Mr. Longoria's Earth Science

December 22, 2005: Even though the Voyager 2 spacecraft paid a close-up visit to Uranus in 1986, the distant planet continues revealing surprises to the eye of NASA's Hubble Space Telescope. Hubble’s high sensitivity and sharp view has uncovered a pair of giant rings girdling the planet. The largest is twice the diameter of the planet’s previously known ring system, first discovered in the late 1970s. Hubble also spied two small satellites, named Mab and Cupid. One of the satellites shares an orbit with the outermost of the new rings. The satellite is probably the source of fresh dust that keeps replenishing the ring with new material knocked off the satellite from meteoroid impacts. Without such replenishment, the dust in the ring would slowly spiral in toward Uranus. Collectively, these new discoveries mean that Uranus has a youthful and dynamic system of rings and moons. Because of the extreme tilt of Uranus's axis, the ring system appears nearly perpendicular relative to r...

When lighted from just one direction, all objects cast a shadow.  A shadow has two parts: the umbra and the penumbra.  The penumbra (from the Latin paene "almost, nearly" and umbra "shadow") is the outer region of a shadow, in which only a portion of the light source is obscured by the occluding body. An observer in the penumbra experiences a partial eclipse . The umbra, the inner region, is the darker part of the shadow.  An observer in the umbra experiences a total eclipse .  Solar Eclipse on Mars The image on the right is of Phobos (one of Mars' moon) taken by the martian land rover.  The event takes place when Phobos passes directly between the Sun and a point on the surface of Mars, obscuring a large part of the Sun's disc for an observer on Mars. During a transit, Phobos can be seen from Mars as a large black disc rapidly moving across the face of the Sun. At the same time, the shadow of Phobos moves across the Martian surface.  The event cou...