Monthly Archives: November 2010

Note: No Trees Were Harmed in the Making of this Post

Posted on by .

 

What on Earth was that? A branch? A piece of coral? The petrified arm of an Ent? No, as many of you guessed, it’s a fulgurite!

A what?

Fulgurites form in a flash – when lightning strikes simple beach sand or desert soil on a surface that conducts electricity, such as water, at a temperature of at least 3,270 degrees Fahrenheit (1,800 degrees Celsius). The extreme heat forces the grains of sand (or sometimes soil or rock) to melt and fuse together. The product cools, producing a hollowed glass structure that mimics the appearance of a tree root or large branch.

Photographer Stan Celestian found this 14-inch sand fulgurite on the outskirts of Queen Creek, Arizona on May 4, 2005. He submitted the image recently to the Earth Science Picture of the Day Web site , where it appeared on October 26th.

Why the odd shape, you might wonder? The lightning bolt fans out in several directions as it hits the water in an attempt to release its energy. The length of each “branch” of a fulgurite is equivalent to how quickly each path of the lightning strike exhausted itself of energy.

Fulgurites are rare enough to cost hundreds of dollars depending on size and shape, and intriguing enough to be the focus of research projects. A 2009 University of Arizona-Tucson study , for example, found that fulgurites contain a partially-oxidized form of phosphorus called phosphite that early microbes may have thrived on as a nutrient.

This summer, a NASA-funded study revealed that fulgurites can experience a range of temperatures during formation.

So, next time you want to impress your friends with arcane but fascinating trivia, ask if they know what a fulgurite is. When they scratch their heads and offer blank stares, boot up your laptop, show them our What On Earth #5 post and explain this fluke of nature. You’re sure to dazzle them with your extra-ordinary intelligence and one of the marvels of science.

Gretchen Cook-Anderson, NASA’s Earth Science News Team

Flyby Over the South Pole

Posted on by .

Fly over the South Pole at lunch, back to the tip of Patagonia by supper — just another day of drudgery collecting scientific data.

The second year of NASA’s Operation IceBridge is heading into its final week of research flights, which the team of scientists, pilots and flight crew began from their home base of Punta Arenas, Chile on Oct. 26. The multi-year campaign employs NASA’s DC-8 to fly multiple trips over Antarctica and its surrounding sea ice to measure the incremental changes that will help scientists make better judgments about sea level rise and the impact a warming climate is having on the mountainous, ice-bound continent. IceBridge crews have encountered rough weather and made long flights over magnificent, desolate landscapes, measuring ice sheet thickness, sea ice composition, snow cover and even the bedrock far underneath the icy cover. With these multiple flights and with multiple instruments on the plane, the mission is partly designed to do the work of a satellite.

The past few decades in Earth science are often referred to as the “satellite era.” Scientists’ ability to monitor so many aspects of the planet from constantly orbiting radars, spectrometers, radiometers, imagers and lidars revolutionized the way Earth’s systems could be observed. One of the most significant changes was that satellites offered consistent, global measurements over years and years — they provide continuity. NASA’s ICESat (Ice, Cloud, land and Elevation Satellite) mission was making important observations of the planet’s rapidly changing poles from 2003 until 2010, when the payload shut down. ICESat II isn’t set to launch until 2015, creating a potentially significant five-year gap in measurements. At a time when scientists pursue every change in glaciers and ice sheets with necessary urgency, that was unacceptable, and where IceBridge came in.

“We wanted to avoid an ‘oh my god’ moment when we came back in 2015 with IceSAT II,” said IceBridge scientist Seelye Martin, while talking to reporters on a media teleconference on Monday afternoon. Martin said the prospect of turning on ICESat II’s laser altimeter and finding that enormous changed had occurred and had gone unobserved partly drove the Ice Bridge planning. “We wanted continuity in the polar region. We didn’t want anysurprises.”

The timing of the IceBridge media day coincided with a big piece in the New York Times looking at not only what’s happening at the poles and with sea level rise, but what is happening with the scientific effort within NASA and beyond to study the poles. The satellite “gap” plays a role in that story, too:

The satellite difficulties are onesymptom of a broader problem: because no scientifically advanced countryhas made a strategic priority of studying land ice, scientists lackelementary information that they need to make sense of what ishappening.

Theydo not know the lay of the land beneath most of the world’s glaciers,including many in Greenland, in sufficient detail to calculate how fastthe ice might retreat. They have only haphazard readings of the depthand temperature of the ocean near Greenland, needed to figure out why somuch warm water seems to be attacking the ice sheet.

Theinformation problems are even more severe in Antarctica. Much of thatcontinent is colder than Greenland, and its ice sheet is believed to bemore stable, over all. But in recent years, parts of the ice sheet havestarted to flow rapidly, raising the possibility that it willdestabilize in the same way that much of the world’s other ice has.

For more on-the-ground — or up-in-the-air — reporting from IceBridge, check out the mission twitter or blog. You can also chat with Ice Bridge scientists on Thursday, Nov. 18, at 1 p.m. EST. The page will be open for question submittals about a half-hour before the chat begins.


— By Patrick Lynch, NASA’s Earth Science News Team


— photo at top courtesy Kathryn Hansen, NASA’s Earth Science News Team

Speaking of Contrails…

Posted on by .

The prospect of a renegade missile transfixed newscasters last week after a videographer captured imagery of an unusual contrail near the coast of California. The now notorious plume initially baffled commentators as it seemed to point vertically into space and appeared larger than a standard airplane contrail.

The reality, which trickled out in the days following the uproar, turned out to be far less dramatic than some of the more inventive theories circulating. Most experts now say the mysterious plume was the product of a jet. The time of day and the particular trajectory of the jet conspired to create the illusion.

Sure, it might seem like a letdown, but here at What on Earth we would argue that jet contrails are perfectly fascinating in their own right. Where on Earth do they come from? The cirrus-cloud like condensation trails form when water vapor condenses and freezes around tiny airborne particles called aerosols that spill from jet engines. 

NASA Langley Research Center, in Hampton, Va., hosts a thorough website that’s well-worth a look for those who happen to be contrail-curious. Langley points out, for example, that contrails are hardly monolithic, noting that there are actually three major varieties of contrails: short-lived, persistent, and persistent spreading.  Here’s how Langley describes the three types: 

Short-lived contrails look like short white lines following along behind the plane, disappearing almost as fast as the airplane goes across the sky, perhaps lasting only a few minutes or less. The air that the airplane is passing through is somewhat moist, and there is only a small amount of water vapor available to form a contrail. The ice particles that do form quickly return again to a vapor state.

Persistent (non-spreading) contrails look like long white lines that remain visible after the airplane has disappeared. This shows that the air where the airplane is flying is quite humid, and there is a large amount of water vapor available to form a contrail. Persistent contrails can be further divided into two classes: those that spread and those that don’t. Persistent contrails look like long, narrow white pencil-lines across the sky.

Persistent spreading contrails look like long, broad, fuzzy white lines. This is the type most likely to affect climate because they cover a larger area and last longer than short-lived or persistent contrails.

Meanwhile, Our Changing Planet, a book co-edited by a number of NASA scientists that offers a good overview of remote sensing, devotes a chapter to climate impacts of the ubiquitous artificial clouds. Via Our Changing Planet:

Persistent contrails also play a role in climate because they reflect sunlight and trap infrared radiation just like their naturally formed cousins.  Thus, the presence of a contrail cluster in an otherwise clear sky can diminish the amount of solar energy reaching the surface during the daytime and increase the amount of infrared radiation absorbed in the atmosphere at all times of day. Currently, the overall impact appears to be a warming effect, but research is continuing to unravel the role of this phenomenon in climate change.    

Another interesting tidbit from Our Changing Planet:

Persistent contrails can often grow into natural-looking cirrus clouds within a few hours, a phenomenon that is best observed from space.  Although they typically last for only 4-6 hours, some clusters have been observed to last more than 14 hours and travel thousands of kilometers before dissipating. These persistent contrails are estimated to have caused cirrus cloud cover to rise by three percent between 1971 and 1996 over the United States and are well-correlated with rising temperatures, though not the only cause of them. Increasing traffic in nearly every country of the world will cause a rise in global cirrus coverage unless the upper troposphere dries out or advances in air traffic management and weather forecasting or in aircraft propulsion systems can be used to minimized contrail formation.   


Indeed. Take a look at this mesmerizing data visualization of just a mere day of air traffic…


–Adam Voiland, NASA’s Earth Science News Team


Photo above of contrails in a star pattern by John Pertig, courtesy of NASA Langley Research Center.

Earth Buzz: Mount Merapi, AGU Blogosphere, and More

Posted on by .


Merapi Blast Lingers
Nearly three weeks ago, Indonesia’s notoriously capricious Mount Merapi roared to life and began to fling towering plumes of ash and gas aloft. NASA’s MODIS instrument on the Terra satellite captured this image of the now waning eruption Wednesday.  (MODIS Rapid Response)

AGU Launches Blogging Network
Confusions about a supposed AGU-sponsored misinformation response team aside, it is true that the American Geophysical Union recently launched a new blog network that is well worth a look. One of their bloggers is writing about how reporters can avoid making common mistakes when covering volcanoes.  (AGU blogosphere)

Making Sense of Multiyear Ice Melt
A new study has quantified the amount ofolder and thicker “multiyear” sea ice lost from the Arctic via melting. “[The] results show that thick multiyear sea ice is not immune tomelt in the Pacific sector of the Arctic Ocean in today’s climate,” the author of the study said. (NASA Portal)

Tiny Particles, Big Impact

Despite their small size, tiny airborne particles called aerosols have major impacts on our climate. The problem: despite considerable advances in recent decades, estimating the precise climate impacts of aerosols remains an immature science. (Earth Observatory)

Overselling an Image
A picture can say a thousand words, especially if you are trying to explain earth science. But images can also mislead if not presented with care. One of NASA’s data visualization specialists explains one of his pet peeves: vertical exaggeration.  (Elegant Figures)

Ed Begley Jr. on Climate
The Emmy award-winning actor and environmentalist guest blogs for My Big Fat Planet, and he’s hoping climate deniers are right. (My Big Fat Planet)

The Adventures of IceBridge
NASA scientists are back in the Southern Hemisphere flying IceBridge missions to Antarctica. Track their progress on the IceBridge blog and Twitter feed. (IceBridge)

Russian Fires Revisited
Remember the raging wildfires that paralyzed Moscow during the summer? A group from Goddard has released a new information that highlights the meteorological ingredients that fueled the disaster. (GES DISC)

Tweet of the Week
Veterans Day photo of the NASA DC-8 contrail taken from the Amundsen-Scott South Pole station on November 4 http://twitpic.com/35wqgw
(IceBridge)

Image courtesy of NASA’s MODIS Rapid Response Team


Volcano Music

Posted on by .


What on Earth was that sound? Was it a bird? A plane? A humpbacked whale?

No, it was fiercely hot gas whooshing through the guts of a volcano — Arenal Volcano in Costa Rica, to be precise. Milton Garces, the director of the Infrasound Laboratory at the University of Hawaii, Manoa, recorded the sound clip we posted last week.

Garces explains the phenomenon this way:

“Much like human voicings are defined by the combination of air flow through the vocal chords, tract, and mouth shapes, this harmonic tremor sound is shaped by the interaction of volcanic gases as they are released and flow through open conduits.”

NASA satellites have got Earth’s volcanoes covered from orbit. They provide round-the-clock monitoring of volcanic eruptions in progress or those possibly on the way. Just two of the satellites used to monitor volcanic activity are Aqua (with its MODIS instrument) and Terra (with its ASTER instrument).

Volcanologists use the satellite data from NASA’s fleet to detect heat and telltale volcanic gases emanating from volcanic vents. Also, Global Positioning System satellite devices allow researchers to gauge subtle changes in the land surface near volcanoes.

And once a volcano pops off, NASA satellites track drifting ash clouds that could threaten aircraft. (You may recall the shenanigans of a certain unpronounceable Icelandic volcano, Eyjafjallajökull, earlier this year.)

As the NASA birds pass silently overhead, Garces clambers up live volcanoes to record their subterranean rumblings. He uses the sounds to diagnose the physical status of volcanic plumbing systems – for example, whether they might be recharging with molten rock (magma) and getting ready to erupt.

These very low frequency waves are called infrasound. In fact, they are too low in their raw form to be audible to humans. So Garces speeds them up artificially to a frequency range the human hearing can detect. Here’s how he explained it to us:

“This signal, which has been sped up by a factor a hundred to make it audible, in reality has a dominant periodicity of about 1 cycle per second (1 Hz). In the field, it sounds like a chugging sound with 1 s puffs, and it is not tonal at all. We lose our sense of tonality at frequencies below around 16 Hz, so infrasound, however harmonious, will be perceived by us more like a beat than a tune.”

In other words, volcano infrasound is pretty interesting to a scientist, but you can’t dance to it — or at least it would be the ultimate slow dance.


— Daniel Pendick,
Geeked on Goddard
; Eyjafjallajokull image
courtesy of NASA Goddard’s MODIS Rapid Response Team