Is Venus’ Rotation Slowing Down?

Venus Express in orbit since 2006 around our nearest planetary neighbor. Credits: ESA

New measurements from ESA’s Venus Express spacecraft shows that Venus’ rotation rate is about 6.5 minutes slower than previous measurements taken 16 years ago by the Magellan spacecraft. Using infrared instruments to peer through the planet’s dense atmosphere, Venus Express found surface features weren’t where the scientists expected them to be.

“When the two maps did not align, I first thought there was a mistake in my calculations as Magellan measured the value very accurately, but we have checked every possible error we could think of,” said Nils Müller, a planetary scientist at the DLR German Aerospace Centre, lead author of a research paper investigating the rotation.

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Using the VIRTIS infrared instrument, scientists discovered that some surface features were displaced by up to 20 km from where they should be given the accepted rotation rate as measured by the Magellan orbiter in the early 1990s.

Over its four-year mission, Magellan determined the length of the day on Venus as being equal to 243.0185 Earth days. But the data from Venus Express indicate the length of the Venus day is on average 6.5 minutes longer.

What could cause the planet to slow down? One possibility may be the raging weather on Venus. Recent atmospheric models have shown that the planet could have weather cycles stretching over decades, which could lead to equally long-term changes in the rotation period. The most important of those forces is due to the dense atmosphere – more than 90 times the pressure of Earth’s and high-speed weather systems, which are believed to change the planet’s rotation rate through friction with the surface.

Earth experiences a similar effect, where it is largely caused by wind and tides. The length of an Earth day can change by roughly a millisecond and depends seasonally with wind patterns and temperatures over the course of a year.

But a change of 6.5 minutes over a little more than a decade is a huge variation.

Other effects could also be at work, including exchanges of angular momentum between Venus and the Earth when the two planets are relatively close to each other. But the scientists are still working to figure out the reason for the slow down.

These detailed measurements from orbit are also helping scientists determine whether Venus has a solid or liquid core, which will help our understanding how the planet formed and evolved. If Venus has a solid core, its mass must be more concentrated towards the center. In this case, the planet’s rotation would react less to external forces.

“An accurate value for Venus’ rotation rate will help in planning future missions, because precise information will be needed to select potential landing sites,” said Håkan Svedhem, ESA’s Venus Express project scientist.

Venus Express will keep monitoring the planet to determine if the rate of rotation continues to change.

Source: ESA

Sandy Streets Over the Atlantic

Dust from the Sahara blows past the Cape Verde islands on Feb. 9, 2012 (Chelys)

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Thick dust from the Sahara blowing over the ocean off the western coast of Africa encounters the islands of Cape Verde, forming a wake of swirling “vortex streets” visible by satellite.


These swirls are also known as von Karman vortices. When wind encounters the island, the disturbance in the flow propagates downwind in the form of a double row of vortices, which alternate their direction of rotation.

Such effects can be seen anywhere a liquid fluid — including air — flows around a solid body. They are named after engineer and fluid dynamicist Theodore von Kármán.

In the image above, the dust and sand is thick enough to nearly block out some of the islands entirely. See the full scale version here on the Chelys “EOSnap” Earth Snapshot site.

Image via EOSnap/Chelys SRRS (Satellite Rapid Response System).

Watch Live Webcast from the Keck Observatory

On Thursday, Feb. 9, 2012, Keck Observatory will be hosting a live webcast of an astronomy talk by Dr. Tom Soifer of Caltech, who is the Director of the Spitzer Science Center. The title of the talk is “Seeing the Invisible Universe,” and Soifer will discuss the latest exciting results from NASA’s Spitzer Space Telescope. The webcast begins at 7 pm Hawaiian Time, 9 pm Pacific Time (5 am GMT, Feb 10) and will be streamed from the Kahilu Theatre in Waimea-Kamuela, on the Big Island of Hawaii. Watch in the window above (click the play button) or watch on the Keck website.

The Moon Trees of Apollo 14

Apollo 14's splashdown in the Pacific on Feb. 9, 1971. (NASA/Ed Hengeveld)

On this day in 1971 Apollo 14 astronauts Alan Shepard, Jr., Stuart Roosa and Edgar Mitchell returned to Earth, splashing down in the Pacific Ocean at 21:05 UT (4:05 p.m. EST). They were recovered by the USS New Orleans, and returned to the U.S. by way of American Samoa. But the three men weren’t the only living creatures to come back from the Moon on Feb. 9, 1971… in fact, human astronauts were in the minority that day.

Al, Stu and Ed shared their lunar voyage with nearly 500 trees.

As Shepard and Mitchell gathered samples near their landing site in a region named Fra Mauro, Apollo 14 pilot and ex-smoke jumper Stuart Roosa orbited above in “Kitty Hawk”, the mission’s Command Module. It may sound like a lonely job, but he was far from alone. Within his personal kit were small containers containing 400-500 seeds, part of a joint NASA/USFS project to examine the effects, if any, of space travel on such organisms.

The seeds were selected from a variety of tree species: redwood, loblolly pine, sycamore, Douglas fir, and sweetgum seeds were all chosen to accompany Roosa on his 34 orbits around the Moon.

A control group of the same seed varieties were kept on Earth for comparison.

Stuart Roosa had worked for the Forest Service in the 1950s before becoming an Air Force test pilot and then eventually an Apollo astronaut. Being charged with the care of the seeds was a particularly symbolic assignment for Roosa, who had once fought wildfires as a smoke jumper.

Even though there was a mishap during the decontamination process after return to Earth, wherein some containers burst open and seeds were inadvertently mixed together, many of the seeds successfully germinated at Forest Service stations in Mississippi and California. The seedlings were eventually sent to locations around the country and around the world to commemorate the success of the Apollo program.

There was even a second generation, called half-moon trees.

A Moon Tree located outside Goddard Space Flight Center. (GSFC)

Many of these “Moon Trees” and their descendants still stand today. In some instances they are marked with a plaque or a sign… in others, no special marking denotes their significance. Those unmarked trees stand as silent reminders of an earlier and perhaps even bolder era of human space flight.

Me, Heather Archuletta, and Greg ___ in front of a 2nd-generation Moon Tree outside the Holliston Police Department in Massachusetts. (© Jason Major)
Me, Heather Archuletta, and Greg Riley in front of a 2nd-generation Moon Tree outside the Holliston Police Department in Massachusetts, Oct. 2013. (© Jason Major)

Read more about the Moon Trees on this page by David Williams of NASA’s Goddard Space Flight Center. And if you know of a Moon Tree that is not on Mr. William’s list, please contact him to have it included. Williams has endeavored to locate the whereabouts and status of these trees since 1996, as there had been no systematic records previously kept of them.

“I think when people are aware of the heritage of the trees, they usually take steps to preserve them,” said Williams in recollection of one tree that was nearly knocked down during a building renovation. “But sometimes people aren’t aware. That’s why we want to locate as many as we can soon. We want to have a record that these trees are — or were — a part of these communities, before they’re gone.”

Join UT’s First Live Interview with Rover Driver Scott Maxwell

Rover Driver Scott Maxwell with a model of MER. Photo courtesy Scott Maxwell

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How often have you wanted to be a fly on the wall during media interviews of top scientists and engineers? Here’s your chance! On Friday, February 10, we’ll be having our first live interview via a Google+ Hangout On Air. We’ve done the weekly Space Hangout for several weeks now and Fraser has done multiple virtual star parties via a Hangout On Air. Now we’ll start the first of what we hope are many live interviews that we’ll share with our readers and fans. We’re excited that Mars rover driver Scott Maxwell, will be joining us, and he will provide insight on the plans for the Opportunity rover’s upcoming winter, a look back at the 8 years and counting for the rovers, a look ahead to the future, and more.

The Hangout On Air will start at 18:00 UTC (1 pm EST,12 noon CST, 10 am PST) or you can check here at the fancy-schmancy time and date announcement Scott put together that shows the time in almost every time zone possible.

How do you find the Hangout? The best way is to join Google+ and “circle” Fraser and the Hangout On Air will show up in his timeline. You can also circle Nancy, who will also provide a link, but within Fraser’s timeline there will also be the opportunity for you to post questions that we can ask Scott during the live interview.

If you can’t watch live, the Hangout will be recorded and we’ll post it later on Friday on Universe Today.

We hope you’ll join us!

New Computer Simulations Show Earth’s Spaghetti-Like Magnetosphere

Supercomputer simulation showing the tangled magnetosphere surrounding Earth. Credit: OLCF

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A new computer simulation is showing Earth’s magnetosphere in amazing detail – and it looks a lot like a huge pile of tangled spaghetti (with the Earth as a meatball). Or perhaps a cosmic version of modern art.

The magnetosphere is formed by the Sun’s magnetic field interacting with Earth’s own magnetic field. When charged particles from a solar storm, also known as a coronal mass ejection (CME), impact our magnetic field, the results can be spectacular, from powerful electrical currents in the atmosphere to beautiful aurorae at high altitudes. Space physicists are using the new simulations to better understand the nature of our magnetosphere and what happens when it becomes extremely tangled.

Using a Cray XT5 Jaguar supercomputer, the physicists can better predict the effects of space weather, such as solar storms, before they actually hit our planet. According to Homa Karimabadi, a space physicist at the University of California-San Diego (UCSD), “When a storm goes off on the sun, we can’t really predict the extent of damage that it will cause here on Earth. It is critical that we develop this predictive capability.” He adds: “With petascale computing we can now perform 3D global particle simulations of the magnetosphere that treat the ions as particles, but the electrons are kept as a fluid. It is now possible to address these problems at a resolution that was well out of reach until recently.”

It helps that the radiation from solar storms can take 1-5 days to reach Earth, providing some lead time to assess the impact and any potential damage.

The previous studies were done using the Cray XT5 system known as Kraken; with the new Cray XT5 Jaguar supercomputer, they can perform simulations three times as large. The earlier simulations contained a “resolution” of about 1 billion individual particles, while the new ones contain about 3.2 trillion, a major improvement.

So next time you are eating that big plate of spaghetti, look up – the universe has its own recipes as well.

The original press release from Oak Ridge National Laboratory is here.

Virtual Star Party – Feb. 8, 2012

Here was the virtual star party that we held last night on Google+. We’ve actually been holding 1-2 of these star parties every week as we figure out the best way to organize and coordinate all the telescopes streaming into the Hangout. I don’t normally post them all on Universe Today, but last night was particularly special, with amazing views of the Rosette Nebula approximately one hour into the broadcast. A big thanks to Gary Gonella for sharing his telescope view with us.

If you’re interested in watching future livestreamed telescope virtual star parties, make sure you circle me on Google+.

What Does a Nebula Sound Like?

What do things sound like out in the cosmos? Of course, sound waves can’t travel through the vacuum of space; however, electromagnetic waves can. These electromagnetic waves can be recorded by devices called spectrographs on many of the world’s most powerful telescopes. Astronomer Paul Francis from the Australian National University has used some of these recordings and converted them into sound by reducing their frequency 1.75 trillion times to make them audible, as the original frequencies are too high to be heard by the human ear.

“This allows us to listen to many parts of the universe for the first time,” Francis wrote on his website. “We can hear the song of a comet, the chimes of stars being born or dying, the choir of a quasar eating the heart of a galaxy, and much more.”
Continue reading “What Does a Nebula Sound Like?”

Lunar Crater Reveals Many Secrets, Including a Not-So-Young Age

Giordano Bruno crater on the Moon
Giordano Bruno crater on the eastern far side limb of the Moon (35.9? N, 102.8? E) is being revealed in great detail by the Lunar Reconnaissance Orbiter Camera.

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The Moon is covered with craters of various shapes and sizes, and in various states of preservation. Scientists have studied these spectacular features for over five decades, yet there are still many things about craters that we just don’t understand. The study of craters is important because we use them to determine the ages of planetary surfaces. Now, very high resolution imagery from the Lunar Reconnaissance Orbiter Camera (LROC) is allowing us to see lunar craters as never before. Under such scrutiny, one very fresh crater is revealing a host of secrets about the crater-forming process and revealing that it’s not as young as some people may have originally thought.

The crater in question is Giordano Bruno, a 22 km diameter crater located on the far side of the Moon, just beyond the eastern limb. Like all craters on the Moon, this one was named after a famous scientist, in this case, a sixteenth century Italian philosopher who was burned at the stake in 1600 for proposing the existence of “countless Earths.” Because of its position on the far side, Giordano Bruno crater was not seen by humans until it was photographed by the Soviet Luna-3 mission in 1959. But then, this crater was immediately recognized as one of significance, because of its very bright and extensive ray system.

Moon Eastern Limb Clementine
The spectacular rays and the brightness of Giordano Bruno crater are evident in this Clementine data mosaic of the eastern limb of the Moon. Giordano Bruno is the bright spot in the upper centre of this image and some of its rays can be seen extending a quarter of the way around the lunar globe.
Image credit: NASA/JPL/USGS

Along with its bright rays, the crisp rim of the crater, it’s very steep slopes, and a lack of observed superposed craters all argued for a very young age for this intriguing crater. Some researchers even suggested that the formation of this crater was observed by medieval monks in 1178, and recorded as a lunar transient event. Other workers think the age should be closer to 1 million years old. This is still very young by the standards of similar-sized lunar craters, but not within written history.

Over the past 2 years, the acquisition of LROC data has allowed Giordano Bruno crater to be studied in much greater detail than ever before. Images taken by the LROC Narrow Angle Cameras (NAC’s) have resolutions of about half a meter per pixel. This means that something the size of a chair would take up one pixel, and your kitchen table would be roughly resolvable as a 2 x 3 pixel rectangle. With resolutions like that, interesting and unexpected features are being revealed.

One of the most spectacular features is a swirl of impact melt on the western edge of the crater floor. This whirlpool-like structure shows that the melt here underwent chaotic mixing while it was liquid. You can also see that parts of the melt are actually mixtures of real melt and rock fragments that have been incorporated during movement of the melt.

Melt Swirl in Giordano Bruno crater, Moon
Like cream in coffee, a swirl captures the incomplete mixing that occurred when a viscous combination of impact melt and rock fragments flowed off the crater walls into some less rocky impact melt, which had pooled at the western edge of the crater.
Image credit: NASA/GSFC/Arizona State University

Recently published work by Dr. Yuriy Shkuratov (from the Astronomical Institute of Kharkov in Ukraine) and his colleagues used a new technique to study this swirl. Multiple images taken under different conditions were combined to provide roughness calculations for the area. Their research shows that there is a depression in the centre of this structure and that higher segments of the whirlpool swirl exhibit greater roughness than the surrounding melt. They interpret this to mean that the cooling impact melt pool was disturbed by melt flows coming off the crater walls. These incoming flows were more viscous because they had incorporated rock fragments and so did not mix as readily with the other melt material.

One of the other features studied by Dr. Shkuratov and his team is a large slump of wall material near the northern rim of Giordano Bruno. Such slumps are common in larger craters and are believed to form during the late stages of crater formation. This means that the slump block should be the same age as the crater. However, Dr. Shkuratov and colleagues have found that, while there are no craters on the slumped material, a number of small craters are located on the inner wall near this large landslide. They interpret this to mean that the slump is a more recent event. This is significant, because up until now, such big changes were not thought to occur so long after crater formation.

Slump Block in Giordano Bruno crater, Moon
A segment of the crater wall detaches and slumps downward. But when?
Image credit: NASA/GSFC/Arizona State University

The most intriguing result of Dr. Shkuratov’s study is the indication of a not-so-young age for Giordano Bruno. A number of very bright landslides, much smaller than the one on the north wall, are observed around the crater. Similarly, small bright craters are found superposed on many parts of the crater walls. These landslides and craters are much brighter than the surrounding materials. On the Moon, brighter means younger, since materials tend to darken as they age, due to a process called “space weathering.” If these craters and landslides are indeed young, this means that the surrounding darker material of Giordano Bruno crater must be older. Data from Japan’s Kaguya mission confirms that these variations in brightness are not related to compositional variations, and so must be age-related. Based on this and other evidence, Dr. Shkuratov’s team conclude that Giordano Bruno crater must be at least one million years old.

So, whatever the medieval monks saw when they recorded the occurrence of a lunar transient event in 1178, it was not the impact that formed Giordano Bruno crater.

Discover the secrets of Giordano Bruno crater for yourself, using LROC data at the ACT-REACT Quick Map web site

Source: The lunar crater Giordano Bruno as seen with optical roughness imagery. Shkuratov et al., Icarus 218, 2012, 525-533, doi:10.1016/j.icarus/2011.12.023.

Two New Moons for Jupiter

Above are the the discovery images for one of Jupiter's newest moons S/2011 J2. This object is faint so it doesn't have much visual information, but the moon was discovered by the optical telescope Magellan telescope on Sept. 27, 2011. You can see the motion of the satellite over 40 minutes between the two exposures while the background stars and galaxies do not move. Jupiter is about 0.5 degrees away from the bottom of these images. Images courtesy of Scott Sheppard

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Advances in technology have lead to the discovery of new planets outside of our Solar System, and now even new moons in our own backyard.

Last September, two satellites – the smallest ever discovered – were found orbiting Jupiter.

That brings the number of Jovian moons to a whopping 66.  The moons – each about 1 km in size – are very distant from Jupiter. It takes the tiny satellites 580 and 726 days to orbit the gas giant.

The discovery could lead us one step closer to understanding the formation and evolution of our solar system. At least that’s the hope of Scott Sheppard, who works at the the Department of Terrestrial Magnetism at the Carnegie Institution of Science in Washington, D.C. It was Sheppard who, with the help of the massive Magellan telescope at Las Campanas, Chile, initially observed the moons.

“The new satellites are part of the outer retrograde swarm of objects around Jupiter. It is likely there are about 100 satellites of this size around Jupiter,” Sheppard said, explaining that Magellan has made it easier to detect objects further away from Earth. “Up until the last decade, the technology wasn’t there to discover these things because they are very small and very faint.”

The two tiny, irregular moons are called S/2011 J1 and S/2011 J2. Thankfully, those names aren’t expected to stick. Once officially confirmed (Sheppard expects it to happen this year), he will have the opportunity to name each. But, Sheppard can’t pick just any moniker. The names, according to the International Astronomical Union, must be related to Jupiter or Zeus, the Roman and Greek mythological figures who served as king of the gods.

Credit: NASA/ESA/E. Karkoschka (U. Arizona)

Maybe that’s why Sheppard hasn’t yet thought of any names for the soon-to-be members of the Jovian moon list. Are there any names that haven’t already been chosen? Europa, Thebe, Io, Callisto, Sinope, Ganymede …

Naming requirements will definitely need to change because, as Sheppard explains, there are a lot more moons to discover around some of our other gas – and ice – giants.

“There are a similar amount of objects orbiting Saturn and Neptune, which are more distant from the Sun,” Sheppard said, citing a survey of the sky conducted by the Carnegie Institution of Washington in the early 2000s. “If larger telescopes are built in the future, we’ll be able to discover more of these objects and find out what the objects are like,” Sheppard said.

And finding more of these smaller, distant, irregular satellites is a key to understanding our past.

Here’s why: Irregular satellites are believed to have been captured by their respective planets because the moons typically orbit in the opposite direction of the planet’s rotation, and, they also have eccentric and highly inclined orbits.

Those types of moons differ from regular satellites, which are believed to have formed from the same materials that comprise the planet. That’s because the moons tend to have nearly circular orbits, and, they orbit their respective planets in the same direction that the planet rotates.

A planet can temporarily capture an object, i.e. Shoemaker-Levy 9, but in the present time, “a planet has no known efficient mechanism to permanently capture satellites. Thus, outer satellite capture must have occurred near the time of planet formation when the Solar System was not as organized as it is now,” Sheppard said.

“The orbital history of a satellite can be very complex … but understanding where a satellite came from can tell us about the formation and evolution of our Solar System.”

Click here to learn more about the Carnegie Institution’s Department of Terrestrial Magnetism. For more information about Jovian moons, go to Scott Sheppard’s Jupiter Satellite Page.