NASA's Cassini Spacecraft is about to make a daring plunge through one of the plumes emerging from Saturn's moon Enceladus.
Enceladus boasts an icy, ostensibly barren landscape riddled with deep canyons, dubbed tiger stripes. Underneath its icy exterior churns a global ocean, heated in part by tidal forces from Saturn and another moon, Dione, with seafloor vents expelling water at at least 194 degrees Fahrenheit. Plumes of water vapor and icy particles jettison from its surface in geyser-like spouts, hinting that there is much more to this snowy moonscape than meets the eye.
Cassini will be soaring through the jets located at the moon's south pole, only 30 miles above the surface.
Although the October 28th flyby won't be the closest we've ever been to Enceladus, it is the closest flyby over the south pole and through the plume. We'll be exploring in situ a region of the plume that Cassini has never sampled before.
So what causes these plumes, and why are they so important? Enceladus' vast, subterranean oceans may be fizzy and full of gas. When the gas and icy particles rise to the surface, they are expelled in plumes shooting from the tiger stripes. The process is similar to shaking up a bottle of soda; the gas has nowhere to go but up and out.
However, the plumes are more than just gas and water: samples show that they also contain many of the building blocks essential to Earth-like life. This lends itself to the exciting possibility that organisms similar to those that thrive in our own deep oceans near volcanic vents exuding carbon dioxide and hydrogen sulfide might exist on Eceladus. Although it is still too early to know exactly how complex potential Enceladus' lifeforms could be, scientists speculate that at the very least microbial life is a real possibility.
In the future, a different spacecraft may journey across the solar system to visit icy Enceladus. This spacecraft, unlike Cassini, could be designed to land on Enceladus' surface, near one of its tiger stripes. Such a lander would be able to take samples more directly, bypassing the plume altogether.
Ideally, it could take samples from the edge of one of the tiger stripes, speculates Spilker. This would ensure that any microbes being expelled from Enceladus' interior would be more plentiful and easier to collect.
Until then, flybys are the best we can do. And the next one should be very good indeed. Tune in on Oct. 28th!
Space-Time Vortex Around The Earth
MXPlank shows the results of an epic physics experiment which confirms the reality of a space-time vortex around our planet.
Is Earth in a vortex of space-time?
A Stanford physics experiment called Gravity Probe B (GP-B) recently finished a year of gathering science data in Earth orbit. The results, which will take another year to analyze, should reveal the shape of space-time around Earth--and, possibly, the vortex.
Time and space, according to Einstein's theories of relativity, are woven together, forming a four-dimensional fabric called "space-time." The tremendous mass of Earth dimples this fabric, much like a heavy person sitting in the middle of a trampoline. Gravity, says Einstein, is simply the motion of objects following the curvaceous lines of the dimple.
If Earth were stationary, that would be the end of the story. But Earth is not stationary. Our planet spins, and the spin should twist the dimple, slightly, pulling it around into a 4-dimensional swirl. This is what GP-B went to space to check
The idea behind the experiment is simple:
Put a spinning gyroscope into orbit around the Earth, with the spin axis pointed toward some distant star as a fixed reference point. Free from external forces, the gyroscope's axis should continue pointing at the star--forever. But if space is twisted, the direction of the gyroscope's axis should drift over time. By noting this change in direction relative to the star, the twists of space-time could be measured.
In practice, the experiment is tremendously difficult.
The four gyroscopes in GP-B are the most perfect spheres ever made by humans. These ping pong-sized balls of fused quartz and silicon are 1.5 inches across and never vary from a perfect sphere by more than 40 atomic layers. If the gyroscopes weren't so spherical, their spin axes would wobble even without the effects of relativity.
According to calculations, the twisted space-time around Earth should cause the axes of the gyros to drift merely 0.041 arcseconds over a year. An arcsecond is 1/3600th of a degree. To measure this angle reasonably well, GP-B needed a fantastic precision of 0.0005 arcseconds. It's like measuring the thickness of a sheet of paper held edge-on 100 miles away.
GP-B researchers invented whole new technologies to make this possible. They developed a "drag free" satellite that could brush against the outer layers of Earth's atmosphere without disturbing the gyros. They figured out how to keep Earth's penetrating magnetic field out of the spacecraft. And they concocted a device to measure the spin of a gyro--without touching the gyro.
Pulling off the experiment was an exceptional challenge. A lot of time and money was on the line, but the GP-B scientists appear to have done it.
"There were not any major surprises" in the experiment's performance, says physics professor Francis Everitt, the Principal Investigator for GP-B at Stanford University. Now that data-taking is complete, he says the mood among the GP-B scientists is "a lot of enthusiasm, and a realization also that a lot of grinding hard work is ahead of us."
A careful, thorough analysis of the data is underway. The scientists will do it in three stages, Everitt explains. First, they will look at the data from each day of the year-long experiment, checking for irregularities. Next they'll break the data into roughly month-long chunks, and finally they'll look at the whole year. By doing it this way, the scientists should be able to find any problems that a more simple analysis might miss.
Eventually scientists around the world will scrutinize the data. Says Everitt, "we want our sternest critics to be us."
The stakes are high. If they detect the vortex, precisely as expected, it simply means that Einstein was right, again. But what if they don't? There might be a flaw in Einstein's theory, a tiny discrepancy that heralds a revolution in physics.
First, though, there are a lot of data to analyze. Stay tuned.
Sunset Solar Eclipse
On October 23rd, 2014, the Moon will pass in front of the sun, off-center, producing a partial solar eclipse visible in most of the United States
Sunsets are always pretty. One sunset this month could be out of this world. On Thursday, Oct. 23rd, the setting sun across eastern parts of the USA will be red, beautiful and - crescent-shaped.
It's a partial solar eclipse. In other words, the New Moon is going to 'take a bite' out of the sun.
A total eclipse is when the Moon passes directly in front of the sun, completely hiding the solar disk and allowing the sun's ghostly corona to spring into view. A partial eclipse is when the Moon passes in front of the sun, off-center, with a fraction of the bright disk remaining uncovered.
The partial eclipse of Oct. 23rd will be visible from all of the United States except Hawaii and New England. Coverage ranges from 12% in Florida to nearly 70% in Alaska. Weather permitting, almost everyone in North America will be able to see the crescent.
The eclipse will be especially beautiful in eastern parts of the USA, where the Moon and sun line up at the end of the day, transforming the usual sunset into something weird and wonderful.
Observers in the Central Time zone have the best view because the eclipse is in its maximum phase at sunset. They will see a fiery crescent sinking below the horizon, dimmed to human visibility by low-hanging clouds and mist.
Warning: Don't stare. Even at maximum eclipse, a sliver of sun peeking out from behind the Moon can still cause pain and eye damage. Direct viewing should only be attempted with the aid of a safe solar filter.
During the eclipse, don't forget to look at the ground. Beneath a leafy tree, you might be surprised to find hundreds of crescent-shaped sunbeams dappling the grass. Overlapping leaves create a myriad of natural little pinhole cameras, each one casting an image of the crescent-sun onto the ground beneath the canopy. When the eclipsed sun approaches the horizon, look for the same images cast on walls or fences behind the trees.
Here's another trick: Criss-cross your fingers waffle-style and let the sun shine through the matrix of holes. You can cast crescent suns on sidewalks, driveways, friends, cats and dogs-you name it. Unlike a total eclipse, which lasts no more than a few minutes while the sun and Moon are perfectly aligned, the partial eclipse will goes on for more than an hour, plenty of time for this kind of shadow play.
A partial eclipse may not be total, but it is totally fun.
The Sounds Of The InterStellar Space
As Voyager 1 recedes from the solar system, researchers are listening for interstellar music (plasma waves) to learn more about conditions outside the heliosphere.
Scifi movies are sometimes criticized when explosions in the void make noise. As the old saying goes, in space, no one can hear you scream. Without air there is no sound.
But if that's true, the sounds of interstellar space were heard by astronomers?
It turns out that space can make music - if you know how to listen.
Some plasma wave data was played for astronomers and The sounds were solid evidence that Voyager 1 had left the heliosphere.
The heliosphere is a vast bubble of magnetism that surrounds the sun and planets. It is, essentially, the sun's magnetic field inflated to enormous proportions by the solar wind. Inside the heliosphere is home. Outside lies interstellar space, the realm of the stars
For decades, researchers have been on the edge of their seats, waiting for the Voyager probes to leave. Ironically, it took almost a year to realize the breakthrough had occurred. The reason is due to the slow cadence of transmissions from the distant spacecraft. Data stored on old-fashioned tape recorders are played back at three to six month intervals. Then it takes more time to process the readings.
The thrill of discovery when some months-old data from the Plasma Wave Instrument reached his desk in the summer of 2013. The distant tones were conclusive: Voyager 1 had made the crossing.
Strictly speaking, the plasma wave instrument does not detect sound. Instead it senses waves of electrons in the ionized gas or plasma that Voyager travels through. No human ear could hear these plasma waves. Nevertheless, because they occur at audio frequencies, between a few hundred and a few thousand hertz, we can play the data through a loudspeaker and listen. The pitch and frequency tell us about the density of gas surrounding the spacecraft.
When Voyager 1 was inside the heliosphere, the tones were low, around 300 Hz, typical of plasma waves coursing through the rarified solar wind. Outside, the frequency jumped to a higher pitch, between 2 and 3 kHz, corresponding to denser gas in the interstellar medium.
So far, Voyager 1 has recorded two outbursts of interstellar plasma music--one in Oct-Nov. 2012 and a second in April-May 2013. Both were excited by bursts of solar activity.
We need solar events to trigger plasma oscillations.
The key players are CMEs, hot clouds of gas that blast into space when solar magnetic fields erupt. A typical CME takes 2 or 3 days to reach Earth, and a full year or more to reach Voyager. When a CME passes through the plasma, it excites oscillations akin to fingers strumming the strings on a guitar. Voyager's Plasma Wave Instrument listens - and learns.
We're in a totally unexplored region of space and expect some surprises out there.
In particular, plasma waves are not excited by solar storms. Shock fronts from outside the solar system could be rippling through the interstellar medium. If so, they would excite new plasma waves that Voyager 1 will encounter as it plunges ever deeper into the realm of the stars.
The next sounds from out there could be surprising indeed.
