26 Years and 3 Billion Miles to Pluto

Posted on by .

Fran Bagenal is a research scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder, who is working on the New Horizons mission to Pluto and the Juno mission to Jupiter. Her main area of expertise is the study of charged particles trapped in planetary magnetic fields. She remembers a young Alan Stern walking into her office in 1989 and suggesting a mission to Pluto.

“Whatever units you use – Kelvin, Fahrenheit or Celsius – it’s bloody cold on Pluto!” I incant in my strongest English accent.

I love giving public talks about Pluto. The audience is dying to see the latest pictures. And the New Horizons mission is a great success story. I recently returned from Toronto, where Pluto was the centerpiece of an annual astronomy evening – as it has been in many towns this past year. The Canadians peppered me with questions well into the night.

Alan Stern and Fran Banenal

In this photo from a meeting of the Outer Planets Science Working Group in April 1991, Alan Stern (left) and Fran Bagenal (right) pitched the case for a mission to Pluto. Credit: Dale Cruikshank

Planetary exploration is a story of people. I start my talks showing how clever people in the mid-20th century used telescopes to pin down basic facts about Pluto (size, mass, temperature, composition, atmosphere, etc). With Voyager 2 completing its exploration of the outer planets in the fall of 1989, Alan Stern — then chairman of the Outer Planets Science Working Group — rallied support to go to Pluto. But in those days, when Pluto was a small, lonely misfit on the edge of the solar system, it was hard to convince people to send a mission just to Pluto. This all changed with the advent of digital photography that allowed the discovery of objects – now thousands of them – in the Kuiper Belt. Pluto became one of a class of objects that hinted at a much more complicated solar system history.

After a year of amazing pictures of Pluto’s complex surface from New Horizons, it feels bizarre to see the fuzzy pictures from Hubble and remember just how little we could see before. I scroll through the New Horizons’ images of convecting nitrogen ice, water ice mountains, puzzling pits, and the photochemistry of haze and tholins on the surface – repeating jokes about confused geologists that always seem to get a laugh.

Toronto audience takes in Paul Schenk’s cool 3-D images

Everyone loves 3-D! This Toronto audience takes in Paul Schenk’s cool 3-D images of Pluto during one of Fran Bagenal’s many public talks. Credit: Chris Sasaki

Sometimes the 3-D pictures are a great success, sometimes not so much. I guess there’s a huge range in human visual perception. But by now the questions are flowing. Some are basic: Why not land on Pluto? Because we preferred to take science instruments than the necessary fuel. Where next? NASA has just approved an extended mission to New Horizons’ next target: an object in the Kuiper Belt known as 2014 MU69. The science team has a running joke that the KBO’s name is “Jim Green”—a reference to NASA’s director of planetary science. This usually elicits chuckles from the group.

Some of the questions during my talks are basic science: Why does Pluto have an atmosphere but not Earth’s moon? Chemistry, location, temperature. What’s the heat source driving the convection? There’s enough heat from the rock inside. (I think.) Then there is the dreaded question: Why not carry a magnetometer? In Toronto, I was lucky to have Sabine Stanley — Toronto planetary physics professor — in the audience, who nodded in strong agreement when I said, “I’m pretty certain Pluto does not have a magnetic dynamo.”

Some questions are about the human side: What did you do for the 9.5 years to get to Pluto? Plan and work on other missions. How come there are so many women on the team? Good leadership (New Horizons Principal Investigator Alan Stern and Jim Elliott, MIT professor and planetary occultation expert) that fosters female participation. And Pluto’s fun!

The past 26 years have been a fantastic ride to Pluto. So much planetary science has emerged, with tons of new physics to study and a topic that engages the public. Yes, there have been ups and downs. But overall, what a great crew the New Horizons team is to work with. What’s next? Europa, Venus, Uranus, Quaoar…anyone?

Fran Bagenal

Fran Bagenal holds 3-D-printed models of the New Horizons spacecraft (left) and the Juno spacecraft (right). Juno successfully went into orbit around Jupiter on July 4 after an almost five-year journey. Credit: Chris Sasaki