to enter interstellar space. Along the way, the Voyager probes (there were two) made headlines for flybys of Jupiter, Saturn and Titan.

Fran Bagenal was a student when the Voyager probes launched, and wrote her doctoral thesis on data the probes collected around Jupiter. The professor of astrophysical and planetary science at the University of Colorado at Boulder, and former chair of NASA’s Outer Planet Assessment Group, has also worked on the Galileo, Deep Space 1, New Horizons and Juno missions.

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Nautilus caught up with Bagenal to discuss the legacy of Voyager and the future of manned and unmanned exploration of space.

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You’ve said there will never be another Voyager. Why not?

One of the reasons is that we had the planets lined up in a particular way that happens every 175 years. It’ll be another 135 years before they line up that way again. The other reason is that Voyagers were part of that first wave of exploration where you design your mission to get first glimpses. You go in with a very open view and you say, “Let’s just look and see what’s there.” The follow on missions tend to be much more targeted. Galileo, for example, was only looking at the Galilean moons around Jupiter. Cassini went to Saturn, spending 13 years exploring the moons, the rings and Titan.

Is Voyager still sending interesting data back?

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Oh yes, absolutely. It’s out in the interstellar medium, Voyager 1 is, and it’s exploring the boundary at the edge of the heliosphere, where the solar wind abuts into the interstellar medium, which is the medium between the stars. This is the first time we’ve ever been out there. We’re measuring the charged particles, the cosmic rays, the magnetic field, the electric field, the waves, the radio waves and so on. This is telling us about how the interstellar medium interacts with our solar system.

Is there new science in old Voyager data?

I’m still analyzing Voyager data, believe it or not. We’ve just published three papers on Voyager data that was taken 33 years ago, at the same time that we’re all celebrating the 40th anniversary of the launch. It was fun. I realized that some of the data I had done my thesis on, from 1979, had not been reanalyzed. And we had new information and new physics that we could fold into the analysis. It was an archeology project to dig back down and find the old data set, then try and understand how to analyze it. All the old code was written in Fortran, and the new undergraduates who were working with me we were using IDL or Python. It’s like going and looking at hieroglyphic scripts.

When will the Voyager mission end?

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We’ll run out of energy at some point. We’re already having to sort of cycle through the instruments and save energy as best we can. The onboard radioisotope solar electric generators have an 88-year half life, so they’re beginning to decay. And you’ve also got to keep the spacecraft warm. I would predict that we’ll cease to be able to communicate with it somewhere around another 15 years time or so.

What will future space probes look like?

Spacecraft are getting smaller and lighter, so they need less propulsion. Their instruments are getting much more efficient so they need less power. Communication is a harder problem because you need to send information over large distances. So you either have to have a big antenna, which takes a lot of power on the spacecraft and is heavy, or—and this is the way I think we should be going—increase the size of the ears on the ground. Computational capabilities of spacecraft are also growing quickly. There’s a great line in the recent PBS special on Voyager explaining that the onboard computer capability is about the same as in your pocket. And I’m not talking your phone, I’m talking your key fob. With large onboard computing capability you can pre-process images and have the probe tell you, “these are the ones you might find interesting, how about we send these down first and then we’ll send down other stuff later.”

What do you make of Breakthrough Starshot and its plans to send probes to the nearest star?

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I don’t understand how it’s supposed to work. The three big issues with exploration are propulsion, power and communication. They’re claiming to do propulsion via lasers, and I find that hard to imagine given the distances they’re talking about, but okay. You probably don’t need a whole lot of power. But how are they going to communicate? They’re talking about sending a chip or something that’s minute to Alpha Centauri, and I’m just finding it extremely hard to see, without a radio antenna, how are they going to communicate with the Earth without a radio dish. I can’t believe that you can do this with laser communication. You can’t even go beyond the order of Mars using laser communication. It just seems a little bonkers to me, to be quite honest with you.

Get outta here: Breakthrough Starshot envisions pushing a tiny spaceship to Alpha Centauri by shining lasers onto an attached lightsail.Breakthrough Prize

Are you excited by the current rumors surrounding the observation of merging neutron stars through gravitational waves?

If it’s outside the solar system I tend to yawn and roll my eyes and move on. In the solar system we have real information, real data, we can look at real stuff. Whereas, you know, the information out there is so sparse, it’s like, “Okay, fine.” It also has to do with the size of the ego of the researchers involved, which seems to increase with the distance from the Earth.

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What are some of the most interesting space physics problems from inside the solar system?

There’s a bunch of them. Why do some planets have internal magnetic fields and others, like Venus, don’t? Why are there so many different types of objects in the Kuiper Belt? What drives behavior in these different objects? What role did the giant planets have in the formation of the solar system? How many of them kicked other objects around? Why is Saturn so different to Jupiter? You can’t approach these problems with one kind of physics. You can do dynamical models, but you also really need to look at the chemistry. You have to use gravity measurements, magnetic field measurements, chemical measurements, spectroscopic measurements, and so on and so forth. The nice thing about planetary science is it’s so interdisciplinary.

Should manned space flight be a priority?

Personally, and this is speaking as an individual, I think there’s nothing that humans can do in space that robots can’t do better, except tourism. So if you’re talking about something other than tourism, that has scientific objectives, then send lots of robots out to do it. The big challenge that NASA has right now is what is the role of humans in space? And I think it isn’t clear at all what this could be other than tourism. And the government shouldn’t be paying for tourism. This is coming from someone who as a teenager stayed up until 4:00 in the morning to watch all the Apollo programs when I was a kid in England. My view has changed now that robots are so effective. Why would you send a chunk of meat up into space? It’s kind of pointless.

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But don’t manned missions inspire us in ways that robots don’t?

Go find a 12 year old and ask, “When did you last watch an astronaut in space?” And then ask them, “How many astronauts are actually in space right now?” I would bet that that 12 year old wouldn’t know. On the other hand, what if you said, “I will give you goggles and gloves that let you, through virtual reality, explore the surface of Mars?” I bet you that 12 year old would be a lot more excited by the possibility of virtually roaming the surface of Mars than watching some middle aged old astronaut prancing about at some slow pace out in space. There are now capabilities for doing virtual reality with the Mars rovers. Things have changed. I’ve watched the jubilation of thousands of people watching a robot fly past Pluto and taking amazing observations. That got people really excited.

What do you make of the argument that we should colonize Mars?

I think it’s bullshit. You know, if you’re a super millionaire you can have these nutty ideas and nobody’s going to say to you, “You’re talking rubbish,” because you’re a millionaire, and so everyone says, “Oh yes, oh yes. You’re so wonderful, you can do whatever.” The movie The Martian made my point. All that effort that was expended, the changing the orbit of the space station and going out and sending something to go catch the guy in a totally unrealistic, unphysical way. And to what end? You saved that one person. Well, okay, it’s Matt Damon, everybody wants to save Matt Damon. But the reality is there will be people dying on Mars. The entertainment industry may want to get involved. They would love to have someone dying live on Mars, right? You can imagine the ratings going through the roof. But the taxpayer shouldn’t be paying for that.

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What’s the case for exploring Venus?

I’m not involved professionally in Venus. But as a human being living on this planet that is suffering from climate change that could potentially lead to a catastrophic environment, I’m very interested in our sister planet. It’s the same size as Earth, just a little closer to the sun, and it has a runaway greenhouse atmosphere with 90 times the carbon dioxide pressure that we have here on Earth. The difference in distance to the sun is not the primary cause of its oven-like surface temperature, it’s the greenhouse gases. It’s bizarre that our sister planet should have become such an inferno. Why that is the case is a damn good question, and not unrelated to our concerns about climate change. The fact that Venus probably doesn’t have oceans means that its geology is different. And why is that so? Venus was completely re-surfaced with lava about 600 million years ago. What was it like before then? Was it actually like Earth?

What might a probe to Venus look like?

Above the surface of Venus, you have a clear atmosphere, and above that you have thick clouds which obscure the surface from telescopes looking at Venus from Earth. Now, if you go up in the atmosphere at some point it’ll cool off. It actually heats up again once you move out into the very tenuous atmosphere at the top. But there is a region in between, where the temperatures are reasonable. And it is possible that you could send a probe to Venus that would float like an air balloon or airship that could sink down and look at the surface then rise when it got too hot. This idea has actually been proposed. It’s not being supported, and I’m frustrated that all this money is going to on Mars missions when Venus really should be a major focus of our attention.

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Our sister planet: This is an image of Venus taken by NASA’s Mariner 10 spacecraft as it flew past Venus on its way to Mercury. The colors—or lack thereof—are what a human eye would see. The planet is totally covered in thick clouds of sulfuric acid over a carbon dioxide atmosphere. Indeed, Venus has a runaway greenhouse atmosphere with toxic clouds—why do we know so little about this neighbor of Earth?NASA

Are you frustrated at the focus on Mars?

I’m annoyed at the fact that so much money is spent on these Mars missions claiming that we’re going to discover water on Mars. Well, we’ve discovered water on Mars now how many times? There isn’t a whole lot of it, but they keep discovering it. And then we claim they’re going to go find life on Mars. Well, it’s pretty clear that there haven’t been large oceans on Mars for several billion years, and it lost its magnetic field about the same sort of time, so the last time there could have been life on Mars, the life on Earth was slime mold. So what are you going to find? Fossil slime mold, big deal. Why are we wasting all this money on Mars? It’s bonkers. It’s wishful thinking and people’s fantasies. It’s also because it’s a lot easier to go to than Venus. So people are like, “Oh well, we know how to send rovers to Mars, let’s send another rover to Mars. Let’s make it a bigger rover, make it a smaller rover.” Let’s stop doing things that we know how to do, let’s do something that’s tough, like go to Venus.

Are women continuing to make inroads into physics?

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This is actually a topic that I’ve been paying a lot of attention to. The number of physics PhDs going to women have been increasing slowly and steadily. But there’s been a disturbing trend in the past 15 years, with the percentage of bachelors degrees going to women in physics coming down. And I don’t know why that is. I’m trying to understand it. What’s infuriating is there is every now and again a debated stirred by a bunch of people who say, “Oh you know, women are not able to do science or are not interested.” And all the sociological studies have shown these things to be not true. And the demographics and the numbers show these things to be not true. But you know, you have to look for a silver lining to every story. I think the fact that there’s been a lot of publicity about, for example, the Google diversity memo has led to a lot of discussion and debate. I hope a lot of parents are talking to their children and encouraging them, both males and females, to study science.

Michael Segal is the editor in chief of Nautilus.

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Watch The Farthest, a documentary on PBS about the Voyager spacecraft.

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