For 886 days between 2001 and 2004, a tiny spacecraft named Genesis sat parked at Lagrange Point L1 quietly collecting solar wind samples. On Sept. 8, 2004, the spacecraft released a sample return capsule which bashed its way onto the Utah desert carrying its little payload. Despite the disastrous crash, solar-wind ions were found buried beneath the surface of the collectors and what they have to tell us about the possible formation of our solar system is pretty amazing.
In March 2005 the international scientific community was given the collectors to study – and one of their prime targets was the evolution of our solar system. How could these tiny particles give us clues as to our origin? According the bulk of evidence, it is surmised the outer layer of the Sun hasn’t changed in several billion years. If we are to agree this is a good basis for modeling our solar nebula, we could begin to understand the chemical processes which formed our solar system. For most rock-forming elements, there appears to be little fractionation of either elements or isotopes between the sun and the solar wind. Or is there?
“The implication is that we did not form out of the same solar nebula materials that created the sun — just how and why remains to be discovered,” said Kevin McKeegan, a Genesis co-investigator from the University of California, Los Angeles and the lead author of one of two Science papers published this week.
Using the deposits found on the collector plates, scientists found a higher rate of common oxygen isotopes and a lowered rate of rare ones – different from Earth’s ratios. The same held true of nitrogen composition.
“These findings show that all solar system objects, including the terrestrial planets, meteorites and comets, are anomalous compared to the initial composition of the nebula from which the solar system formed,” said Bernard Marty, a Genesis co-investigator from Centre de Recherches Petrographiques et Geochimiques in Nancy, France and the lead author of the second new Science paper. “Understanding the cause of such a heterogeneity will impact our view on the formation of the solar system.”
While more studies are in the making, this new evidence provides vital information which may correct how we initially perceived our beginnings. While these elements are the most copious of all, even slight differences make them as distinctive as salt and pepper.
“The sun houses more than 99 percent of the material currently in our solar system so it’s a good idea to get to know it better,” said Genesis principal investigator Don Burnett of the California Institute of Technology in Pasadena, Calif. “While it was more challenging than expected we have answered some important questions, and like all successful missions, generated plenty more.”
The view from above of the ARTEMIS orbits as they make the transition from the kidney-shaped Lissajous orbits on either side of the moon to orbiting around the moon. Credit: NASA/Goddard Space Flight Center
It took one and a half years, over 90 orbit maneuvers, and – wonderfully – many gravitational boosts and only the barest bit of fuel to move two spacecraft from their orbit around Earth to their new home around the Moon.
Along their travels, the spacecraft have been through orbits never before attempted and made lovely curlicue leaps from one orbit to the next. This summer, the two ARTEMIS spacecraft — which began their lives as part of the five-craft THEMIS mission studying Earth’s aurora – will begin to orbit the moon instead. THEMIS is an acronym for the Time History of Events and Macroscale Interaction during Substorms spacecraft.
Even with NASA’s decades of orbital mechanics experience, this journey was no easy feat. The trip required several maneuvers never before attempted, including several months when each craft moved in a kidney-shaped path on each side of the moon around, well, nothing but a gravitational point in space marked by no physical planet or object.
“No one has ever tried this orbit before, it’s an Earth-Moon libration orbit,” says David Folta a flight dynamics engineer at NASA’s Goddard Space Flight Center in Greenbelt, Md. “It’s a very unstable orbit that requires daily attention and constant adjustments.”
The journey for ARTEMIS — short for Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun — began in 2009, after THEMIS had completed some two years of science data collection on the magnetic environment around Earth, the aurora, and how these are affected by the sun.
The spacecraft are solar-powered, but orbits for the two outermost THEMIS spacecraft had slipped over time and were going to be subjected to regular eight-hour periods of darkness. These spacecraft could withstand up to three hours without sunlight, but this much darkness would soon leave the batteries completely discharged.
Teams at UC-Berkeley and Goddard handled the day-to-day control of the THEMIS spacecraft. The Principal Investigator for the mission, Vassilis Angelopoulos of UCLA talked to the teams about moving the two spacecraft to the moon to study the magnetic environment there. But quick models of a conventional boost technique showed that all the remaining fuel would be used simply in transit. There wouldn’t be enough left over for the fuel-hungry process of adjusting direction and speed to actually begin circling the moon.
So Angelopoulos pulled together a new, more complex multi-year-long orbit change plan. The move would rely predominantly on gravity assists from the moon and Earth to move the spacecraft into place. He brought his idea to two engineers who had been involved with launching THEMIS in the first place: David Folta and another flight engineer at Goddard, Mark Woodard. The pair used their own models to validate this new design, and the plan was on.
First step: increase the size of the orbits. The original Earth-centric orbits barely reached half way to the moon. By using small amounts of fuel to adjust speed and direction at precise moments in the orbit, the spacecraft were catapulted farther and farther out into space. It took five such adjustments for ARTEMIS P1 and 27 for ARTEMIS P2.
Next step: make the jump from Earth orbit to the tricky kidney-shaped “Lissajous” orbit, circling what’s known as a Lagrangian point on each side of the moon. These points are the places where the forces of gravity between Earth and the moon balance each other – the point does not actually offer a physical entity to circle around. ARTEMIS P1 made the leap – in a beautiful arc under and around the moon — to the Lagrangian point on the far side of the moon on August 25, 2010. The second craft made the jump to the near side of the moon on October 22. This transfer required a complex series of maneuvers including lunar gravity assists, Earth gravity assists, and deep space maneuvers. The combination of these maneuvers was needed not only to arrive at the correct spot near the moon but also at the correct time and speed.
Using a series of Earth and moon gravity assists – and only the barest bit of fuel – the ARTEMIS spacecraft entered into orbit around the moon’s Lagrangian points in the winter of 2010. Credit: NASA Goddard Space Flight Center/Scientific Visualization Studio
History was made. Numerous satellites orbit Lagrangian points between Earth and the Sun but, while this orbit had been studied extensively, it had never before been attempted.
Not only was this an engineering feat in and of itself, but the spacecraft were now in an ideal spot to study magnetism some distance from the moon. In this position, they could spot how the solar wind – made up of ionized gas known as plasma — flows past the Moon and tries to fill in the vacuum on the other side. A task made complicated since the plasma is forced by the magnetic fields to travel along certain paths.
“It’s a veritable zoo of plasma phenomena,” says David Sibeck, the project manager for THEMIS and ARTEMIS at Goddard. “The Moon carves out a cavity in the solar wind, and then we get to watch how that fills in. It’s anything but boring. There’s microphysics and particle physics and wave particle interaction and boundaries and layers. All things we haven’t had a chance to study before in the plasma.”
Life for the flight engineers was anything but boring too. Keeping something in orbit around a spot that has little to mark it except for the balance of gravity is no simple task. The spacecraft required regular corrections to keep it on track and Folta and Woodard watched it daily.
“We would get updated orbit information around 9 a.m. every day,” says Woodard. “We’d run that through our software and get an estimate of what our next maneuver should be. We’d go back and forth with Berkeley and together we’d validate a maneuver until we knew it was going to work and keep us flying for another week.”
The team learned from experience. Slight adjustments often had bigger consequences than expected. They eventually found the optimal places where corrections seemed to require less subsequent fine-tuning. These sweet spots came whenever the spacecraft crossed an imaginary line joining Earth and the Moon, though nothing in theories had predicted such a thing.
The daily vigilance turned out to be crucial. On October 14, the P1 spacecraft orbit and attitude changed unexpectedly. The first thought was that the tracking system might have failed, but that didn’t seem to be the problem. However, the ARTEMIS team also noticed that the whole craft had begun to spin about 0.001 revolutions per minute faster. One of the instruments that measures electric fields also stopped working. Best guess? The sphere at the end of that instrument’s 82-foot boom had broken off – perhaps because it was struck by something. That sphere was just three ounces on a spacecraft that weighed nearly 190 pounds — but it adjusted ARTEMIS P1’s speed enough that had they caught the anomaly even a few days later they would have had to waste a prohibitive amount of fuel to get back on course.
An artist's concept of the ARTEMIS spacecraft in orbit around the Moon. Credit: NASA
As it is, ARTEMIS will make it to the moon with even more fuel than originally estimated. There will be enough fuel for orbit corrections for seven to 10 years and then enough left over to bring the two craft down to the moon.
“We are thrilled with the work of the mission planners,” says Sibeck. “They are going to get us much closer to the moon than we could have hoped. That’s crucial for providing high quality data about the moon’s interior, its surface composition, and whether there are pockets of magnetism there.”
On January 9, 2011, ARTEMIS P1 jumped over the moon and joined ARTEMIS P2 on the side of the Moon closest to Earth. Now the last steps are about to begin.
On June 27, P1 will spiral in toward the moon and enter lunar orbit. On July 17, P2 will follow. P2 will travel in the same direction with the Moon, or in prograde; P1 will travel in the opposite direction, in retrograde.
“We’ve been monitoring ARTEMIS every day and developing maneuvers every week. It’s been a challenge, but we’ve uncovered some great things,” says Folta, who will now focus his attention on other NASA flights such as the MAVEN mission to Mars that is scheduled to launch in 2013. “But soon we’ll be done with this final maneuvering and, well, we’ll be back to just being ARTEMIS consultants.”
See additional ARTEMIS imagery and video at this link.
Check out this way cool time-lapse movie of NASA’s Curiosity Mars rover as its being packed up for her trip to Florida.
The video covers a 4 day period from June 13 to 17 and is condensed to just 1 minute. Watch the JPL engineers and technicians prepare Curiosity and the descent stage for shipping to the Kennedy Space Center in Florida and place it inside a large protective shipping container. Continue reading “Packing a Mars Rover for the Trip to Florida”
Spectacular view of the Degas crater from MESSENGER in Mercury orbit. This high-resolution view of Degas crater was obtained as a targeted observation (90 m/pixel). Impact melt coats its floor, and as the melt cooled and shrank, it formed the cracks observed across the crater. For context, Mariner 10’s view of Degas is shown at left. Degas is 52 km in diameter and is centered at 37.1° N, 232.8° E. Credit: NASA/The Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
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NASA’s MESSENGER probe to Mercury, the scorched, innermost planet of our solar system, is sending back so much startling and revolutionary data and crystal clear images that the results are forcing scientists to toss out previously cherished theories and formulate new ones even as the results continues to pour in. And the mission has barely begun to explore Mercury’s inner secrets, exterior surface and atmospheric environment.
MESSENGER became the first spacecraft ever to orbit planet Mercury on March 18, 2011 and has just completed the first quarter of its planned one year long mission – that’s the equivalent of one Mercury year.
MESSENGER has collected a treasure trove of new data from the seven instruments onboard yielding a scientific bonanza; these include extensive global imagery, measurements of the planet’s surface chemical composition, topographic evidence for significant amounts of water ice, magnetic field and interactions with the solar wind, reported the science team at a press conference at NASA Headquarters.
Schematic illustration of the operation of MESSENGER's X-ray Spectrometer (XRS). When X-rays emitted from the Sun’s corona strike the planet, they can induce X-ray fluorescence from atoms at the surface. Detection of these fluorescent X-rays by the XRS allows determination of the surface chemical composition. Credit: NASA/The Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
“We are delighted to share the findings of the first 25% of our year long mission,” said MESSENGER principal investigator Sean Solomon of the Carnegie Institution of Washington at a press briefing for reporters. “We receive new data back almost every day.”
“MESSENGER has snapped over 20,000 images to date,” said Solomon, at up to 10 meters per pixel. The probe has also taken over two million laser-ranging topographic observations, discovered vast volcanic plains, measured the abundances of many key elements and confirmed that bursts of energetic particles in Mercury’s magnetosphere result from the interaction of the planets magnetic field with the solar wind.
“We are assembling a global overview of the nature and workings of Mercury for the first time.”
“We had many ideas about Mercury that were incomplete or ill-formed, from earlier flyby data,” explained Solomon. “Many of our older theories are being cast aside into the dust bin as new observations from new orbital data lead to new insights. Our primary mission has another three Mercury years to run, and we can expect more surprises as our solar system’s innermost planet reveals its long-held secrets.”
Magnetic field lines differ at Mercury's north and south poles As a result of the north-south asymmetry in Mercury's internal magnetic field, the geometry of magnetic field lines is different in Mercury's north and south polar regions. In particular, the magnetic "polar cap" where field lines are open to the interplanetary medium is much larger near the south pole. This geometry implies that the south polar region is much more exposed than in the north to charged particles heated and accelerated by solar wind–magnetosphere interactions. The impact of those charged particles onto Mercury's surface contributes both to the generation of the planet's tenuous atmosphere and to the "space weathering" of surface materials, both of which should have a north-south asymmetry given the different magnetic field configurations at the two poles. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
NASA’s Mariner 10 was the only previous robotic probe to explore Mercury, during three flyby’s back in the mid-1970’s early in the space age.
MESSENGER was launched in 2004 and the mission goal is to produce the first global scientific observations of Mercury and piece together the puzzle of how Mercury fits in with the origin and evolution of our solar system.
There was very little prior imaging coverage of Mercury’s northern polar region.
“We’ve now filled in many of the gaps,” said Messenger scientist Brett Denevi of Johns Hopkins University’s Applied Physics Laboratory (APL). “We now see large smooth plains that are thought to be volcanic in origin.”
“Now we’re seeing for the first time their full extent, which is around 4 million square kilometers (1.54 million square miles). That’s about half the size of the continental United States.” MESSENGER is currently filling in coverage of Mercury’s north polar region, which was seen only partially during the Mariner 10 and MESSENGER flybys. Flyby images indicated that smooth plains were likely important in Mercury’s northernmost regions. MESSENGER's orbital images show that the plains are among the largest expanses of volcanic deposits on Mercury, with thicknesses of several kilometers in many places. The estimated extent of these plains is outlined in yellow. This mosaic is a combination of flyby and orbital coverage in a polar stereographic projection showing latitudes from 50° to 90° N. The longitude at the 6 o'clock position is 0°. Credit: NASA/The Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
“We see all kinds of evidence for volcanism and tectonic deformation of the plains from orbit where we can look straight down,” added Denevi. “In the new images we see ghost craters from pre-existing impact craters that were later covered over by lava.’
Color images of the whole planet – with a resolution of about 1 kilometer per pixel – tell the researchers about the chemical composition and rock types on Mercury’s surface.
“We don’t know the composition yet.”
“We are very excited to study these huge volcanic deposits near the north pole with the implications for the evolution of Mercury’s crust and how it formed,” said Denevi.
“Targeted new high resolution imaging is helping us see landforms unlike anything we’ve seen before on Mercury or the moon.”
MESSENGER’s orbital images have been overlaid on an image from the second flyby shown in Image 1.2a. Even for previously imaged portions of the surface, orbital observations reveal a new level of detail. This region is part of the extensive northern plains, and evidence for a volcanic origin can now be seen. Several examples of “ghost” craters, preexisting craters that were buried by the emplacement of the plains, are seen near the center of the mosaic. Credit: NASA/The Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Determining whether Mercury harbors caches of polar water ice is another one of the many questions the MESSENGER science team hopes to answer.
Two decades ago, Earth-based radar images showed deposits thought to consist of water ice near Mercury’s north and south poles. Researchers postulated a theory that these icy deposits are preserved on the cold, permanently shadowed floors of high-latitude impact craters, similar to those on Earth’s moon.
Early results from topographic measurements are promising.
“The very first scientific test of that hypothesis using Messenger data from orbit has passed with flying colors.”
“The area of possible polar water ice is quite a bit larger than on the moon,” said Solomon. “Its probably meters or more in depth based on radar measurements.”
“And we may have the irony that the planet closest to the sun may have more water ice at its poles than even our own moon.”
“Stay tuned. As this mission evolves, we will be relying on the geochemical and remote sensing instruments which take time to collect observations. The neutron and gamma ray spectrometers have the ability to tell us the identity of these icy materials,” said Solomon.
The same scene as that in Image 1.3a is shown after the application of a statistical method that highlights differences among the eight color filters, making variations in color and composition easier to discern. Credit: NASA/The Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of WashingtonThis topographic contour map was constructed from the several MLA profiles (lines of white circles) that pass through and near the crater circled in Image 3.4. The color scale at right is in km, and north is at the 4 o’clock position. Calculations show that the topography of the crater is consistent with the prediction that the southernmost portion of the crater floor is in permanent shadow. Credit: NASA/The Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of WashingtonA cross-section of Mercury’s magnetosphere (in the noon-midnight plane, i.e., the plane containing the planet-Sun line and Mercury’s spin axis) provides context for the energetic electron events observed to date with the MESSENGER XRS and GRS high-purity germanium (HpGe) detectors. The Sun is toward the right; dark yellow lines indicate representative magnetic field lines. Blue and green lines trace the regions along MESSENGER's orbit from April 2 to April 10 during which energetic electrons were detected and MESSENGER's orbit was within ± 5° of the noon-midnight plane. The presence of events on the dayside, their lack in the southern hemisphere, and their frequency of occurrence at middle northern latitudes over all longitudes point to a more complex picture of magnetospheric activity than found at Earth. Credit: NASA/The Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
How would you like to help choose an additional destination or two for a spacecraft heading to the outer solar system? A new citizen science project from the Zooniverse — called Ice Hunters — will allow the public to help discover a potential new, icy follow-on destination for NASA’s New Horizons spacecraft, which is currently en route to make the first flyby of the Pluto system. However, after it zooms past Pluto, the spacecraft will have the capability to explore other Kuiper Belt Objects. But, the destination has yet to be chosen. That’s where you can help.
“Projects like this make the public part of modern space exploration,” said Dr. Pamela Gay. “The New Horizon’s mission was launched knowing we’d have to discover the object it would visit after Pluto. Now is the time to make that discovery and thanks to IceHunters, anyone can be that discoverer.”
With Ice Hunters, the public can help scientists search through specially-obtained deep telescopic images for currently unknown objects in the Kuiper Belt. While the images you’ll be perusing in Ice Hunters won’t be the beautiful astronomical images seen in the Galaxy Zoo classification of galaxies or the Moon Zoo images of the Moon, the science rewards in Ice Hunters will be spectacular.
And there’s more: there’s also the potential for discovering variable stars and asteroids.
What’s cool is that you’ll be searching for KBO’s and potential dwarf planets in much the same way that Clyde Tombaugh found Pluto: comparing images of the same region of the Kuiper Belt and looking for objects that move or vary in brightness.
“The New Horizons project is breaking new ground in many ways,” said New Horizons Principal Investigator Alan Stern. “We’re flying by a new kind of planet and we’ll be making the most distant encounters with planetary bodies in the history of space exploration, and now we’re employing citizen science to help find our potential extended mission flyby targets, perhaps a billion kilometers farther than even distant Pluto and its moons. We’re very excited to be working with Zooniverse and breaking this new kind of ground. We hope the public will be excited to join in with us and with Zooniverse to make a little history of their own by discovering our next flyby target after Pluto.”
Somewhere, on the outer edges of the solar system an icy body lurks undiscovered, orbiting on a path that will just happen to carry it toward a potential rendezvous with the New Horizons spacecraft.
New Horizons will flyby Pluto in 2015, and there will be enough gas in the spacecraft’s tank to fly toward at least one and possibly two Kuiper Belt Objects in the distant outer solar system. The expected date of the KBO flyby will be between 2016 and 2020, depending on the object chosen and its distance from Pluto.
Your mission, should you choose to accept, is to find the most interesting KBO possible for New Horizons to visit. If that object can be found , it will become the most distant object ever visited by a spacecraft from Earth.
The Kuiper Belt is a region of the outer solar system, extending past Neptune, (from 30AU) out to nearly twice Neptune’s orbit (out to roughly 55AU), which contains icy bodies in a variety of different sizes up to thousands of kilometers across. The first KBO other than Pluto was only discovered in 1992, and the KBO population is still not well mapped. Ice Hunters will do its part to study one small slice of the Kuiper Belt as it looks for an object along New Horizon’s trajectory after its Pluto flyby.
Using some of the largest telescopes in the world, scientists have imaged that region, producing millions of pictures for that could contain images of the rare objects that are orbiting toward just the right location, along with many other small worlds on different trajectories.
In “difference” images, which are created by subtracting observations taken at two different times, scientists can mostly (but not entirely) remove the light from constant sources like stars and galaxies. Left behind are the things that move or vary in brightness, which is what the users of IceHunters will be looking for. Since the stars never subtract off perfectly, the images appear messy, and computers can’t be trained to find objects as effectively as people can.
“When you’re looking for something special in masses of messy, real-world data, sometimes there’s no substitute for the human eye, and Zooniverse Ice Hunters will put thousands of eyes to work on this important job,” said John Spencer of Southwest Research Institute, a member of the New Horizons science team who is coordinating the search effort.
Just as other Zooniverse projects have easy-to-use websites, IceHunters.org is no different. “Using just about any modern web-browser, users can circle potential KBOs and mark with a star the locations of asteroids,” said web developer Cory Lehan from Southern Illinois University Edwardsville, who has participated in several Zooniverse web designs. “The website is filled with examples to help get people started. Anyone should be able to take part – No Flash required.”
So check out Ice Hunters and start discovering today!
You can follow Universe Today senior editor Nancy Atkinson on Twitter: @Nancy_A. Follow Universe Today for the latest space and astronomy news on Twitter @universetoday and on Facebook.
The Johannes Kepler ATV (Automated Transfer Vehicle) has undocked from the International Space station and will re- enter Earth’s atmosphere on June 21st ending its mission in fiery destruction.
The ATV has been docked with the ISS since February, where it delivered supplies, acted as a giant waste disposal and boosted the orbit of the International Space Station with its engines.
The X-wing ATV delivered approximately 7 tonnes of supplies to the station and will be leaving with 1,200kg of waste bags, including unwanted hardware.
The Johannes Kepler ATV-2 approaches the International Space Station. Docking of the two spacecraft occurred on Feb. 24, 2011. Credit: NASA
On June 21st at 17:07 GMT the craft will fire its engines and begin its suicide mission, tumbling and burning up as a bright manmade fireball over the Pacific Ocean. Any leftover debris will strike the surface of the Pacific ocean at 20:50 GMT.
During the ATV’s re-entry and destruction there will be a prototype onboard flight recorder (Black Box) transmitting data to Iridium satellites, as some aspects of a controlled destructive entry are still not well known.
ESA says that this area is used for controlled reentries of spacecraft because it is uninhabited and outside shipping lanes and airplane routes. Extensive analysis by ESA specialists will ensure that the trajectory stays within safe limits.
There still are some chances to see the ISS and Johannes Kepler ATV passing over tonight, but if you in a location where you can see the south Pacific skies starting at about 20:00 GMT, keep an eye out for a glorious manmade fireball.
A shower of debris results as the ATV continues its plunge through the atmosphere. Credit: ESA
Jets can be seen streaming out of the nucleus, or main body, of comet Hartley 2 in this image from NASA's EPOXI mission. The nucleus is approximately 2 kilometers (1.2 miles) long and .4 kilometers (.25 miles) across at the narrow "neck." Credit: NASA/JPL-Caltech/UMD
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No, EPOXI isn’t the name of a new super glue, but an abbreviation for the continuation of Deep Impact. While the original mission to study Comet 9P/Tempel was a huge success, the spacecraft continues to explore objects of opportunity. Its name is derived from Extrasolar Planet Observations and Characterization (EPOCh) and the Deep Impact Extended Investigation (DIXI)… and it’s now fulfilling another goal as it swings by Comet Hartley 2. It approached, encountered and departed, sending back 117,000 images and spectral findings – along with some surprising observations.
“From all the imaging we took during approach, we knew the comet was a little skittish even before flyby,” said EPOXI Project Manager Tim Larson of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It was moving around the sky like a knuckleball and gave my navigators fits, and these new results show this little comet is downright hyperactive.”
What EPOXI found was a “hyperactive comet” – one that didn’t react in anticipated ways. From a distance of 431 miles (694 kilometers), the spacecraft watched as water and carbon-dioxide jets erupted from the flying space rock’s surface. While this in itself isn’t unusual, the fact that it didn’t happen uniformly caused scientists to sit up and take notice. Jets occurred at both ends of the comet with the strongest activity centered on the small end. Water vapor ejected from the central portion showed a notable lack of carbon-dioxide and ice, leading investigators to speculate the material was re-deposited from the ends of Hartley 2.
“Hartley 2 is a hyperactive little comet, spewing out more water than most other comets its size,” said Mike A’Hearn, principal investigator of EPOXI from the University of Maryland, College Park. “When warmed by the sun, dry ice — frozen carbon dioxide — deep in the comet’s body turns to gas jetting off the comet and dragging water ice with it.”
A large, diffuse cloud of CN gas surrounds the nucleus of Hartley 2 in this image from NASA's EPOXI mission. The gas forms a cloud of more than 200,000 kilometers (about 124,000 miles) in radius, compared to the comet's size of about 2 kilometers (1.24 miles). Credit: NASA/JPL-Caltech/UMDIs Hartley 2 unique? No. Scientists are aware of at least a dozen comets that behave similarly, but this is the first we’ve been able to examine closely via a spacecraft. These odd comets are extremely active for their size and may be driven by carbon dioxide or carbon monoxide. “These could represent a separate class of hyperactive comets,” said A’Hearn. “Or they could be a continuum in comet activity extending from Hartley 2-like comets all the way to the much less active, “normal” comets that we are more used to seeing.”
What makes this new class of comets so unusual? Just three ingredients: deposits around the inactive center which may have originated at the ends, a tumbling state of rotation and a large end containing ubiquitous inclusions which can span`approximately 165 feet (50 meters) high and 260 feet (80 meters) wide. EPOXI also picked up another surprise at Hartley 2’s smaller end – shiny cubicals reaching 16 stories tall and two to three times more reflective than other average surface materials. But that’s not all. For nine days in September, the energetic comet expelled 10 million times more CN gas in its coma – a dramatic and unexpected change called the “CN anomaly”. It was analyzed by McFadden and Dennis Bodewits, a former postdoctoral fellow at NASA Goddard who is now at the University of Maryland, and their colleagues. This comet exhaust normally includes a similar amount of dust, but not in this case.
“We aren’t sure why this dramatic change happened,” says McFadden. “We know that Hartley 2 gives off considerably more CN gas than comet Tempel 1, which was studied earlier by a probe released by the Deep Impact spacecraft. But we don’t know why Hartley 2 has more CN, and we don’t know why the amount coming off the comet changed so drastically for a short period of time. We’ve never seen anything like this before.”
The edge of the solar system. Image Credit: NASA/JPL-Caltech
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It may be some 10.8 billion miles from home, but Voyager 1 is sending back some surprising data from the edge Even more recent transmissions show the gallant probe is closer to interstellar space than ever. “We’ve reached the boundary of the heliosheath, Jim… and it ain’t dead.”
It has taken 34 years, but Voyager 1 has now defiantly encountered the edge – the area where the speed of the solar plasma has decreased from 150,000 miles an hour down to zero. As released in the June 16th issue of Nature, a team of Voyager scientists led by Stamatios Krimigis of the Johns Hopkins University Applied Physics Laboratory speculates “the outflow of the solar wind may have stopped because of the pressure from the interstellar magnetic field in the region between stars.”
For the last three years the incredible little probe has been busy overseeing the predominant part of the plasma’s velocity in the heliosheath – a virtual pool of energetic ions and electrons. Now measurements have slipped from 40 miles per second to zero. This was first noted in April when Voyager’s speed matched the assessments.
“This tells us that Voyager 1 may be close to the heliopause, or the boundary at which the interstellar medium basically stops the outflow of solar wind,” says Krimigis, principal investigator for Voyager’s Low-Energy Charged Particle instrument. “The extended transition layer of near-zero outflow contradicts theories that predict a sharp transition to the interstellar flow at the heliopause – and means, once again, we will need to rework our models.”
Because we’re literally breaking new science ground, these new findings on velocities could fluctuate – meaning that more monthly readings are in order. When will we know? A good indicator would be when hot particles turn cold… a signal that interstellar space has been breached. This could occur as soon as the end of 2012.
Just another reason we might be around just a little bit longer…
What will the June 15th lunar eclipse look like from the Moon itself? Luckily, we’ve got the Lunar Reconnaissance Orbiter circling the Moon, and we can find out. However, most of the instruments on LRO will be powering down during the eclipse, but one instrument, called Diviner, will stay on. “It will be like a nap with one eye open!” the LRO spacecraft said on Facebook. The Diviner Lunar Radiometer instrument will record how quickly different areas on the moon’s day side cool off during the eclipse. Since large boulders cool more slowly than a fine-grained or dusty surface, Diviner will be able to see what areas are covered with boulders and what regions are blanketed by dust. Continue reading “How LRO Plans to Watch the Lunar Eclipse from the Moon”
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:
