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SDO is designed to amaze—and it got off to a good start.
"The observatory did something amazing before it even left the atmosphere," says SDO project scientist Dean Pesnell of the Goddard Space Flight Center.
Moments after launch, SDO's Atlas V rocket flew past a sundog hanging suspended in the blue Florida sky and, with a rippling flurry of shock waves, destroyed it. Click on the image below to launch a video recorded by 13-year-old Anna Herbst at NASA's Banana River viewing site—and don't forget to turn up the volume to hear the reaction of the crowd.
"I couldn't believe my eyes," says Anna. "The shock waves were so cool." Anna traveled with classmate Amelia Phillips three thousand miles from Bishop, California, to witness the launch. "I'm so glad we came," says Amelia. "I've never seen anything like it!"
Sundogs are formed by plate-shaped ice crystals in high, cold cirrus clouds. As the crystals drift down from the sky like leaves fluttering from trees, aerodynamic forces tend to align their broad faces parallel to the ground. When sunlight hits a patch of well-aligned crystals at just the right distance from the sun, voila!--a sundog.
"When the Atlas V rocket penetrated the cirrus, shock waves rippled through the cloud and destroyed the alignment of the crystals," explains atmospheric optics expert Les Cowley. "This extinguished the sundog."
In the past, says Cowley, there have been anecdotal reports of atmospheric disturbances destroying sundogs—for instance, "gunfire and meteor shock waves have been invoked to explain their disruption. But this is the first video I know of that shows the effect in action."
Right: Sundogs are formed by the refracting action of plate-shaped ice crystals. Image credit: Les Cowley/Atmospheric Optics [more]
The effect on the crowd was electric.
"When the sundog disappeared, we started screaming and jumping up and down," says Pesnell. "SDO hit a home run: Perfect launch, rippling waves, and a disappearing sundog. You couldn't ask for a better start for a mission."
SDO is now in orbit. "The observatory is doing great as the post-launch checkout continues," he reports. "We'll spend much of the first month moving into our final orbit and then we'll turn on the instruments. The first jaw-dropping images should be available sometime in April."
Believe it or not, Pesnell says, the best is yet to come.View my blog's last three great articles....
Unlocking those secrets will require the guile of a veteran explorer. Like a wily old baseball pitcher who uses knuckle balls to keep winning, the aging Spirit still has a few tricks up its sleeve. It will do its next trick without moving a single mechanical muscle.
Right: Spirit's view of its own predicament. The rover is now parked for the winter with its solar panels tilted only 9 degrees toward the sun. [more]
"In this case, it's a good thing Spirit is immobile," says principal investigator Steve Squires. "We can track its radio signal to determine its motion through space."
Mars is rotating around its own axis and orbiting the Sun. With the rover stationary, the radio's only motion will be the motion of Mars. Because the scientists already know the specifics of the red planet's orbit, they'll be able to use Spirit's radio signal to hone in on how the planet spins around its own axis.
"Mars wobbles, or precesses, as it spins," says Bruce Banerdt of NASA's Jet Propulsion Laboratory. "We'll measure that wobble by looking at the timing of the radio signal—how long it takes to go back and forth between Spirit's transmitter and our receivers on Earth."
"Mars completes an entire wobble only once every 170,000 years," he continues. "So we'll be measuring a very tiny motion—looking at minute changes. But these miniscule numbers speak volumes about Mars' core."
First, it will help scientists figure out if the core is solid or liquid. There are clues that it was molten at some time in the ancient past. A molten core is a fluid that moves and conducts electricity, so it sets up a powerful magnetic field. Researchers see remnants of that field today but are unsure how much of the core, if any, is still molten.
"If Mars' core is solid through and through, the nature of the wobble will be subtly different from the wobble if the core is liquid," says Squires.
Spin a hard-boiled egg and then spin a raw egg. You'll see a distinct difference in the way they rotate.
Right: An artist's concept of the Martian core. Credit: NASA/JPL.
The moment of inertia of a spinning object—in this case, a planet—is a number that describes how easy or how hard it is to change the spin. "The MOI affects the speed at which the axis of Mars wobbles, so the wobble speed indirectly tells us the MOI," says Banerdt.
They'll add the MOI to what they already know about Mars—its size and mass. "Combining these three things with our understanding of how iron and rock behave inside a planet will allow us to set limits on the size and density of the Martian core. And the density will tell us what elements must be mixed with iron to make up the core."
"This research has implications that reverberate through all kinds of basic questions about the formation of the solar system and its planets. I have to tip my hat to Spirit. It keeps coming up with new tricks."
But first the rover has to survive the long, hard winter. Baseball great Rogers Hornsby summed it up: "People ask me what I do in winter when there's no baseball. I'll tell you what I do. I stare out the window and wait for spring."
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Newly released images from last November's swoop over Saturn's icy moon Enceladus by NASA's Cassini spacecraft reveal a forest of new jets spraying from prominent fractures crossing the south polar region and yield the most detailed temperature map to date of one fracture.
The new images from the imaging science subsystem and the composite infrared spectrometer teams also include the best 3-D image ever obtained of a "tiger stripe," a fissure that sprays icy particles, water vapor and organic compounds. There are also views of regions not well-mapped previously on Enceladus, including a southern area with crudely circular tectonic patterns.
The images and additional information are online at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.
"Enceladus continues to astound," said Bob Pappalardo, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "With each Cassini flyby, we learn more about its extreme activity and what makes this strange moon tick."
For Cassini's visible-light cameras, the Nov. 21, 2009 flyby provided the last look at Enceladus' south polar surface before that region of the moon goes into 15 years of darkness, and includes the most detailed look yet at the jets.
Scientists planned to use this flyby to look for new or smaller jets not visible in previous images. In one mosaic, scientists count more than 30 individual geysers, including more than 20 that had not been seen before. At least one jet spouting prominently in previous images now appears less powerful.
"This last flyby confirms what we suspected," said Carolyn Porco, imaging team lead based at the Space Science Institute in Boulder, Colo. "The vigor of individual jets can vary with time, and many jets, large and small, erupt all along the tiger stripes."
A new map that combines heat data with visible-light images shows a 40-kilometer (25-mile) segment of the longest tiger stripe, known as Baghdad Sulcus. The map illustrates the correlation, at the highest resolution yet seen, between the geologically youthful surface fractures and the anomalously warm temperatures that have been recorded in the south polar region. The broad swaths of heat previously detected by the infrared spectrometer appear to be confined to a narrow, intense region no more than a kilometer (half a mile) wide along the fracture.
In these measurements, peak temperatures along Baghdad Sulcus exceed 180 Kelvin (minus 135 degrees Fahrenheit), and may be higher than 200 Kelvin (minus 100 degrees Fahrenheit). These warm temperatures probably result from heating of the fracture flanks by the warm, upwelling water vapor that propels the ice-particle jets seen by Cassini's cameras. Cassini scientists will be testing this idea by investigating how well the hot spots correspond with the jet sources.
"The fractures are chilly by Earth standards, but they're a cozy oasis compared to the numbing 50 Kelvin (-370 Fahrenheit) of their surroundings," said John Spencer, a composite infrared spectrometer team member based at Southwest Research Institute in Boulder, Colo. "The huge amount of heat pouring out of the tiger stripe fractures may be enough to melt the ice underground. Results like this make Enceladus one of the most exciting places we've found in the solar system."
Some of Cassini's scientists infer that the warmer the temperatures are at the surface, the greater the likelihood that jets erupt from liquid. "And if true, this makes Enceladus' organic-rich, liquid sub-surface environment the most accessible extraterrestrial watery zone known in the solar system," Porco said.
The Nov. 21 flyby was the eighth targeted encounter with Enceladus. It took the spacecraft to within about 1,600 kilometers (1,000 miles) of the moon's surface, at around 82 degrees south latitude.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md., where the instrument was built.
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