Posted on by Nancy Atkinson

Where In The Universe Challenge #22

It’s time once again for this week’s Where In The Universe challenge. Take a look at the image above and try to determine where in the universe this image was taken. Give yourself extra points if you can name the spacecraft responsible for taking this image. As always, no peeking below before you make your guess. And comments are welcome if you want to share how well you did!

Make your guess, and then proceed.

This prominent circular feature, known as the Richat Structure, is found on our home planet Earth, in the Sahara Desert. Lots of astronauts have noted it and taken pictures of it because it forms a conspicuous 50-kilometer-wide (30-mile-wide) bullet’s-eye on the otherwise rather featureless expanse of the desert. Initially it was thought to be an impact crater, but it is now known to be an eroded circular anticline (structural dome) of layered sedimentary rocks.

This image was generated from a Landsat satellite image draped over an elevation model produced by the Shuttle Radar Topography Mission (SRTM), so if you said either a satellite or an astronaut took this image, you can consider yourself correct. The view uses a 6-times vertical exaggeration to greatly enhance topographic expression. To give a scale for this image, the height of the mesa ridge in the back center of the view is about 285 meters (about 935 feet) tall. This is a color enhanced image, using both visible and infrared bands, which helps to differentiate bedrock (browns), sand (yellow, some white), minor vegetation in drainage channels (green), and salty sediments (bluish whites). Some shading of the elevation model was included to further highlight the topographic features.

This is quite a striking image from the old home planet.

See a hi-resolution image here.

Source: NASA Earth Observatory

Posted on by Nancy Atkinson

Evidence of Rain on Mars

Sedimentary deposits in Delta Nanedi on Mars. Credit: NASA's HiRISE Camera

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Images of layered sedimentary deposits and deltas on Mars have provided evidence for lakes and flowing rivers that carried eroded material downstream. A team of researchers also believes there is evidence for precipitation in the Red Planet’s past. “For years scientists have been suspecting that the current appearance of the landscape has, in part, been shaped by rivers that cut into the surface,” said Ernst Hauber of the German Aerospace Center. “We can see layered sediments where these valleys open into impact craters. The shape of certain sediments is typical for deltas formed in standing water.” Hauber and his team also believe that surface runoff from rain or snowmelt completes the picture of past water on Mars.

The researchers explored the Xanthe Terra area located near the equator in the Martian highlands using image from four cameras on three different spacecraft; High-Resolution Stereo Camera (HRSC) on board the European Mars Express mission, the Mars Orbiter Camera (MOC) from NASA’s Mars Global Surveyor Mission and the HiRISE and CTX camera experiments on board NASA’s Mars Reconnaissance Orbiter (MRO) mission.

A crater lake and river on the Xanthe Terra region. Credit: ESA/DL
A crater lake and river on the Xanthe Terra region. Credit: ESA/DL

The images paint this picture of Mars’ past: About four billion years ago, there were lakes on the Red Planet which may have been fed by short-lived rivers that were, in turn, fed by precipitation. These lakes filled craters that were formed by the impact of meteorites. Water accumulated in places where rivers broke through the crater rims. Deltas were formed at the mouths of the rivers, similar to how they are formed where rivers flow into lakes or seas on Earth.

Junction of the Nanedi valleys in the Xanthe highlands on Mars. Credit: ESA/DLR/FU Berlin (G. Neukum).
Junction of the Nanedi valleys in the Xanthe highlands on Mars. Credit: ESA/DLR/FU Berlin (G. Neukum).

The researchers say were also able to narrow down the period when the craters were filled with lakes by analyzing the distribution of impact craters of different sizes, which gives an indication of the age of a planetary surface. The more craters are counted on a surface, the older the area is. The crater counts revealed that water was flowing through the valleys between about 3.8 and 4 billion years ago.

The valleys themselves could have formed relatively fast, and the deposits could have formed over a period ranging from decades to millennia.

But what led the researchers to surmise that there must have been precipitation on early Mars? “This is actually not at all self-evident: for a long time, scientists have been trying to figure out whether the valleys on Mars were formed by groundwater seepage and headward erosion, or by surface runoff caused by rainfall or snowmelt”, said Hauber. His team believes surface runoff was the cause. “Our findings also point in this direction and we are convinced that both processes have played an important role in Xanthe Terra”.

However, this situation did not last very long. Between 3.5 and 3.8 billion years ago, the precipitation became less intense and the valleys dried up. Erosion on Mars has been minimal ever since, which has contributed to the fact that deposits can still be observed although they should in fact be very susceptible to erosion. Today, Mars is a dry desert planet and water is no longer flowing through its valleys.

Source: German Aerospace Center

Posted on by Nancy Atkinson

Shuttle Mission to Hubble Delayed

Atlantis and Endeavour on pads 39 A and B. Credit: NASA

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Because of delays and complications from Hurricane Ike, the launch date for space shuttle Atlantis’ STS-125 mission to service the Hubble Space Telescope has been delayed four days until Oct. 14 at 10:19 p.m. EDT. The delay is not a surprise. The crew and mission controllers missed out on a week of valuable training time when they were forced to evacuate the Houston area when Hurricane Ike which hit on September 13. “You come to the question of either slipping the launch or cutting out events,” said STS-125 Commander Scott Altman when the crew arrived at Kennedy Space Center on Tuesday to prepare for a launch rehearsal. “All [our training] needs to be done and we have to make it happen before we fly… And that, of course, may mean a bit of a slip.” With Atlantis’ launch delay, subsequently shuttle Endeavour’s STS-126 supply mission to the International Space Station, also will move from Nov. 12 to Nov. 16 at 7:07 p.m. EST.

The astronauts are training for a grueling mission, with five back-to-back spacewalks to install two new science instruments, as well as repair two others and to install six new gyroscopes, six batteries, a fine guidance sensor and insulation.

“The bottom line to me is this mission is really hard,” said John Grunsfeld, lead spacewalker and veteran of two previous Hubble repair missions. “After 109, I thought we’d really maxed out what we could do on a space mission. This time, we’ve added a lot of content with inspections (for the shuttle heat shield). From an EVA standpoint, we’ve gone from doing heart surgery on Hubble to what is comparable to doing brain surgery on Hubble with the instrument repairs. So this is going to be a very complex mission, it’s going to be very hard.”

STS-125 crew. Credit: NASA
STS-125 crew. Credit: NASA

From left are, Mission Specialist Megan McArthur, Pilot Gregory C. Johnson, Mission Specialist Mike Massimino, Commander Scott Altman and Mission Specialists Andrew Feustel, John Grunsfeld and Michael Good.

Fellow spacewalker Mike Massimino said the crew will do everything they can to be ready, and the short delay will allow the team to be fully prepared. “We’ve been training hard and long and I feel pretty confident we’re going to be able to pull those two repairs off,” he said. “I think we’re ready for them and it’s just to be fresh, have it fresh in your mind, we’re going to hopefully recover those NBL runs and do a little more training in the simulator. But I think we’re as ready as we’re ever going to be to do that. Hopefully it’ll go as we expect it to. There’ll probably be some surprises in there that we didn’t anticipate. But I think we’re going to be ready to react to those as well.”

If the shuttle does indeed launch on Oct. 14, the first spacewalk would be on October 17.

Sources: NASA, CBS Space Place

Posted on by Nancy Atkinson

Phoenix Lander Successful in Moving “Headless” Rock

"Headless" after being moved. Credit: NASA/JPL/Caltech/U of AZ

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The robotic arm on NASA’s Phoenix Mars Lander slid a rock out of the way during the mission’s 117th Martian day (Sept. 22, 2008) in order to take a look at the soil underneath the rock, and to see at what depth the subsurface ice was under the rock. The lander’s Surface Stereo Imager took this image later the same day, showing the rock, called “Headless,” after the arm pushed it about 40 centimeters (16 inches) from its previous location. “The rock ended up exactly where we intended it to,” said Matt Robinson of NASA’s Jet Propulsion Laboratory, robotic arm flight software lead for the Phoenix team. And what was underneath the rock? Take a look:

Post flip. Credit: NASA/JPL/Caltech/Uof AZ
It’s hard to tell, exactly since the ground was disturbed from the moving. Some white material appears to be where the rock used to sit, but the Phoenix science team will have to study the area more closely. Look for official word from the team soon. It looks from this second image as though the thermal and conductivity probe was stuck in the ground a few times around the rock, searching for clues of any water molecules in the soil (look for the two separate marks left by the probe just to the right of the trench.)
Phoenix sol 118. Credit: NASA/JPL/Caltech/U of AZ

RAC (via the SSI). Credit: NASA/JPL/Caltech/U of AZ
RAC (via the SSI). Credit: NASA/JPL/Caltech/U of AZ

Also in recent days, the two Phoenix cameras took portraits of each other. Above is the Robotic Arm Camera (RAC) and below is the the Surface Stereo Imager:

Phoenix Surface Stereo Image-twitterpic. Credit: Twitter
Phoenix Surface Stereo Image-twitterpic. Credit: Twitter

Source: Phoenix Gallery

Posted on by Nancy Atkinson

Saturn’s Eerie Radio Emissions Mapped in 3-D

Projection of radio sources onto plane perpendicular to line between Cassini and the centre of Saturn

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While Saturn and its rings are beautiful and wondrous, the sounds of Saturn are eerie and strange. Scientists have been trying to understand the bizarre radio emissions that come from the ringed planet, called the Saturn Kilometric Radiation (SKR). Scientists have used observations from NASA’s Cassini spacecraft build a 3-D picture of these intense radio emissions emanating from Saturn’s magnetic field. The SKR radio emissions are generated by high-energy electrons spiraling around magnetic field lines threaded through Saturn’s auroras.

Previous Cassini observations have shown that the SKR is closely correlated with the intensity of Saturn’s UV aurora and the pressure of the solar wind. “The animation shows radio sources clustered around curving magnetic field lines,” said Dr. Baptiste Cecconi, of LESIA, Observatoire de Paris. “Because the radio signals are beamed out from the source in a cone-shape, we can only detect the sources as Cassini flies through the cone. When Cassini flies at high altitudes over the ring planes, we see the sources clearly clustered around one or two field lines. However, at low latitudes we get more refraction and so the sources appear to be scattered.”

Link to 3-D animation.

The active area of the magnetic field matched up with near-polar latitudes degrees in both the northern and southern hemisphere, the location of Saturn’s UV aurora.

“For the purposes of the model, we’ve imagined a screen that cuts through the middle of Saturn, set up at right-angles to the line between Cassini and the centre of the planet. We’ve mapped the footprints of the radio sources projected onto the screen, which tilts as Cassini moves along its orbital path and its orientation with respect to Saturn changes. We’ve also traced the footprints of the magnetic field lines back to the cloud tops of Saturn,” said Cecconi.

Listen to the sounds of Saturn.

Although there were some minor differences between emissions in the northern and southern hemispheres, the emissions were strongest in the western part of Saturn’ss sunlit hemisphere. This area corresponds to a region of Saturn’s magnetopause where electrons are thought to be accelerated by the interaction of the solar wind and Saturn’s magnetic field.

The measurements were made using Cassini’s Radio and Plasma Wave Science (RPWS) experiment.

Cecconi presented his results at the European Planetary Science Congress on Tuesday, September 23rd.

Source: European Planetary Science Congress

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Posted on by Nancy Atkinson

Scientists Detect “Dark Flow:” Matter From Beyond the Visible Universe

Just as unseen dark energy is increasing the rate of expansion of the universe, there’s something else out there causing an unexpected motion in distant galaxy clusters. Scientists believe the cause is the gravitational attraction of matter that lies beyond the observable universe, and they are calling it “Dark Flow,” in the vein of two other cosmological mysteries, dark matter and dark energy. “The clusters show a small but measurable velocity that is independent of the universe’s expansion and does not change as distances increase,” said lead researcher Alexander Kashlinsky at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The distribution of matter in the observed universe cannot account for this motion.”

“We never expected to find anything like this,” he said.

Using NASA’s Wilkinson Microwave Anisotropy Probe’s (WMAP) three-year view of the microwave background and a catalog of clusters, the astronomers detected hundreds of galaxy clusters that appear to be carried along by a mysterious cosmic flow. The bulk cluster motions are traveling at nearly 2 million miles per hour. The clusters are heading toward a 20-degree patch of sky between the constellations of Centaurus and Vela.

Several astronomers teamed up to identify some 700 X-ray clusters that exhibited a subtle spectral shift. This sample includes objects up to 6 billion light-years — or nearly half of the observable universe — away.

They found this motion is constant out to at least a billion light-years. “Because the dark flow already extends so far, it likely extends across the visible universe,” Kashlinsky says.

The finding flies in the face of predictions from standard cosmological models, which describe such motions as decreasing at ever greater distances.

Cosmologists view the microwave background – a flash of light emitted 380,000 years after the big bang – as the universe’s ultimate reference frame. Relative to it, all large-scale motion should show no preferred direction.

Big-bang models that include a feature called inflation offer a possible explanation for the flow. Inflation is a brief hyper-expansion early in the universe’s history. If inflation did occur, then the universe we can see is only a small portion of the whole cosmos.

WMAP data released in 2006 support the idea that our universe experienced inflation. Kashlinsky and his team suggest that their clusters are responding to the gravitational attraction of matter that was pushed far beyond the observable universe by inflation. “This measurement may give us a way to explore the state of the cosmos before inflation occurred,” he says.

The next step is to narrow down uncertainties in the measurements. “We need a more accurate accounting of how the million-degree gas in these galaxy clusters is distributed,” says Atrio-Barandela.

“We’re assembling an even larger and deeper catalog of X-ray clusters to better measure the flow,” Ebeling adds. The researchers also plan to extend their analysis by using the latest WMAP results, released in March.

The result will appear in the October 20 edition of Astrophysical Journal Letters, which is available electronically this week.

Preprint of Dark Flow Paper, results and implications

Preprint of Dark Flow Paper, technical details

Source: NASA

Posted on by Nancy Atkinson

Saturn’s Rings May Be Billions of Years Old

Saturn's rings. Credit: NASA/JPL

Saturn’s enigmatic rings may be much older and also much more massive than previously thought, according to a new study. Because Saturn’s rings look so clean and bright, it was thought the rings were younger than the planet itself, which is estimated to be about 4.5 billion years old. But using data from the Cassini spacecraft’s UVIS (Ultraviolet Imaging Spectrograph) instrument, Principal Investigator Dr. Larry Esposito and his team used computer simulations to study colliding particles in Saturn’s rings and their erosion by meteorites. Their results support the possibility that Saturn’s rings formed billions of years ago, perhaps at the time when giant impacts excavated the great basins on the Moon. The findings also suggest that giant exoplanets may also commonly have rings.

“Both Cassini observations and theoretical calculations can allow the rings of Saturn to be billions of years old. This means we humans are not just lucky to see rings around Saturn. This would lead us to expect massive rings also to surround giant planets circling other stars,” said Esposito.

Also, simulations run by Esposito’s colleagues Glen Stewart and Stuart Robbins from the University of Colorado showed that Saturn’s ring particles clump together, meaning previous estimates of the mass might be too low, perhaps by a factor of 3.

Saturns rings strip. Credit: NASA/JPL
Saturns rings strip. Credit: NASA/JPL

Meteorites slowly grind and shatter the particles in the ring. Gradually, a layer of dust and fragments builds up and covers each particle, making each particle more massive while “cleaning up” the rings.

Recycling of ring material extends their lifetime and reduces the darkening that was expected previous to this study if the rings were older.

One problem with this proposal for more massive and ancient rings is that the Pioneer 11 space mission to Saturn in 1979 measured the ring mass indirectly by observing charged particles created by cosmic rays bombarding the rings.

“Those mass estimates were similar to the ones from Voyager star occultations, apparently confirming the previous low mass value. However, we now recognize that the charged particles are double-valued. That means they could arise from either a small or large mass. We now see that the larger mass value could be consistent with the underestimates due to ring clumpiness,” said Esposito.

Source: European Planetary Science Congress

Posted on by Nancy Atkinson

Opportunity’s Next Adventure: The Big Drive

The Big Drive to Endeavour-crater. Credit: NASA/JPL

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Opportunity, the intrepid Mars Exploration Rover, is going to put the pedal to the metal and head out for a crater nearly 12 kilometers (7 miles) away. That would match the distance the rover has traveled since landing in 2004. But the call of the unknown is compelling the rover science team to make the attempt. “We may not get there, but it is scientifically the right direction to go anyway,” said Steve Squyres, principal investigator for the science instruments on Opportunity and its twin rover, Spirit. For an “aging” rover (what age is 4 in rover years?), this might be setting the bar pretty high. But maybe it’s the journey and not the destination.

“This is a bolder, more aggressive objective than we have had before,” said John Callas, the project manager the rovers. “It’s tremendously exciting. It’s new science. It’s the next great challenge for these robotic explorers.”

“This crater is staggeringly large compared to anything we’ve seen before.” The crater, named Endeavour, is 22 kilometers (13.7 miles) across. “I would love to see that view from the rim,” Squyres said. “But even if we never get there, as we move southward we expect to be getting to younger and younger layers of rock on the surface. Also, there are large craters to the south that we think are sources of cobbles that we want to examine out on the plain. Some of the cobbles are samples of layers deeper than Opportunity will ever see, and we expect to find more cobbles as we head toward the south.”

The rover team estimates Opportunity may be able to travel about 110 yards each day it is driven toward the Endeavour crater. Even at that pace, the journey could take two years. But why not go for it, and see how long the rovers can last?

Opportunity's shadow with Victoria Crater in the background. Credit: NASA/JPL/ASU
Opportunity's shadow with Victoria Crater in the background. Credit: NASA/JPL/ASU

Opportunity, like Spirit, is well past its expected lifetime on Mars, and might not keep working long enough to reach the crater. However, two new resources not available during the 4-mile drive toward Victoria Crater in 2005 and 2006 are expected to aid in this new trek.

One is imaging from orbit of details smaller than the rover itself, using the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter, which arrived at the Red Planet in 2006.

“HiRISE allows us to identify drive paths and potential hazards on the scale of the rover along the route,” Callas said. “This is a great example of how different parts of NASA’s Mars Exploration Program reinforce each other.”

Also, Opportunity now has a better “brain” for driving across the the plains of Mars. A new version of flight software uplinked to Opportunity and Spirit in 2006, boosts their ability to autonomously choose routes and avoid hazards such as sand dunes.

During its first year on Mars, Opportunity found geological evidence that the area where it landed had surface and underground water in the distant past. The rover’s explorations since have added information about how that environment changed over time. Finding rock layers above or below the layers already examined adds windows into later or earlier periods of time.

Source: JPL

Posted on by Nancy Atkinson

Anything Under That Rock on Mars? Phoenix to Take a Peek

The rock "Headless." NASA/JPL-Caltech/University of Arizona/ Texas A&M University

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Ever wondered what might crawl out from under a rock on Mars? The Phoenix lander is going to attempt to find out today by trying to nudge a rock aside today with its robotic arm to see what might be underneath. Engineers have developed a plan to try moving a rock on the north side of the lander. This rock, roughly the size and shape of a VHS videotape, is called “Headless.” Even though the Phoenix mission has been extended for a second time – the mission is now on through December, the team feels like it’s time to pull out all the stops and do as much work as possible. “We’re getting towards fall in the northern plains of Mars and our sun is dropping lower day by day,” said mission principal investigator Peter Smith on NPR’s Science Friday. “Our days are getting precious.” So, even though Phoenix’s robotic arm was not designed to move rocks, the team wants to give it a shot. “The appeal of studying what’s underneath is so strong we have to give this a try,” said Michael Mellon, a Phoenix science team member at the University of Colorado, Boulder.

“We don’t know whether we can do this until we try,” said Ashitey Trebi Ollennu, a robotics engineer at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “The idea is to move the rock with minimum disturbance to the surface beneath it. You have to get under it enough to lift it as you push it and it doesn’t just slip off the scoop.”

The lander receives commands for the whole day in the morning, so there’s no way to adjust in mid-move if the rock starts slipping. Phoenix took stereo-pair images of Headless to provide a detailed three-dimensional map of it for planning the arm’s motions. On Saturday, Sept. 20, the arm enlarged a trench close to Headless. Commands sent to Phoenix Sunday evening, Sept. 21, included a sequence of arm motions for today, intended to slide the rock into the trench.

If the technique works, the move would expose enough area for digging into the soil that had been beneath Headless.

Morning frost on Mars. NASA/JPL-Caltech/University of Arizona/ Texas A&M University
Morning frost on Mars. NASA/JPL-Caltech/University of Arizona/ Texas A&M University

The scientific motive is related to a hard, icy layer found beneath the surface in trenches that the robotic arm has dug near the lander. Excavating down to that hard layer underneath a rock might provide clues about processes affecting the ice.

“The rocks are darker than the material around them, and they hold heat,” Mellon said. “In theory, the ice table should deflect downward under each rock. If we checked and saw this deflection, that would be evidence the ice is probably in equilibrium with the water vapor in the atmosphere.”

An alternative possibility, if the icy layer were found closer to the surface under a rock, could by the rock collecting moisture from the atmosphere, with the moisture becoming part of the icy layer.

Source: JPL

Posted on by Nancy Atkinson

Planetary Scientists Studying Changes in Red Spot Junior

As far as storms go, nothing will rival Jupiter’s Great Red Spot (GRS). But of interest is a smaller and newer storm called Oval BA, a giant anticyclone on Jupiter also known as Red Spot Junior. ‘Smaller’ is a relative term, as although Oval BA is about half the size of GRS, it has a diameter about the size of our Earth. It formed in 2000 as several vortices converged. However, recently Oval BA has undergone some changes. Suddenly it turned from white to red in a period of just a few months, and planetary scientists are trying to understand the processes that could cause the changes. While they are able to explain some of Red Spot Junior’s attributes, they are puzzled by others.

“Our group has made an in-depth analysis of all the aspects regarding the history and evolution of Oval BA,” said Dr. Santiago Pérez-Hoyos, of the Planetary Science Group of the University of the Basque Country in Spain. “The most strongly reddened region was an annulus around its centre. However, when we calibrated images taken with the Hubble Space Telescope, we found that it didn’t actually alter in red or infrared wavelengths during the period. Instead, it became darker in blue and ultraviolet wavelengths, which made it appear visually redder.”

The apparent reddening was first reported by amateur astronomers in early 2006, but it was not until April that professional astronomers were able to image the impressive alteration of the second largest storm in the Solar System after the Great Red Spot (GRS).

Using data from Cassini, the Hubble Space Telescope, NASA’s New Horizons mission and computer models the Planetary Science Group analyzed possible causes for the color change, including alterations to dynamical, photochemical and diffusion processes.

Pérez-Hoyos said, “The most likely cause appears to be an upward and inward diffusion of either a colored compound or a coating vapor that may interact later with high energy solar photons at the upper levels of Oval BA.”

The group were able to rule out that the reddening was caused by any dynamical processes. They found no change to the strength of the “hurricane” and, although some changes in the circulation around the spot had taken place, the maximum wind speeds (which may range up to 400 kilometers per hour or more) were consistent with measurements previous to 2000 of the storms that combined to form Oval BA.

The group modeled the wind flow in detail using high resolution simulations, in order to understand why the red material may be confined to the annulus region and how the color change happened in the observed time scales. The model accounts well for the temperature and wind structure inside the oval BA.

Models also showed that the change could not be attributed to interactions of Oval BA with the GRS, which were relatively close at the time. The flow around both vortices is in the zonal directions and is so strong that separates both storms

The oval height did not change over the period and there were no large changes in the temperature gradient of the oval.

Pérez-Hoyos said, “There is much to be understood about this problem yet. Future spacecraft missions and a continuous observation of the planet (as done by amateur astronomers) will surely give us new clues on the behaviour of Jupiter’s atmosphere that will result in a better understanding of it.”
The team presented their findings at the European Planetary Science Congress in Münster on Monday, 22nd September.

Source: European Planetary Conference