John Spencer Biography

Spencer leads Hubble observations of an enormous volcanic plume rising hundreds of kilometres above Jupiter's moon Io.

New Horizons observes giant volcanic plumes and changing surface features on Io.

New Horizons records a giant plume from Io's Tvashtar volcano and traces its changing structure.

New Horizons detects Pluto's large moon Charon from deep space as the spacecraft continues its approach to the Pluto system.

New Horizons images Pluto's small moon Hydra during its long-range approach, extending spacecraft observations of the satellite system.

New Horizons detects Pluto's moon Nix during approach, adding another small satellite to its own imaging record.

New Horizons photographs Kerberos and Styx for the first time, bringing all five known Pluto moons into spacecraft view.

New Horizons images show Charon as a geologically varied world with enormous canyons and contrasting terrains.

New Horizons images show nitrogen-rich ices flowing across Pluto in glacier-like patterns, evidence of recent geologic activity.

New Horizons observations reveal that Pluto's small moons are irregular bodies with unexpectedly complex rotational behaviour.

New Horizons images show that Arrokoth consists of two joined lobes, revealing an unusual contact-binary structure.