Merle Walker1955
Photoelectric observations establish a roughly 6.4-day brightness periodicity for Pluto, providing the first reliable measurement of its rotation period.
United States · Science / Astronomy. Chronological records rendered directly from the World History Database.
Photoelectric observations establish a roughly 6.4-day brightness periodicity for Pluto, providing the first reliable measurement of its rotation period.
Infrared photometry provides evidence that methane frost is a dominant reflective material on Pluto's surface.
Methane-frost observations imply Pluto has a comparatively high albedo and a diameter smaller than earlier estimates.
James Christy identifies evidence of Pluto's first known moon, later named Charon, in photographic observations.
Hubble observations record strong large-scale brightness differences across Pluto's surface at unprecedented spatial resolution.
Hubble's Faint Object Camera images Pluto through much of a rotation, enabling an image-based map of most of its surface.
The Hubble surface map confirms a dark equatorial belt and bright polar regions on Pluto.
Hubble results produce the first image-based surface map of Pluto, revealing about a dozen major bright and dark regions.
Hubble observations indicate Pluto's surface patterns are strongly influenced by migrating nitrogen and methane frosts.
Hubble completes a series of observations later combined into detailed maps showing changes in Pluto's surface appearance.
New Hubble maps assembled from 2002-2003 observations reveal measurable changes in Pluto's surface color and brightness patterns.
Approach images begin showing distinct surface features on Pluto with steadily improving detail.
New Horizons' Ralph spectrometer detects frozen methane on Pluto during approach, confirming the molecule from spacecraft observations.
New Horizons measurements determine Pluto is about 2,370 kilometres in diameter, larger than many pre-encounter estimates.
New Horizons returns its last and most detailed full-disk image of Pluto before closest approach.
Close-up images reveal youthful water-ice mountains rising about 3.5 kilometres above Pluto's surface.
Mission scientists conclude that nitrogen, carbon monoxide and methane ices can flow across Pluto at its extremely low temperatures.
New Horizons images show nitrogen-rich ices flowing across Pluto in glacier-like patterns, evidence of recent geologic activity.
A New Horizons methane map shows that methane ice is distributed unevenly across Pluto's surface.
High-resolution New Horizons images reveal rugged mountains, faulted blocks and detailed textures along the edge of Sputnik Planitia.
Enhanced-color imagery reveals the unusual ridged and scaly terrain of Tartarus Dorsa, nicknamed Pluto's snakeskin terrain.
New Horizons compositional mapping identifies numerous exposed regions of water ice on Pluto's surface.
Topographic analysis identifies Wright Mons and Piccard Mons as possible large cryovolcanoes formed by icy volcanic activity.
The New Horizons team reports more than fifty Pluto-system discoveries four months after the flyby as stored data continue reaching Earth.
Highest-resolution images show erosion and faulting sculpting rugged badlands and a major canyon system in Pluto's northern terrain.
Close-up imagery reveals aligned pits in Pluto's nitrogen-rich ice, probably formed through fracturing and volatile-ice loss.
New Horizons studies identify widespread past and present glacial activity, including eroded and hanging valleys on Pluto.
New Horizons results strengthen evidence that Pluto may retain a subsurface water-ice ocean beneath its crust.
The International Astronomical Union approves the first official names for surface features discovered on Pluto by New Horizons.
Tombaugh Regio and Burney crater become official Pluto feature names honoring Clyde Tombaugh and Venetia Burney.
Analysis of New Horizons imagery confirms dune fields near Sputnik Planitia, showing that Pluto's thin atmosphere can mobilize surface particles.
Pluto's dunes are interpreted as deposits of sand-sized methane-ice grains shaped by winds near the margins of Sputnik Planitia.
New analysis finds evidence that liquid nitrogen has recently risen through cracks to wet parts of northern Sputnik Planitia.
This factsheet is generated from stored World History Database records matching the country, broad category, detailed category and exact Event value shown above. Duplicate display records are collapsed; database wording is otherwise preserved. Source provenance varies by record, so formal academic citation should be checked against the relevant primary source, archive or specialist historical reference.