A type of basalt lava flow characterized by a smooth glassy skin, and
constructed of innumerable "flow units" called "toes"; pahoehoe flows
advance at rates of 1 to 10 meters (3 to 33 feet) hour and are associated with
low-effusion-rate eruptions with little to no fountaining.
A circular feature on the surface of dark icy moons such as
Ganymede and
Callisto lacking
the relief associated with craters;
Pamlimpsests are thought to be impact craters where the topographic relief
of the crater has been eliminated by slow adjustment of the icy surface.
A central uplift characterized by a ring of peaks rather than a
single peak; peak rings are typical of larger terrestrial craters
above about 50 kilometers (30 miles) in diameter.
The visible surface of the Sun; the upper surface of a convecting
layer of gases in the outer portion of the sun whose temperature causes
it to radiate light at visible wavelengths;
sunspots
and faculae are observed in the photosphere.
A volcanic eruption or explosion of steam, mud or other material
that is not incandescent; this form of eruption is caused by the heating
and consequent expansion of ground water due to an adjacent igneous
heat source.
American astronomer. His photographs of Mars, among the earliest obtained, provided a basis for his opposition to Lowell's observations of supposed canals on Mars. Discovered Saturn's moon Phoebe.
Microscopic features in grains of quartz or feldspar consisting
of very narrow planes of glassy material arranged in parallel sets that
have distinct orientations with respect to the grain's crystal structure.
A low-density gas in which the individual atoms are charged, even
though the total number of positive and negative charges is equal,
maintaining an overall electrical neutrality.
An eruption of hot gases above the
photosphere of the
Sun. Prominences are most
easily visible close to the limb of the Sun, but some are also
visible as bright streamers on the photosphere.
