Airplanes can punch holes in clouds and make it rain, new research shows. As propeller or jet airplanes pass through the right atmospheric conditions, they make liquid water droplets freeze and immediately drop as snow, leaving a circular fissure behind.

Odd clouds can sometimes elude explanation for decades, and these mysterious gaps in the sky, aptly called hole-punch clouds or channel clouds, have been puzzling sky gazers and scientists alike since the 1940s. A 1968 article in the magazine Weatherwise called them “A Meteorological Whodunit?”

As recently as October 2009, headlines touted a “Mystery UFO Halo Over Moscow.” Earlier studies had suggested a link between hole-punch clouds and airplanes, though the mechanism was unclear.

Previous research also suggests that propeller planes could make snow fall when they flew through supercooled clouds, where water droplets remain liquid despite subfreezing temperatures. But until recently, a direct connection between airplanes, hole-punch clouds and snowfall was missing. Now, a team of atmospheric scientists report observing all three in the June Bulletin of the American Meteorological Society.

Andrew Heymsfield of the National Center for Atmospheric Research and colleagues flew a research plane through the snow produced by a hole-punch cloud west of Denver International Airport in 2007. The plane was loaded with instruments for studying how ice forms in clouds. Radar from the ground picked up a strange echo in their wake, indicating oddly-shaped snowflakes.

“We didn’t know it, but we went right through this precipitation feature that was spotted from the ground,” Heymsfield said.

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With sea ice levels in the Arctic at record lows this month, a new report comparing scientists’ predictions calls for caution in over-interpreting a few weeks worth of data from the North Pole.

The Sea Ice Outlook, which will be released this week, brings together more than a dozen teams’ best guesses at how much sea ice will disappear by the end of the warm season in September. This year began with a surprise. More sea ice appeared than anticipated, nearing its mean level from 1979-2007. But then ice levels plummeted through May and into June. Scientists have never seen the Arctic with less ice at this time of year in the three decades they’ve been able to measure it, and they expect below average ice for the rest of the year.

But looking ahead, the ultimate amount of sea ice melt is hard to determine. Some trends, like the long-term warming of the Arctic and overall decreases in the thickness of sea ice, argue for very low levels of sea ice. But there are countervailing factors, too: The same weather pattern that led to higher-than-normal temperatures in the Arctic this year is also changing the circulation of sea ice, which could keep it in colder water and slow the melting.

“For this date, it’s the lowest we’ve seen in the record, but will that pattern hold up? We don’t know. The sea ice system surprises us,” said Mark Serreze, director of the National Snow and Ice Data Center.

The loss of summer sea ice over decades is one of the firmest predictions of climate models: Given the current patterns of fossil fuel use and the amount of carbon dioxide already in the atmosphere, sea-ice-free summers in the arctic are a virtual certainty by the end of century, and possibly much sooner. As the globe heats up, the poles are disproportionately affected. Warmer temperatures melt ice, revealing the dark sea water that had previously been covered. That changes the albedo, or reflectivity, of the area, allowing it to absorb more heat. That, along with many other feedback loops makes predicting change in the Arctic immensely difficult.

In 2007, the extent of sea ice in the Arctic declined rapidly. The drop from the previous year was so precipitous that it garnered worldwide attention and media coverage. In the last couple of years, the extent of sea ice in the Arctic, measured by the amount of square miles it covers, has recovered. This series of events, which underscored the year-to-year variability of the measurement, has made researchers cautious about describing events in the Arctic.

“In hindsight, probably too much was read into 2007, and I would take some blame for that,” Serreze said. “There were so many of us that were astounded by what happened, and maybe we read too much into it.”

Some good may have come out of the astonishing ice loss that year, though. It was in the wake of that shocking summer that the Arctic science community came together to try a new approach to climate science. All the big groups working on modeling the sea ice system would reveal their methods, and make predictions, allowing scientists to learn from each and see what worked.

“When this started in 2007, it was pretty scary for a lot of the scientists, putting these numbers out there,” said Helen Wiggins, program coordinator of the Arctic Research Consortium of the United States. “It’s a different way to do science. It’s more a community synthesizing exercise.”

With climate modelers increasingly under attack over the past year, the partnership to create the Sea Ice Outlook, which is organized through Study of Environmental Arctic Change, could be a model for other groups of scientists. Data-heavy, model-dependent fields exposing the mechanisms of the science to scrutiny may be squirm-inducing, but it has already yielded good results. “There has been cross-pollination with datasets and different types of data,” Wiggins said.

“It’s been a very valuable exercise because you put your cards on the table and see who is going to get it right,” Serreze agreed.

All but one of the predictions from the Sea Ice Outlook expect the minimum coverage of sea ice to fall between 4.2 and 5.7 million square kilometers (1.6 and 2.2 million square miles). One group predicts just a million square kilometers, which would easily break the 2007 record minimum of 4.3 million square kilometers. In 2009, the sea ice minimum was 5.3 million kilometers.

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Like vacationers taking a pit stop on a long road trip, zircon mineral grains from the northern Appalachians may have stopped off in Michigan before ending up on the Colorado Plateau, a new study suggests. The finding, reported in the June Geology, is a major boost to the notion that a continent-spanning, Amazon-like river system once carried sediments west across North America.

sciencenewsA large proportion of the zircons found in Jurassic-era sandstones throughout a Texas-sized portion of the Colorado Plateau originated in the Appalachians (SN: 8/30/03, p. 131), previous analyses have shown. Those erosion-resistant mineral grains were carried westward by an immense river, deposited on floodplains and then stirred back up innumerable times before ending up in massive dune fields that later solidified into western sandstones, says William R. Dickinson, a geologist at the University of Arizona in Tucson.

The new find by Dickinson and his colleagues is the first to identify any of the Appalachian zircons’ rest stops on their long journey west. Rocks of the proper age are rare in the Midwest and the northern Great Plains, where the river presumably ran. Those rocks either eroded away long ago or are covered by thick layers of soil and glacial debris scraped south from Canada during recent ice ages, says Dickinson. The only easily accessible outcrops of such rocks in central North America are in central Michigan, where quarries reach deep enough to expose mid-Jurassic sandstone.

In their attempt to trace the transcontinental river system, the researchers took a 20-kilogram hunk of Michigan sandstone from one of those quarries and then extracted and analyzed its zircons. About 40 percent of zircons in the sample were between 905 million and 1.3 billion years old, and about 10 percent were between 285 and 510 million years old. Most if not all of these zircons probably eroded from the northern Appalachians, the researchers suggest. The overall age distribution of zircons from the Michigan sample is strikingly similar to those found in the sandstones of the Colorado Plateau, a hint that all of the zircons eroded from the same sources.

“It’s not as good as a barcode, but the match is really quite good,” says Scott D. Samson, a geochemist at Syracuse University in New York who was not involved with the work.

The new study notes one prominent difference between the Michigan and Colorado Plateau sandstones: While the western samples contain abundant zircons ranging between 510 and 725 million years old, zircons of that age range are completely missing from the Michigan sample.

Most likely, the researchers note, zircons of that age originated in the southern Appalachians, and tributaries draining that area would have fed into the large river that carried material west to the Colorado Plateau but not as far north as Michigan.

To garner more evidence for a Jurassic-era, continent-crossing river, researchers could scour ancient sandstones for other erosion-resistant minerals such as monazite, Samson says. Bits of that mineral are rarer than zircons but have a distinct chemical signature that could help researchers pin down their origins, he notes.

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Honeybee remains found in a 3,000-year-old apiary have given archaeologists a one-of-a-kind window into the beekeeping practices of the ancient world.

“Beekeeping is known only from a few Egyptian sources, from a few tombs and paintings. No actual hives have been found,” said Hebrew University of Jerusalem archaeologist Amihai Mazar.

The hives were uncovered in 2007 at an excavation in Tel Rehov, Israel, home to the flourishing Bronze and Iron Age city of Rehov. Mazar and his team found more than 100 hives, capable of housing an 1.5 million bees and producing half a ton of honey.

In a paper published June 8 in the Proceedings of the National Academy of Sciences, the researchers analyzed bees preserved in honeycomb that was charred, but not completely burnt by fire that likely destroyed the rest of the apiary.

Unfortunately for would-be makers of ancient honey, heat damaged the bees’ DNA, making it impossible to revive their genes in modern bees. But the researchers were at least able to identify them as Apis mellifera anatoliaca, a subspecies found only in what is now Turkey. It’s possible that A. m. anatoliaca’s range has changed, but more likely that Rehov’s beekeepers traded for them.

Local bees are notoriously difficult to handle. During the 20th century, when beekeepers tried to establish a modern industry in Tel Rehov, they ended up importing A. m. anatoliaca — a literally sweet example of history repeating itself.

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New Hubble images reveal what happened to one of Jupiter’s main cloud belts: It’s hiding behind ammonia clouds.

“Weather forecast for Jupiter’s Southern Equatorial Belt: cloudy with a chance of ammonia,” planetary scientist Heidi Hammel of the Space Science Institute in Boulder, Colorado said in a press release Wednesday.

The gas giant’s characteristic band of dark clouds started fading late last year and had vanished completely by early May, 2010. Images taken with Hubble’s Wide Field Camera 3 on June 7 — just over three days after an unknown object smacked into the planet — found a layer of white ammonia ice crystal clouds. The ammonia clouds float at a higher altitude than the missing brown clouds, obscuring them from view.

The images show a preview of what’s to come for the dark stripe, too. A chain of dark spots along the boundary of Jupiter’s south tropical zone peek through the white cloud layer as the ammonia thins and dissipates.

“The Hubble images tell us these spots are holes resulting from localized downdrafts. We often see these types of holes when a change is about to occur,” said planetary scientist Amy Simon-Miller of NASA.

The clouds blocking the famous equatorial stripe should clear out similarly in a couple of months, the team predicts.

“The Southern Equatorial Belt last faded in the early 1970s. We haven’t been able to study this phenomenon at this level of detail before,” Simon-Miller added. “The changes of the last few years are adding to an extraordinary database on dramatic cloud changes on Jupiter.”

The images also provided clues to the identity of the mystery object that hit Jupiter on June 3. A lack of dark debris at the impact site, which would have been kicked up by the object exploding beneath the clouds, suggests that the object was relatively small and burned up in Jupiter’s atmosphere like a meteor.

“Hubble was only one of several observatories that looked for signs of Jupiter’s impact scar, with more results on their way,” planetary scientist Leigh Fletcher of the University of Oxford noted on Twitter. “Gemini, Keck, VLT and IRTF were all racing to find signs of the impact within hours of the event taking place.”

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The Cassini spacecraft made its deepest dip ever into the atmosphere of Titan, Saturn’s largest moon, at 8:28 p.m. Eastern time on June 20. The data it collected will help determine whether the moon has its own magnetic field.

“For Titan scientists, this is one of the most anticipated flybys of the whole mission,” wrote space physicist Cesar Bertucci of the Institute of Astronomy and Space Physics in Buenos Aires, Argentina in a blog post. That’s saying something, as Cassini has already orbited Saturn for six years and may last seven more.

The flyby took Cassini within 547 miles of Titan’s surface, about two and a half times the altitude of the International Space Station. Although this distance shaved only 43 miles off the next nearest approach, the flyby was the first to take the spacecraft below Titan’s ionosphere, a layer of charged particles in the upper atmosphere. The ionosphere shielded the spacecraft from Saturn’s much larger magnetic field, allowing scientists the first hints of whether Titan has a magnetic field of its own.

Earlier measurements by the Voyager spacecraft and an earlier Cassini flyby at 590 miles showed that Titan’s magnetic field is weak at best, and certainly no match for Saturn’s. But that doesn’t mean it’s not there, Bertucci said. “We’d like to know what the internal field might be, no matter how small.”

Measuring the field will provide insight into the moon’s internal structure. In planets like Saturn or Earth, long-lived magnetic fields are driven by currents in a metallic, liquid core. These currents arise as the planet rotates. With its thick atmosphere of nitrogen and methane and its liquid hydrocarbon lakes, Titan resembles the early Earth more than any other body in the solar system, making the moon an ideal natural laboratory for studying the origins of life. If Cassini picks up a magnetic field, it might mean that Titan, like Earth, has a liquid core.

But it might not. There are two other explanations for a magnetic Titan, Bertucci wrote. Like Mars, Titan may once have had a liquid core that has since frozen, leaving behind residual magnetism in the crust. Or, if a conducting layer like an ocean lies on or below the crust, part of the surface could have temporarily picked up some of Saturn’s magnetism before Cassini got there.

The data should finish its downlink to Earth by the end of today, and a preliminary report on all the measurements from the flyby should be available by the end of the week, Bertucci told Wired Science.

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To watch the uncanny synchronization of a starling flock in flight is to wonder if the birds aren’t actually a single entity, governed by something beyond the usual rules of biology. New research suggests that’s true.

Mathematical analysis of flock dynamics show how each starling’s movement is influenced by every other starling, and vice versa. It doesn’t matter how large a flock is, or if two birds are on opposite sides. It’s as if every individual is connected to the same network.

That phenomenon is known as scale-free correlation, and transcends biology. The closest fit to equations describing starling flock patterns come from the literature of “criticality,” of crystal formation and avalanches — systems poised on the brink, capable of near-instantaneous transformation.

In starlings, “being critical is a way for the system to be always ready to optimally respond to an external perturbation, such as predator attack,” wrote researchers led by University of Rome theoretical physicist Giorgio Parisi in a June 14 Proceedings of the National Academy of Sciences paper.

Parisi’s team recorded starling flocks on the outskirts of Rome. Some had just over 100 birds, and others more than 4,000. Regardless of size, the correlations of a bird’s orientation and velocity with the other birds’ orientation and velocity didn’t vary. If any one bird turned and changed speed, so would all the others.

In particle physics, synchronized orientation is found in systems with “low noise,” in which signals are transmitted without degrading. But low noise isn’t enough to produce synchronized speeds, which are found in critical systems. The researchers give the example of ferromagnetism, where particles in a magnet exhibit perfect interconnection at a precise, “critical” temperature.

“More analysis is necessary to prove this definitively, but our results suggest” that starling flocks are a critical system, said study co-author Irene Giardina, also a University of Rome physicist.

According to the researchers, the “most surprising and exotic feature” of the flocks was their near-instantaneous signal-processing speed. “How starlings achieve such a strong correlation remains a mystery to us,” they wrote.

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BOULDER, Colorado — Oil gushing from the Deepwater Horizon site in the Gulf of Mexico will reach the Atlantic Ocean within six months, says oceanographer Synte Peacock. Exactly when is all down to an eddy that broke off of the infamous Loop Current southwest of Florida on June 12.

sciencenewsPeacock, of the National Center for Atmospheric Research in Boulder, Colorado, usually studies how the ocean’s water absorbs atmospheric gases. But after the Deepwater Horizon platform exploded April 20, she realized her computer models could be used to follow where the oil gushing from the seafloor might end up.

Her simulations, announced in a press release June 3, made headlines worldwide. No surprise: The simulations suggested that, once the oil became caught up in the Loop Current, it would be funneled into the Atlantic within weeks.

Talking with reporters at NCAR on June 14, Peacock explained how some news outlets misrepresented her work by glossing over a few major caveats. Most important, the work simulated the movement of dye (not viscous oil) injected in the upper layers of the ocean (not the deep seafloor) for a total of two months (not the ongoing no-end-in-sight disaster).

The simulations underscore how complicated it can be to track the movement of subsurface oil. “We saw large differences in details in how oil dispersed, depending on local eddies and currents in the gulf,” she says. Still, “no matter what you do it’s very, very hard in our model to find a scenario where dye is kept within the gulf for a period of longer than six months.”

The Loop Current circulates clockwise off the southwestern coast of Florida. About once or twice a year, it pinches off an eddy that either wanders around the gulf before dying out, or eventually reattaches with the main Loop Current.

The unusual thing about the Loop Current this year, Peacock says, is that it was located much more to the south and east than usual when it pinched off its new eddy. Eddies have popped off in this location twice before in recent years, she says. One of those times the eddy wandered to the west, toward Texas, before dissipating. The other time it reattached with the Loop.

Where the new eddy goes will strongly influence exactly where the oil ends up, she says. When it does reach the Atlantic, she notes, the oil will not necessarily wash ashore on beaches in a goopy mess. The oil might stay far out to sea, or be extremely diluted by the time it gets to the Atlantic.

Her team is now working on simulations of what will happen if the oil keeps gushing for months to come.

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A 3.6 million-year-old fossil from one of humanity’s earliest ancestors is more human-like than expected — and much taller.

The discovery makes Lucy, the best-known fossil of all, appear to be exceptionally short by comparison. Lucy and the new skeleton are both Australopithecus afarensis, the first fully bipedal primate and a direct ancestor of humanity. Unlike Lucy and every other A. afarensis fossil, the new skeleton has complete forelimb and hindlimb bones, allowing researchers to estimate its size more accurately.

The new A. afarensis specimen stood between 5 and 5 1/2 feet tall, towering over Lucy’s 3-foot height. Other fossil fragments suggested that Lucy was an unreliable measuring stick for A. afarensis, but the new fossil is the most conclusive evidence yet. Dubbed “Kadanuumuu,” or Big Man, it is described June 21 in the Proceedings of the National Academy of Sciences.

Big Man’s limbs also appear well-suited for running, in contrast to the shortened gait implied by Lucy’s skeleton. The proportions compare to those found two million years later in Homo erectus, and would not be out of place in a modern human, said study co-author Owen Lovejoy, a Kent State University paleoanthropologist.

“The difference between Australopithecus and humans is much less than everyone expected,” said Lovejoy. “Upright walking and running were pretty advanced at 3.6 million years ago, and they didn’t change much over the next two million years. Most of the changes in that period of time took place elsewhere.”

Lovejoy was also part of the team that discovered Ardipithecus ramidus, a 4.4 million-year-old possible human ancestor that was officially described last October. Ardipithecus was far less chimp-like than expected.

That raises the possibility that it’s the other Great Apes, rather than humans, whose bodies have evolved the most over the last few million years.

Big Man, with a rib cage shaped more like our own than that of a chimpanzee or gorilla, reinforces that notion.

“Chimps and gorillas are again the unusual form. Hominids and ourselves bear many primitive traits that haven’t been specialized like they have in gorillas,” said Lovejoy.

“The classic cartoon of the ape turning into the human doesn’t work at all.”

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While the oil disaster’s terrible toll on birds and turtles will at least be measured, less charismatic creatures tend to be ignored. That’s why conservationists are organizing a citizen science project to count the Gulf Coast’s ghost crabs.

Also known as sand crabs, they’re not classically cute, but they’re an important part of coastal food webs. Because the crabs are relatively easy to spot, it’s possible for people to help scientists estimate their numbers, providing baseline counts for comparison against future surveys.

“A lot of people are speculating that this spill could have severe effects on marine invertebrates,” said Drew Wheelan, a conservation coordinator for the American Birding Association, who came up with the idea for a ghost crab count. “Ghost crabs are conspicuous and easy to count.”

Wheelan modeled his project after an ongoing Gulf Coast bird count organized by the Audubon Society and Cornell Lab of Ornithology. Since early May, birders have submitted approximately 150,000 observations from Gulf states. That data will be invaluable to scientists trying to quantify the oil’s impacts, especially in areas where precise population counts didn’t previously exist.

University of Florida zoologist Sea McKeon designed the ghost crab-counting methodology, which is described on Wheelan’s blog, along with instructions for submitting data. It involves measuring distances between tideline crab burrows at a specific time and place each day for as long as possible, and requires little more than a measuring tape, notebook and pen, GPS reading and some sunscreen.

Wheelan said counts need to start as soon as possible in areas where oil hasn’t yet come ashore. Pre-disaster data is needed, and BP — which is trying to bar journalists and citizens from many affected areas — may close beaches as oil approaches.

Wheelan is still counting birds, too. During an ABA film project, Wheelan was interrogated by a policeman who appeared to take orders from BP.

But for now, “at least in Florida and Alabama and Mississippi, people are still able to travel on beaches” and count crabs, said Wheelan.

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