A process of erosion where water leaks to the surface through the
pores of rocks; as the water flows away, it slowly removes material to form
valleys and channel networks.
A line of cliffs produced by faulting or erosion;
a relatively straight, clifflike face or slope of considerable linear
extent, breaking the general continuity of the land by separating surfaces
lying at different levels.
A tenuous flow of gas and energetic charged particles, mostly
protons and electrons -- plasma -- which stream
from the Sun; typical solar wind velocities are almost 350 kilometers (217 miles)
per second.
Light speed equals 299,792,458 meters/second (186,000 miles/second).
Einstein's Theory
of Relativity implies that nothing can go faster
than the speed of light.
The cold region of a planetary atmosphere above the
convecting regions (the
troposphere), usually without vertical motions
but sometimes exhibiting strong horizontal jet streams.
A dense, high-pressure phase of quartz that has so far been
identified only in shock-metamorphosed, quartz-bearing rocks from
meteorite impact craters.
An area seen as a dark spot on the
photosphere of the Sun. Sunspots are
concentrations of magnetic flux, typically occurring in
bipolar clusters or groups. They appear dark because they are cooler than
the surrounding photosphere.
A star which is in the proccess of exploding. It is thought to be caused by gravitational collapse. During this time the star's brightness sharply increases and makes it easily identifiable to astronomers. Sometimes supernovas leave behind dense cores.
The orbital radius at which the satellite's orbital period is equal to the
rotational period of the planet. A synchronous satellite with an
orbital inclination of zero (same plane as the planet's equator)
stays fixed in the sky from the perspective of an observer on the
planet's surface. These orbits are commonly used for communications
satellites).
A satellite's rotational period is equal to its orbital period;
this causes the same side of a satellite to always face the planet.
Synchronous rotation occurs when a planet's gravity produces a tidal
bulge in its satellite. The gravitational attraction and bulge acts like a torque,
which slows down the satellite until it reaches a synchronous rotation.
