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Astrophysicist, Goddard Spaceflight Center
What do you think are the most significant events that have occurred in the past fifty years of robotic planetary exploration? Why?
I was awestruck by the first pictures of eroded slopes and gullies on Mars. The year was 2007 and the pictures came from Mars Reconnaissance Orbiter (MRO).
The Viking lander showed a red desert with rocks, which was amazing at the time, but the slopes and gullies from MRO looked so much like typical scenes on Earth that a light-bulb clicked in my brain --- Mars and Earth are not that different.
The pictures from the Cassini-Huygens lander on Titan were also unforgettable.
They were fuzzy, but clearly showed lakes. We believe the lakes are filled with liquid ethane and methane instead of water. What a strange world that is -- we must get back for a closer look.
In your field of work, what are some examples of the great achievements and discoveries in planetary science and robotic exploration throughout the past 50 years?
I am interested in the regions around planets where their magnetic fields are important: the so-called magnetospheres. Every planet has one, and large planets like Jupiter and Saturn have enormous ones.
They are nearly impossible to study from a distance, so the most important achievements for my field were the first fly-bys of the outer planets by the Pioneer and Voyager spacecraft.
As these spacecraft swooped past Jupiter and Saturn we got the first measurements from inside the magnetospheres of these two planets.
Both planets are amazing, but my favorite is Jupiter. The magnetic field is intense and traps large quantities of particles.
In fact, it was found that particles from the volcanoes on Jupiter's moon Io are picked up by Jupiter's magnetic field and eventually spiral into the planet and cause the aurorae.