Returning guest Dr. Kelsi Singer talks about two of the icy moons of our solar system, Ganymede and Iapetus. She talks about the types of craters we see on their surfaces, and what they can teach us about the moons themselves.

Jon talks about JPL's Horizons, an amazing, publicly available system that keeps track of every known object in the solar system. Planets, moons, asteroids, spacecraft, you name it: over 715,000 in total. We discuss how this system is used by engineers, scientists, lawyers, art fans, and marine biologists.

This week's guest is Dr Paul Chodas, who directs JPL's Center for Near-Earth Object Studies. He explains how predicting where an asteroid is going can get complicated when the asteroid gets close to a planet. He also talks about an app that lets you explore how a hypothetical asteroid could be deflected.

Dr. Kevin Walsh visits the show to talk about a new NASA mission that will launch later this year: OSIRIS REx! This spacecraft will visit an asteroid, grab a bit of surface material, and return the material to Earth for further study. Dr. Walsh talks about the mission and explains how you can help scientists pick the best place on the asteroid for the spacecraft to grab a sample.

Professor Erik Asphaug stops by the show to discuss AOSAT-1, a tiny spacecraft that will contain experiments to study the surface of asteroids. AOSAT-1 will rotate once every minute, creating a force inside that exactly mimics gravity on an asteroid. We discuss how AOSAT-1, a cubesat, is being designed and built, and how it may launched from the space station in a "cubesat cannon".

Dr. Kimberly Ennico Smith, New Horizons deputy project scientist, stops by the show to talk about the new data currently being transmitted to Earth, what it's like to work on this mission, and the violent past of Pluto's moon Charon.

Dr. Alejandro Soto visits the show to talk about the different atmospheres found on planets and moons in our solar system. We talk about wind on Mars, the opening scene of The Martian, Pluto's thin atmosphere, and what it is like on Saturn's moon Titan.

Dr. Krista Soderlund talks about the ice giants, Uranus and Neptune. She tells us about their unusual rings and moons, and how studying them can teach us about exoplanets.

Dr. Christiansen stops by the show to talk about exoplanets and the Kepler Space Telescope. We share an Australian beverage and she explains how astronomers look for exoplanets, and how the discovery of "hot Jupiters" was a huge surprise to astronomers.

Dr. Lisa Storrie-Lombardi talks about the Spitzer Space Telescope. She tells us how Spitzer made the first observation of light from a planet outside our solar system. She also describes how engineers are constantly innovating, letting Spitzer make better and more sensitive observations.