Are Saturn’s rings young or old?

View larger. | Saturn, via the Cassini spacecraft. Image via NASA/JPL-Caltech/Space Science Institute/Europlanet.

Four decades ago, when I was first learning astronomy, we all assumed that Saturn’s iconic rings had always been there, as old as the solar system itself. We assumed that Saturn formed with its rings, which are vast and glorious, stretching nearly 200,000 miles (300,000 km) above the planet’s equator. The rings seemed so integral to Saturn itself. But then came the visits to Saturn by Voyagers 1 and 2. Their observations suggested that the rings might be younger than the planet – much younger – a temporary phenomenon, lasting only millions of years in the 4 1/2 billion year lifetime of our solar system. And in recent years, data from the Cassini spacecraft (2004-2017) seemed to nail down the idea that Saturn’s rings are from 10 million to 100 million years old. Now we hear that insight from Cassini wasn’t the final word, either. A team of researchers has reignited the debate about the age of Saturn’s rings with a study that dates the rings as most likely to have formed in the early solar system.

The authors suggest that processes that preferentially eject dusty and organic material out of Saturn’s rings – a “ring rain” that falls in part onto Saturn – could make the rings appear younger than they really are. Cassini, in fact, encountered this ring rain when it dived between Saturn’s rings and its upper atmosphere during its Grand Finale in 2017.

The idea is being discussed this week by astronomers at a joint meeting of the European Planetary Science Congress and the AAS Division for Planetary Sciences in Geneva, Switzerland. It was published just in time for this meeting, on September 16, 2019, in the peer-reviewed journal Nature Astronomy.

Voyager 2 captured the images to make this composite, taken through ultraviolet, violet and green filters. The image was considered mind-blowingly detailed at the time. The Voyager 1 and 2 Saturn encounters occurred nine months apart, in November 1980 and August 1981. Those missions were what first sparked speculation that Saturn’s rings might be younger than astronomers had always assumed. Image via NASA/JPL-Caltech.

A statement from the new study’s authors said:

Cassini’s dive through the rings during the mission’s Grand Finale in 2017 provided data that was interpreted as evidence that Saturn’s rings formed just a few tens of millions of years ago, around the time that dinosaurs walked the Earth. Gravity measurements taken during the dive gave a more accurate estimate of the mass of the rings, which are made up of more than 95% water ice and less than 5% rocks, organic materials and metals. The mass estimate was then used to work out how long the pristine ice of the rings would need to be exposed to dust and micrometeorites to reach the level of other ‘pollutants’ that we see today. For many, this resolved the mystery of the age of the rings.

But not all scientists were convinced. In an article about Saturn’s rings in Scientific American in August, ring expert Luke Dones of the Southwest Research Institute was quoted as saying:

I have no objection to young rings. I just think no one has found a very plausible way of making them. It requires an unlikely event.

In other words, in the early solar system, when there was a lot of debris flying around, it’s easy to imagine the dynamic processes capable of creating the rings: the capture of debris by Saturn’s gravity and/or the breakup of comets, asteroids, or even small moons. Once the rings began to form, it’s also easy to imagine the separate ring particles colliding with each other and breaking up even smaller, spreading out around Saturn to form its rings. But, the Scientific American article said:

… it is just too hard, some critics say, to craft such expansive rings in the relatively placid solar system of now and near-yesteryear.

Astronomer Aurélien Crida, via OCA. He is lead author of the new study suggesting Saturn’s rings are very old.

Aurélien Crida of the Observatoire de la Côte d’Azur, is lead author of the new study. Here’s why he believes the debate is not yet settled; he said:

We can’t directly measure the age of Saturn’s rings like the rings on a tree-stump, so we have to deduce their age from other properties like mass and chemical composition. Recent studies have made assumptions that the dust flow is constant, the mass of the rings is constant, and that the rings retain all the pollution material that they receive.

However, there is still a lot of uncertainty about all these points and, when taken with other results from the Cassini mission, we believe that there is a strong case that the rings are much, much older.

Crida and his colleagues argue in their study that the mass measured during the Cassini mission finale is in “extraordinarily good agreement” with models of the dynamical evolution of massive rings dating back to the primordial solar system.

Galileo discovered Saturn’s rings in 1610. Through his early telescope, he thought they looked like “handles,” or perhaps large moons on either side of Saturn. Christiaan Huygens then took up the observations of Saturn and published this compilation image, showing how Saturn’s appearance had changed from 1610 to 1646, in his Systema Saturnium. It was Huygens who revealed the mystery of Saturn’s rings, saying were “It [Saturn] is surrounded by a thin, flat, ring, nowhere touching, inclined to the ecliptic.” Read more history of our knowledge of Saturn’s rings.

Nadia Drake, who authored Scientific American’s Saturn article in August, described Saturn’s rings as “icy particles ranging in size from microscopic to mobile home.” Crida and colleagues described the individual components in Saturn’s rings more prosaically as:

… particles and blocks ranging in size from meters down to micrometers. Viscous interactions between the blocks cause the rings to spread out and carry material away like a conveyor-belt. This leads to mass loss from the innermost edge, where particles fall into the planet, and from the outer edge, where material crosses the outer boundary into a region where moonlets and satellites start to form.

More massive rings spread more rapidly and lose mass faster. The models show that whatever the initial mass of the rings, there is a tendency for the rings to converge on a mass measured by Cassini after around 4 billion years, matching the timescale of the formation of the solar system.

Crida summed up his team’s position, saying:

From our present understanding of the viscosity of the rings, the mass measured during the Cassini Grand Finale would be the natural product of several billion years of evolution, which is appealing. Admittedly, nothing forbids the rings from having been formed very recently with this precise mass and having barely evolved since. However, that would be quite a coincidence.

Hsiang-Wen (Sean) Hsu of LASP and his colleagues reported in 2018 that they successfully collected microscopic material streaming from Saturn’s rings. Read more.

Hsiang-Wen Hsu of the Laboratory for Atmospheric and Space Physics (LASP) in Boulder, Colorado, was part of a team that announced results in October 2018 related to a “ring rain.” The results, via Cassini, showed that 600 kilograms (1,300 pounds) of silicate grains fall on Saturn from the rings every second. Other studies have shown the presence of organic molecules in Saturn’s upper atmosphere that are thought to derive from the rings. Hsu commented:

These results suggest that the rings are ‘cleaning’ themselves of pollutants. The nature of this potential ring-cleaning process is still mysterious.

However, our study shows that the exposure age is not necessarily linked to the formation age, thus the rings may appear artificially young.

View larger. | Another Cassini image of Saturn’s rings, via NASA/JPL-Caltech/Space Science Institute/Europlanet.

Bottom line: Cassini data seemed to indicate rings lasting only 10 million to 100 million years. A new study suggests that dusty and organic material ejected from Saturn’s rings – a “ring rain” – could make the rings appear younger than they really are. As things stand now, we don’t know if Saturn’s rings are young or old; we only know that astronomers are continuing to learn about them.

Source: Are Saturn’s rings actually young?

Via Europlanet

from EarthSky https://ift.tt/2AnsnRs

View larger. | Saturn, via the Cassini spacecraft. Image via NASA/JPL-Caltech/Space Science Institute/Europlanet.

Four decades ago, when I was first learning astronomy, we all assumed that Saturn’s iconic rings had always been there, as old as the solar system itself. We assumed that Saturn formed with its rings, which are vast and glorious, stretching nearly 200,000 miles (300,000 km) above the planet’s equator. The rings seemed so integral to Saturn itself. But then came the visits to Saturn by Voyagers 1 and 2. Their observations suggested that the rings might be younger than the planet – much younger – a temporary phenomenon, lasting only millions of years in the 4 1/2 billion year lifetime of our solar system. And in recent years, data from the Cassini spacecraft (2004-2017) seemed to nail down the idea that Saturn’s rings are from 10 million to 100 million years old. Now we hear that insight from Cassini wasn’t the final word, either. A team of researchers has reignited the debate about the age of Saturn’s rings with a study that dates the rings as most likely to have formed in the early solar system.

The authors suggest that processes that preferentially eject dusty and organic material out of Saturn’s rings – a “ring rain” that falls in part onto Saturn – could make the rings appear younger than they really are. Cassini, in fact, encountered this ring rain when it dived between Saturn’s rings and its upper atmosphere during its Grand Finale in 2017.

The idea is being discussed this week by astronomers at a joint meeting of the European Planetary Science Congress and the AAS Division for Planetary Sciences in Geneva, Switzerland. It was published just in time for this meeting, on September 16, 2019, in the peer-reviewed journal Nature Astronomy.

Voyager 2 captured the images to make this composite, taken through ultraviolet, violet and green filters. The image was considered mind-blowingly detailed at the time. The Voyager 1 and 2 Saturn encounters occurred nine months apart, in November 1980 and August 1981. Those missions were what first sparked speculation that Saturn’s rings might be younger than astronomers had always assumed. Image via NASA/JPL-Caltech.

A statement from the new study’s authors said:

Cassini’s dive through the rings during the mission’s Grand Finale in 2017 provided data that was interpreted as evidence that Saturn’s rings formed just a few tens of millions of years ago, around the time that dinosaurs walked the Earth. Gravity measurements taken during the dive gave a more accurate estimate of the mass of the rings, which are made up of more than 95% water ice and less than 5% rocks, organic materials and metals. The mass estimate was then used to work out how long the pristine ice of the rings would need to be exposed to dust and micrometeorites to reach the level of other ‘pollutants’ that we see today. For many, this resolved the mystery of the age of the rings.

But not all scientists were convinced. In an article about Saturn’s rings in Scientific American in August, ring expert Luke Dones of the Southwest Research Institute was quoted as saying:

I have no objection to young rings. I just think no one has found a very plausible way of making them. It requires an unlikely event.

In other words, in the early solar system, when there was a lot of debris flying around, it’s easy to imagine the dynamic processes capable of creating the rings: the capture of debris by Saturn’s gravity and/or the breakup of comets, asteroids, or even small moons. Once the rings began to form, it’s also easy to imagine the separate ring particles colliding with each other and breaking up even smaller, spreading out around Saturn to form its rings. But, the Scientific American article said:

… it is just too hard, some critics say, to craft such expansive rings in the relatively placid solar system of now and near-yesteryear.

Astronomer Aurélien Crida, via OCA. He is lead author of the new study suggesting Saturn’s rings are very old.

Aurélien Crida of the Observatoire de la Côte d’Azur, is lead author of the new study. Here’s why he believes the debate is not yet settled; he said:

We can’t directly measure the age of Saturn’s rings like the rings on a tree-stump, so we have to deduce their age from other properties like mass and chemical composition. Recent studies have made assumptions that the dust flow is constant, the mass of the rings is constant, and that the rings retain all the pollution material that they receive.

However, there is still a lot of uncertainty about all these points and, when taken with other results from the Cassini mission, we believe that there is a strong case that the rings are much, much older.

Crida and his colleagues argue in their study that the mass measured during the Cassini mission finale is in “extraordinarily good agreement” with models of the dynamical evolution of massive rings dating back to the primordial solar system.

Galileo discovered Saturn’s rings in 1610. Through his early telescope, he thought they looked like “handles,” or perhaps large moons on either side of Saturn. Christiaan Huygens then took up the observations of Saturn and published this compilation image, showing how Saturn’s appearance had changed from 1610 to 1646, in his Systema Saturnium. It was Huygens who revealed the mystery of Saturn’s rings, saying were “It [Saturn] is surrounded by a thin, flat, ring, nowhere touching, inclined to the ecliptic.” Read more history of our knowledge of Saturn’s rings.

Nadia Drake, who authored Scientific American’s Saturn article in August, described Saturn’s rings as “icy particles ranging in size from microscopic to mobile home.” Crida and colleagues described the individual components in Saturn’s rings more prosaically as:

… particles and blocks ranging in size from meters down to micrometers. Viscous interactions between the blocks cause the rings to spread out and carry material away like a conveyor-belt. This leads to mass loss from the innermost edge, where particles fall into the planet, and from the outer edge, where material crosses the outer boundary into a region where moonlets and satellites start to form.

More massive rings spread more rapidly and lose mass faster. The models show that whatever the initial mass of the rings, there is a tendency for the rings to converge on a mass measured by Cassini after around 4 billion years, matching the timescale of the formation of the solar system.

Crida summed up his team’s position, saying:

From our present understanding of the viscosity of the rings, the mass measured during the Cassini Grand Finale would be the natural product of several billion years of evolution, which is appealing. Admittedly, nothing forbids the rings from having been formed very recently with this precise mass and having barely evolved since. However, that would be quite a coincidence.

Hsiang-Wen (Sean) Hsu of LASP and his colleagues reported in 2018 that they successfully collected microscopic material streaming from Saturn’s rings. Read more.

Hsiang-Wen Hsu of the Laboratory for Atmospheric and Space Physics (LASP) in Boulder, Colorado, was part of a team that announced results in October 2018 related to a “ring rain.” The results, via Cassini, showed that 600 kilograms (1,300 pounds) of silicate grains fall on Saturn from the rings every second. Other studies have shown the presence of organic molecules in Saturn’s upper atmosphere that are thought to derive from the rings. Hsu commented:

These results suggest that the rings are ‘cleaning’ themselves of pollutants. The nature of this potential ring-cleaning process is still mysterious.

However, our study shows that the exposure age is not necessarily linked to the formation age, thus the rings may appear artificially young.

View larger. | Another Cassini image of Saturn’s rings, via NASA/JPL-Caltech/Space Science Institute/Europlanet.

Bottom line: Cassini data seemed to indicate rings lasting only 10 million to 100 million years. A new study suggests that dusty and organic material ejected from Saturn’s rings – a “ring rain” – could make the rings appear younger than they really are. As things stand now, we don’t know if Saturn’s rings are young or old; we only know that astronomers are continuing to learn about them.

Source: Are Saturn’s rings actually young?

Via Europlanet

from EarthSky https://ift.tt/2AnsnRs

What makes a red rainbow?

View larger. | Double red rainbow on July 21, 2015, by Steve Lacy, near Las Cruces, New Mexico.

It’s rare to see a red rainbow. I’ve seen only one in all my decades of skywatching … although, I admit, I live in a place where it doesn’t rain much. I spotted my sole red rainbow early one morning decades ago, around sunup, while driving on the dirt road leading from Chaco Canyon in New Mexico. That is such a magical place, and I fancied at the time that the magic of the canyon helped create the red rainbow. Not so.

Les Cowley of the great website Atmospheric Optics says that red rainbows are created when there is a low sun so that, he says, the blue and green of its rays are weakened by scattering during the long journey through the atmosphere. In that way, red rainbows are akin to red sunrises and sunsets. Les explained:

Sunset and sunrise rays travel long paths through the lower atmosphere where they are scattered by air molecules and dust. Short wavelength blues and greens are scattered most strongly leaving the remaining transmitted light proportionately richer in reds and yellows. The result, glorious sunsets and red rainbows.

Frances Pelletier caught this double red rainbow on February 9, 2016, from Myrtle Beach, South Carolina.

In 2014, astrophotographer Göran Strand of Sweden kindly gave us permission to publish the photo below, which shows an ordinary double rainbow (if any rainbow, especially a double rainbow, can be called ordinary), followed by a double red rainbow. It illustrates how red rainbows are made. Göran told Earthsky that he shot the upper image in the afternoon, with the sun about 27 degrees above the horizon. He shot the lower photo with the sun 2 degrees above the horizon.

Notice two things in the photo below: the heights of the two rainbows above the horizon, and their colors.

The height of a rainbow depends on the sun. The lower the sun, the higher the rainbow. You can see evidence of this fact by looking at the red rainbow photo, shot when the sun was setting. See how much higher in the sky it arcs than the other double rainbow?

View larger. | Göran Strand of Sweden captured this double rainbow in 2014 … and, shortly afterwards, caught it again as the sun sank lower, and it became a double red rainbow. Used with permission. Visit Göran’s astrophotography website or his Facebook page.

Interested in double rainbows, by the way, and in how regular rainbows are made? All rainbows happen when sunlight shines through raindrops. If the sun is behind you, and if you see the sun sunlight emerging from many raindrops at once, you see a mosaic of light spread out in an arc in the sky: a rainbow. Double rainbows happen when sunlight inside a raindrop is reflected twice instead of once.

Here are more photos of red rainbows from the EarthSky community. Thank you all!

Red rainbow at sunset – May 25, 2015 – over Bluewater, Ontario, Canada. Photo by Kelly Schenk.

Red rainbow over Roque del Conde, on the island of Tenerife, submitted to EarthSky by Roberto Porto.

Here’s another beautiful shot of a red rainbow, from EarthSky Facebook friend Jesper Kristensen. It’s from August 14, 2014. Thank you, Jesper.

Bottom line: If you’re watching a sunset, and there’s rain in the air, turn in the direction opposite the sun and watch for the elusive red rainbow. Red rainbows happen when the sun is on the horizon. They’re created for much the same reason that a sunset or sunrise looks red. When the sun is low, its blue and green light is weakened by scattering during the long journey to your eyes through Earth’s atmosphere. The red light travels through more directly. Voila … a red rainbow.

from EarthSky https://ift.tt/34RiFog

View larger. | Double red rainbow on July 21, 2015, by Steve Lacy, near Las Cruces, New Mexico.

It’s rare to see a red rainbow. I’ve seen only one in all my decades of skywatching … although, I admit, I live in a place where it doesn’t rain much. I spotted my sole red rainbow early one morning decades ago, around sunup, while driving on the dirt road leading from Chaco Canyon in New Mexico. That is such a magical place, and I fancied at the time that the magic of the canyon helped create the red rainbow. Not so.

Les Cowley of the great website Atmospheric Optics says that red rainbows are created when there is a low sun so that, he says, the blue and green of its rays are weakened by scattering during the long journey through the atmosphere. In that way, red rainbows are akin to red sunrises and sunsets. Les explained:

Sunset and sunrise rays travel long paths through the lower atmosphere where they are scattered by air molecules and dust. Short wavelength blues and greens are scattered most strongly leaving the remaining transmitted light proportionately richer in reds and yellows. The result, glorious sunsets and red rainbows.

Frances Pelletier caught this double red rainbow on February 9, 2016, from Myrtle Beach, South Carolina.

In 2014, astrophotographer Göran Strand of Sweden kindly gave us permission to publish the photo below, which shows an ordinary double rainbow (if any rainbow, especially a double rainbow, can be called ordinary), followed by a double red rainbow. It illustrates how red rainbows are made. Göran told Earthsky that he shot the upper image in the afternoon, with the sun about 27 degrees above the horizon. He shot the lower photo with the sun 2 degrees above the horizon.

Notice two things in the photo below: the heights of the two rainbows above the horizon, and their colors.

The height of a rainbow depends on the sun. The lower the sun, the higher the rainbow. You can see evidence of this fact by looking at the red rainbow photo, shot when the sun was setting. See how much higher in the sky it arcs than the other double rainbow?

View larger. | Göran Strand of Sweden captured this double rainbow in 2014 … and, shortly afterwards, caught it again as the sun sank lower, and it became a double red rainbow. Used with permission. Visit Göran’s astrophotography website or his Facebook page.

Interested in double rainbows, by the way, and in how regular rainbows are made? All rainbows happen when sunlight shines through raindrops. If the sun is behind you, and if you see the sun sunlight emerging from many raindrops at once, you see a mosaic of light spread out in an arc in the sky: a rainbow. Double rainbows happen when sunlight inside a raindrop is reflected twice instead of once.

Here are more photos of red rainbows from the EarthSky community. Thank you all!

Red rainbow at sunset – May 25, 2015 – over Bluewater, Ontario, Canada. Photo by Kelly Schenk.

Red rainbow over Roque del Conde, on the island of Tenerife, submitted to EarthSky by Roberto Porto.

Here’s another beautiful shot of a red rainbow, from EarthSky Facebook friend Jesper Kristensen. It’s from August 14, 2014. Thank you, Jesper.

Bottom line: If you’re watching a sunset, and there’s rain in the air, turn in the direction opposite the sun and watch for the elusive red rainbow. Red rainbows happen when the sun is on the horizon. They’re created for much the same reason that a sunset or sunrise looks red. When the sun is low, its blue and green light is weakened by scattering during the long journey to your eyes through Earth’s atmosphere. The red light travels through more directly. Voila … a red rainbow.

from EarthSky https://ift.tt/34RiFog

Tsunamis, wildfires followed dinosaur-killing impact

Image via Curtin University.

Scientists have long believed that the end of the dinosaurs came as a result of a giant asteroid that crashed into Earth about 66 million years ago. Now, a new study by an international team of geologists, published in the peer-reviewed journal Proceedings of the National Academy of Sciences on September 9, 2019, has found hard evidence of the theory by analyzing the hundreds of feet of rocks that filled the impact crater within the first 24 hours after impact.

The geologists say the evidence shows that the asteroid impact caused wildfires, triggered tsunamis and blasted so much sulfur into the atmosphere that it blocked the sun, which caused the global cooling that ultimately doomed the non-avian dinosaurs.

The researcher drilled 1,640 to 4,265 feet (500 to 1,300 meters) into the seafloor below the Chicxulub crater off the coast of what’s now Mexico, in order to extract core samples of the rocks which filled the crater within 24 hours after the asteroid hit.

Location of Chicxulub crater. Image via Wikipedia.

Sean Gulick, a research professor at the University of Texas Institute for Geophysics (UTIG) at the Jackson School of Geosciences, is lead author of the study. Gulick said in a statement:

It’s an expanded record of events that we were able to recover from within ground zero. It tells us about impact processes from an eyewitness location.

Curtin University geochemist Kliti Grice is a study co-author. She said:

The asteroid impact that formed the Chicxulub crater on the Yucatán Peninsula in Mexico, where this research was carried out, is thought to be the cause of the late Cretaceous Period mass extinction event which led to 76 per cent of all plant and animal species world-wide, including all non-flying dinosaurs, being killed off.

According to the researchers, most of the material that filled the crater within hours of the asteroid’s impact was either produced at the impact site, or swept in by seawater pouring back into the crater. Just one day deposited about 425 feet (130 meters) of material, said the geologists, a rate that’s among the highest ever encountered in the geologic record. That breakneck rate of accumulation means that the rocks in the crater record what was happening within and around the crater in the minutes and hours after the impact.

According to a University of Texas statement:

Researchers estimate the asteroid hit with the equivalent power of 10 billion atomic bombs of the size used in World War II. The blast ignited trees and plants that were thousands of miles away and triggered a massive tsunami that reached as far inland as Illinois. Inside the crater, researchers found charcoal and a chemical biomarker associated with soil fungi within or just above layers of sand that shows signs of being deposited by resurging waters. This suggests that the charred landscape was pulled into the crater with the receding waters of the tsunami.

A portion of the drilled cores from the rocks that filled the crater. Scientists found melted and broken rocks such as sandstone, limestone and granite — but no sulfur-bearing minerals, despite the area’s high concentration of sulfur containing rocks. This finding suggests that the impact vaporized these rocks forming sulfate aerosols in the atmosphere, causing cooling on the global scale. Image via International Ocean Discovery Program.

One of the most important findings from the research is what was missing from the core samples. The area surrounding the impact crater is full of sulfur-rich rocks. But there was no sulfur in the core. This lack supports the idea that when the asteroid hit, sulfur from the crater was vaporized into the atmosphere, where it wreaked havoc on the Earth’s climate, reflecting sunlight away from the planet and causing global cooling. Researchers estimate that at least 325 billion metric tons would have been released by the impact. To put that in perspective, that’s about four orders of magnitude greater than the sulfur that was spewed during the 1883 eruption of Krakatoa — which cooled the Earth’s climate by an average of 2.2 degrees Fahrenheit (1.2 degrees Celsius) for five years.

Although the asteroid impact created mass destruction at the regional level, it was this global climate change that caused a mass extinction, killing off the dinosaurs along with most other life on the planet at the time, Gulick said.

The real killer has got to be atmospheric. The only way you get a global mass extinction like this is an atmospheric effect.

Geologists Sean Gulick, of University of Texas and Joanna Morgan, of Imperial College London, on the 2016 research expedition that retrieved cores from the submerged and buried impact crater. Image via The University of Texas at Austin/Jackson School of Geosciences.

Bottom line: A new study analyzed rock from deep within the Chicxulub impact crater to learn what happened immediately after the asteroid impact that doomed the dinosaurs.

Source: The first day of the Cenozoic

Via The University of Texas at Austin and Curtin University

from EarthSky https://ift.tt/2NlIGXe

Image via Curtin University.

Scientists have long believed that the end of the dinosaurs came as a result of a giant asteroid that crashed into Earth about 66 million years ago. Now, a new study by an international team of geologists, published in the peer-reviewed journal Proceedings of the National Academy of Sciences on September 9, 2019, has found hard evidence of the theory by analyzing the hundreds of feet of rocks that filled the impact crater within the first 24 hours after impact.

The geologists say the evidence shows that the asteroid impact caused wildfires, triggered tsunamis and blasted so much sulfur into the atmosphere that it blocked the sun, which caused the global cooling that ultimately doomed the non-avian dinosaurs.

The researcher drilled 1,640 to 4,265 feet (500 to 1,300 meters) into the seafloor below the Chicxulub crater off the coast of what’s now Mexico, in order to extract core samples of the rocks which filled the crater within 24 hours after the asteroid hit.

Location of Chicxulub crater. Image via Wikipedia.

Sean Gulick, a research professor at the University of Texas Institute for Geophysics (UTIG) at the Jackson School of Geosciences, is lead author of the study. Gulick said in a statement:

It’s an expanded record of events that we were able to recover from within ground zero. It tells us about impact processes from an eyewitness location.

Curtin University geochemist Kliti Grice is a study co-author. She said:

The asteroid impact that formed the Chicxulub crater on the Yucatán Peninsula in Mexico, where this research was carried out, is thought to be the cause of the late Cretaceous Period mass extinction event which led to 76 per cent of all plant and animal species world-wide, including all non-flying dinosaurs, being killed off.

According to the researchers, most of the material that filled the crater within hours of the asteroid’s impact was either produced at the impact site, or swept in by seawater pouring back into the crater. Just one day deposited about 425 feet (130 meters) of material, said the geologists, a rate that’s among the highest ever encountered in the geologic record. That breakneck rate of accumulation means that the rocks in the crater record what was happening within and around the crater in the minutes and hours after the impact.

According to a University of Texas statement:

Researchers estimate the asteroid hit with the equivalent power of 10 billion atomic bombs of the size used in World War II. The blast ignited trees and plants that were thousands of miles away and triggered a massive tsunami that reached as far inland as Illinois. Inside the crater, researchers found charcoal and a chemical biomarker associated with soil fungi within or just above layers of sand that shows signs of being deposited by resurging waters. This suggests that the charred landscape was pulled into the crater with the receding waters of the tsunami.

A portion of the drilled cores from the rocks that filled the crater. Scientists found melted and broken rocks such as sandstone, limestone and granite — but no sulfur-bearing minerals, despite the area’s high concentration of sulfur containing rocks. This finding suggests that the impact vaporized these rocks forming sulfate aerosols in the atmosphere, causing cooling on the global scale. Image via International Ocean Discovery Program.

One of the most important findings from the research is what was missing from the core samples. The area surrounding the impact crater is full of sulfur-rich rocks. But there was no sulfur in the core. This lack supports the idea that when the asteroid hit, sulfur from the crater was vaporized into the atmosphere, where it wreaked havoc on the Earth’s climate, reflecting sunlight away from the planet and causing global cooling. Researchers estimate that at least 325 billion metric tons would have been released by the impact. To put that in perspective, that’s about four orders of magnitude greater than the sulfur that was spewed during the 1883 eruption of Krakatoa — which cooled the Earth’s climate by an average of 2.2 degrees Fahrenheit (1.2 degrees Celsius) for five years.

Although the asteroid impact created mass destruction at the regional level, it was this global climate change that caused a mass extinction, killing off the dinosaurs along with most other life on the planet at the time, Gulick said.

The real killer has got to be atmospheric. The only way you get a global mass extinction like this is an atmospheric effect.

Geologists Sean Gulick, of University of Texas and Joanna Morgan, of Imperial College London, on the 2016 research expedition that retrieved cores from the submerged and buried impact crater. Image via The University of Texas at Austin/Jackson School of Geosciences.

Bottom line: A new study analyzed rock from deep within the Chicxulub impact crater to learn what happened immediately after the asteroid impact that doomed the dinosaurs.

Source: The first day of the Cenozoic

Via The University of Texas at Austin and Curtin University

from EarthSky https://ift.tt/2NlIGXe

We stand corrected

View larger at EarthSky Community Photos. Image via Dr Ski, who said: “In the above image, I moved the camera a bit to expose just a small portion of the sun’s limb to get those cool diffraction spikes (caused by the small aperture blades).”

Our friend Dr Ski, in Valencia, Philippines, has been noticing images of the sun posted at EarthSky Community Photos, and he gave us a stern talking-to.

The sun can create some dramatic images. But all of posts I see here that promote unsafe solar viewing and are very disturbing!

He offered these guidelines for taking images of the sun:

1) Always have something handy to block the sun (like your hand!) when looking for solar phenomena or trying to compose a shot.

2) Never aim your camera at the sun without something to block the solar disc.

3) Never use your electronic viewfinder, if you have one.

4) Telephoto lenses are a bad idea; they magnify the sun’s intensity.

5) Use your slowest aperture (e.g. f16) and slowest ISO (e. g. ISO100). Even at those slow conditions, the shutter speed will be fast enough to preclude the use a tripod! (although a tripod helps in fine-tuning your composition)

6) Always block the sun’s disc! Then you won’t get those annoying lens flares that might be mistaken for Neptune.

Thanks so much Dr Ski!

Bottom line: How protect you eyes when taking photos of the sun.

from EarthSky https://ift.tt/305eINd

View larger at EarthSky Community Photos. Image via Dr Ski, who said: “In the above image, I moved the camera a bit to expose just a small portion of the sun’s limb to get those cool diffraction spikes (caused by the small aperture blades).”

Our friend Dr Ski, in Valencia, Philippines, has been noticing images of the sun posted at EarthSky Community Photos, and he gave us a stern talking-to.

The sun can create some dramatic images. But all of posts I see here that promote unsafe solar viewing and are very disturbing!

He offered these guidelines for taking images of the sun:

1) Always have something handy to block the sun (like your hand!) when looking for solar phenomena or trying to compose a shot.

2) Never aim your camera at the sun without something to block the solar disc.

3) Never use your electronic viewfinder, if you have one.

4) Telephoto lenses are a bad idea; they magnify the sun’s intensity.

5) Use your slowest aperture (e.g. f16) and slowest ISO (e. g. ISO100). Even at those slow conditions, the shutter speed will be fast enough to preclude the use a tripod! (although a tripod helps in fine-tuning your composition)

6) Always block the sun’s disc! Then you won’t get those annoying lens flares that might be mistaken for Neptune.

Thanks so much Dr Ski!

Bottom line: How protect you eyes when taking photos of the sun.

from EarthSky https://ift.tt/305eINd

Use Big Dipper to find North Star

Tonight’s chart shows Polaris and the Big and Little Dippers for a September evening. You can use the Big Dipper to find Polaris, which is also known as the North Star. Notice that a line from the two outermost stars in the bowl of the Big Dipper points to Polaris. And notice that Polaris marks the tip of the handle of the Little Dipper.

The northern sky is a large clock, with Polaris at its center. The hour hand is a line drawn through Dubhe and Merak, the two pointer stars of the Big Dipper. Because the stars make a full circle in 23 hours 56 minutes instead of exactly 24 hours, this star clock is not exactly the same as the one on the wall, but with a little practice you can learn to read it well.

The Big and Little Dippers: All you need to know

EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store

View larger. | Keith Breazeal’s photo of a meteor streaking past the Big Dipper during the 2015 Perseid meteor shower. Captured at the Bear River Dam in the California Sierra Nevada mountains. Can you find Polaris in this photo?

The Big Dipper swings full circle – 360 degrees – around Polaris in about 23 hours and 56 minutes. In 24 hours, the Big Dipper actually swings more than full circle, or 361 degrees. Does that make a difference? Yes! It means that – if you look at the same time each evening – the Big Dipper will appear just a little bit lower in the northwestern evening sky.

If you’re in the northern U.S., Canada or at a similar latitude, the Big Dipper is circumpolar for you – always above the horizon. Image via burro.astr.cwru.edu

A month from now at mid-evening, the Big Dipper will be noticeably lower in the northwest. It’ll actually beneath the horizon as seen from the southern latitudes in the United States – although it’s circumpolar, or always above the northern horizon, as seen from the northern U.S., Canada and similarly northern latitudes.

The constant motion from night to night of these stars circling Polaris is a bit like a bear circling its prey, looking for a way to attack. Several ancient cultures from the Greeks and Romans to the Micmac Indians likened these stars to a bear.

In Greek mythology, the Big Dipper asterism represents the hindquarters and tail of the constellation Ursa Major, the Great Bear. The Micmacs saw the three stars of the Big Dipper handle as hunters chasing the bear.

Watch the Big and Little Dippers circle around Polaris tonight! To locate Polaris, the North Star, just draw a line between the two outer stars in the bowl of the Big Dipper.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

from EarthSky https://ift.tt/34O5RPB

Tonight’s chart shows Polaris and the Big and Little Dippers for a September evening. You can use the Big Dipper to find Polaris, which is also known as the North Star. Notice that a line from the two outermost stars in the bowl of the Big Dipper points to Polaris. And notice that Polaris marks the tip of the handle of the Little Dipper.

The northern sky is a large clock, with Polaris at its center. The hour hand is a line drawn through Dubhe and Merak, the two pointer stars of the Big Dipper. Because the stars make a full circle in 23 hours 56 minutes instead of exactly 24 hours, this star clock is not exactly the same as the one on the wall, but with a little practice you can learn to read it well.

The Big and Little Dippers: All you need to know

EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store

View larger. | Keith Breazeal’s photo of a meteor streaking past the Big Dipper during the 2015 Perseid meteor shower. Captured at the Bear River Dam in the California Sierra Nevada mountains. Can you find Polaris in this photo?

The Big Dipper swings full circle – 360 degrees – around Polaris in about 23 hours and 56 minutes. In 24 hours, the Big Dipper actually swings more than full circle, or 361 degrees. Does that make a difference? Yes! It means that – if you look at the same time each evening – the Big Dipper will appear just a little bit lower in the northwestern evening sky.

If you’re in the northern U.S., Canada or at a similar latitude, the Big Dipper is circumpolar for you – always above the horizon. Image via burro.astr.cwru.edu

A month from now at mid-evening, the Big Dipper will be noticeably lower in the northwest. It’ll actually beneath the horizon as seen from the southern latitudes in the United States – although it’s circumpolar, or always above the northern horizon, as seen from the northern U.S., Canada and similarly northern latitudes.

The constant motion from night to night of these stars circling Polaris is a bit like a bear circling its prey, looking for a way to attack. Several ancient cultures from the Greeks and Romans to the Micmac Indians likened these stars to a bear.

In Greek mythology, the Big Dipper asterism represents the hindquarters and tail of the constellation Ursa Major, the Great Bear. The Micmacs saw the three stars of the Big Dipper handle as hunters chasing the bear.

Watch the Big and Little Dippers circle around Polaris tonight! To locate Polaris, the North Star, just draw a line between the two outer stars in the bowl of the Big Dipper.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

from EarthSky https://ift.tt/34O5RPB

Mystery green blob appears and disappears in distant galaxy

This visible-light image of the Fireworks Galaxy (NGC 6946) comes from the Sloan Digital Sky Survey. It’s overlaid with data from NASA’s NuSTAR X-ray telescope (in blue and green). The mystery green blob is toward the middle of the galaxy, apparently coincident with one of its spiral arms. Image via NASA/JPL-Caltech.

The universe is full of mysteries, and now there’s a new one for astronomers to puzzle over. A space-based X-ray observatory – NASA’s NuSTAR – saw what astronomers described as a green blob in the galaxy known as NGC 6946, aka the Fireworks Galaxy. The blob appeared within a 10-day period and then disappeared again just as quickly.

A new peer-reviewed paper discussing the intriguing finding was published in The Astronomical Journal on August 9, 2019.

It’s really unusual for a celestial object to appear and then vanish again over such a short time period. The object was given the label ULX-4, as it was the fourth ULX – ultraluminous X-ray source – found in that galaxy.

NuSTAR’s primary mission at the time had been to study a supernova in the galaxy, which appears as a bright blue-green spot in the upper right of the image above. The mystery green blob is closer to the galaxy’s center in the image, apparently coincident with one of its spiral arms.

Hannah Penn Earnshaw is a postdoctoral scholar in physics at Caltech. She’s lead author of the new study about the mystery green blob. Image via Caltech.

The mystery object probably isn’t a supernova, however, because it was only detected in X-ray but not visible light images. It had first been seen by NuSTAR, and then later was found to have disappeared by NASA’s Chandra X-ray Observatory.

One of the main questions right now is how the object appeared and disappeared so quickly. According to Hannah Earnshaw, a postdoctoral researcher at Caltech:

Ten days is a really short amount of time for such a bright object to appear. Usually with NuSTAR, we observe more gradual changes over time, and we don’t often observe a source multiple times in quick succession. In this instance, we were fortunate to catch a source changing extremely quickly, which is very exciting.

So if the object isn’t a supernova, then what is it?

Artist’s concept of the NuSTAR spacecraft. Image via NASA/JPL-Caltech.

One possibility is that it is a black hole. According to that theory, the greenish light came from a black hole that was consuming another object, perhaps a star. We tend to think of black holes as “sucking in” material, but the immense gravity from the black hole could also rip the object apart, with the resulting debris going into orbit around the black hole. That debris can be heated to millions of degrees, emitting X-rays. So even though light can’t escape from inside a black hole, the light emitted by super-heated debris orbiting the black hole can easily be seen.

Usually, ULXs are long-lived, since black holes will feed for a long time on the stars they destroy. But if, say, a small star is destroyed more quickly, then that could explain short-term events like ULX-4.

ULX-4 could also possibly be a neutron star, an extremely dense object that forms when a star explodes, but isn’t massive enough to create a black hole. They can also have disks of debris orbiting them, creating slow-feeding ultraluminous X-ray sources. Material is channeled down to the surface in “columns” by powerful magnetic fields. But material can be blocked by those magnetic fields from reaching the surface if the neutron star is spinning too fast.

One possible explanation for ULX-4 is that it is a black hole. This image is the first black hole ever photographed, in the center of the galaxy M87. Image via Event Horizon Telescope/JPL-Caltech.

The only times you would then see the neutron star as a bright source of X-rays would be at the moment when the magnetic field barrier wavers a bit. This could explain the sudden appearance and disappearance of the light coming from ULX-4. According to Earnshaw:

It would kind of be like trying to jump onto a carousel that’s spinning at thousands of miles per hour. This result is a step towards understanding some of the rarer and more extreme cases in which matter accretes onto black holes or neutron stars.

Further observations will be needed to determine which of these theories – if either of them – is the right one. There may still turn out to be a different explanation altogether. Space is full of weird and mysterious phenomena, and “the case of the appearing and disappearing green blob” is certainly an odd one!

Another view of the beautiful Fireworks Galaxy. This one was posted as an Astronomy Picture of the Day on January 1, 2011. Image via Adam Block/Mt. Lemmon SkyCenter/U. Arizona/APOD.

Bottom line: A mysterious “green blob” of light appeared in the Fireworks Galaxy, and then just as quickly disappeared again.

Source: A Broadband Look at the Old and New ULXs of NGC 6946

Via Jet Propulsion Laboratory

from EarthSky https://ift.tt/2O6jAvc

This visible-light image of the Fireworks Galaxy (NGC 6946) comes from the Sloan Digital Sky Survey. It’s overlaid with data from NASA’s NuSTAR X-ray telescope (in blue and green). The mystery green blob is toward the middle of the galaxy, apparently coincident with one of its spiral arms. Image via NASA/JPL-Caltech.

The universe is full of mysteries, and now there’s a new one for astronomers to puzzle over. A space-based X-ray observatory – NASA’s NuSTAR – saw what astronomers described as a green blob in the galaxy known as NGC 6946, aka the Fireworks Galaxy. The blob appeared within a 10-day period and then disappeared again just as quickly.

A new peer-reviewed paper discussing the intriguing finding was published in The Astronomical Journal on August 9, 2019.

It’s really unusual for a celestial object to appear and then vanish again over such a short time period. The object was given the label ULX-4, as it was the fourth ULX – ultraluminous X-ray source – found in that galaxy.

NuSTAR’s primary mission at the time had been to study a supernova in the galaxy, which appears as a bright blue-green spot in the upper right of the image above. The mystery green blob is closer to the galaxy’s center in the image, apparently coincident with one of its spiral arms.

Hannah Penn Earnshaw is a postdoctoral scholar in physics at Caltech. She’s lead author of the new study about the mystery green blob. Image via Caltech.

The mystery object probably isn’t a supernova, however, because it was only detected in X-ray but not visible light images. It had first been seen by NuSTAR, and then later was found to have disappeared by NASA’s Chandra X-ray Observatory.

One of the main questions right now is how the object appeared and disappeared so quickly. According to Hannah Earnshaw, a postdoctoral researcher at Caltech:

Ten days is a really short amount of time for such a bright object to appear. Usually with NuSTAR, we observe more gradual changes over time, and we don’t often observe a source multiple times in quick succession. In this instance, we were fortunate to catch a source changing extremely quickly, which is very exciting.

So if the object isn’t a supernova, then what is it?

Artist’s concept of the NuSTAR spacecraft. Image via NASA/JPL-Caltech.

One possibility is that it is a black hole. According to that theory, the greenish light came from a black hole that was consuming another object, perhaps a star. We tend to think of black holes as “sucking in” material, but the immense gravity from the black hole could also rip the object apart, with the resulting debris going into orbit around the black hole. That debris can be heated to millions of degrees, emitting X-rays. So even though light can’t escape from inside a black hole, the light emitted by super-heated debris orbiting the black hole can easily be seen.

Usually, ULXs are long-lived, since black holes will feed for a long time on the stars they destroy. But if, say, a small star is destroyed more quickly, then that could explain short-term events like ULX-4.

ULX-4 could also possibly be a neutron star, an extremely dense object that forms when a star explodes, but isn’t massive enough to create a black hole. They can also have disks of debris orbiting them, creating slow-feeding ultraluminous X-ray sources. Material is channeled down to the surface in “columns” by powerful magnetic fields. But material can be blocked by those magnetic fields from reaching the surface if the neutron star is spinning too fast.

One possible explanation for ULX-4 is that it is a black hole. This image is the first black hole ever photographed, in the center of the galaxy M87. Image via Event Horizon Telescope/JPL-Caltech.

The only times you would then see the neutron star as a bright source of X-rays would be at the moment when the magnetic field barrier wavers a bit. This could explain the sudden appearance and disappearance of the light coming from ULX-4. According to Earnshaw:

It would kind of be like trying to jump onto a carousel that’s spinning at thousands of miles per hour. This result is a step towards understanding some of the rarer and more extreme cases in which matter accretes onto black holes or neutron stars.

Further observations will be needed to determine which of these theories – if either of them – is the right one. There may still turn out to be a different explanation altogether. Space is full of weird and mysterious phenomena, and “the case of the appearing and disappearing green blob” is certainly an odd one!

Another view of the beautiful Fireworks Galaxy. This one was posted as an Astronomy Picture of the Day on January 1, 2011. Image via Adam Block/Mt. Lemmon SkyCenter/U. Arizona/APOD.

Bottom line: A mysterious “green blob” of light appeared in the Fireworks Galaxy, and then just as quickly disappeared again.

Source: A Broadband Look at the Old and New ULXs of NGC 6946

Via Jet Propulsion Laboratory

from EarthSky https://ift.tt/2O6jAvc

'Trollbots' Swarm Twitter with Attacks on Climate Science Ahead of UN Summit

This is a re-post from Inside Climate News by Marianne Lavelle

CNN's seven-hour climate change town hall for presidential candidates was not a TV ratings bonanza, but it set off a marked surge of activity on Twitter aimed at ridiculing the Democrats and dismissing the science.

"Climate change" became the top two-word trending topic on Twitter for several hours after the event among the accounts being tracked by Bot Sentinel, a free platform designed to track what it considers untrustworthy or automated accounts. It was quite an unusual feat for the topic to beat out—even temporarily—the phrase that sits almost constantly atop the trending list for accounts on Bot Sentinel's watchlist: "President Trump."

Scientists, activists and politicians who are engaged in climate policy say they are being besieged by a surge of online attacks. It is difficult to divine whether the bursts of "climate change"-related Twitter activity are spontaneous or part of coordinated campaigns; some experts say that likely a small number of influencers are touching off postings by a far larger number of followers. But in a post-2016 world that is keenly aware of the role that social media played in the election of Donald Trump, the targets of climate attacks are concerned about the potential for online onslaughts to manipulate opinion and neutralize growing public support for climate action.

"I believe this is a concerted effort, likely by bad state actors and fossil fuel interests, to create disinformation, discord and division as we approach the all-important UN Summit and children's youth event later this month," said climate scientist Michael Mann of Pennsylvania State University, a frequent target of attacks.

Twitter did not immediately respond to a request for comment on the activity.

Tracking 'Trollbot' Attacks

Bot Sentinel has become a tool for those trying to fight the spread of disinformation on Twitter. The platform uses an algorithm to identify accounts it labels as "trollbots"—those that frequently retweet known propaganda accounts, exhibit repetitive behavior or violate Twitter's terms of service by harassing other users. Following CNN's climate forum on Sept. 4, there was an unusually high 700 mentions of climate change in a 24-hour period from the 100,000-some accounts Bot Sentinel is tracking as trollbots.

When a topic like "climate change" trends among the trollbots, it is likely there is some amount of coordination involved, said software developer Christopher Bouzy, founder of the year-old Bot Sentinel platform.

"What we are noticing is these phrases are more than likely being pushed by accounts that have an agenda," Bouzy said.

"It's fascinating to see this stuff happen in real time," he said. "Sometimes we can see literally five or 10 accounts able to manipulate a hashtag because they have so many people following them. It doesn't take that many accounts to get something going."

Following the CNN climate forum, for example, many accounts began sharing video clip montages of the event edited together by Trump's re-election campaign and by the far-right web outlet the Gateway Pundit to portray the candidates in the worst possible light.  

"Democrat #Socialists want to ban: - everything made from plastic - red meat - nuclear power...I don't think even Venezuelans have ever been this brainwashed!" commented @Condor_Law, an account rated "alarming" by Bot Sentinel—84 percent of its posts exhibit patterns that match the activity of trollbots (spreading information from sites known to be unreliable or violating Twitters terms of service and doing so repetitively.) "The Dems position is ban straws, portion our meat, take our guns, take our cars, abort on a massive scale for population control, and all so we can die from climate change in 11 years!!" another accounted rated "alarming," @JenniferKrist28, chimed in.

Mann, the climate scientist, found himself on the receiving end of some of this activity after he posted a Tweet thanking CNN for a "full evening of informed, detailed climate change conversation." "Climate change is a hoax," replied @fdnymt, another account identified as exhibiting trollbot behavior by Bot Sentinel.

Swedish teen climate activist Greta Thunberg, who traveled to the United States for the UN Summit, has been a frequent target of toxic online attacks. Soon after Thunberg started her two-week sailboat voyage across the Atlantic, British political donor and co-founder of the Leave.EU campaign Arron Banks tweeted, "freak yachting accidents do happen in August." Following the lead of figures like Banks, lesser-known Twitter handles have piled on.

Thunberg has brushed off the attacks: "When haters go after your looks and differences, it means they have nowhere left to go," she tweeted. "I have Aspergers and that means I'm sometimes a bit different from the norm. And - given the right circumstances- being different is a superpower."  U.S. climate change denier Steve Milloy, who served on Trump's transition team, responded to the teenager on Twitter, "I don't know about you... but I am not going communist because Greta the Climate Puppet believes she has 'superpowers.'"

In Canada, Politicians and an Election Targeted

Government policies on climate change also appear to be triggering toxic online activity. Early this week, Canada Environment Minister Catherine McKenna, who is implementing that nation's carbon tax policy, said that she has been assigned an additional security detail because of abuse she has received both online and in person.

And last week, a Canadian government agency issued a report concluding there was evidence of a campaign of coordinated, false social media postings around last April's election for premier of Alberta—a campaign in which climate policy was a key issue. The majority of the questionable postings were in support of the eventual winner, conservative Jason Kenney, who won the election while pledging to repeal the province's carbon tax, which he did in May, and to create a "war room" to combat the oil industry's opponents.

The government agency, Rapid Response Mechanism Canada, was created as part of the G7 nation's effort to respond to foreign influence in democratic elections. RRM Canada said there was no evidence of foreign actors involved in the questionable social media activity around the Alberta election. But, the agency said, "some national actors were disseminating material using tactics that were similar to those used by foreign actors."

Gerald Kutney, an Ottawa-based consultant and author of a 2014 book on climate politics, said it has become difficult to discern what is genuine discussion and what is coordinated attack messaging on Twitter around climate change.

"It's no longer social media, it's bot media," he said. "It's difficult to know the difference."

Twitter Deactivated a Way to Block 'Trollbots'

Kutney endured so many online attacks after he got into a debate on climate change last fall with the Dilbert cartoon creator and prominent Trump supporter Scott Adams that he found a way to call for online help. He launched a hashtag, #climatebrawl, to signal when someone is under attack by climate deniers on Twitter. That hashtag, too, has often been swarmed by climate deniers; he doesn't know if these are human-controlled or automated accounts.

Bouzy said he got the idea for Bot Sentinel after seeing the impact of social media on the 2016 election in the United States. It is designed to identify coordinated online messaging campaigns regardless of politics; Bouzy said the algorithm is indifferent to whether accounts lean left or right.

At one point, Bouzy said Bot Sentinel had a feature that allowed users to block trollbots from their Twitter feeds, but he said Twitter deactivated the import tool without warning, rendering the feature unusable.

Bot Sentinel still gives Twitter users a way to analyze the behavior of individual accounts and see which topics are sparking trollbot activity.

"There are coordinated campaigns being run every single day. It's pretty much open season on these platforms," Bouzy said. "We're just trying to give people a heads-up that this is happening—this is a narrative that's being pushed right now. You may want to be careful."

from Skeptical Science https://ift.tt/2LTAjz3

This is a re-post from Inside Climate News by Marianne Lavelle

CNN's seven-hour climate change town hall for presidential candidates was not a TV ratings bonanza, but it set off a marked surge of activity on Twitter aimed at ridiculing the Democrats and dismissing the science.

"Climate change" became the top two-word trending topic on Twitter for several hours after the event among the accounts being tracked by Bot Sentinel, a free platform designed to track what it considers untrustworthy or automated accounts. It was quite an unusual feat for the topic to beat out—even temporarily—the phrase that sits almost constantly atop the trending list for accounts on Bot Sentinel's watchlist: "President Trump."

Scientists, activists and politicians who are engaged in climate policy say they are being besieged by a surge of online attacks. It is difficult to divine whether the bursts of "climate change"-related Twitter activity are spontaneous or part of coordinated campaigns; some experts say that likely a small number of influencers are touching off postings by a far larger number of followers. But in a post-2016 world that is keenly aware of the role that social media played in the election of Donald Trump, the targets of climate attacks are concerned about the potential for online onslaughts to manipulate opinion and neutralize growing public support for climate action.

"I believe this is a concerted effort, likely by bad state actors and fossil fuel interests, to create disinformation, discord and division as we approach the all-important UN Summit and children's youth event later this month," said climate scientist Michael Mann of Pennsylvania State University, a frequent target of attacks.

Twitter did not immediately respond to a request for comment on the activity.

Tracking 'Trollbot' Attacks

Bot Sentinel has become a tool for those trying to fight the spread of disinformation on Twitter. The platform uses an algorithm to identify accounts it labels as "trollbots"—those that frequently retweet known propaganda accounts, exhibit repetitive behavior or violate Twitter's terms of service by harassing other users. Following CNN's climate forum on Sept. 4, there was an unusually high 700 mentions of climate change in a 24-hour period from the 100,000-some accounts Bot Sentinel is tracking as trollbots.

When a topic like "climate change" trends among the trollbots, it is likely there is some amount of coordination involved, said software developer Christopher Bouzy, founder of the year-old Bot Sentinel platform.

"What we are noticing is these phrases are more than likely being pushed by accounts that have an agenda," Bouzy said.

"It's fascinating to see this stuff happen in real time," he said. "Sometimes we can see literally five or 10 accounts able to manipulate a hashtag because they have so many people following them. It doesn't take that many accounts to get something going."

Following the CNN climate forum, for example, many accounts began sharing video clip montages of the event edited together by Trump's re-election campaign and by the far-right web outlet the Gateway Pundit to portray the candidates in the worst possible light.  

"Democrat #Socialists want to ban: - everything made from plastic - red meat - nuclear power...I don't think even Venezuelans have ever been this brainwashed!" commented @Condor_Law, an account rated "alarming" by Bot Sentinel—84 percent of its posts exhibit patterns that match the activity of trollbots (spreading information from sites known to be unreliable or violating Twitters terms of service and doing so repetitively.) "The Dems position is ban straws, portion our meat, take our guns, take our cars, abort on a massive scale for population control, and all so we can die from climate change in 11 years!!" another accounted rated "alarming," @JenniferKrist28, chimed in.

Mann, the climate scientist, found himself on the receiving end of some of this activity after he posted a Tweet thanking CNN for a "full evening of informed, detailed climate change conversation." "Climate change is a hoax," replied @fdnymt, another account identified as exhibiting trollbot behavior by Bot Sentinel.

Swedish teen climate activist Greta Thunberg, who traveled to the United States for the UN Summit, has been a frequent target of toxic online attacks. Soon after Thunberg started her two-week sailboat voyage across the Atlantic, British political donor and co-founder of the Leave.EU campaign Arron Banks tweeted, "freak yachting accidents do happen in August." Following the lead of figures like Banks, lesser-known Twitter handles have piled on.

Thunberg has brushed off the attacks: "When haters go after your looks and differences, it means they have nowhere left to go," she tweeted. "I have Aspergers and that means I'm sometimes a bit different from the norm. And - given the right circumstances- being different is a superpower."  U.S. climate change denier Steve Milloy, who served on Trump's transition team, responded to the teenager on Twitter, "I don't know about you... but I am not going communist because Greta the Climate Puppet believes she has 'superpowers.'"

In Canada, Politicians and an Election Targeted

Government policies on climate change also appear to be triggering toxic online activity. Early this week, Canada Environment Minister Catherine McKenna, who is implementing that nation's carbon tax policy, said that she has been assigned an additional security detail because of abuse she has received both online and in person.

And last week, a Canadian government agency issued a report concluding there was evidence of a campaign of coordinated, false social media postings around last April's election for premier of Alberta—a campaign in which climate policy was a key issue. The majority of the questionable postings were in support of the eventual winner, conservative Jason Kenney, who won the election while pledging to repeal the province's carbon tax, which he did in May, and to create a "war room" to combat the oil industry's opponents.

The government agency, Rapid Response Mechanism Canada, was created as part of the G7 nation's effort to respond to foreign influence in democratic elections. RRM Canada said there was no evidence of foreign actors involved in the questionable social media activity around the Alberta election. But, the agency said, "some national actors were disseminating material using tactics that were similar to those used by foreign actors."

Gerald Kutney, an Ottawa-based consultant and author of a 2014 book on climate politics, said it has become difficult to discern what is genuine discussion and what is coordinated attack messaging on Twitter around climate change.

"It's no longer social media, it's bot media," he said. "It's difficult to know the difference."

Twitter Deactivated a Way to Block 'Trollbots'

Kutney endured so many online attacks after he got into a debate on climate change last fall with the Dilbert cartoon creator and prominent Trump supporter Scott Adams that he found a way to call for online help. He launched a hashtag, #climatebrawl, to signal when someone is under attack by climate deniers on Twitter. That hashtag, too, has often been swarmed by climate deniers; he doesn't know if these are human-controlled or automated accounts.

Bouzy said he got the idea for Bot Sentinel after seeing the impact of social media on the 2016 election in the United States. It is designed to identify coordinated online messaging campaigns regardless of politics; Bouzy said the algorithm is indifferent to whether accounts lean left or right.

At one point, Bouzy said Bot Sentinel had a feature that allowed users to block trollbots from their Twitter feeds, but he said Twitter deactivated the import tool without warning, rendering the feature unusable.

Bot Sentinel still gives Twitter users a way to analyze the behavior of individual accounts and see which topics are sparking trollbot activity.

"There are coordinated campaigns being run every single day. It's pretty much open season on these platforms," Bouzy said. "We're just trying to give people a heads-up that this is happening—this is a narrative that's being pushed right now. You may want to be careful."

from Skeptical Science https://ift.tt/2LTAjz3