A team of mainly Dutch astronomers said on November 9, 2017 that it has observed moving shadows on a dust disk around a young star designated HD135344B. The star is 450 light-years away. It’s in a formation stage and shows striking spiral arms. On multiple days, the astronomers captured an image of this star and its dust disk. They used the SPHERE instrument on the Very Large Telescope in Chile, which can block the image of a central star in order to capture orbiting exoplanets or the details of dust disks like this one, with the goal of learning more about star formation. These astronomers believe that processes in the inner disk cast their shadows at the outer disk.
The discovery builds on an earlier publication in which the researchers made one image of the disk. By making multiple images, the astronomers clearly saw variations in the shadows. As a result, they could study the shadows in more detail …
The astronomers saw subtle variations of brightness in the outer dust disk. They presume this is because the gas and dust in the inner disk quickly turn around the star. The astronomers do not know yet which process causes the quick turning of the dust.
Astronomer Tomas Stolker is the first author of the paper about the shadows. He said the turning of the dust may be due to:
… winds, or swirls or clashes of pebbles.
The astronomers expect 1 or more large exoplanets – Jupiter-like worlds – to emerge from this dust disk eventually. Read more about this research from Astronomie.nl.
View larger. | Dust disk around the star HD 135344B. The star itself is removed from the picture. Image via Tomas Stolker/ astronomie.nl.
Bottom line: For several days, astronomers imaged the young star HD 135344B and its dust disk. They saw moving shadows on the disk, which they believe is caused by a turning of the gas and dust in the star’s inner disk. Hence we learn more about the process by which stars and planets form.
from EarthSky http://ift.tt/2yxLjdE
A team of mainly Dutch astronomers said on November 9, 2017 that it has observed moving shadows on a dust disk around a young star designated HD135344B. The star is 450 light-years away. It’s in a formation stage and shows striking spiral arms. On multiple days, the astronomers captured an image of this star and its dust disk. They used the SPHERE instrument on the Very Large Telescope in Chile, which can block the image of a central star in order to capture orbiting exoplanets or the details of dust disks like this one, with the goal of learning more about star formation. These astronomers believe that processes in the inner disk cast their shadows at the outer disk.
The discovery builds on an earlier publication in which the researchers made one image of the disk. By making multiple images, the astronomers clearly saw variations in the shadows. As a result, they could study the shadows in more detail …
The astronomers saw subtle variations of brightness in the outer dust disk. They presume this is because the gas and dust in the inner disk quickly turn around the star. The astronomers do not know yet which process causes the quick turning of the dust.
Astronomer Tomas Stolker is the first author of the paper about the shadows. He said the turning of the dust may be due to:
… winds, or swirls or clashes of pebbles.
The astronomers expect 1 or more large exoplanets – Jupiter-like worlds – to emerge from this dust disk eventually. Read more about this research from Astronomie.nl.
View larger. | Dust disk around the star HD 135344B. The star itself is removed from the picture. Image via Tomas Stolker/ astronomie.nl.
Bottom line: For several days, astronomers imaged the young star HD 135344B and its dust disk. They saw moving shadows on the disk, which they believe is caused by a turning of the gas and dust in the star’s inner disk. Hence we learn more about the process by which stars and planets form.
Jupiter and Venus have their spectacular conjunction Monday morning – November 13, 2017 – but keep watching for these planets after that as well! The waning crescent moon is about to join the show, sliding first past Mars on November 14 and 15, and then continuing to move downward – closer to the sunrise each morning – to pass Venus and Jupiter before this week ends.
First … the moon and Mars on Tuesday and Wednesday mornings. The planet Mars is much fainter than Jupiter or Venus, but the moon can help you find it. Also, notice the bright star Arcturus on our chart. From the Southern Hemisphere, Arcturus will be difficult or impossible to see. But Northern Hemisphere observers will see it. Its color is orangish … not very different from Mars, but more twinkly.
If you want to see Mars, remember, it’s faint and far across the solar system now. Be sure to look for it before dawn, or about one and one-half to two hours before sunrise. This rather faint world will quickly fade from view once the predawn darkness gives way to morning twilight. In fact, since dazzling planets Jupiter and Venus won’t climb up over your eastern horizon until shortly before before sunrise, there will be a very narrow window of time – or maybe no time at all – during which you can see Venus, Jupiter and Mars all at the same time. In other words … the light of the coming dawn will cause Mars to fade from view.
From the Southern Hemisphere, Jupiter and Venus rise even closer to the time of sunrise than they do at northerly latitudes.
Take a good look at Mars before dawn these next few mornings, as it casts its meek light in the predawn sky. Earth in its smaller, faster orbit around the sun is slowly but surely catching up with Mars, the fourth planet outward from the sun. Earth will pass between the sun and Mars – and so reach what astronomers call opposition – on July 27, 2018. Then, Earth will be about six times closer to Mars than it is now. Mars, in turn, will shine nearly 40 times more brilliantly in our sky than it does now.
In fact, 2018 will be a spectacular year for Mars! The planet has a 15-year cycle of varying brightnesses at opposition. The peak of that cycle will come again in 2018.
By mid-February 2018, Mars will have doubled in brilliance, shining on par with the 1st-magnitude stars Spica and Antares. Moreover, Mars will be coupling up with the star Antares on the sky’s dome in mid-February 2018, giving sky watchers an opportunity to view the red planet Mars and red star Antares shining next to each other on the great dome of sky.
Their similarity in brightness and color will let you learn firsthand why this star was given the name Antares, which means like Mars.
Bottom line: Use the moon to find the planet Mars on the mornings of November 14 and 15, and then watch for Mars to brighten in the morning sky for many months to come.
from EarthSky http://ift.tt/2hskDEN
Jupiter and Venus have their spectacular conjunction Monday morning – November 13, 2017 – but keep watching for these planets after that as well! The waning crescent moon is about to join the show, sliding first past Mars on November 14 and 15, and then continuing to move downward – closer to the sunrise each morning – to pass Venus and Jupiter before this week ends.
First … the moon and Mars on Tuesday and Wednesday mornings. The planet Mars is much fainter than Jupiter or Venus, but the moon can help you find it. Also, notice the bright star Arcturus on our chart. From the Southern Hemisphere, Arcturus will be difficult or impossible to see. But Northern Hemisphere observers will see it. Its color is orangish … not very different from Mars, but more twinkly.
If you want to see Mars, remember, it’s faint and far across the solar system now. Be sure to look for it before dawn, or about one and one-half to two hours before sunrise. This rather faint world will quickly fade from view once the predawn darkness gives way to morning twilight. In fact, since dazzling planets Jupiter and Venus won’t climb up over your eastern horizon until shortly before before sunrise, there will be a very narrow window of time – or maybe no time at all – during which you can see Venus, Jupiter and Mars all at the same time. In other words … the light of the coming dawn will cause Mars to fade from view.
From the Southern Hemisphere, Jupiter and Venus rise even closer to the time of sunrise than they do at northerly latitudes.
Take a good look at Mars before dawn these next few mornings, as it casts its meek light in the predawn sky. Earth in its smaller, faster orbit around the sun is slowly but surely catching up with Mars, the fourth planet outward from the sun. Earth will pass between the sun and Mars – and so reach what astronomers call opposition – on July 27, 2018. Then, Earth will be about six times closer to Mars than it is now. Mars, in turn, will shine nearly 40 times more brilliantly in our sky than it does now.
In fact, 2018 will be a spectacular year for Mars! The planet has a 15-year cycle of varying brightnesses at opposition. The peak of that cycle will come again in 2018.
By mid-February 2018, Mars will have doubled in brilliance, shining on par with the 1st-magnitude stars Spica and Antares. Moreover, Mars will be coupling up with the star Antares on the sky’s dome in mid-February 2018, giving sky watchers an opportunity to view the red planet Mars and red star Antares shining next to each other on the great dome of sky.
Their similarity in brightness and color will let you learn firsthand why this star was given the name Antares, which means like Mars.
Bottom line: Use the moon to find the planet Mars on the mornings of November 14 and 15, and then watch for Mars to brighten in the morning sky for many months to come.
An artist’s impression of Mesozoic animals. It shows Dilophosaurus (dinosaur) at the back, Kayentatherium (Mesozoic mammal) in the center, and Kayentachelys (turtle) at the front. Image via Mark Witton.
According to a long-standing theory, the common ancestor to all today’s mammals was nocturnal – active only at night. When did mammals begin to be active during the daytime? A new study, published November 6, 2017 in Nature Ecology & Evolution, suggests that mammals began switching to daylight activities after the dinosaurs were wiped out, some 66 million years ago.
The research team analyzed data on 2,415 species of mammals still alive today. They computer algorithms to reconstruct the likely activity patterns of these ancient ancestors, which lived millions of years ago. The results of the study indicate that mammals switched to daytime activity shortly after the dinosaurs disappeared.
But this change didn’t happen overnight, said the researchers.
Instead, it involved an intermediate stage lasting millions of years of mixed day-and-night activities. This stage coincided with the events that decimated the dinosaurs.
Roi Maor is a PhD student at Tel Aviv University and lead author of the study. Maor said in a statement:
We were very surprised to find such close correlation between the disappearance of dinosaurs and the beginning of daytime activity in mammals, but we found the same result unanimously using several alternative analyses.
The team found that the ancestors of simian primates – such as gorillas, gibbons and tamarins – were among the first to give up nocturnal activity altogether. This discovery fits well, the researchers said, with the fact that these primates are the only mammals that have evolved adaptations to seeing well in daylight.
It’s very difficult to relate behavior changes in mammals that lived so long ago to ecological conditions at the time, so we can’t say that the dinosaurs dying out caused mammals to start being active in the daytime. However, we see a clear correlation in our findings.
Bottom line: According to a new study, mammals started being active in the daytime after dinosaurs were wiped out about 66 million years ago, coinciding with the demise of the dinosaurs.
An artist’s impression of Mesozoic animals. It shows Dilophosaurus (dinosaur) at the back, Kayentatherium (Mesozoic mammal) in the center, and Kayentachelys (turtle) at the front. Image via Mark Witton.
According to a long-standing theory, the common ancestor to all today’s mammals was nocturnal – active only at night. When did mammals begin to be active during the daytime? A new study, published November 6, 2017 in Nature Ecology & Evolution, suggests that mammals began switching to daylight activities after the dinosaurs were wiped out, some 66 million years ago.
The research team analyzed data on 2,415 species of mammals still alive today. They computer algorithms to reconstruct the likely activity patterns of these ancient ancestors, which lived millions of years ago. The results of the study indicate that mammals switched to daytime activity shortly after the dinosaurs disappeared.
But this change didn’t happen overnight, said the researchers.
Instead, it involved an intermediate stage lasting millions of years of mixed day-and-night activities. This stage coincided with the events that decimated the dinosaurs.
Roi Maor is a PhD student at Tel Aviv University and lead author of the study. Maor said in a statement:
We were very surprised to find such close correlation between the disappearance of dinosaurs and the beginning of daytime activity in mammals, but we found the same result unanimously using several alternative analyses.
The team found that the ancestors of simian primates – such as gorillas, gibbons and tamarins – were among the first to give up nocturnal activity altogether. This discovery fits well, the researchers said, with the fact that these primates are the only mammals that have evolved adaptations to seeing well in daylight.
It’s very difficult to relate behavior changes in mammals that lived so long ago to ecological conditions at the time, so we can’t say that the dinosaurs dying out caused mammals to start being active in the daytime. However, we see a clear correlation in our findings.
Bottom line: According to a new study, mammals started being active in the daytime after dinosaurs were wiped out about 66 million years ago, coinciding with the demise of the dinosaurs.
Before the November 13, 2017 sunrise, watch for the super-close pairing of the sky’s two brightest planets, Venus and Jupiter. They’ll be in the sunrise direction, low in the eastern sky at dawn. Depending on where you live worldwide, Venus and Jupiter will come closest together on the sky’s dome on the morning of November 13 or 14. They’ll be snuggling plenty close on both dates, close enough to fit easily inside the same binocular field (or possibly even a single field of view in a low-powered telescope).
At their closest, Venus and Jupiter will be 0.3o apart. That’s less than the apparent diameter of the moon (0.5o).
What’s more, you won’t want to miss the waning crescent moon swinging by these worlds later this week. See the chart below.
Watch as the waning crescent moon swings by 3 morning planets and a bright star in the November 2017 morning sky.
The Northern Hemisphere has the big advantage for spotting the dazzling twosome at morning dawn. That’s because the ecliptic – marking the path of the sun, moon and planets in our sky – makes a relatively perpendicular angle with respect to the eastern horizon before dawn now, as seen from the northern half of Earth’s globe. The steep angle of the ecliptic places the planets more above the sunrise than to one side of it, making them easier to see.
Venus and Jupiter rise sooner before the sun at more northerly latitudes. For instance, at mid-northern latitudes (like those in the United States or Europe), they rise better than an hour before the sun. At the equator (0o latitude), these two worlds come up about 50 minutes before sunrise; and at temperate latitudes in the Southern Hemisphere, Venus and Jupiter rise 40 minutes (or less) before sunrise.
Click here for an almanac to know the precise time that Venus and Jupiter rise into your sky.
No matter where on Earth you live, you’ll want to find an unobstructed horizon in the direction of sunrise to maximize your chances of spotting Venus and Jupiter near the horizon. Better yet, stand atop a hill or balcony, to peek farther over the horizon than you would from level ground.
After the morning of November 13, you’ll see Jupiter climb higher up in the morning sky day by day. Meanwhile, Venus will plunge sunward day by day, to be lost in the sunrise glare by year’s end.
Bottom line: Watch for the super-close pairing of the sky’s 2 brightest planets, Venus and Jupiter, around November 13, 2017. They’ll be in the sunrise direction, low in the east at dawn.
from EarthSky http://ift.tt/2fHnKea
Before the November 13, 2017 sunrise, watch for the super-close pairing of the sky’s two brightest planets, Venus and Jupiter. They’ll be in the sunrise direction, low in the eastern sky at dawn. Depending on where you live worldwide, Venus and Jupiter will come closest together on the sky’s dome on the morning of November 13 or 14. They’ll be snuggling plenty close on both dates, close enough to fit easily inside the same binocular field (or possibly even a single field of view in a low-powered telescope).
At their closest, Venus and Jupiter will be 0.3o apart. That’s less than the apparent diameter of the moon (0.5o).
What’s more, you won’t want to miss the waning crescent moon swinging by these worlds later this week. See the chart below.
Watch as the waning crescent moon swings by 3 morning planets and a bright star in the November 2017 morning sky.
The Northern Hemisphere has the big advantage for spotting the dazzling twosome at morning dawn. That’s because the ecliptic – marking the path of the sun, moon and planets in our sky – makes a relatively perpendicular angle with respect to the eastern horizon before dawn now, as seen from the northern half of Earth’s globe. The steep angle of the ecliptic places the planets more above the sunrise than to one side of it, making them easier to see.
Venus and Jupiter rise sooner before the sun at more northerly latitudes. For instance, at mid-northern latitudes (like those in the United States or Europe), they rise better than an hour before the sun. At the equator (0o latitude), these two worlds come up about 50 minutes before sunrise; and at temperate latitudes in the Southern Hemisphere, Venus and Jupiter rise 40 minutes (or less) before sunrise.
Click here for an almanac to know the precise time that Venus and Jupiter rise into your sky.
No matter where on Earth you live, you’ll want to find an unobstructed horizon in the direction of sunrise to maximize your chances of spotting Venus and Jupiter near the horizon. Better yet, stand atop a hill or balcony, to peek farther over the horizon than you would from level ground.
After the morning of November 13, you’ll see Jupiter climb higher up in the morning sky day by day. Meanwhile, Venus will plunge sunward day by day, to be lost in the sunrise glare by year’s end.
Bottom line: Watch for the super-close pairing of the sky’s 2 brightest planets, Venus and Jupiter, around November 13, 2017. They’ll be in the sunrise direction, low in the east at dawn.
Mikkel Valentin Hansen in Denmark caught this very bright meteor on November 8, 2017 and wrote:
I got my first set of aurora-shots, amazing experience. After it had died down, I saw a small meteor in my peripheral view. I then kindly and quietly asked our dear Universe, if maybe I could get a bit more aurora, or a meteor. I kept shooting until my remote died, changed the batteries in it and in my camera, and then changed the interval from 5 seconds to 1 second. Then, 20-30 seconds later, this giant came flying straight down right in front of me. I could do nothing but laugh out loud …
I started doing astrophotography a year ago, almost exactly, and this was the best anniversary-gift anyone could ask for.
Thank you, Mikkel!
from EarthSky http://ift.tt/2Aw9VUR
Photo by Mikkel Valentin Hansen.
Mikkel Valentin Hansen in Denmark caught this very bright meteor on November 8, 2017 and wrote:
I got my first set of aurora-shots, amazing experience. After it had died down, I saw a small meteor in my peripheral view. I then kindly and quietly asked our dear Universe, if maybe I could get a bit more aurora, or a meteor. I kept shooting until my remote died, changed the batteries in it and in my camera, and then changed the interval from 5 seconds to 1 second. Then, 20-30 seconds later, this giant came flying straight down right in front of me. I could do nothing but laugh out loud …
I started doing astrophotography a year ago, almost exactly, and this was the best anniversary-gift anyone could ask for.
A chronological listing of news articles posted on the Skeptical Science Facebook page during the past week.
Editor's Pick
Conservatives probably can’t be persuaded on climate change. So now what?
One more round of “messaging” won’t do it.
When it comes to climate change, US conservatives inhabit a unique position, as part of the only major political party in the democratic world to reject the legitimacy of climate science and any domestic policy or international agreement meant to address it. Instead, the GOP is working actively to increase production and consumption of fossil fuels and to slow the transition to renewable energy.
How can conservatives be moved on climate change?
I recently heard a podcast that helped me order my thoughts on this perennial debate. It was Political Research Digest, a weekly 15-minute research round-up hosted by Michigan State University political scientist Matt Grossman for the Niskanen Center. (Grossman is the author of Asymmetric Politics, a crucial text for understanding American political parties. The podcast is nerdy and good.)
In the third episode, Grossman takes a look at some recent literature on climate change opinion and how, if at all, it can be shifted among conservatives.
It begins well, with an excellent lay of the land. But the discussion of how to move forward goes off course, in a very familiar way. It stops short of contemplating the uncomfortable but increasingly likely possibility that persuading conservatives on this subject has become impossible, and what that might mean for those concerned about the looming dangers of climate change.
Let’s start with a look a few basic facts about public opinion on climate.
A chronological listing of news articles posted on the Skeptical Science Facebook page during the past week.
Editor's Pick
Conservatives probably can’t be persuaded on climate change. So now what?
One more round of “messaging” won’t do it.
When it comes to climate change, US conservatives inhabit a unique position, as part of the only major political party in the democratic world to reject the legitimacy of climate science and any domestic policy or international agreement meant to address it. Instead, the GOP is working actively to increase production and consumption of fossil fuels and to slow the transition to renewable energy.
How can conservatives be moved on climate change?
I recently heard a podcast that helped me order my thoughts on this perennial debate. It was Political Research Digest, a weekly 15-minute research round-up hosted by Michigan State University political scientist Matt Grossman for the Niskanen Center. (Grossman is the author of Asymmetric Politics, a crucial text for understanding American political parties. The podcast is nerdy and good.)
In the third episode, Grossman takes a look at some recent literature on climate change opinion and how, if at all, it can be shifted among conservatives.
It begins well, with an excellent lay of the land. But the discussion of how to move forward goes off course, in a very familiar way. It stops short of contemplating the uncomfortable but increasingly likely possibility that persuading conservatives on this subject has become impossible, and what that might mean for those concerned about the looming dangers of climate change.
Let’s start with a look a few basic facts about public opinion on climate.
Mosaic image of Saturn’s moon Enceladus – a moon with active geysers – via the Cassini spacecraft in 2009. Enceladus is only about 300 miles (500 km) across. It has an icy crust. Cassini data has suggest a saltwater lake or ocean beneath Enceladus’ ice. Could there be organisms living in that water? Image via NASA/ JPL/ Space Science Institute.
There was exciting news last week about Saturn’s fascinating moon Enceladus, a geologically active world that sprays water-ice particles, water vapor and organic compounds from fissures on its surface. On November 6, 2017, European and U.S. researchers announced results from a new modeling study, which might solve a decade-old puzzle about what keeps this little outer solar system moon active, as opposed to just freezing solid. The study showed that – if this moon has a highly porous core – heat from friction could power its hydrothermal activity for billions of years. Then on November 9 – during the New Space Age conference at Seattle’s Museum of Flight – Russian billionaire Yuri Milner described a vision to send the first privately funded interplanetary space mission to look for life at Enceladus.
Enceladus. For decades prior to the Cassini mission, scientists wondered why this was the brightest world in our solar system. Cassini found that the fresh coating on this moon’s surface originates from its geysers, which are connected to subsurface saltwater liquid. Image via NASA.
Russian billionaire Yuri Milner asked at the New Space Age conference on November 9: “Can we design a low-cost, privately funded mission to Enceladus which can be launched relatively soon?” Image via Rusnanotekh.com.
New mission? Yuri Milner is known for his financial support of the search for life beyond Earth, via Breakthrough Listen (a search using radio telescopes) and Breakthrough Starshot (a plan to send swarms of nano-spacecraft through the star system next door, Alpha Centauri).
…is a plan to bring the search for life beyond Earth closer to home. In the past, astrobiologists have speculated that microbial life could lurk far below the surface of Mars, or beneath a miles-thick layer of ice on Europa, one of Jupiter’s moons.
But, Milner said at the conference:
…the most promising recent candidate is Enceladus, one of the moons of Saturn.
As reported by Boyle, Milner said at the conference that he and others – including Carolyn Porco (on Twitter @CarolynPorco), who headed NASA’s imaging team for Cassini mission – formed “a little workshop” around the idea of a private space mission to Enceladus. Milner asked:
Can we design a low-cost, privately funded mission to Enceladus which can be launched relatively soon, and that can look more thoroughly at [the plumes of water-ice particles, water vapor and organic compounds spewing from Enceladus], to try to see what’s going on there?
Milner told GeekWire that he’s unsure of a timeframe for a private mission, but hopefully it could happen sooner than missions being considered by NASA or ESA, including ELF, ELSAH and E2T.
He indicated to Geekwire he is considering funding a feasibility study for a private mission to Enceladus.
This graphic illustrates how water might be heated via friction inside Saturn’s moon Enceladus, to sustain the moon’s geologic activity. Read a description of what’s happening in this image, via ESA.
New insights. The new study about Enceladus’ interior uses data from the Cassini spacecraft – whose mission to Saturn lasted from 2004 to September, 2017 – and is based on computer modeling. The study was published a couple of days before the New Space Age conference, on November 6, in the peer-reviewed journal Nature Astronomy. The researchers said in a statement that their study helps resolve a question they’ve grappled with for a decade, since Cassini discovered active geysers on Enceladus.
That is, where does the energy to power the extraordinary geologic activity on Enceladus come from?
Researchers believe that the temperature inside Enceladus – a tiny world, only 300 miles (500 km) across, in the cold outer solar system – must be at least 194 degrees Fahrenheit (90 degrees Celsius). But what keeps the interior of the moon so warm?
The amount of energy required to produce these temperatures is more than scientists think could be provided by decay of radioactive elements in the interior. Gaël Choblet of the University of Nantes in France, who led the new study, said:
Where Enceladus gets the sustained power to remain active has always been a bit of a mystery, but we’ve now considered in greater detail how the structure and composition of the moon’s rocky core could play a key role in generating the necessary energy.
Choblet and co-authors found that a loose, rocky core with 20 to 30 percent empty space would do the trick. Their simulations show that as Enceladus orbits Saturn, rocks in the porous core flex and rub together, generating heat. The loose interior also allows water from the ocean to percolate deep down, where it heats up, then rises, interacting chemically with the rocks. The models show this activity should be at a maximum at the moon’s poles. Plumes of the warm, mineral-laden water gush from the seafloor and travel upward, thinning the moon’s ice shell from beneath to only half a mile to 3 miles (1 to 5 km) at the south pole. (The average global thickness of the ice is thought to be about 12 to 16 miles, or 20 to 25 km.) And this same water is then expelled into space through fractures in the ice.
NASA’s Cassini Project Scientist Linda Spilker at the agency’s Jet Propulsion Laboratory in Pasadena, California commented:
This powerful research makes use of newer details — namely that the ocean is global and has hydrothermal activity — that we just didn’t have until the past couple of years. It’s an insight that the mission needed time to build, one discovery upon another.
Cassini ended its journey with a dramatic plunge into Saturn’s atmosphere this past September 15. Although space researchers will be analyzing its data for years to come, it’s clear they’re already itching to go back to Saturn!
The video below provides a brief overview of Enceladus and includes information from Cassini’s final flyby of the moon:
Cassini spacecraft image from 2010 of Saturn’s moon Enceladus. The moon is backlit, with its dark outline crowned by glowing jets, or geysers, from the south polar region. The jets emanate from the fissures known to scientists as tiger stripes. Image via NASA/JPL/SSI.
Bottom line: A study suggests Enceladus’ geologic activity can be maintained over billions of years if the moon’s interior is porous. In Seattle, space visionaries including Yuri Milner discussed a return to Saturn and its moon Enceladus via a private space mission.
from EarthSky http://ift.tt/2ABZqQK
Mosaic image of Saturn’s moon Enceladus – a moon with active geysers – via the Cassini spacecraft in 2009. Enceladus is only about 300 miles (500 km) across. It has an icy crust. Cassini data has suggest a saltwater lake or ocean beneath Enceladus’ ice. Could there be organisms living in that water? Image via NASA/ JPL/ Space Science Institute.
There was exciting news last week about Saturn’s fascinating moon Enceladus, a geologically active world that sprays water-ice particles, water vapor and organic compounds from fissures on its surface. On November 6, 2017, European and U.S. researchers announced results from a new modeling study, which might solve a decade-old puzzle about what keeps this little outer solar system moon active, as opposed to just freezing solid. The study showed that – if this moon has a highly porous core – heat from friction could power its hydrothermal activity for billions of years. Then on November 9 – during the New Space Age conference at Seattle’s Museum of Flight – Russian billionaire Yuri Milner described a vision to send the first privately funded interplanetary space mission to look for life at Enceladus.
Enceladus. For decades prior to the Cassini mission, scientists wondered why this was the brightest world in our solar system. Cassini found that the fresh coating on this moon’s surface originates from its geysers, which are connected to subsurface saltwater liquid. Image via NASA.
Russian billionaire Yuri Milner asked at the New Space Age conference on November 9: “Can we design a low-cost, privately funded mission to Enceladus which can be launched relatively soon?” Image via Rusnanotekh.com.
New mission? Yuri Milner is known for his financial support of the search for life beyond Earth, via Breakthrough Listen (a search using radio telescopes) and Breakthrough Starshot (a plan to send swarms of nano-spacecraft through the star system next door, Alpha Centauri).
…is a plan to bring the search for life beyond Earth closer to home. In the past, astrobiologists have speculated that microbial life could lurk far below the surface of Mars, or beneath a miles-thick layer of ice on Europa, one of Jupiter’s moons.
But, Milner said at the conference:
…the most promising recent candidate is Enceladus, one of the moons of Saturn.
As reported by Boyle, Milner said at the conference that he and others – including Carolyn Porco (on Twitter @CarolynPorco), who headed NASA’s imaging team for Cassini mission – formed “a little workshop” around the idea of a private space mission to Enceladus. Milner asked:
Can we design a low-cost, privately funded mission to Enceladus which can be launched relatively soon, and that can look more thoroughly at [the plumes of water-ice particles, water vapor and organic compounds spewing from Enceladus], to try to see what’s going on there?
Milner told GeekWire that he’s unsure of a timeframe for a private mission, but hopefully it could happen sooner than missions being considered by NASA or ESA, including ELF, ELSAH and E2T.
He indicated to Geekwire he is considering funding a feasibility study for a private mission to Enceladus.
This graphic illustrates how water might be heated via friction inside Saturn’s moon Enceladus, to sustain the moon’s geologic activity. Read a description of what’s happening in this image, via ESA.
New insights. The new study about Enceladus’ interior uses data from the Cassini spacecraft – whose mission to Saturn lasted from 2004 to September, 2017 – and is based on computer modeling. The study was published a couple of days before the New Space Age conference, on November 6, in the peer-reviewed journal Nature Astronomy. The researchers said in a statement that their study helps resolve a question they’ve grappled with for a decade, since Cassini discovered active geysers on Enceladus.
That is, where does the energy to power the extraordinary geologic activity on Enceladus come from?
Researchers believe that the temperature inside Enceladus – a tiny world, only 300 miles (500 km) across, in the cold outer solar system – must be at least 194 degrees Fahrenheit (90 degrees Celsius). But what keeps the interior of the moon so warm?
The amount of energy required to produce these temperatures is more than scientists think could be provided by decay of radioactive elements in the interior. Gaël Choblet of the University of Nantes in France, who led the new study, said:
Where Enceladus gets the sustained power to remain active has always been a bit of a mystery, but we’ve now considered in greater detail how the structure and composition of the moon’s rocky core could play a key role in generating the necessary energy.
Choblet and co-authors found that a loose, rocky core with 20 to 30 percent empty space would do the trick. Their simulations show that as Enceladus orbits Saturn, rocks in the porous core flex and rub together, generating heat. The loose interior also allows water from the ocean to percolate deep down, where it heats up, then rises, interacting chemically with the rocks. The models show this activity should be at a maximum at the moon’s poles. Plumes of the warm, mineral-laden water gush from the seafloor and travel upward, thinning the moon’s ice shell from beneath to only half a mile to 3 miles (1 to 5 km) at the south pole. (The average global thickness of the ice is thought to be about 12 to 16 miles, or 20 to 25 km.) And this same water is then expelled into space through fractures in the ice.
NASA’s Cassini Project Scientist Linda Spilker at the agency’s Jet Propulsion Laboratory in Pasadena, California commented:
This powerful research makes use of newer details — namely that the ocean is global and has hydrothermal activity — that we just didn’t have until the past couple of years. It’s an insight that the mission needed time to build, one discovery upon another.
Cassini ended its journey with a dramatic plunge into Saturn’s atmosphere this past September 15. Although space researchers will be analyzing its data for years to come, it’s clear they’re already itching to go back to Saturn!
The video below provides a brief overview of Enceladus and includes information from Cassini’s final flyby of the moon:
Cassini spacecraft image from 2010 of Saturn’s moon Enceladus. The moon is backlit, with its dark outline crowned by glowing jets, or geysers, from the south polar region. The jets emanate from the fissures known to scientists as tiger stripes. Image via NASA/JPL/SSI.
Bottom line: A study suggests Enceladus’ geologic activity can be maintained over billions of years if the moon’s interior is porous. In Seattle, space visionaries including Yuri Milner discussed a return to Saturn and its moon Enceladus via a private space mission.
