The planetary pileups of popular solar system orbits

Some orbits are apparently more popular than others in young solar systems emerging around baby stars - which often results in "planet pileups" and "planet deserts."


Sophisticated computer simulations have revealed a rather plausible explanation for a phenomenon that has long puzzled astronomers. 

Essentially, rather than occupying orbits at regular distances from a star, giant gas planets similar to Jupiter and Saturn appear to prefer residing within certain regions of mature solar systems while staying clear of others.

The planet pileups of popular solar system orbits"Our results show that the final distribution of planets does not vary smoothly with distance from the star," explained Ilaria Pascucci, an assistant professor at the University of Arizona's Lunar and Planetary Laboratory. "Instead, it has clear 'deserts' - deficits of planets - and 'pileups' of planets at particular locations."


Pascucci and Richard Alexander of the University of Leicester identified high-energy radiation from baby sun-like stars as the likely force that carves gaps in protoplanetary disks, the clouds of gas and dust that swirl around young stars and provide the raw materials for planets. The gaps then act as barricades, corralling planets into certain orbits.

Of course, the exact locations of those gaps depend on the planets' mass, but they generally occur in an area between 1 and 2 astronomical units from the star. One astronomical unit, or AU, marks the average distance from the Earth to the sun. 

According to conventional wisdom, a solar system starts out from a cloud of gas and dust. At the center of the prospective solar system, material clumps together, forming a young star. As the baby star grows, its gravitational force increases as well, and it attracts dust and gas from the surrounding cloud.

Accelerated by the growing gravitation of its star, the cloud spins faster and faster, and eventually flattens into what is called a protoplanetary disk. Once the bulk of the star's mass has formed, it is still fed material by its protoplanetary disk, but at a significantly lower rate.

"For a long time, it was assumed that the process of accreting material from the disk onto the star was enough to explain the thinning of the protoplanetary disk over time," said Pascucci. "Our new results suggest that there is another process at work that takes material out of the disk."

That process, called photo-evaporation, works by high-energy photons streaming out of the star and heating the dust and gas on the surface of the protoplanetary disk.

"The disk material that is very close to the star is very hot, but it is held in place by the star's strong gravity," Alexander noted. "Further out in the disk where gravity is much weaker, the heated gas evaporates into space."

However, even further out in the disk, the radiation emanating from the star is not intense enough to heat the gas sufficiently to cause much evaporation. Yet at a distance between 1 and 2 AU, the balancing effects of gravitation and heat clear a gap.

While studying protoplanetary disks, Pascucci also discovered that gas on the surface of the disk was gravitationally unbound and leaving the disk system via photoevaporation. These were the first observations proving that photoevaporation does occur in real systems.

Encouraged by those findings, Alexander and Pascucci subsequently used the ALICE High Performance Computing Facility at the University of Leicester to simulate protoplanetary discs undergoing accretion of material to the central star that took the effects of photo-evaporation into account.

"We don't yet know exactly where and when planets form around young stars, so our models considered developing solar systems with various combinations of giant planets at different locations and different stages in time," Alexander said.

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Solar Storm Blasts Electrons from Earth's Van Allen Belts

Scientists say they have solved the mystery of why electrically-charged particles intent in radiation belts thousands of kilometers above the Earth suddenly vanish and then reappear during periods of heightened solar activity.

NASA-funded researchers at the University of California, Los Angeles (UCLA) tracked the electrons using data collected at once with 11 different spacecraft.

Their findings show that when bursts of solar energy released by storms on the sun strike Earth’s magnetic field, they send electrons in the so-called Van Allen radiation belts hurtling into external space. Within a few days, the depleted radiation rings once again swell with a whole new crop of the sun’s highly-charged electrons, which are so active that they move at almost the speed of light.

The UCLA researchers note that the highly charged particles that escape the Van Allen belts forever stream outward, rather than raining down into Earth’s atmosphere as some theories suggest.

The Van Allen belts are a method of bubble-shaped rings of radiation that encircle the planet. Earth's protective magnetic field holds the Van Allen belts in their spot several tens of thousands of kilometers above its surface, and protects the planet from deadly solar, cosmic and other types of space radiation.

The Van Allen belts are named after late NASA astrophysicist James Van Allen, who confirmed occurrence of the radiation rings in 1958. The revolutionary scientist died in 2006 at the age of 91.

Moon and planets offer triple treat on Friday

Look toward the southwestern horizon just after sunset on Friday night and you’ll see a triple feature of Venus, Mercury, and the two-day old moon. And there's another planet treat in time for the pre-Halloween weekend, too.

You'll need a good low horizon and a clear sky to see the first three objects since they will be very low in the sky, less than 10 degrees up. Binoculars may help. For reference, a closed first held out at arm's length covers about 10 degrees of the night sky.

The accompanying sky map of the moon and planets here shows their locations on Friday evening.

The moon will be a razor-thin crescent, and the so-called "dark" side of the moon — actually its far side facing away from Earth, which is not always dark — should be well lit by sunlight reflecting off the Earth.

Venus should appear very bright, weather permitting. This may be the first glimpse you get of it this season, but it will soon be blazing bright every evening. Mercury will be directly under Venus.

All three objects will be very low because of the shallow angle the ecliptic — the path the sun takes across the sky — makes with the horizon on Friday. Notice that the sun is setting well to the south of the west point on the horizon, now that we're more than a month past the fall equinox.

The only days the sun sets due west is right on the equinoxes, which were March 20 and Sept. 23 this year.

A few minutes after sunset, turn around and look at the eastern horizon. You will see Jupiter rising there slightly north of due east, the brightest object in that part of the sky.

At 10 p.m. EDT on Friday, Jupiter will be opposition, exactly opposite the sun in the sky. On this night, Jupiter rises at sunset and sets at sunrise, so is visible all night long.

Binoculars or a small telescope can reveal Jupiter's four bright moons, allowing you to follow them as they constantly shift position, orbiting around the giant planet.

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Doomsday comet makes closest approach to Earth

ANTICIPATED by doomsayers as a potentially catastrophic event, Comet Elenin traversed the closest point in its trajectory around Earth (35,000km) early Sunday morning just before sunrise. But save for a few keen observers and astronomers, this went largely unnoticed.

When discovered by astronomer Leonid Elenin in December 2010, the passing of the 3-5 km wide chunk of space ice was predicted to be the astronomical event of the year, which in turn inspired an overkill of apocalyptic theories.

Amateur astronomers and conspiracy theorists put forth the idea that Comet Elenin was responsible for a variety of anomalous events seen throughout 2011; from the scattered outbursts of political uprisings to the earthquake in Japan.

Others extrapolated these prophecies to Comet Elenin representing the end of the world.
However, sometime during the middle of August, Comet Elenin began disintegrating as it crossed the solar system and traveled through the sun’s solar flares. And so at around 4 am Sunday morning, the comet passed within view of ground telescopes in an event that astronomers described as “largely uneventful.”

“I could see a hazy group of dim chunks of rock sitting in the sky, moving very slowly,” said Samir Nawar, a professor at the National Research Institute of Astronomy and Geophysics (NRIAG) in Helwan.

“But it was far less interesting than looking at the sun or the moon on any other day of the year, and a lot less noticeable,” he joked, referring to the Earth’s temperate climate and tides.
On the issue of conspiracy theories, Nawar went on to say that there is an obsession with space phenomena, which are far away and little understood; and that even if Comet Elenin had not disintegrated, the event would have still passed largely unnoticed. –AA

“People like to play on the fact that there are a lot of ‘maybes’ with these ‘unknown’ phenomena,” he continued. “But the truth is there are few maybes; there is a lot of accuracy with understanding space science, more than there is an understanding of what’s at the bottom of the oceans. If there was any issue of concern, NASA or any professional astronomer would be the first to raise the issue.”

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New Proof That Comets Watered the Earth

By rights, the earth should not be the cosmic garden it is. In a solar system of planets and moons that are solid rock or mostly gas, shrouded in clouds or atmosphere-free, scorchingly hot or bitterly cold, there's only one that's dripping wet. Earthlings like to refer to our home planet as the solar system's water world, and it's a jolly good thing it's as wet as it is, because without plenty of water, life (at least as we know it) would be impossible.

All the same, it's likely our planet was once a far drier, dustier place. You need only look at two of our nearby rocky neighbors — Mercury and Venus — for a reminder of what living so close to the blast furnace of the sun can do to you. Our atmosphere helps us retain the abundant water we do have, but how did it get to us in the first place?

One popular theory has long been comets. The solar system swarms with these little rogue bodies — perhaps a trillion of them, according to astronomers' back-of-the-envelope estimates — and shortly after the sun and planets formed, they were everywhere, flying randomly and free to collide with anything in their way. Since comets are essentially dirty snowballs made of rock, gas and water ice, a few crash landings on earth could have provided all the water we needed quite nicely.

But there was a problem with that theory. All of the comets astronomers observed were indeed packed with water ice, but a lot of it was what's known as heavy water, in which the hydrogen in the H2O mix is an isotope known as deuterium, with one proton and one neutron in its nucleus. The hydrogen found in ordinary water has no neutron. Since the overwhelming share of the water in earth's oceans is made with the light hydrogen atom, astronomers calculated that comets could have accounted for only about 10% of what's there. Now, according to a new paper published in the journal Nature, it appears that those scientists may have been wrong — and the reason for their error is that they were simply looking at the wrong comets.

The paper, co-authored by researchers at the California Institute of Technology, is based on observations conducted by the Herschel Space Observatory, a spacecraft launched by the European Space Agency in 2009. Herschel looked specifically at comet Hartley 2, a small comet discovered in 1986 with an estimated diameter of .75 to .99 mi. (1.2 to 1.6 km). Analyzing the chemical composition of Hartley 2's corona — or the gassy veil surrounding the main comet body — Herschel discovered that its concentration of heavy water was only about half that of any comets observed before. While that wouldn't entirely explain earth's particular heavy- and light-water mix, it does bring the chemistry a lot more into line — and gives the cometary explanation for earthly water a big boost.

"Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early earth," says physicist Dariusz Lis of Caltech, a co-author of the paper.

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How Common Are Earth-Moon Planetary Systems

Earth's Moon might have played an important role in the development and evolution of life on Earth. The Moon was formed via a giant impact in which a Mars-size projectile collided with the young Earth. The ejected material accumulated in orbit around our planet and formed the Moon. After its formation, the Moon was much closer to Earth than it is today, which caused high tides several times per day.

This may have helped promote the very early evolution of life. In addition, a stable climate of more than a billion years may be essential to guarantee a suitable environment for life. But without its satellite, Earth would suffer chaotic variations of the direction of its spin axis, which would in turn result in dramatic variations of the climate.

Therefore, concerning the habitability of extrasolar planets, it is reasonable to ask: How common are Earth-Moon planetary systems?

Sebastian Elser, Prof. Ben Moore and Dr. Joachim Stadel of the University of Zurich, Switzerland, along with Ryuji Morishima of NASA's Jet Propulsion Laboratory in Pasadena, California, ran a large set of N-body simulations to study the formation of the rocky planets in our solar system via the collisional growth of thousands of small rocky bodies in a disk around the Sun.

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Plenty of room on planet Earth

The world now has almost seven billion people and rising. The population may surpass nine billion by 2050. We, together with our 20 billion chickens and four billion cattle, sheep and pigs, will utterly dominate the planet. Can the planet take it? Can we take it?

Yes. Not only is such a huge population going to prove indefinitely "sustainable;" it is actually likely that the ecological impact of nine billion in 2050 will be lighter, not heavier: there will be less pollution and more space left over for nature than there is today.

Consider three startling facts. The world population quadrupled in the 20th century, but the calories available per person went up, not down. The world population doubled in the second half of the century, but the total forest area on the planet went up slightly, not down. The world population increased by a billion in the last 13 years, but the number living in absolute poverty (less than a dollar a day, adjusted for inflation) fell by around a third.

Clearly it is possible at least for a while to escape the fate forecast by Robert Malthus, the pessimistic mathematical cleric, in 1798. We've been proving Malthus wrong for more than 200 years. And now the population explosion is fading. Fertility rates are falling all over the world: in Bangladesh it's down from 6.8 children per woman in 1955 to 2.7 today; China - 5.6 to 1.7; Iran - 7 to 1.7; Nigeria - 6.5 to 5.2; Brazil 6.1 to 1.8; Yemen - 8.3 to 5.1.

The rate of growth of world population has halved since the 1960s; the absolute number added to the population each year has been falling for more than 20 years. According to the United Nations, population will probably cease growing by 2070. This miraculous collapse of fertility has not been caused by Malthusian misery or coercion (except in China), but by the opposite: enrichment, urbanization, female emancipation, education and above all the defeat of child mortality - which means women start to plan families rather than continue breeding.

Increasing prosperity means eating more food, though. Can we really feed today's let alone tomorrow's billions? In 60 years we have trebled the total harvest of the three biggest crops: wheat, rice and corn. Yet the acreage devoted to growing these crops has barely changed. This is because fertilizer, irrigation, pesticides and new varieties have greatly increased yields.

They continue to do so. Growth regulators boost the yield of wheat. Genetic modification boosts the yield of cotton (while increasing the biodiversity in fields). New enzymes promise to cut the phosphate output and increase weight gain of pigs. These technologies save rainforest by sparing land from the plow. If we went back to organic farming, the world would have to cultivate more than twice as much land as we do.

Already huge swaths of the world are being released from farming and reforested. New England is now 80 per cent woodland, where it was once 70 per cent farmland. Italy and England have more woodland than they have for centuries. Moose, coyotes, beavers and bears are back in places where they have not been for centuries. France has a wolf problem; Scotland a deer problem. It is the poor countries, not the affluent ones, that are losing forest. Haiti, with its near total dependence on renewable power (wood), is 98 per cent deforested and counting.

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Next Mars Rover Gets a Test Taste of Mars Conditions

A space-simulation chamber at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is temporary home this month for the Curiosity rover, which will land on Mars next year.
Tests inside the 25-foot-diameter chamber (7.6-meters) are putting the rover through various sequences in environmental conditions resembling Martian surface conditions. After the chamber's large door was sealed last week, air was pumped out to near-vacuum pressure, liquid nitrogen in the walls dropped the temperature to minus 130 degrees Celsius (minus 202 degrees Fahrenheit), and a bank of powerful lamps simulated the intensity of sunshine on Mars.

Other portions of NASA's Mars Science Laboratory spacecraft, including the cruise stage, descent stage and backshell, remain in JPL's Spacecraft Assembly Facility, where Curiosity was assembled and where the rover will return after the simulation-chamber tests. In coming months, those flight system components and the rover will be shipped to NASA's Kennedy Space Center in Florida for final preparations before the launch period of Nov. 25 to Dec. 18, 2011.




The mission will use Curiosity to study one of the most intriguing places on Mars -- still to be selected from among four finalist landing-site candidates. It will study whether a selected area of Mars has offered environmental conditions favorable for microbial life and for preserving evidence about whether Martian life has existed.
JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory mission for the NASA Science Mission Directorate, Washington.

Hinode Observes Annular Solar Eclipse

On January 4, the Hinode satellite captured these breathtaking images of an annular solar eclipse. An annular eclipse occurs when the moon, slightly more distant from Earth than on average, moves directly between Earth and the sun, thus appearing slightly smaller to observers' eyes; the effect is a bright ring, or annulus of sunlight, around the silhouette of the moon. Hinode, a Japanese mission in partnership with NASA, NAOJ, STFC, ESA, and NSC, currently in Earth orbit, is studying the Sun to improve our understanding of the mechanisms that power the solar atmosphere and drive solar eruptions.

SORCE's Solar Spectral Surprise

Two satellite instruments aboard NASA's Solar Radiation & Climate Experiment (SORCE) mission -- the Total Solar Irradiance Monitor (TIM) and the Solar Irradiance Monitor (SIM) -- have made daily measurements of the sun's brightness since 2003.

The two instruments are part of an ongoing effort to monitor variations in solar output that could affect Earth's climate. Both instruments measure aspects of the sun's irradiance, the intensity of the radiation striking the top of the atmosphere.

Instruments similar to TIM have made daily irradiance measurements of the entire solar spectrum for more than three decades, but the SIM instrument is the first to monitor the daily activity of certain parts of the spectrum, a measurement scientists call solar spectral irradiance.

'Greener' Climate Prediction Shows Plants Slow Warming

A new NASA computer modeling effort has found that additional growth of plants and trees in a world with doubled atmospheric carbon dioxide levels would create a new negative feedback – a cooling effect – in the Earth's climate system that could work to reduce future global warming.

The cooling effect would be -0.3 degrees Celsius (C) (-0.5 Fahrenheit (F)) globally and -0.6 degrees C (-1.1 F) over land, compared to simulations where the feedback was not included, said Lahouari Bounoua, of Goddard Space Flight Center, Greenbelt, Md. Bounoua is lead author on a paper detailing the results that will be published Dec. 7 in the journal Geophysical Research Letters.

Without the negative feedback included, the model found a warming of 1.94 degrees C globally when carbon dioxide was doubled.

NASA-Funded Research Discovers Life Built With Toxic Chemical

NASA-funded astrobiology research has changed the fundamental knowledge about what comprises all known life on Earth.

Researchers conducting tests in the harsh environment of Mono Lake in California have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes arsenic for phosphorus in its cell components.

"The definition of life has just expanded," said Ed Weiler, NASA's associate administrator for the Science Mission Directorate at the agency's Headquarters in Washington. "As we pursue our efforts to seek signs of life in the solar system, we have to think more broadly, more diversely and consider life as we do not know it."

This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth. The research is published in this week's edition of Science Express.

Sunspot 1112 Crackling with Solar Flares

NASA - Fast-growing sunspot 1112 is crackling with solar flares. The three strongest of this 24 hour period: an M3-flare at 1910 UT on Oct. 16th, a C1-flare at 0900 UT and another C1-flare at 1740 UT on Oct. 17th. So far, none of the blasts has hurled a substantial CME toward Earth.

In addition, a vast filament of magnetism is cutting across the sun's southern hemisphere, measuring about 400,000 km. A bright 'hot spot' just north of the filament's midpoint is UV radiation from sunspot 1112. The proximity is no coincidence; the filament appears to be rooted in the sunspot below. If the sunspot flares, it could cause the entire structure to erupt. But so far, none of the flares has destabilized the filament.

Cassini takes Saturn Moons in Paintball Fight

Scientists using data from NASA's Cassini spacecraft have learned that distinctive, colorful bands and splotches embellish the surfaces of Saturn's inner, mid-size moons. The reddish and bluish hues on the icy surfaces of Mimas, Enceladus, Tethys, Dione and Rhea appear to be the aftermath of bombardments large and small.



A paper based on the findings was recently published online in the journal Icarus. In it, scientists describe prominent global patterns that trace the trade routes for material exchange between the moons themselves, an outer ring of Saturn known as the E ring and the planet's magnetic environment. The finding may explain the mysterious Pac-Man thermal pattern on Mimas, found earlier this year by Cassini scientists, said lead author Paul Schenk, who was funded by a Cassini data analysis program grant and is based at the Lunar and Planetary Institute in Houston.

"The beauty of it all is how the satellites behave as a family, recording similar processes and events on their surfaces, each in its own unique way," Schenk said. "I don't think anyone expected that electrons would leave such obvious fingerprints on planetary surfaces, but we see it on several moons, including Mimas, which was once thought to be rather bland."

Schenk and colleagues processed raw images obtained by Cassini's imaging cameras from 2004 to 2009 to produce new, high-resolution global color maps of these five moons. The new maps used camera frames shot through visible-light, ultraviolet and infrared filters which were processed to enhance our views of these moons beyond what could be seen by the human eye.

Europa's buried Ice Chemistry

The frigid ice of Jupiter's moon Europa may be hiding more than a presumed ocean: it is likely the scene of some unexpectedly fast chemistry between water and sulfur dioxide at extremely cold temperatures. Although these molecules react easily as liquids—they are well-known ingredients of acid rain—Mark Loeffler and Reggie Hudson at NASA's Goddard Space Flight Center in Greenbelt, Md., now report that they react as ices with surprising speed and high yield at temperatures hundreds of degrees below freezing. Because the reaction occurs without the aid of radiation, it could take place throughout Europa's thick coating of ice—an outcome that would revamp current thinking about the chemistry and geology of this moon and perhaps others.

"When people talk about chemistry on Europa, they typically talk about reactions that are driven by radiation," says Goddard scientist Mark Loeffler, the first author on the paper being published Oct. 2 in Geophysical Research Letters. That's because the moon's temperature hovers around 86 to 130 Kelvin, or about –300 to –225 °F. In this extreme cold, most chemical reactions require an infusion of energy from radiation or light. On Europa, the energy comes from particles from Jupiter's radiation belts. Because most of those particles penetrate just fractions of an inch into the surface, models of Europa's chemistry typically stop there.

"Once you get below Europa's surface, it's cold and solid, and you normally don't expect things to happen very fast under those conditions," explains co-author Reggie Hudson, the Associate Lab Chief of Goddard's Astrochemistry Laboratory.

Spring on Titan Brings Sunshine and Patchy Clouds

The northern hemisphere of Saturn's moon Titan is set for mainly fine spring weather, with polar skies clearing since the equinox in August last year. The visual and infrared mapping spectrometer (VIMS) aboard NASA's Cassini spacecraft has been monitoring clouds on Titan regularly since the spacecraft entered orbit around Saturn in 2004. Now, a group led by Sébastien Rodriguez, a Cassini VIMS team collaborator based at Université Paris Diderot, France, has analyzed more than 2,000 VIMS images to create the first long-term study of Titan's weather using observational data that also includes the equinox. Equinox, when the sun shone directly over the equator, occurred in August 2009.

Rodriguez is presenting the results and new images at the European Planetary Science Congress in Rome on Sept. 22.

Though Titan's surface is far colder and lacks liquid water, this moon is a kind of "sister world" to Earth because it has a surface covered with organic material and an atmosphere whose chemical composition harkens back to an early Earth. Titan has a hydrological cycle similar to Earth's, though Titan's cycle depends on methane and ethane rather than water.

A season on Titan lasts about seven Earth years. Rodriguez and colleagues observed significant atmospheric changes between July 2004 (early summer in Titan's southern hemisphere) and April 2010 (the very start of northern spring). The images showed that cloud activity has recently decreased near both of Titan's poles. These regions had been heavily overcast during the late southern summer until 2008, a few months before the equinox.

Over the past six years, the scientists found that clouds clustered in three distinct latitude regions of Titan: large clouds at the north pole, patchy clouds at the south pole and a narrow belt around 40 degrees south. "However, we are now seeing evidence of a seasonal circulation turnover on Titan – the clouds at the south pole completely disappeared just before the equinox and the clouds in the north are thinning out," Rodriguez said. "This agrees with predictions from models and we are expecting to see cloud activity reverse from one hemisphere to another in the coming decade as southern winter approaches."

NASA's Magnetospheric Mission Passes Major Milestone

The universe is still an arcane place that scientists know very little about, but a new NASA Solar Terrestrial Probe mission is going to shed light on one especially mysterious event called magnetic reconnection. It occurs when magnetic lines of force cross, cancel, and reconnect releasing magnetic energy in the form of heat and charged-particle kinetic energy.


On the sun, magnetic reconnection causes solar flares more powerful than several atomic bombs combined. In Earth's atmosphere, magnetic reconnection dispenses magnetic storms and auroras, and in laboratories on Earth it can cause big problems in fusion reactors.

Although the study of magnetic reconnection dates back to the 1950s and despite numerous scientific papers addressing this perplexing issue, scientists still cannot agree on one accepted model.

In 2014, NASA is scheduled to launch a satellite that will greatly increase our understanding of this phenomenon when it launches the Magnetospheric Multiscale (MMS) mission, a suite of four identical spacecraft that will study magnetic reconnection in the best possible laboratory – the Earth’s magnetosphere. The spacecraft will obtain measurements necessary to test prevailing theories as to how reconnection is enabled and how it progresses.

Artist conception of the four Magnetospheric Multiscale (MMS) spacecraft investigating magnetic reconnection within Earth's magnetic field (magnetosphere). Credit: Southwest Research Institute

Recently, NASA and members of an independent review board painstakingly reviewed every aspect of the MMS mission, and successfully completed the mission’s critical design review. This technical review is held to ensure that a mission can proceed into fabrication, demonstration and test and can meet stated performance requirements, including cost, schedule, risk and other system constraints.

According to MMS deputy project scientist Mark Adrian of NASA’s Goddard Space Flight Center in Greenbelt, Md., “This is the last hurdle before the spacecraft and instrument teams begin to build actual flight hardware.”

MMS was approved for implementation in June 2009 following a successful Preliminary Design Review in May 2009.

Dr. James L. Burch of the Southwest Research Institute in San Antonio, Texas, will lead the MMS science team. According to Burch, “Magnetic reconnection is a fundamental physical process that occurs throughout the universe,” says Burch. “MMS will enable us to study this dynamic process in the near-Earth space environment, where it transfers energy from the solar wind to the magnetosphere and drives disturbances known as space weather.”

Goddard is the lead Center for the mission. Engineers there will perform the required environmental testing, build the spacecraft and integrate all four sets of instruments into the MMS satellites, support launch vehicle integration and operations, and develop the Mission Operations Center which to monitor and control the spacecraft.

MMS will carry identical suites of plasma analyzers, energetic particle detectors, magnetometers, and electric field instruments as well as a device to prevent spacecraft charging from interfering with the highly sensitive measurements required in and around the diffusion regions.

Scientists and engineers at Goddard have designed and will build one of the instruments – the Fast Plasma Instrument, which will measure the ion and electron distributions and the electric and magnetic fields with unprecedentedly high millisecond time resolution and accuracy.

Currently, MMS is scheduled to launch in August 2014 from Cape Canaveral Air Force Station, FL aboard an Atlas V rocket.

NASA's Avionics Testing: There's More Than One String to This Fiddle

"Having more than one string on a fiddle" is an old phase used to describe someone or something with multiple talents or uses. This expression could be used to describe NASA's avionics string testing -- a developmental testing process that allows engineers to find and fix any bugs in a system by inputting commands and scrutinizing the electronics system’s responses.

NASA and ATK Aerospace Systems of Magna, Utah, prime contractor for the Ares I first stage avionics system, currently are conducting a series of string tests at ATK's test facility in Clearfield, Utah.

So exactly what is an avionics system and how is NASA using string testing to help design the next generation of solid-rocket-motor-based launch systems?

The avionics system is the "brains" for a launch vehicle, consisting of the electronics system, equipment and associated sensors responsible for controlling key guidance, launch, navigation and recovery hardware. The first stage avionics works with the upper stage flight computers and guidance systems to control the vehicle during first stage ascent and executes recovery of the first stage after staging.

During testing, control boxes of the first stage avionics system are wired together in a line -- the so-called string – with multiple strings making up the entire avionics system. The strings are connected to a ground computer which simulates the upper stage flight computer by issuing commands to the appropriate control box, requiring a particular response.


"System level or "string" testing is a widely recognized process that allows our team to locate and identify functional and performance-related problems within the hardware," said Kendall Junen, avionics and control team lead for Ares Projects at NASA's Marshall Space Flight Center in Huntsville, Ala. "It involves taking various system requirements and testing the hardware in controlled laboratory scenarios to determine how well the system performs."

"This laboratory allows us to test like you fly. We can assemble the entire avionics system and put it through precise, flight-like scenarios," he said. "We can test the system's reaction to certain computer-generated anomalies and identify potential performance issues associated with specific hardware."

Next Stop, Titan: Looking at the Land o' Lakes

NASA's Cassini spacecraft will be eyeing the north polar region of Saturn's moon Titan this weekend, scanning the moon's land o' lakes.

At closest approach on early morning Saturday, June 5 UTC, which is Friday afternoon, June 4 Pacific time, Cassini will glide to within about 2,000 kilometers (1,300 miles) of the Titan surface.

Cassini will make infrared scans of the north polar region, which was in darkness for the first several years of Cassini's tour around the Saturn system. The lighting has improved as northern spring has started to dawn over the area.

The visual and infrared spectrometer will be prime during closest approach, but the imaging science subsystem cameras will also be taking pictures. Among the scientific bounties, Cassini team members are hoping to get another good look at Kraken Mare, the largest lake on Titan, which covers a greater area than the Caspian Sea on Earth.

Although this latest flyby is dubbed "T69," planning changes early in the orbital tour made this the 70th targeted flyby of Titan.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL.

WISE Makes Progress on its Space Rock Catalog

NASA's Wide-field Infrared Survey Explorer, or WISE, is busy surveying the landscape of the infrared sky, building up a catalog of cosmic specimens -- everything from distant galaxies to "failed" stars, called brown dwarfs.

Closer to home, the mission is picking out an impressive collection of asteroids and comets, some known and some never seen before. Most of these hang out in the Main Belt between Mars and Jupiter, but a small number are near-Earth objects -- asteroids and comets with orbits that pass within about 48 million kilometers (30 million miles) of Earth's orbit. By studying a small sample of near-Earth objects, WISE will learn more about the population as a whole. How do their sizes differ, and how many objects are dark versus light?

"We are taking a census of a small sample of near-Earth objects to get a better idea of how they vary," said Amy Mainzer, the principal investigator of NEOWISE, a program to catalog asteroids seen with WISE.

So far, the mission has observed more than 60,000 asteroids, both Main Belt and near-Earth objects. Most were known before, but more than 11,000 are new.

"Our data pipeline is bursting with asteroids," said WISE Principal Investigator Ned Wright of UCLA. "We are discovering about a hundred a day, mostly in the Main Belt."

About 190 near-Earth asteroids have been observed to date, of which more than 50 are new discoveries. All asteroid observations are reported to the NASA-funded International Astronomical Union's Minor Planet Center, a clearinghouse for data on all solar system bodies at the Smithsonian Astrophysical Observatory in Cambridge, Mass.

"It's a really exciting time for asteroid science," said Tim Spahr, who directs the Minor Planet Center. "WISE is another tool to add to our tool belt of instruments to discover and study the asteroid population."

A network of ground-based telescopes follows up and confirms the WISE finds, including the NASA-funded University of Arizona Spacewatch and Catalina Sky Survey projects, both near Tucson, Ariz., and the NASA-funded Magdalena Ridge Observatory near Socorro, N.M.

Some of the near-Earth asteroids detected so far are visibly dark, but it's too early to say what percentage. The team needs time to properly analyze and calibrate the data. When results are ready, they will be published in a peer-reviewed journal. WISE has not found an asteroid yet that would be too dark for detection by visible-light telescopes on the ground.