A Farmer's Dilemma: To Till or Not To Till

As winter turns to spring, farmers are preparing to plant this year's crops. For some, tilling their fields is a thing of the past.

By Kim Mullin

Photo: USDA Natural Resources Conservation Service

When you think of a farmer at work in the fields, do you picture a tractor pulling a plow and turning the soil? In my mind, it is a red tractor, and the soil is rich and dark.

For many people, turning the soil may be an obvious part of growing crops. Of course it is required! Isn't that what farmers do!?! It turns out that the answer to that question isn't easy. Yes, many farmers turn, or till, the soil. But increasing percentages of farmers are opting not to till some or all of their fields, for a variety of reasons.

As farmers prepare to plant new crops this spring, they must weigh the pros and cons of till and no-till farming. On the one hand, tilling a field in preparation for planting aerates and warms the soil, and also buries weeds, animal waste, and leftover crops. However, once the soil is turned, it is much more vulnerable to erosion from wind and water and is likely to have increased run-off of soil and chemicals into local waterways.

On the other hand, leaving a field untilled allows leftover crops to act as mulch and helps protect the soil from erosion and run-off. However, planting seeds through this layer of mulch is more difficult and requires expensive machinery. This method also may require more herbicide to control weeds, and, in some places, crop yields may be lower because the mulch keeps the soil cooler and seeds germinate later in the season.

Can you Dig It? Science and Farming

So what is a farmer to do? With no one right answer, farmers must experiment to learn what works best with their soil and the crops they choose to grow. Do you have an interest in the science behind farming? Try out these Science Buddies Project Ideas:

• Dust Busters: How No-Plow Farmers Try to Save Our Soil : Run your own till vs. no-till trials to see how the two farming methods compare when it comes to moisture retention and surface run-off.


• Earthworms: Nature's Tiller? : Earthworms do their own tilling and aerating of the soil. With worms, grass clippings, and a few pots of soil, you can see for yourself how effective they are at this job.


• May the Best Plant Win! Experiment with Genetically Modified Seeds : What type of seed to use—conventional or genetically modified—is another choice that many farmers face. Put yourself in their shoes, and explore the benefits and drawbacks of RoundUp®-resistant plants.


• Run-off and Fertilizer Use* : When fertilizers are applied to farm crops or gardens, how much of it is absorbed by plants and soil, and how much makes its way into local waterways? Create a run-off simulator to find out!


• Bacteria Can Fix It! A Comparison of Nitrogen-Fixing Bacteria and Nitrogen Fertilizers : Plants need nitrogen to grow, but what is the best way for a farmer or gardener to deliver it? Grow clover with nitrogen fertilizer and nitrogen-fixing bacteria and compare your results.


• 
  

Getting Dirty in the Name of Science

Spring is a great time to talk with kids about plant life cycles. Dig in the dirt, plant a few seeds, or just head outside and observe how plant life is changing as the weather changes where you live.

from Science Buddies Blog http://ift.tt/1NA9B8D

As winter turns to spring, farmers are preparing to plant this year's crops. For some, tilling their fields is a thing of the past.

By Kim Mullin

Photo: USDA Natural Resources Conservation Service

When you think of a farmer at work in the fields, do you picture a tractor pulling a plow and turning the soil? In my mind, it is a red tractor, and the soil is rich and dark.

For many people, turning the soil may be an obvious part of growing crops. Of course it is required! Isn't that what farmers do!?! It turns out that the answer to that question isn't easy. Yes, many farmers turn, or till, the soil. But increasing percentages of farmers are opting not to till some or all of their fields, for a variety of reasons.

As farmers prepare to plant new crops this spring, they must weigh the pros and cons of till and no-till farming. On the one hand, tilling a field in preparation for planting aerates and warms the soil, and also buries weeds, animal waste, and leftover crops. However, once the soil is turned, it is much more vulnerable to erosion from wind and water and is likely to have increased run-off of soil and chemicals into local waterways.

On the other hand, leaving a field untilled allows leftover crops to act as mulch and helps protect the soil from erosion and run-off. However, planting seeds through this layer of mulch is more difficult and requires expensive machinery. This method also may require more herbicide to control weeds, and, in some places, crop yields may be lower because the mulch keeps the soil cooler and seeds germinate later in the season.

Can you Dig It? Science and Farming

So what is a farmer to do? With no one right answer, farmers must experiment to learn what works best with their soil and the crops they choose to grow. Do you have an interest in the science behind farming? Try out these Science Buddies Project Ideas:

• Dust Busters: How No-Plow Farmers Try to Save Our Soil : Run your own till vs. no-till trials to see how the two farming methods compare when it comes to moisture retention and surface run-off.


• Earthworms: Nature's Tiller? : Earthworms do their own tilling and aerating of the soil. With worms, grass clippings, and a few pots of soil, you can see for yourself how effective they are at this job.


• May the Best Plant Win! Experiment with Genetically Modified Seeds : What type of seed to use—conventional or genetically modified—is another choice that many farmers face. Put yourself in their shoes, and explore the benefits and drawbacks of RoundUp®-resistant plants.


• Run-off and Fertilizer Use* : When fertilizers are applied to farm crops or gardens, how much of it is absorbed by plants and soil, and how much makes its way into local waterways? Create a run-off simulator to find out!


• Bacteria Can Fix It! A Comparison of Nitrogen-Fixing Bacteria and Nitrogen Fertilizers : Plants need nitrogen to grow, but what is the best way for a farmer or gardener to deliver it? Grow clover with nitrogen fertilizer and nitrogen-fixing bacteria and compare your results.


• 
  

Getting Dirty in the Name of Science

Spring is a great time to talk with kids about plant life cycles. Dig in the dirt, plant a few seeds, or just head outside and observe how plant life is changing as the weather changes where you live.

from Science Buddies Blog http://ift.tt/1NA9B8D

Before and after cyclone Pam

Photo credit: William Dyer

Cyclone Pam was a Category 5 storm when it struck the island nation of Vanuatu in the South Pacific on March 13 and 14, 2015. Pam tore down miles of dense foliage, stripped vegetation, and coated leaves in damaging salt spray, turning lush green landscapes brown.

Two of the hardest hit islands were Tanna and Erromango. On March 17 — three days after the storm hit — NASA’s Landsat 8 satellite acquired images, which compared with earlier images of the same islands, show the widespread effects of the storm. According to scientists from Tropical Storm Risk, the island of Erromango likely faced the most severe winds. Their analysis suggests that Erromango saw gusts up to 320 kilometers (200 miles) per hour. Before Pam, Erromango appeared dark green due its lush tropical vegetation.

January 28, 2015. Image credit: NASA

Here’s how Erromango looked after cyclone Pam.

March 17, 2015. Image credit; NASA

While Erromango is home to just a few thousand people, about 30,000 people live on the island of Tanna. Here is Tanna before Pam.

January 28, 2015. Image credit: NASA

With top gusts of 260 kilometers (160 miles) per hour, Tanna faired slightly better than Erromango. Here’s Tanna days after cyclone Pam.

March 17, 2015. Image credit: NASA

Closer to the ground, 27-year-old pilot William Dyer, who helped conduct aerial assessments of Vanuatu’s many island chains, snapped photos of the islands in the days after Pam hit, and shared them alongside photos he’d taken before the storm.

Photo credit: William Dyer

Pam took a heavy human toll. The storm killed six people and seriously injured many more, according to media reports. Thousands of people have been left homeless Meanwhile, ongoing water and food shortages mean the humanitarian situation could worsen.

How you can help: Donate to the disaster relief effort.

The same spot on the island of Emae before and after cyclone Pam. Photo credit: William Dyer

Read more from NASA’s Earth Observatory

from EarthSky http://ift.tt/1Fau0gs

Photo credit: William Dyer

Cyclone Pam was a Category 5 storm when it struck the island nation of Vanuatu in the South Pacific on March 13 and 14, 2015. Pam tore down miles of dense foliage, stripped vegetation, and coated leaves in damaging salt spray, turning lush green landscapes brown.

Two of the hardest hit islands were Tanna and Erromango. On March 17 — three days after the storm hit — NASA’s Landsat 8 satellite acquired images, which compared with earlier images of the same islands, show the widespread effects of the storm. According to scientists from Tropical Storm Risk, the island of Erromango likely faced the most severe winds. Their analysis suggests that Erromango saw gusts up to 320 kilometers (200 miles) per hour. Before Pam, Erromango appeared dark green due its lush tropical vegetation.

January 28, 2015. Image credit: NASA

Here’s how Erromango looked after cyclone Pam.

March 17, 2015. Image credit; NASA

While Erromango is home to just a few thousand people, about 30,000 people live on the island of Tanna. Here is Tanna before Pam.

January 28, 2015. Image credit: NASA

With top gusts of 260 kilometers (160 miles) per hour, Tanna faired slightly better than Erromango. Here’s Tanna days after cyclone Pam.

March 17, 2015. Image credit: NASA

Closer to the ground, 27-year-old pilot William Dyer, who helped conduct aerial assessments of Vanuatu’s many island chains, snapped photos of the islands in the days after Pam hit, and shared them alongside photos he’d taken before the storm.

Photo credit: William Dyer

Pam took a heavy human toll. The storm killed six people and seriously injured many more, according to media reports. Thousands of people have been left homeless Meanwhile, ongoing water and food shortages mean the humanitarian situation could worsen.

How you can help: Donate to the disaster relief effort.

The same spot on the island of Emae before and after cyclone Pam. Photo credit: William Dyer

Read more from NASA’s Earth Observatory

from EarthSky http://ift.tt/1Fau0gs

Mostly Mute Monday: Volcanic Lightning (Synopsis) [Starts With A Bang]

“If you are caught on a golf course during a storm and are afraid of lightning, hold up a 1-iron. Not even God can hit a 1-iron.” -Lee Trevino

When it comes to lightning, you inevitably think of thunderstorms, rain, and the exchange of huge amounts of charge between the clouds above and the Earth. But there’s another sight that’s perhaps even more spectacular.

Image credit: Francisco Negroni / Associated Press, Agenci Uno / European Press Photo Agency.

During volcanic eruptions, the high temperatures, volatile atoms-and-molecules and disrupted airflow can create an incredible separation of charge, leading to the remarkable phenomenon of volcanic lightning.

Image credit: Francisco Negroni / Associated Press, Agenci Uno / European Press Photo Agency.

Come see some spectacular examples (and science) on today’s Mostly Mute Monday!

from ScienceBlogs http://ift.tt/1Dltkre

“If you are caught on a golf course during a storm and are afraid of lightning, hold up a 1-iron. Not even God can hit a 1-iron.” -Lee Trevino

When it comes to lightning, you inevitably think of thunderstorms, rain, and the exchange of huge amounts of charge between the clouds above and the Earth. But there’s another sight that’s perhaps even more spectacular.

Image credit: Francisco Negroni / Associated Press, Agenci Uno / European Press Photo Agency.

During volcanic eruptions, the high temperatures, volatile atoms-and-molecules and disrupted airflow can create an incredible separation of charge, leading to the remarkable phenomenon of volcanic lightning.

Image credit: Francisco Negroni / Associated Press, Agenci Uno / European Press Photo Agency.

Come see some spectacular examples (and science) on today’s Mostly Mute Monday!

from ScienceBlogs http://ift.tt/1Dltkre

Pine Beetle Caused Forest Death And Climate Change [Greg Laden's Blog]

There is some interesting new research on the relationship between the Mountain Pine Beetle, major die-offs of forests in North America, and climate change.

The Mountain Pine Beetle (Dendroctonus ponderosae) is a kind of “bark beetle” (they don’t bark, they live in bark) native to western North America. They inhabit a very wide range of habitats and are found from British Columbia all the way south to Mexico. In British Columbia alone, the pine beetle, though a fairly complex process, has managed to destroy 16 of 55 million acres of forest. This epidemic of tree death is seen in mountain forest regions all across the western United States. The beetles affect a number of species of pine trees.

The beetle lays its eggs under the pine tree bark, and in so doing, introduces a fungus that penetrates adjoining wood. This fungus has the effect of suppressing the the tree’s response to the Pine Beetle’s larvae, which proceed to eat part of the tree. This suppressive effect blocks water and nutrient transport, together with the larvae eating part of the tree, quickly kills the host tree. The process can take just a few weeks. It takes longer for the tree to actually look dead (note the evergreen tree you cut and put in your living room for Christmas is dead the whole time it is looking nice and green and cheery). By the time the tree looks dead, i.e., the needles turn brown and fall off, it has been a dead-tree-standing for months and the Pine Beetles have moved on to find other victims.

It has long been thought that climate change has contributed to the western epidemic of Pine Beetles, as well as a similar epidemic in the Southeastern US (different species of beetles). The primary mechanism would be increasing winter extreme low temperatures. The very low temperatures would kill off the larvae, removing the threat of the beetle’s spread locally after that winter. Extreme winter temperatures have warmed by around 4 degrees C since 1960 across much of the beetle’s range. The lack of killing colds itself does not cause a beetle epidemic, but simply allows it, or produces a “demographic release.” If the beetles are already there, they have the opportunity to spread.

A recent study, just out, (see reference below) confirms this basic model but also adds a considerable degree of complexity. The study shows that there is not as strong of a correlation between raising winter temperatures above typical killing levels and the spread of the beetle. The study indicates that demographic release form an increase in extreme winter lows is part of the equation, but the situation is more complex and likely warming in general enhances beetle spread and reproduction during the summer part of its lifecycle, and may weaken the trees to make them more vulnerable to attack. In addition, other non-climate related factors probably play a role.

The study looked at several regions and assembled data on beetle frequency and spread over time, and various climate related data. From the abstract:

We used climate data to analyze the history of minimum air temperatures and reconstruct physio- logical effects of cold on D. ponderosae. We evaluated relations between winter temperatures and beetle abundance using aerial detection survey data… At the broadest scale, D. ponderosae population dynamics between 1997 and 2010 were unrelated to variation in minimum temperatures, but relations between cold and D. ponderosae dynamics varied among regions. In the 11 coldest ecoregions, lethal winter temperatures have become less frequent since the 1980s and beetle-caused tree mortality increased—consistent with the climatic release hypothesis. However, in the 12 warmer regions, recent epidemics cannot be attributed to warming winters because earlier winters were not cold enough to kill D. ponderosae…There has been pronounced warming of winter temperatures throughout the western US, and this has reduced previous constraints on D. ponderosae abundance in some regions. However, other considerations are necessary to understand the broad extent of recent D. ponderosae epidemics in the western US.

“This amount of warming could be the difference between pests surviving in areas that were historically unfavorable and could permit more severe and prolonged pest outbreaks in regions where historical outbreaks were halted by more frequent cold bouts,” says first author Aaron Weed, an ecologist at the National Park Service.

In the 11 coldest regions, winter temperatures cold enough to e lethal to D. ponderosae have become less frequent since the 1980s, and this is associated with an increase in tree mortality, confirming the link between warming conditions and increased parasite caused tree death. However, in the 12 regions with the warmest climate, recent epidemics are not clearly linked to warming winters simply because the earlier, colder, winters were already not cold enough to repress the tree-killing mountain pine beetle. This suggests that other factors may play a role in the epidemics in the western United States.

Evens so, the pattern of warming (including increase of minimum winter temperature) correlates to the demographic release of the mountain pine beetle. The authors note that “warming year-round temperatures that influence generation time and adult emergence synchrony … and drought effects that can weaken tree defenses …” are plausible explanations, but further note that a simple single explanation is not likely to be sufficient to explain the overall phenomenon.

This is, in a sense, a numbers game. A cold winter does not kill off all of the beetles. However, no matter how cold the winter is, no beetles will be wiped out if they are not there to begin with. So, demographic release, which makes possible but does not cause an outbreak, could cause an abundance of beetles across a much larger area where, no matter what natural suppression may occur, they will then become more abundant over time.

As noted, the trees themselves matter. We can safely assume that generally changes in overall climate will mean that plant communities adapted to a given region might lose that adaptive edge and be subject to a number of problems which can then be exploited by a potentially spreading parasite. These changes in viability of plant communities are not all climate change related. Forest management, disturbance, and regional demographics (as forests age, they tend to change what they do) are also factors in this complex set of ecological relationships.

The bottom line. This study confirms the effects of warming, especially the increase of winter low temperatures, on the potential for D. ponderosae to spread rapidly locally and regionally. The study also calls into question the simplistic model that this is all that happens to explain the widespread epidemic of this beetle. Other factors, including other aspects of global warming, also contribute to the epidemics. In addition, and importantly, the study demonstrates a high degree of variability in the outcome of ecological and climate change.

This epidemic is probably the largest observed kill-off of forests caused by a parasite. So far it is much more severe in its effects than forest fires, but over the long to medium term, we will probably see increased frequency and severity of forest fires because of the abundance of fuel provided by the die-off.

Soucre:



Weed, A. S., Bentz, B. J., Ayres, M. P., & Holmes, T. P. (2015). Geographically variable response of Dendroctonus ponderosae to winter warming in the western United States. Landscape Ecology. doi:10.1007/s10980–015–0170-z

Text for the image at the top of the post, from the USDA:

The Mountain Pine Beetle is at epidemic levels throughout the western United States, including here in the Rocky Mountain Region … Forests affected here include several in Colorado, Wyoming, South Dakota and Nebraska. In northern Colorado and southeastern Wyoming, Mountain Pine Beetles have impacted more than 4 million acres since the first signs of outbreak in 1996. The majority of outbreaks have occurred in three forests: Arapaho-Roosevelt, White River and Medicine Bow/Routt.

from ScienceBlogs http://ift.tt/1EVj7wv

There is some interesting new research on the relationship between the Mountain Pine Beetle, major die-offs of forests in North America, and climate change.

The Mountain Pine Beetle (Dendroctonus ponderosae) is a kind of “bark beetle” (they don’t bark, they live in bark) native to western North America. They inhabit a very wide range of habitats and are found from British Columbia all the way south to Mexico. In British Columbia alone, the pine beetle, though a fairly complex process, has managed to destroy 16 of 55 million acres of forest. This epidemic of tree death is seen in mountain forest regions all across the western United States. The beetles affect a number of species of pine trees.

The beetle lays its eggs under the pine tree bark, and in so doing, introduces a fungus that penetrates adjoining wood. This fungus has the effect of suppressing the the tree’s response to the Pine Beetle’s larvae, which proceed to eat part of the tree. This suppressive effect blocks water and nutrient transport, together with the larvae eating part of the tree, quickly kills the host tree. The process can take just a few weeks. It takes longer for the tree to actually look dead (note the evergreen tree you cut and put in your living room for Christmas is dead the whole time it is looking nice and green and cheery). By the time the tree looks dead, i.e., the needles turn brown and fall off, it has been a dead-tree-standing for months and the Pine Beetles have moved on to find other victims.

It has long been thought that climate change has contributed to the western epidemic of Pine Beetles, as well as a similar epidemic in the Southeastern US (different species of beetles). The primary mechanism would be increasing winter extreme low temperatures. The very low temperatures would kill off the larvae, removing the threat of the beetle’s spread locally after that winter. Extreme winter temperatures have warmed by around 4 degrees C since 1960 across much of the beetle’s range. The lack of killing colds itself does not cause a beetle epidemic, but simply allows it, or produces a “demographic release.” If the beetles are already there, they have the opportunity to spread.

A recent study, just out, (see reference below) confirms this basic model but also adds a considerable degree of complexity. The study shows that there is not as strong of a correlation between raising winter temperatures above typical killing levels and the spread of the beetle. The study indicates that demographic release form an increase in extreme winter lows is part of the equation, but the situation is more complex and likely warming in general enhances beetle spread and reproduction during the summer part of its lifecycle, and may weaken the trees to make them more vulnerable to attack. In addition, other non-climate related factors probably play a role.

The study looked at several regions and assembled data on beetle frequency and spread over time, and various climate related data. From the abstract:

We used climate data to analyze the history of minimum air temperatures and reconstruct physio- logical effects of cold on D. ponderosae. We evaluated relations between winter temperatures and beetle abundance using aerial detection survey data… At the broadest scale, D. ponderosae population dynamics between 1997 and 2010 were unrelated to variation in minimum temperatures, but relations between cold and D. ponderosae dynamics varied among regions. In the 11 coldest ecoregions, lethal winter temperatures have become less frequent since the 1980s and beetle-caused tree mortality increased—consistent with the climatic release hypothesis. However, in the 12 warmer regions, recent epidemics cannot be attributed to warming winters because earlier winters were not cold enough to kill D. ponderosae…There has been pronounced warming of winter temperatures throughout the western US, and this has reduced previous constraints on D. ponderosae abundance in some regions. However, other considerations are necessary to understand the broad extent of recent D. ponderosae epidemics in the western US.

“This amount of warming could be the difference between pests surviving in areas that were historically unfavorable and could permit more severe and prolonged pest outbreaks in regions where historical outbreaks were halted by more frequent cold bouts,” says first author Aaron Weed, an ecologist at the National Park Service.

In the 11 coldest regions, winter temperatures cold enough to e lethal to D. ponderosae have become less frequent since the 1980s, and this is associated with an increase in tree mortality, confirming the link between warming conditions and increased parasite caused tree death. However, in the 12 regions with the warmest climate, recent epidemics are not clearly linked to warming winters simply because the earlier, colder, winters were already not cold enough to repress the tree-killing mountain pine beetle. This suggests that other factors may play a role in the epidemics in the western United States.

Evens so, the pattern of warming (including increase of minimum winter temperature) correlates to the demographic release of the mountain pine beetle. The authors note that “warming year-round temperatures that influence generation time and adult emergence synchrony … and drought effects that can weaken tree defenses …” are plausible explanations, but further note that a simple single explanation is not likely to be sufficient to explain the overall phenomenon.

This is, in a sense, a numbers game. A cold winter does not kill off all of the beetles. However, no matter how cold the winter is, no beetles will be wiped out if they are not there to begin with. So, demographic release, which makes possible but does not cause an outbreak, could cause an abundance of beetles across a much larger area where, no matter what natural suppression may occur, they will then become more abundant over time.

As noted, the trees themselves matter. We can safely assume that generally changes in overall climate will mean that plant communities adapted to a given region might lose that adaptive edge and be subject to a number of problems which can then be exploited by a potentially spreading parasite. These changes in viability of plant communities are not all climate change related. Forest management, disturbance, and regional demographics (as forests age, they tend to change what they do) are also factors in this complex set of ecological relationships.

The bottom line. This study confirms the effects of warming, especially the increase of winter low temperatures, on the potential for D. ponderosae to spread rapidly locally and regionally. The study also calls into question the simplistic model that this is all that happens to explain the widespread epidemic of this beetle. Other factors, including other aspects of global warming, also contribute to the epidemics. In addition, and importantly, the study demonstrates a high degree of variability in the outcome of ecological and climate change.

This epidemic is probably the largest observed kill-off of forests caused by a parasite. So far it is much more severe in its effects than forest fires, but over the long to medium term, we will probably see increased frequency and severity of forest fires because of the abundance of fuel provided by the die-off.

Soucre:



Weed, A. S., Bentz, B. J., Ayres, M. P., & Holmes, T. P. (2015). Geographically variable response of Dendroctonus ponderosae to winter warming in the western United States. Landscape Ecology. doi:10.1007/s10980–015–0170-z

Text for the image at the top of the post, from the USDA:

The Mountain Pine Beetle is at epidemic levels throughout the western United States, including here in the Rocky Mountain Region … Forests affected here include several in Colorado, Wyoming, South Dakota and Nebraska. In northern Colorado and southeastern Wyoming, Mountain Pine Beetles have impacted more than 4 million acres since the first signs of outbreak in 1996. The majority of outbreaks have occurred in three forests: Arapaho-Roosevelt, White River and Medicine Bow/Routt.

from ScienceBlogs http://ift.tt/1EVj7wv

Passing comets painted Mercury black

A limb mosaic of the planet Mercury as seen from the MESSENGER spacecraft’s Wide Angle Camera & Dual Imaging System. Image via NASA/Johns Hopkins University/Applied Physics Laboratory/Carnegie Institution of Washington.

Scientists announced this morning (March 30, 2015) that Mercury’s dark, barely reflective surface may be the result of a steady dusting of carbon from passing comets. In other words, over billions of years, comets have slowly painted Mecury’s surface black. The scientists published in the journal Nature Geoscience.

A body’s reflectivity is called its albedo by astronomers. One of the most reflective worlds in our solar system – a world with a very high albedo – is Saturn’s moon Enceladus, whose surface is covered by highly reflective ice. Now think of the opposite end of the albedo scale, of a dark surface, like that of Mercury. What could make a planet’s surface so dark? In fact, the dark surface of the sun’s innermost world has long been a mystery to scientists. According to a statement from Brown University:

On average, Mercury is much darker than its closest airless neighbor, our moon. Airless bodies are known to be darkened by micrometeorite impacts and bombardment of solar wind, processes that create a thin coating of dark iron nanoparticles on the surface.

But spectral data from Mercury suggests its surface contains very little nanophase iron, certainly not enough to account for its dim appearance.

Megan Bruck Syal is a postdoctoral researcher at Lawrence Livermore National Laboratory. She performed this research while a graduate student at Brown. She said:

One thing that hadn’t been considered was that Mercury gets dumped on by a lot of material derived from comets.

If you ever see a total eclipse of the sun, like the one in this photo by Paul D. Maley, you might see a little dot near the sun – Mercury! That’s because Mercury is the sun’s innermost planet. It orbits in the same realm of the solar system as many comets when they are at their closest to the sun, and hence at their most active.

Like planets, comets are bound in orbit by the sun. But unlike planets, many comets have highly elliptical orbits; that is, they swing out far from the sun at the outer part of their orbit, then dive in close to the sun, sometimes very close. Little Mercury is in the part of the solar system where many comets are coming nearest the sun in their orbits. At such times, comets are at their most active. The Brown University statement said:

As comets approach Mercury’s neighborhood near the sun, they often start to break apart. Cometary dust is composed of as much as 25 percent carbon by weight, so Mercury would be exposed to a steady bombardment of carbon from these crumbling comets.

Using a model of impact delivery and a known estimate of how many micrometeorites might be expected to strike Mercury, Megan Bruck Syal was able to estimate how often cometary material would impact Mercury, too. She also showed how much carbon would stick to Mercury’s surface, and how much would be thrown back into space.

Her calculations suggest that, after billions of years of bombardment, Mercury’s surface should be anywhere from 3 to 6 percent carbon.

How much would Mercury darken, via all that impacting carbon? To find out, the team turned to the NASA Ames Vertical Gun Range. The 14-foot canon simulates celestial impacts by firing projectiles at up to 16,000 miles (about 25,000 km) per hour. At the gun range, the team:

… launched projectiles in the presence of sugar, a complex organic compound that mimics the organics in comet material. The heat of an impact burns the sugar up, releasing carbon. Projectiles were fired into a material that mimics lunar basalt, the rock that makes up the dark patches on the nearside of the moon.

They fired toward a material like that on the moon’s surface, in order to see if they could make a dark material turn darker. And they did accomplish that. The experiments showed that tiny carbon particles did become deeply embedded in the target material. The process reduced the amount of light reflected by the target material to less than 5 percent – about the same as the darkest parts of Mercury.

Read more about this study from Brown University.

Bottom line: Scientists say that comets passing near the sun are painting the surface of the innermost planet Mercury black.

from EarthSky http://ift.tt/1bJoaJg

A limb mosaic of the planet Mercury as seen from the MESSENGER spacecraft’s Wide Angle Camera & Dual Imaging System. Image via NASA/Johns Hopkins University/Applied Physics Laboratory/Carnegie Institution of Washington.

Scientists announced this morning (March 30, 2015) that Mercury’s dark, barely reflective surface may be the result of a steady dusting of carbon from passing comets. In other words, over billions of years, comets have slowly painted Mecury’s surface black. The scientists published in the journal Nature Geoscience.

A body’s reflectivity is called its albedo by astronomers. One of the most reflective worlds in our solar system – a world with a very high albedo – is Saturn’s moon Enceladus, whose surface is covered by highly reflective ice. Now think of the opposite end of the albedo scale, of a dark surface, like that of Mercury. What could make a planet’s surface so dark? In fact, the dark surface of the sun’s innermost world has long been a mystery to scientists. According to a statement from Brown University:

On average, Mercury is much darker than its closest airless neighbor, our moon. Airless bodies are known to be darkened by micrometeorite impacts and bombardment of solar wind, processes that create a thin coating of dark iron nanoparticles on the surface.

But spectral data from Mercury suggests its surface contains very little nanophase iron, certainly not enough to account for its dim appearance.

Megan Bruck Syal is a postdoctoral researcher at Lawrence Livermore National Laboratory. She performed this research while a graduate student at Brown. She said:

One thing that hadn’t been considered was that Mercury gets dumped on by a lot of material derived from comets.

If you ever see a total eclipse of the sun, like the one in this photo by Paul D. Maley, you might see a little dot near the sun – Mercury! That’s because Mercury is the sun’s innermost planet. It orbits in the same realm of the solar system as many comets when they are at their closest to the sun, and hence at their most active.

Like planets, comets are bound in orbit by the sun. But unlike planets, many comets have highly elliptical orbits; that is, they swing out far from the sun at the outer part of their orbit, then dive in close to the sun, sometimes very close. Little Mercury is in the part of the solar system where many comets are coming nearest the sun in their orbits. At such times, comets are at their most active. The Brown University statement said:

As comets approach Mercury’s neighborhood near the sun, they often start to break apart. Cometary dust is composed of as much as 25 percent carbon by weight, so Mercury would be exposed to a steady bombardment of carbon from these crumbling comets.

Using a model of impact delivery and a known estimate of how many micrometeorites might be expected to strike Mercury, Megan Bruck Syal was able to estimate how often cometary material would impact Mercury, too. She also showed how much carbon would stick to Mercury’s surface, and how much would be thrown back into space.

Her calculations suggest that, after billions of years of bombardment, Mercury’s surface should be anywhere from 3 to 6 percent carbon.

How much would Mercury darken, via all that impacting carbon? To find out, the team turned to the NASA Ames Vertical Gun Range. The 14-foot canon simulates celestial impacts by firing projectiles at up to 16,000 miles (about 25,000 km) per hour. At the gun range, the team:

… launched projectiles in the presence of sugar, a complex organic compound that mimics the organics in comet material. The heat of an impact burns the sugar up, releasing carbon. Projectiles were fired into a material that mimics lunar basalt, the rock that makes up the dark patches on the nearside of the moon.

They fired toward a material like that on the moon’s surface, in order to see if they could make a dark material turn darker. And they did accomplish that. The experiments showed that tiny carbon particles did become deeply embedded in the target material. The process reduced the amount of light reflected by the target material to less than 5 percent – about the same as the darkest parts of Mercury.

Read more about this study from Brown University.

Bottom line: Scientists say that comets passing near the sun are painting the surface of the innermost planet Mercury black.

from EarthSky http://ift.tt/1bJoaJg

Big Blog News: I’m Now Also at Forbes [Uncertain Principles]

I hinted once or twice that I had news coming, and this is it: I’ve signed up to be a blog contributor at Forbes writing about, well, the sorts of things I usually write about. I’m pretty excited about the chance to connect with a new audience; the fact that they’re paying me doesn’t hurt, either…

The above link goes to my contributor page there, which will be your one-stop-shopping source for what I write at Forbes. There are two posts up this morning, a self-introduction, and an attempt to define physics and what makes it unique. The “Follow” button has an option for an RSS feed; this isn’t full-text, but that’s not my decision to make. I can’t do anything about the inspirational-quote splash pages, either, so don’t ask.

What does this mean for Uncertain Principles here at ScienceBlogs? Less than you might think– I’m not moving the whole operation, mostly because Forbes is interested in a specific set of things, and some of what I do is more appropriate for ScienceBlogs. In particular, more math-y physics education sorts of things will stay here (like last week’s angular momentum posts), and a lot of the inside-baseball stuff about academia. I’ll be sort of feeling out what goes where for a while, I’m sure, but you can expect new content in both places.

I have been and continue to be happy with ScienceBlogs and the folks who run it; they’ve done right by me over the years, and I’m happy to continue to support them. This move is a chance to write for a new platform, reaching a different audience than we get here at SB, and I’m excited to have that opportunity. And, of course, many thanks to Alex Knapp for inviting me to write for Forbes.

So, that’s the exciting news in Chateau Steelypips. The other big news is that today is the first day of Spring term classes, so I need to get back to my day job, now…

from ScienceBlogs http://ift.tt/1EqV65C

I hinted once or twice that I had news coming, and this is it: I’ve signed up to be a blog contributor at Forbes writing about, well, the sorts of things I usually write about. I’m pretty excited about the chance to connect with a new audience; the fact that they’re paying me doesn’t hurt, either…

The above link goes to my contributor page there, which will be your one-stop-shopping source for what I write at Forbes. There are two posts up this morning, a self-introduction, and an attempt to define physics and what makes it unique. The “Follow” button has an option for an RSS feed; this isn’t full-text, but that’s not my decision to make. I can’t do anything about the inspirational-quote splash pages, either, so don’t ask.

What does this mean for Uncertain Principles here at ScienceBlogs? Less than you might think– I’m not moving the whole operation, mostly because Forbes is interested in a specific set of things, and some of what I do is more appropriate for ScienceBlogs. In particular, more math-y physics education sorts of things will stay here (like last week’s angular momentum posts), and a lot of the inside-baseball stuff about academia. I’ll be sort of feeling out what goes where for a while, I’m sure, but you can expect new content in both places.

I have been and continue to be happy with ScienceBlogs and the folks who run it; they’ve done right by me over the years, and I’m happy to continue to support them. This move is a chance to write for a new platform, reaching a different audience than we get here at SB, and I’m excited to have that opportunity. And, of course, many thanks to Alex Knapp for inviting me to write for Forbes.

So, that’s the exciting news in Chateau Steelypips. The other big news is that today is the first day of Spring term classes, so I need to get back to my day job, now…

from ScienceBlogs http://ift.tt/1EqV65C

Greenland glacier melt increases mercury discharge

Zackenberg Research Station. Photo credit: Aarhus University, Department of Bioscience

This article is republished with permission from GlacierHub. This post was written by Yunziyi Lang.

Mercury contamination has long been a threat to animal carnivores and human residents in the Arctic. Mercury exports from river basins to the ocean form a significant component of the Arctic mercury cycle, and are consequently of importance in understanding and addressing this contamination.

Jens Søndergaard of the Arctic Research Centre of Aarhus University, Denmark and his colleagues have been conducting research on this topic in Greenland for a number of years. They published results of their work in the journal Science of the Total Environment in February 2015. Søndergaard and his colleagues assessed the mercury concentrations in and exports from the Zackenberg River Basin in northeast Greenland for the period 2009 – 2013. This basin is about 514 square kilometers in area, of which 106 square kilometers are covered by glaciers. Glacial outburst floods have been regularly observed in Zackenberg River since 1996. This study hypothesized that the frequency, magnitude, and timing of the glacial outburst floods and associated meteorological conditions would significantly influence the riverine mercury budget. Indeed, they found significant variation from year to year, reflecting weather and floods. The total annual mercury release varied from 0.71 kg to over 1.57 kg. These are significant amounts of such a highly toxic substance.

Stream in Zackenberg drainage. Imge credit: Mikkel Tamstrof

Søndergaard and his colleagues found that sediment-bound mercury contributed more to total releases than mercury that was dissolved in the river. Initial snowmelt, sudden erosion events, and glacial lake outburst floods all influenced daily riverine mercury exports from Zackenberg River Basin during the summer, the major period of river flow. The glacial lake outburst floods were responsible for about 31 percent of the total annual riverine mercury release. Summer temperatures and the amount of snowfall from the previous winter also played important roles in affecting the annual levels of mercury release. The authors note that releases are likely to increase, because global warming is contributing to greater levels of permafrost thawing in the region; this process, in turn, destabilizes river banks, allowing mercury contained in them to be discharged into rivers.

Greenland Seal. Image credit: Greenland Travel/Flickr

Mercury produces adverse health effects even at low levels. It is commonly known that mercury is toxic to the nervous system. According to the U.S. Environmental Protection Agency (EPA), consuming mercury-contaminated fish accounts for the primary route of exposure for most human populations. Mercury can also threaten the health of the seabirds and marine mammals which consume fish—and which Greenlandic populations. The release of riverine mercury in Zackenberg might not have strong influence in this remote region of northeast Greenland, far from human settlements and with few fisheries to date. However, the total yearly released mercury from all the river basins in Greenland is more significant, and is growing. There is a significant risk of transport in marine ecosystems through food chains, causing mercury poisoning among humans and wildlife in Greenland and in adjacent coastal countries.

from EarthSky http://ift.tt/1G8aT8c

Zackenberg Research Station. Photo credit: Aarhus University, Department of Bioscience

This article is republished with permission from GlacierHub. This post was written by Yunziyi Lang.

Mercury contamination has long been a threat to animal carnivores and human residents in the Arctic. Mercury exports from river basins to the ocean form a significant component of the Arctic mercury cycle, and are consequently of importance in understanding and addressing this contamination.

Jens Søndergaard of the Arctic Research Centre of Aarhus University, Denmark and his colleagues have been conducting research on this topic in Greenland for a number of years. They published results of their work in the journal Science of the Total Environment in February 2015. Søndergaard and his colleagues assessed the mercury concentrations in and exports from the Zackenberg River Basin in northeast Greenland for the period 2009 – 2013. This basin is about 514 square kilometers in area, of which 106 square kilometers are covered by glaciers. Glacial outburst floods have been regularly observed in Zackenberg River since 1996. This study hypothesized that the frequency, magnitude, and timing of the glacial outburst floods and associated meteorological conditions would significantly influence the riverine mercury budget. Indeed, they found significant variation from year to year, reflecting weather and floods. The total annual mercury release varied from 0.71 kg to over 1.57 kg. These are significant amounts of such a highly toxic substance.

Stream in Zackenberg drainage. Imge credit: Mikkel Tamstrof

Søndergaard and his colleagues found that sediment-bound mercury contributed more to total releases than mercury that was dissolved in the river. Initial snowmelt, sudden erosion events, and glacial lake outburst floods all influenced daily riverine mercury exports from Zackenberg River Basin during the summer, the major period of river flow. The glacial lake outburst floods were responsible for about 31 percent of the total annual riverine mercury release. Summer temperatures and the amount of snowfall from the previous winter also played important roles in affecting the annual levels of mercury release. The authors note that releases are likely to increase, because global warming is contributing to greater levels of permafrost thawing in the region; this process, in turn, destabilizes river banks, allowing mercury contained in them to be discharged into rivers.

Greenland Seal. Image credit: Greenland Travel/Flickr

Mercury produces adverse health effects even at low levels. It is commonly known that mercury is toxic to the nervous system. According to the U.S. Environmental Protection Agency (EPA), consuming mercury-contaminated fish accounts for the primary route of exposure for most human populations. Mercury can also threaten the health of the seabirds and marine mammals which consume fish—and which Greenlandic populations. The release of riverine mercury in Zackenberg might not have strong influence in this remote region of northeast Greenland, far from human settlements and with few fisheries to date. However, the total yearly released mercury from all the river basins in Greenland is more significant, and is growing. There is a significant risk of transport in marine ecosystems through food chains, causing mercury poisoning among humans and wildlife in Greenland and in adjacent coastal countries.

from EarthSky http://ift.tt/1G8aT8c