The horseshoe-shaped filament expanded and -popped- about 600,000 km above the stellar surface. Rather than flying off toward Earth, however, most of the hot glowing plasma the filament contained simply fell back to the sun. There will be no Earth-effects from the blast.

SPLASHES OF GREEN: For the third day in a row, a high-speed solar wiind stream is buffeting Earth's magnetic field, energizing bright auroras around the Arctic Circle. "There was quite a heavy outburst last night (Aug. 27)," reports Bernt Olsen from Kvaløya, Norway. "Even though the arctic nights still are bright, we could still see splashes of green in the sky."

NOAA forecasters estimate a 30% chance of geoomagnetic activity during the next 24 hours as the solar wind continues to blow. High-latitude sky watchers should remain alert for auroras.

August 2010 Northern Lights Gallery
[previous Augusts: 2009, 2008, 2007, 2006, 2005, 2004, 2003]

SMALLEST FULL MOON OF THE YEAR: If you thought this week's full Moon looked a bit small, you were right. It was the smallest full Moon of the year. Anthony Ayiomamitis of Athens, Greece, offers this comparison:

It shows the largest full Moon of the year (Jan. 30) vs. the smallest (Aug. 25th). "The difference between the two full moons is around 14.5% and certainly easily noticeable by the naked eye," says Ayiomamitis.

Johannes Kepler explained the difference 401 years ago: The Moon's orbit around Earth is an ellipse. One side of the orbit (perigee) is 50,000 km closer to Earth than the other (apogee). The full Moon of Aug. 25th was a distant apogee Moon, and that's why it looked so small.

FULL MOON: How can you tell this Moon is full? Is it the enormous disk? The glaring moonlight? No. The real clue is the orange color of the office windows.

FARSIDE ERUPTION: This morning around 0500 UT, something exploded on the far side of the sun. NASA's STEREO-A spacecraft had a direct view of the blast, which produced a C4-class solar flare and hurled a bright coronal mass ejection (CME) over the sun's western limb:

Click to view a 0.7 MB movie of the CME

Based on STEREO-A imagery, the source of the eruption appears to be farside sunspot complex 1093-1099. Magnetic fields connecting the two sunspot groups became unstable and--bang! The blast was not directed toward Earth, so no geomagnetic storms are in the offing.

more images: from NASA's Solar Dynamics Observatory (SDO) in Earth orbit

RED SPOTS IN CONJUNCTION: What happens when a raging cyclone as wide as Earth bumps into another storm twice as large? The answer lies in the midnight sky. Two storms on Jupiter--the Great Red Spot and Oval BA--are having just such a close encounter. Amateur astronomer Anthony Wesley sends this picture from Exmouth, Australia:

The bigger storm is the Great Red Spot, which has been swirling around Jupiter for centuries. The smaller is upstart Oval BA, which formed less than ten years ago. Because the storms travel around Jupiter at different rates, they pass one another periodically, approximately every two years. And when they do ... not much happens. Previous encounters have shown, surprisingly, that the two colossal storms can converge and emerge in tact. Could this time be different?

"Oval BA and the Great Red Spot will be passing one another in the days ahead," says Wesley. "I plan to monitor developments."

more images: from Brian Combs of Buena Vista, GA; from Efrain Morales Rivera of Aguadilla, Puerto Rico; from Ralf Vandebergh of the Netherlands

GREEN SNOW: Tonight's weather forecast in Antarctica calls for a 35% chance of green snow. Yes, green. It turns that color during geomagnetic storms, as shown in this August 1st photo from Nick Roden of Australia's Davis Station on the Antarctic coast:

"We've had some fantastic aurora displays lately--bright enough to reflect from the snow," says Roden. In addition to the green auroras, there is also a green laser lancing up from the research station in the background. "That's our LIDAR, which we use to study the upper atmosphere."

A new episode of green may be in the offing. A coronal mass ejection (CME) is expected to deliver a glancing blow to Earth's magnetic field on Aug. 17th or 18th, and NOAA forecasters estimate a 35% chance of polar geomagnetic activity when the cloud arrives.

August 2010 Northern Lights Gallery
[previous Augusts: 2009, 2008, 2007, 2006, 2005, 2004, 2003]

August 16, 2010:  For the next few months, Venus will be softly resplendent in the evening sky, a treat for stargazers – but looks can be deceiving.

Consider this: The Venusian surface is hot enough to melt lead. The planet's 96% carbon dioxide atmosphere is thick and steamy with a corrosive mist of sulfuric acid floating through it. The terrain is forbidding, strewn with craters and volcanic calderas – and bone dry.

Takeshi Imamura can't wait to get there.

Imamura is the project scientist for Akatsuki, a Japanese mission also called the Venus Climate Orbiter. The spacecraft is approaching Venus and will enter orbit on December 7, 2010. Imamura believes a close-up look at Venus could teach us a lot about our own planet.

"In so many ways, Venus is similar to Earth. It has about the same mass, is approximately the same distance from the sun, and is made of the same basic materials," says Imamura. "Yet the two worlds ended up so different. We want to know why."

Although a parade of U.S. and Soviet spacecraft has visited Venus since 1961, no one yet knows how it became Earth's "evil twin." Did it suffer from a case of global warming run amok – or something else? When Akatsuki reaches Venus in December, it will begin to solve some of the mysteries hidden in the thick Venusian atmosphere.

"By comparing Venus's unique meteorology to Earth's, we'll learn more about the universal principles of meteorology and improve the climate models we use to predict our planet's future."

Particularly puzzling is Venus's "super-rotation."  Fierce, blistering winds propel an atmosphere filled with storms and sulfuric acid clouds in a churning maelstrom around Venus at over 220 miles per hour, 60 times faster than the planet itself rotates.

The acid clouds of Venus, photographed by the ESA's Venus Express spacecraft. [more]

"Venus's atmosphere is in perpetual motion, as if a living thing," says Imamura.

Within this swirling cauldron are other Venusian riddles to be solved: What is the origin of the 12-mile thick layer of sulfuric acid clouds that shrouds the planet? And how does Venus' lightning crackle through this strange brew?

Akatsuki, bristling with cameras, will circle the exotic planet's equator in an elliptical orbit for at least 2 years, monitoring the atmosphere at different altitudes using various wavelengths (IR, UV, and visible). With this data and data from the spacecraft's radio dish, scientists will reconstruct a 3D model of the atmosphere's structure and dynamics.

"The spacecraft's orbit will match the circulation of Venus's clouds, allowing the instruments to monitor cloud movement from directly above for 20 hours at a time. We'll assemble the images to produce a cloud motion time-lapse movie, much like a weather forecaster on television might show you of Earth."

The instruments will also scrutinize the planet's surface for volcanic activity that could be contributing to the sulfur contents of the atmosphere. "If any active volcanoes are spouting hot lava on Venus, one of our infrared cameras will detect the thermal emission," says Imamura.

In addition, Akatsuki's Lightning and Airglow Camera will hunt for lightning in order to settle a longstanding debate. "On Earth, the standard theory of lightning requires water ice particles on which positive or negative charges are induced via collisions," explains Imamura. "But there are no ice particles in Venus's hot, dry atmosphere--so how does Venusian lightning get started? It may be that charge separation can occur in sulfuric acid clouds--or perhaps some unknown solid particles exist in the atmosphere and play an important role."

Imamura can scarcely contain his curiosity. "As a young boy I loved to watch clouds, stars, oceans, rocks, and creatures. I wanted to understand why they look and behave as they do. Now I am curious in the same way about Venus. Nature is so full of mysteries!"

Beginning in December, some of Venus's mysteries will be revealed. Stay tuned.

Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA

Venus is covered in hundreds of volcanoes, but whether they remain active today is much debated, providing an important scientific goal for Venus Express.

The mission has already found clues pointing to volcanism on geologically recent timescales, within the last few hundreds of thousands to millions of years.

A previous analysis of infrared radiation from the surface pointed to lava flows atop a volcano with a composition distinct from those of their surroundings, suggesting that the volcano had erupted in the planet’s recent past.

Now, an analysis of sulphur dioxide concentration in the upper atmosphere over six years provides another clue.

Immediately after arriving at Venus in 2006, the spacecraft recorded a significant increase in the average density of sulphur dioxide in the upper atmosphere, followed by a sharp decrease to values roughly ten times lower by today.

A similar fall was also seen during NASA’s Pioneer Venus mission, which orbited the planet from 1978 to 1992.

At that time, the preferred explanation was an earlier injection of sulphur dioxide from one or more volcanoes, with Pioneer Venus arriving in time for the decline.

“If you see a sulphur dioxide increase in the upper atmosphere, you know that something has brought it up recently, because individual molecules are destroyed there by sunlight after just a couple of days,” says Dr. Emmanuel Marcq of Laboratoire Atmosphères, Milieux, Observations Spatiales, France, and lead author of the paper published in Nature Geoscience.

“A volcanic eruption could act like a piston to blast sulphur dioxide up to these levels, but peculiarities in the circulation of the planet that we don’t yet fully understand could also mix the gas to reproduce the same result,” adds co-author Dr. Jean-Loup Bertaux, Principal Investigator for the instrument on Venus Express that made the detections.

Venus has a ‘super-rotating’ atmosphere that whips around the planet in just four Earth-days, much faster than the 243 days the planet takes to complete one rotation about its axis.

Such rapid atmospheric circulation spreads the sulphur dioxide around, making it difficult to isolate any individual points of origin for the gas.

Dr. Marcq’s team speculate that if volcanism was responsible for the initial increase, then it could come from a relatively gentle increased output of several active volcanoes rather than one dramatic eruption.

“Alternatively, and taking into account the similar trend observed by Pioneer Venus, it’s possible that we are seeing decadal-scale variability in the circulation of the atmosphere, which is turning out to be even more complex than we could ever have imagined,” he notes.

“By following clues left by trace gases in the atmosphere, we are uncovering the way Venus works, which could point us to the smoking gun of active volcanism,” adds Håkan Svedhem, ESA’s Project Scientist for Venus Express.

PERSEID METEOR SHOWER: The Perseid meteor shower isn't done yet. According to the International Meteor Organization, dark-sky observers are counting as many as 80 Perseids per hour, including many fireballs. The show could continue for another 12 hours or so as Earth continues its passage through the debris stream of Comet Swift-Tuttle.

Last night the shower was very active in Arizona. "Here are a dozen Perseids I saw flying over the Steward Observatory on Mount Lemmon," says astronomer David A Harvey

We also had a nice show in Norway even though the sky was still not completely dark at 62^o North!" reports Runar Sandnes. "Meteors came sometimes in showers of 2 or 3."

Darrell Oake of Dartmouth, Nova Scotia, adds this report: "It was a nice clear night, the sky was filled with stars, and then--bam!--a fireball streaked across the heavens. My son Jacoté was cold, but when that first meteor lit up the sky, he was hooked and stayed up all night taking in all nature could dish out."

Browse the gallery for more reports and images.

Key Perseid Resources:

• Live Meteor Radar -- listen to Perseid radar echoes
• New: 2010 Perseid Photo Gallery -- submit your images!
• Perseid Fireball Cam -- flashes in the night, from NASA
• Planets Align for the Perseids -- from Science@NASA
• Worldwide Meteor Counts -- from the IMO
• Perseid Twitter Feed -- from meteor researcher Bill Cooke

INCOMING CME: The solar eruption of August 7th might affect Earth after all. Newly-arriving data from the Solar and Heliospheric Observatory (SOHO) show a CME heading our way with a significant Earth-directed component. Click on the image to launch a "difference movie" of the expanding cloud: 

The impact of this lopsided CME probably won't trigger a major geomagnetic storm---but the SOHO data show it could be bigger than expected. High latitude sky watchers should be alert for auroras when the cloud arrives probably on August 10th.

EXTRA! SOLAR RADIO BURSTS: The August 7th flare produced intense radio bursts detectable by ordinary shortwave receivers on Earth. In New Mexico, amateur radio astronomer Thomas Ashcraft picked up strong emissions around 21 MHz. "Listen to some of the sounds than came out of the loudspeakers," he says. "This was a complex flare and very exciting. Yet it is still small stuff compared to what is coming in the future as Solar Cycle 24 intensifies."

SOLAR BLAST JUST MISSES EARTH: On August 7th (1825 UT), magnetic fields around sunspot 1093 became unstable and erupted, producing a strong M1-class solar flare. Several amateur astronomers caught the active region in mid-flare, while NASA's Solar Dynamics Observatory recorded an extreme ultraviolet movie of the entire event:

The eruption hurled a coronal mass ejection (CME) into space, just missing a direct sun-Earth line. Forecasters expect the cloud to deliver no more than a glancing blow to our planet's magnetic field when it billows by on August 9th or 10th--not be a major space weather event.

Future eruptions could turn out differently. Active region 1093 is rotating toward Earth. By the end of this weekend, we'll be in the line of fire if its magnetic fields become unstable again. Space Weather Phone subscribers will be the first to know.

EXTRA! SOLAR RADIO BURSTS: The flare produced intense radio bursts detectable by ordinary shortwave receivers on Earth. In New Mexico, amateur radio astronomer Thomas Ashcraft picked up strong emissions around 21 MHz. "Listen to some of the sounds than came out of the loudspeakers," he says. "This was a complex flare and very exciting. Yet it is still small stuff compared to what is coming in the future as Solar Cycle 24 intensifies."