NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 9, 2011. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
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As we anticipate the Dawn spacecraft going into orbit of Vesta within the next 36 hours, here’s the latest image taken as the spacecraft approaches Vesta, taken on July 9 from a distance of about 41,000 kilometers (26,000 miles). Surface details are coming into focus a little more than from the previous image that was released. The Dawn mission is exciting, as it will be the first spacecraft to enter orbit around a main-belt asteroid, and as we’ve said before, it will be intriguing for scientists to study this lumpy little world in detail and perhaps figuring out what Vesta really is.
Below is an “enhanced” look at this view of Vesta by Stu Atkinson.
Some astronomers classify Vesta as an asteroid, some a protoplanet, and some are on the fence. It’s not really considered a dwarf planet, but the classification could be re-evaluated when Dawn gets in orbit of Vesta and studies it in detail.
An enhanced view of Vesta from the July 9, 2011 image taken by the Dawn spacecraft. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, enhancements by Stu Atkinson.
Stu sent us this image with the caveat that he created it for his own amusement/entertainment, and that it’s not a scientifically enhanced image — i.e., it’s not to be 100% relied upon for feature identification, etc. But it’s a little clearer and sharper than the original from NASA/JPL. Thanks Stu!
Engineers expect the spacecraft to be captured into orbit at approximately 10 p.m. PDT Friday, July 15 (1 a.m. EDT Saturday, July 16). They expect to hear from the spacecraft and confirm that it performed as planned during a scheduled communications pass that starts at approximately 11:30 p.m. PDT on Saturday, July 16 (2:30 a.m. EDT Sunday, July 17). When Vesta captures Dawn into its orbit, engineers estimate there will be approximately 9,900 miles (16,000 kilometers) between the spacecraft and Vesta. At that point, the two will be approximately 117 million miles (188 million kilometers) from Earth.
“It has taken nearly four years to get to this point,” said Robert Mase, Dawn project manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Our latest tests and check-outs show that Dawn is right on target and performing normally.”
Engineers have been subtly shaping Dawn’s trajectory for years to match Vesta’s orbit around the sun with its ion engine. Unlike other missions, where dramatic propulsive burns put spacecraft into orbit around a planet, Dawn will ease up next to Vesta. Then the asteroid’s gravity will capture the spacecraft into orbit. However, until Dawn nears Vesta and makes accurate measurements, the asteroid’s mass and gravity will only be estimates. So the Dawn team will need a few days to refine the exact moment of orbit capture.
Launched in September 2007, Dawn will depart for its second destination, the dwarf planet Ceres, in July 2012. The spacecraft will be the first to orbit two bodies in our solar system.
Stay tuned for more details and updates on the Dawn mission.
The Dawn spacecraft took this image of Vesta on July 1, 2011. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
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The Dawn spacecraft is getting closer to asteroid/protoplanet Vesta, and the view is getting better! Here’s the latest image, which was obtained with Dawn’s framing camera on July 1, 2011 and just released today. It was taken from a distance of about 62,000 miles (100,000 kilometers). Each pixel in the image corresponds to roughly 5.8 miles (9.3 kilometers). Features like craters are starting to sharpen as the spacecraft moves closer, as well as the lumps, bumps and variations in color.
The most exciting part of this mission will be finally figuring out what Vesta really is. Here, it’s looking more like a squished version of our own Moon; a little smoother than I was expecting from some of the earlier images.
Some astronomers classify Vesta as an asteroid, some a protoplanet, and some are on the fence. It’s not really considered a dwarf planet, but the classification could be re-evaluated when Dawn gets in orbit of Vesta and studies it in detail.
Below is an “enhanced” view by Stu Atkinson:
The latest Vesta image from Dawn, with enhancements by Stu Atkinson.
Stu sent us this image with the caveat that he created it for his own amusement/entertainment, and that it’s not a scientifically enhanced image — i.e., it’s not to be 100% relied upon for feature identification, etc. But some of the craters show up a tad better.
Vesta is pretty much an enigma: too big for an asteroid and more evolved than other asteroid. But it is kind of too small for a planet (even a dwarf one). But that’s why it is so interesting so scientists and getting Dawn in orbit will be exciting.
Areas within Eberswalde crater (left) and Gale crater (right) are the two finalists for the landing site of NASA's Mars Science Laboratory mission. Credit: NASA
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Although a rumor came out about a week and a half ago that Gale Crater was the scientists’ preferred landing site for the Mars Science Laboratory, officially NASA says the finalists are now down to two: Gale and Eberswalde craters. The final selection will likely be made sometime this month, no earlier than July 11. As of now, MSL, a.k.a Curiosity scheduled to head to Mars during a Nov. 25 to Dec. 18, 2011 launch window.
Gale Crater contains ancient lakebed deposits and sitting in the middle of the crater is an enticing 5-kilometer-tall mound of rock, stacked with layers. This could provide the rover a study a variety of environments that produced clay deposits near the mountain’s base to later environments that produced sulfate deposits partway up the slope.
Eberswalde is the site of what scientists think is a former river delta, where organic materials could be waiting to be analyzed. NASA says that as a clay-bearing site where a river once flowed into a lake, Eberswalde crater offers a chance to use knowledge that oil industry geologists have accumulated about where in a delta to look for any concentrations of carbon chemistry, a crucial ingredient for life.
Officially out of the running are Mawrth Vallis and Holden Crater, the other two finalist sites.
The spacecraft will arrive at Mars in August 2012, and land via its unusual “sky crane” landing system. (See a video of it here.) Researchers will use the rover’s 10 science instruments for at least two years to investigate whether the landing area has ever offered environmental conditions favorable for microbial life.
A 150-kilometer-wide hollow on Mars named Gale Crater has emerged as the front-runner for the potential landing site for the Mars Science Laboratory rover, Curiosity, which will head to Mars this fall. Nature News and the Planetary Society Blog report that following a meeting of project scientists last month, Gale came out on top of four different locations as the preferred destination for the next Mars rover. However, the final decision has not been made or announced, and NASA Associate Administrator Ed Weiler has the final word. He is expected to make the final decision on Friday with a formal announcement of the site to follow next week.
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According to planetary scientist Matt Golombek, who was part of the selection committee, Gale Crater has a high diversity of geologic materials with different compositions, created under different conditions. Most interesting is evidence of different minerals arranged in stratigraphical context. “Stratigraphy records multiple early Mars environments in sequential order,” Golombek said at a teleconference for Solar System Ambassadors and Solar System Educators earlier this year. “Gale is characteristic of a family of craters that were filled, buried and exhumed, and will provide insights into an important Martian process.”
Gale Crater stratigraphy. Image courtesy Matt Golombek.
The actual landing ellipse is a smooth area with few craters, which is a great and safe place for landing. But the MSL rover – which is the size of a small car – could then take a few 100 sols and head out for more interesting terrain where the sedimentary strata is deposited. There’s a giant 5-kilometer high hill in the middle of the crater, and the rover could traverse up through the lower most layers.
The flythough video of Gale Crater, top, was put together by UnmannedSpaceflight‘s Doug Ellison, who used a mix of HRSC, CTX and HiRISE elevation models, combined with a pair of possible traverse paths for MSL.
The final four landing sites for MSL. Image courtesy Matt Golombek.
The three other choices also have their good points. All the different landing site choices lie between 30 degrees latitude north and 30 degrees south with low elevations – which is a good thing when trying to land on Mars, Golombek said, because that gives you more of Mars’ thin atmosphere to work with. “All the sites are scientifically rich and safe for landing, with small differences between them,” Golombek said.
Eberswalde Crater. Credit: NASA/JPL
Eberswalde Crater has interesting, rough terrain with flow features that are “clear evidence for a river that entered into a standing body of water at sometime into the past on Mars,” Golombek said. “There’s not much disagreement in science community that this is a ancient delta on Mars.”
This region would provide geologic evidence for how the minerals were deposited and evidence for clay minerals.
“Clays are trappers and preservers of biogenic materials, so going to places where these minerals were deposited in calm water is very enticing,” Golombek said.
Holden Crater. Credit: NASA/JPL
Holden Crater is the smoothest and flattest of the four choices. Southeast of the landing ellipse is an area of minerals that look enticing.
“There are mega breccias – rocks that were thrown up in giant impacts in the earliest days of Mars, so we could study those as well at Holden Crater,” Golombek. “But we’d have to drive pretty far to get there. There are also deposits that were certainly deposited in lake or a relatively quiet fluvial setting.”
Mawrth Vallis. Credit: NASA/JPL
Mawrth Vallis holds complex mineralogy and has some of the oldest and longest sequence of rocks among the four sites and has phyllosilicate-bearing stratigraphy within the landing ellipse. Phyllosilicates, or sheet silicates, are an important group of minerals that includes water-bearing and clay minerals and are an important constituent of sedimentary rocks, which can tell the scientists much about Mars’ past.
Golombek praised the Mars Reconnaissance Orbiter mission for providing a extraordinary amount of data to allow the science team to make the best choice.
“The amount of data we have beforehand is unprecedented in Mars exploration,” he said, “with HiRISE(High Resolution Imaging Science Experiment camera) images at 25 cm per pixel, so we can see one meter-size boulders directly on the surface and we have almost complete coverage of the landing ellipses. CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) provides visible and near infrared data to show minearology. The coverage we have is just spectacular.”
First complete image of the far side of the sun taken on June 1, 2011. Click image for larger version. Credit: NASA/STEREO.
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Far out! This is the first complete image of the solar far side, the half of the sun invisible from Earth. Captured on June 1, 2011, the composite image was assembled from NASA’s two Solar TErrestrial RElations Observatory (STEREO) spacecraft. STEREO-Ahead’s data is shown on the left half of image and STEREO-Behind’s data on the right.
You may recall that the two STEREO spacecraft reached opposition (180 degree separation) on February 6 of this year and the science team released a “complete” 360 degree view of the Sun. However, a small part of the sun was inaccessible to their combined view until June 1. This image represents the first day when the entire far side could be seen.
The image is aligned so that solar north is directly up. The seam between the two images is inclined because the plane of Earth’s – and STEREO’s – orbit, known as the “ecliptic”, is inclined with respect to the sun’s axis of rotation. The data was collected by STEREO’s Extreme Ultraviolet Imagers in the SECCHI instrument suites.
The video below explains why seeing the entire Sun is helpful to scientists:
The Spirit rover's last panoramic image, taken before its fourth Martian winter on on Sol 2175, or February, 2010. Credit: Mosaic by Marco De Lorenzo and Ken Kremer, image NASA/JPL/Cornell University.
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Today’s Astronomy Picture of the Day (APOD) features an image mosaic put together in part by Universe Today’s Ken Kremer, along with his imaging partner Marco De Lorenzo. It’s the last thing the Spirit rover ever saw: a panoramic view of the Home Plate region of Gusev Crater where the rover now silently sits. In the background are the Columbia Hills, where Spirit climbed and investigated Husband Hill. Visible are parts of Spirit herself and the stark but enticing landscape where Spirit will be forever mired in sand.
Congrats to Ken and Marco for being featured on APOD!
The sun has set for the Spirit rover on Mars. Credit: NASA
If you’re feeling a little sad today at the news that the Spirit rover is “dead,” you’re not alone. And we all know we’re anthropomorphizing here, but it is hard not to. As MER project manager John Callas said at yesterday’s press conference, the MER rovers are “the cutest darn things out in the solar system,” and yes, we’ve become attached to them. Below are a few quotes we’ve gathered from Steve Squyres, Scott Maxwell, and some of the other people who have been involved with the MER mission in various capacities.
Feel free to add your best memories of Spirit’s mission in the comment section.
Rover Driver Scott Maxwell with a model of MER. Photo courtesy Scott Maxwell
Rover Driver Scott Maxwell. Maxwell has been part of the rover driving team since before the MER rovers lauched. He is publishing the diary he has kept, five years delayed on his Mars and Me blog.
“My take on this is that I know I’m supposed to be sad and I know that at some point I will be really sad, but at the moment it is hard to be sad because that feeling is overwhelmed by the pride of what Spirit accomplished,” Maxwell told Universe Today. “She accomplished an enormous amount in the six years plus that she was active on Mars, and we have every good reason to be proud of her. That is dominating my reaction to this announcement today. It terrible that she’s gone but I’m so proud of her, she did so much, she lived so long and accomplished such great things it’s hard to feel any other way.”
Will Spirit’s official loss put a big hole in Maxwell’s day?
“In terms of my practical day to day operations, not so much,” he said. “My day is filled with taking care of Opportunity and working on the upcoming Mar Science Lab mission, so actually I didn’t have that much to do with Spirit the past year. The way it will affect me is that I won’t be getting the weekly planning schedule for Spirit anymore, so in that way Spirit is going to disappear out of my world.”
Maxwell’s cat died a few months ago he finds he sometimes has an unconscious expectation that the cat will greet him when Maxwell returns home, but then he realizes the cat isn’t there anymore. “That’s the kind of hole that Spirit will leave in my life, where I’ll be unconsciously looking for scheduling emails, or data or information about Spirit, and it is not going to be there, and that place that she has occupied in my life is just not going to be there anymore. I’ve had time to get used to that over the past year, of not actively driving her, so I’ve gone through that transition and I’ll go through this transition next.”
MER PI Steve Squyres. Credit: NASA
Steve Squyres, MER Principal Investigator
“What’s most remarkable to me about Spirit’s mission is just how extensive her accomplishments became,” Squyres said in a JPL press release. “What we initially conceived as a fairly simple geologic experiment on Mars ultimately turned into humanity’s first real overland expedition across another planet. Spirit explored just as we would have, seeing a distant hill, climbing it, and showing us the vista from the summit. And she did it in a way that allowed everyone on Earth to be part of the adventure.”
Squyres said Spirit’s unexpected discovery of concentrated silica deposits was one of the most important findings by either rover.
“It showed that there were once hot springs or steam vents at the Spirit site, which could have provided favorable conditions for microbial life,” he said.
The silica-rich soil was next to a low plateau called Home Plate, which was Spirit’s main destination after the traverse long distances and climbed up and down Husband Hill. “What Spirit showed us at Home Plate was that early Mars could be a violent place, with water and hot rock interacting to make what must have been spectacular volcanic explosions. It was a dramatically different world than the cold, dry Mars of today,” said Squyres.
Chris Potts points to Gusev Crater on Mars on January 4, 2004, after the MER navigation team landed the Spirit rover on Mars with unprecedented accuracy. Photo courtesy of Chris Potts
Chris Pottswas the Deputy Navigation Team Chief for both MER rovers.
“My thoughts immediately go back to the night Spirit landed in Gusev Crater on Jan. 3, 2004,” Potts told Universe Today. “It was a nerve wracking evening, thinking about the dangers involved with bringing Spirit from 12,000 mph to a safe landing via menacing bounces inside the airbags. No one could dare imagine that Spirit would continue on to explore Mars for over 6 years. Such an engineering feat requires the best from everyone involved, from the early designers to the operations team that extracted every last bit that Spirit had to offer. Spirit overcame so many obstacles on the journey, that the rover seemed to have a destiny that would not be denied. Spirit has finally reached the inevitable mission end, but I like to imagine the future when space tourists will follow Spirit’s tracks and continue to marvel at what the rover was able to accomplish.”
Doug Ellison, founder of UnmannedSpaceflight.com, where imaging enthusiasts get together to work with data being produced by robotic missions. He started the website, in part, because of the remarkable images being returned by the MER mission.
“I’ve been trying to figure out the words to describe how it feels,” Ellison told Universe Today. “Like losing a family member isn’t that short of the mark. When those early raw JPG’s were put onto their website so quickly I just couldn’t help myself. I found myself making color composites, panoramas, anaglyphs…and that’s what triggered the making of what became UMSF. It’s been a 7 year adventure that’s been shared through more than 125,000 images. We all lived that adventure through those pictures, together.”
Ellison said it is heartbreaking to see Spirit’s part of the mission come to an end. “Mars always had the power to end things, and she did, on her terms and not ours,” he said. “That’s as it should be, Spirit went down fighting in the battle against freezing temperatures on a barren near airless planet. My only regret is that we’ll never truly know exactly what caused Spirit to stay quiet.”
“We think of ‘Spirit’ as that robot on Mars,” he continued. “Without the team of scientists and engineers here on the ground who figured out what to do with that robot, the adventure we’ve been on, together, would never have happened. She’s part of this large team. She’s the teams feet with every drive she made. She’s their eyes with every picture she took. She’s their hands with every rock she studied. And, for many of us, she’s also its heart. The sol-to-sol rhythm of seeing new pictures and planning new adventures was the heartbeat of this large family that wasn’t just the mission personnel at JPL, Cornell and elsewhere – it wasn’t even just Spirit – it was all of us. That family was the thousands and thousands of people who followed along all over the world, it was the robot that did the dirty work, the engineers who kept her safe and the scientists who made the most of her. That family is now one member short – but it still exists. It formed around this little robot called Spirit, and will carry on through other projects.”
“Spirit didn’t die. She just moved on. I feel so very very sorry for the engineers who spent so long designing, building, and then for more than 6 years, using that little robot. But most of all, I feel sorry for Curiosity. As someone at UMSF suggested – that rover’s now sat in the clean room thinking ‘How the heck am I supposed to follow an act like that?'”
Neil Mottinger.
Neil Mottingerfrom JPL worked on the navigation team for the launch and trajectory of the two spacecraft that brought Spirit and Opportunity to Mars.
“It’s an incredible testimony to engineering that this plucky little craft survived 3 winters, when it wasn’t designed to survive any such weather conditions at all,” Mottinger told Universe Today. “Dust storms didn’t drown its ability to generate electricity thanks to the dust devils that repeatedly cleaned the panels. May its tenacity remind us all to strive for greater goals and push on way beyond the immediate horizons before us.”
Stu Atkinson,member of UMSF, poet and writer penned this poem about the end of Spirit’s mission. You can also read a short story he wrote about a year ago of what could have happened in some households when Spirit died.
MER Project Manager John Callas. Credit: JPL
John Callas has written a letter to his MER team, and in part said, “But let’s remember the adventure we have had. Spirit has climbed mountains, survived rover-killing dust storms, rode out three cold, dark winters and made some of the most spectacular discoveries on Mars. She has told us that Mars was once like Earth. There was water and hot springs, the conditions that could have supported life. She has given us a foundation to further explore the Red Planet and to understand ourselves and our place in the universe.
“But in addition to all the scientific discoveries Spirit has given us in her long, productive rover life, she has also given us a great intangible. Mars is no longer a strange, distant and unknown place. Mars is now our neighborhood. And we all go to work on Mars every day. Thank you, Spirit. Well done, little rover. And to all of you, well done, too.”
We’ll be adding more quotes about Spirit as they come in.
A composite image of how the Spirit rover probably looks, stuck in Gusev Crater. Credit: NASA, image editing by Stu Atkinson.
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In the wee hours of May 25, 2011 the scientists and engineers of the Mars Exploration Rover team will send the last command in attempt to contact the Spirit rover. Over the past year, they have sent over 1,200 commands and haven’t heard anything in reply from the stuck and likely frozen rover. “We have exhausted all the likely scenarios for contacting Spirit, and the likelihood of success is now practically zero,” said John Callas, Project Manager for the Mars Exploration Rover mission. “And at this point, the season is declining and we couldn’t do any of the planned science objectives even if we heard from her now. The Deep Space Network will occasionally listen for Spirit when resources permit, but we have decided not to do anything past the last commands that will done tonight.”
The Spirit rover, as seen by the HiRISE camera on the Mars Reconnaissance Orbiter. Credit: NASA, image enhanced by Stu Atkinson.
Spirit, the plucky rover that landed on Mars on January 3, 2004, overcame many difficulties and endured waaay past her 90-day warranty. For nearly six years, she traveled long distances, climbed hills — something the rovers weren’t really designed to do — she roved and stopped at interesting rocks along the way, all the while beaming back the information she garnered, enlightening us all about the nature of Mars, past and present.
Spirit became embedded in soft Martian soil in May of 2009 and that was the beginning of the end. The team spent months planning for her extrication, and then months again attempting to drive her out, but they ran out of time and power in the approaching Martian winter. The team was unable to put the rover in a favorable position to catch rays of sunlight on her solar panels, and after another freezing, grueling winter, Spirit has now likely succumbed to the harsh environment on Mars.
“We drove it, literally, until its wheels came off and at the beginning of the mission, we never expected that would be the way this project would end up,” said Dave Lavery, MER program director at NASA Headquarters.
The last commands will be sent early on May 25, 0700 UTC, which is just after midnight at JPL in Pasadena, California.
So, this is it. This is end of the Spirit rover mission.
“We always knew we would get to this point,” Callas said during a teleconference with the press, “and really, that’s what we wanted to do, to utilize these rovers as much as possible and wear them out. We are here today because we really wore Spirit out. If on sol 90 (the 90th Martian day of the mission) someone would have said this was going to last another 6 years, we just wouldn’t have believed it.”
The MER Spirit Rover (credit: NASA)
Asked what Spirit’s lasting legacy would be, Callas told Universe Today, “In addition to the great exploration and scientific discoveries, I think the great intangible that goes with Spirit is that she has made Mars a familiar place for us. It is no longer a mysterious location. For six years we’ve had people who go to work on Mars every day, via the rovers.”
The original plan was to try and contact Spirit once a week through the end of 2011, but the team has come to realize that the probability of success was practically zero and they would be wasting valuable resources, both human time and listening resources from the DSN. So the decision was made to end the attempts to contact Spirit.
The Spirit rover's solar panels were covered with dust until a gust of wind blew it off in 2006. Credit: NASA.
One of the challenges that Spirit faced is that it always had dust on the solar arrays, Callas said, even during the first winter on the Columbia Hills. After a timely dust cleaning event by a dust devil, the team was able tilt Spirit to gather sunshine and she survived. The second winter she achieved a 10% tilt and survived; the third winter, the team was able to find a 30% tilt – again she survived. But the 4th winter, there just wasn’t the right geography in the sand pits of Troy that would enable Spirit to survive after it became embedded.
What is the mood of the rover team? “We all are taking realistic look, as this mission was originally supposed to last only 90 sols, and we thought if we were extraordinarily lucky we’d get twice that much time and that the first Martian winter would be the end of the mission” said Lavery. “Realistically, in every possible definition of the word, we looking at this as a massive success in terms of longevity and the massive science return we got out of the project. As this particular chapter of Spirit’s mission comes to a close, this is very much a celebration of the accomplishments of the rover and the success it has had, and looking forward to the next steps of Mars exploration.”
Lavery added that the teams are not looking at this as a funeral, but more like an Irish wake. “I’m sure we’ll be telling stories of when Spirit was a wee little rover,” he said. There will be a science team meeting in July and they will use that opportunity to bring together all who were involved in development and science planning to come together and have some sort of event at that time.
“They are cutest darn things out in the solar system,” Callas said. “Yes, we are attached to these beautiful, accomplished little proxies out on the surface of Mars. We have sadness that we have to say goodbye to Spirit, but we have to remember the great accomplishments and the blessings we’ve received for having this rover operate for all this time, for over six years.”
A look at the nearly buried wheels on the Spirit rover on Mars. Credit: NASA/JPL
Spirit made many discoveries – finding carbonates which told scientists much about the past habitability of Mars and that it likely had a thicker atmosphere at one point. Then, even failure brought discovery, as the malfunction of the right front wheel in 2004 meant the team had to relearn to drive the rover, driving it backwards, dragging the wheel behind. This churned up the top soil and revealed what was under the surface: amorphous silica, which is evidence for an ancient hydrothermal system on Mars, which means not only water but an energy source that could have been driving a type of ecosystem in one particular location on Mars.
“There’s an enormous amount that can and still will be written about Spirit and the discoveries she’s made. The science team will be writing papers for a long while,” said Lavery. “But there’s also the inspiration that the rover provided to the team and really to the entire country that we were able to put together a project that went to another planet and survived well past its designed lifetime. The sense of wonder and sense of accomplishments go well beyond the mission itself.”
Yes, we knew this day was coming. Spirit roved her way into our hearts and into the science books. She will not be forgotten.
The aeroshell for the Mars Science Laboratory. Credit: Lockheed Martin
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UPDATE:According to JPL’s Scott Maxwell on Twitter, the aeroshell was not damaged during the improper lifting, which is good news, as there should be no impact to the launch schedule.
The backshell for the Mars Science Laboratory was damaged last week at Kennedy Space Center when it was lifted improperly, according to Aviation Week. Engineers are now examining the backshell to determine the nature of the damage and how serious it is. There is no word yet on whether this could impact the launch of the Curiosity rover, which is currently set for November 25 of this year. The launch window extends to December 18, but after that the mission would have to wait about 26 months for the next favorable launch window.
An agency spokesman was quoted as saying the damage to the backshell did not appear to be serious. An Air Force C-17 carrying the backshell, cruise stage and heat shield arrived at Kennedy Space Center on May 12, while the rover and its unique the descent stage scheduled to arrive in June. The accident apparently involved the backshell being lifted with a crane in the wrong attitude, placing out-of-specification strain on clamps holding it together.
New results from NASA's Galaxy Evolution Explorer and the Anglo-Australian Telescope atop Siding Spring Mountain in Australia confirm that dark energy (represented by purple grid) is a smooth, uniform force that now dominates over the effects of gravity (green grid). The observations follow from careful measurements of the separations between pairs of galaxies (examples of such pairs are illustrated here).Image credit: NASA/JPL-Caltech
A five-year survey of 200,000 galaxies, stretching back seven billion years in cosmic time, has led to one of the best independent confirmations that dark energy is driving our universe apart at accelerating speeds. The survey used data from NASA’s space-based Galaxy Evolution Explorer and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.
The findings offer new support for the favored theory of how dark energy works — as a constant force, uniformly affecting the universe and propelling its runaway expansion. They contradict an alternate theory, where gravity, not dark energy, is the force pushing space apart. According to this alternate theory, with which the new survey results are not consistent, Albert Einstein’s concept of gravity is wrong, and gravity becomes repulsive instead of attractive when acting at great distances.
“The action of dark energy is as if you threw a ball up in the air, and it kept speeding upward into the sky faster and faster,” said Chris Blake of the Swinburne University of Technology in Melbourne, Australia. Blake is lead author of two papers describing the results that appeared in recent issues of the Monthly Notices of the Royal Astronomical Society. “The results tell us that dark energy is a cosmological constant, as Einstein proposed. If gravity were the culprit, then we wouldn’t be seeing these constant effects of dark energy throughout time.”
Dark energy is thought to dominate our universe, making up about 74 percent of it. Dark matter, a slightly less mysterious substance, accounts for 22 percent. So-called normal matter, anything with atoms, or the stuff that makes up living creatures, planets and stars, is only approximately four percent of the cosmos.
The idea of dark energy was proposed during the previous decade, based on studies of distant exploding stars called supernovae. Supernovae emit constant, measurable light, making them so-called “standard candles,” which allows calculation of their distance from Earth. Observations revealed dark energy was flinging the objects out at accelerating speeds.
his diagram illustrates two ways to measure how fast the universe is expanding -- the "standard candle" method, which involves exploded stars in galaxies, and the "standard ruler" method, which involves pairs of galaxies. Image credit: NASA/JPL-Caltech
Dark energy is in a tug-of-war contest with gravity. In the early universe, gravity took the lead, dominating dark energy. At about 8 billion years after the Big Bang, as space expanded and matter became diluted, gravitational attractions weakened and dark energy gained the upper hand. Billions of years from now, dark energy will be even more dominant. Astronomers predict our universe will be a cosmic wasteland, with galaxies spread apart so far that any intelligent beings living inside them wouldn’t be able to see other galaxies.
The new survey provides two separate methods for independently checking the supernovae results. This is the first time astronomers performed these checks across the whole cosmic timespan dominated by dark energy. The team began by assembling the largest three-dimensional map of galaxies in the distant universe, spotted by the Galaxy Evolution Explorer. The ultraviolet-sensing telescope has scanned about three-quarters of the sky, observing hundreds of millions of galaxies.
“The Galaxy Evolution Explorer helped identify bright, young galaxies, which are ideal for this type of study,” said Christopher Martin, principal investigator for the mission at the California Institute of Technology in Pasadena. “It provided the scaffolding for this enormous 3-D map.”
The astronomers acquired detailed information about the light for each galaxy using the Anglo-Australian Telescope and studied the pattern of distance between them. Sound waves from the very early universe left imprints in the patterns of galaxies, causing pairs of galaxies to be separated by approximately 500 million light-years.
This “standard ruler” was used to determine the distance from the galaxy pairs to Earth — the closer a galaxy pair is to us, the farther apart the galaxies will appear from each other on the sky. As with the supernovae studies, this distance data were combined with information about the speeds at which the pairs are moving away from us, revealing, yet again, the fabric of space is stretching apart faster and faster.
The team also used the galaxy map to study how clusters of galaxies grow over time like cities, eventually containing many thousands of galaxies. The clusters attract new galaxies through gravity, but dark energy tugs the clusters apart. It slows down the process, allowing scientists to measure dark energy’s repulsive force.
“Observations by astronomers over the last 15 years have produced one of the most startling discoveries in physical science; the expansion of the universe, triggered by the Big Bang, is speeding up,” said Jon Morse, astrophysics division director at NASA Headquarters in Washington. “Using entirely independent methods, data from the Galaxy Evolution Explorer have helped increase our confidence in the existence of dark energy.”
For more information see the Australian Astronomical Observatory
