Comment

Comment by Robert Dickinson 6 hours ago

At the Summit of Olympus Mons

Credit: G. Neukum (FU Berlin) et al., DLR, ESA

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From martian orbit, the Mars Express cameras looked down on the largest volcano in the solar system. The result was this stunningly detailed overhead view of the caldera or summit crater region of Olympus Mons. Fittingly named for the lofty abode of the gods of Greek mythology, Olympus Mons rises 21 kilometers above the surrounding plain or to about 3 times the height of Mt. Everest. The area pictured is 102 kilometers across and the caldera pits are up to 3 kilometers deep. For comparison, hawaiian volcanic calderas range up to 18 kilometers in diameter. Outlined by steep cliffs, Olympus Mons itself is about 600 kilometers in diameter. 

Comment by Robert Dickinson 6 hours ago

Particle Sizes in Saturn's Rings

Credit: RSS, JPL, ESA, NASA

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What size particles compose Saturn's rings? To help find out, the robot Cassini spacecraft now orbiting Saturn broadcast radio waves of three different wavelengths right through the rings to Earth earlier this month. The experiment was sensitive to ring particle sizes because ring particles much larger than a broadcast radio wavelength will reflect those radio waves away. Three different wavelengths were used: approximately 1 centimeter, 3.5 centimeters, and 13 centimeters. The results are coded into the above false-color digitally reconstructed image. In the above image, the color purple indicates regions populated predominantly by ring particles larger than 5 centimeters, while the color green indicates regions with a significant population of small ring particles less than even 1 centimeter. The white center of Saturn's B-ring indicates that the density of ring particles was too high to make a good determination. Other radio observations indicate that some ring particles can be as large as several meters across. The impressive nature and clarity of the above sharp image may help determine clues about the origin of Saturn's beautiful but enigmatic ring system. 

Comment by Robert Dickinson 6 hours ago

Venus Near the Moon

Credit & Copyright: Jay Ouellet

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The two brightest objects in the night sky appeared to go right past each other last week. On the night of May 19, Earth's Moon and the planet Venus were visible in the same part of the sky, and at closest approach were less than one degree apart. The conjunction was captured in the above image taken from near Quebec City, Quebec, Canada. Venus appears on the lower left of the above photo. The spires that appear to emanate from Venus are diffraction spikes caused by the camera itself. The image is so clear that craters on the Moon are resolved. Of course, the real physical distance between the two heavenly bodies was not unusually small -- the apparent conjunction was really just an illusion of perspective. Although Earth's Moon passes Venus once each month, such a close passing visible in the evening sky is more rare. 

Comment by Robert Dickinson 6 hours ago

Jupiter's Three Red Spots

Credit NASA, ESA, M. Wong, I. de Pater (UC Berkeley), et al.

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For about 300 years Jupiter's banded atmosphere has shown a remarkable feature to telescopic viewers, a large swirling storm system known as The Great Red Spot. In 2006, another red storm system appeared, actually seen to form as smaller whitish oval-shaped storms merged and then developed the curious reddish hue. Now, Jupiter has a third red spot, again produced from a smaller whitish storm. All three are seen in this image made from data recorded on May 9 and 10 with the Hubble Space Telescope's Wide Field and Planetary Camera 2. The spots extend above the surrounding clouds and their red color may be due to deeper material dredged up by the storms and exposed to ultraviolet light, but the exact chemical process is still unknown. For scale, the Great Red Spot has almost twice the diameter of planet Earth, making both new spots less than one Earth-diameter across. The newest red spot is on the far left (west), along the same band of clouds as the Great Red Spot and is drifting toward it. If the motion continues, the new spot will encounter the much larger storm system in August. Jupiter's recent outbreak of red spots is likely related to large scale climate change as the gas giant planet is getting warmer near the equator. 

Comment by Robert Dickinson 6 hours ago

Io: The Prometheus Plume

Credit: Galileo Project, JPL, NASA

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What's happening on Jupiter's moon Io? Two sulfurous eruptions are visible on Jupiter's volcanic moon Io in this color composite image from the robotic Galileo spacecraft that orbited Jupiter from 1995 to 2003. At the image top, over Io's limb, a bluish plume rises about 140 kilometers above the surface of a volcanic caldera known as Pillan Patera. In the image middle, near the night/day shadow line, the ring shaped Prometheus plume is seen rising about 75 kilometers above Io while casting a shadow below the volcanic vent. Named for the Greek god who gave mortals fire, the Prometheus plume is visible in every image ever made of the region dating back to the Voyager flybys of 1979 - presenting the possibility that this plume has been continuously active for at least 18 years. The above digitally sharpened image of Io was originally recorded in 1997 from a distance of about 600,000 kilometers. Recent analyses of Galileo data has uncovered evidence of a magma ocean beneath Io's surface. 

Comment by Robert Dickinson 6 hours ago

Eclipsed Moon Montage

Credit & Copyright: Sebastien Gauthier

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After watching this month's lunar eclipse, amateur astronomer Sebastien Gauthier carefully composed this montage of telescopic images of the Moon sliding through planet Earth's shadow. While the deepest part of the total eclipse corresponds to the central exposure, the play of light across the lunar surface nicely demonstrates that the planet's shadow is not uniformly dark as it extends into space. In fact, lunar maria and montes are still visible in the dimmed, reddened sunlight scattered into the cone-shaped shadow region, or umbra, by Earth's atmosphere. For this eclipse, the Moon's trajectory took it North of the umbra's darker core, seen here cast over the Moon's cratered southern highlands. Gauthier's telescope and camera equipment were set up near the Trois-Rivieres College Champlain Observatory in Quebec, Canada. 

Comment by Robert Dickinson 6 hours ago

The More You Know: The Levels of the Sky

May. 27, 2012

Comment by Robert Dickinson yesterday

The Dark Gorge, Austria

Apr. 28, 2012

Comment by Robert Dickinson yesterday

Canyon Steps, Pailon del Diablo, Ecuador

May. 26, 2012

Comment by Robert Dickinson yesterday

Sequoia National Park, Sierra, Nevada

May. 25, 2012

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