2013년 8월 31일 토요일

Earth Life Likely Came from Mars, Study Suggests

We may all be Martians.

Evidence is building that Earth life originated on Mars and was brought to this planet aboard a meteorite, said biochemist Steven Benner of The Westheimer Institute for Science and Technology in Florida.

An oxidized form of the element molybdenum, which may have been crucial to the origin of life, was likely available on the Red Planet's surface long ago, but unavailable on Earth, said Benner, who presented his findings today (Aug. 28; Aug. 29 local time) at the annual Goldschmidt geochemistry conference in Florence, Italy.

"It’s only when molybdenum becomes highly oxidized that it is able to influence how early life formed," Benner said in a statement. "This form of molybdenum couldn’t have been available on Earth at the time life first began, because 3 billion years ago, the surface of the 
Earth had very little oxygen, but Mars did. It’s yet another piece of evidence which makes it more likely life came to Earth on a Martian meteorite, rather than starting on this planet."
Organic compounds are the building blocks of life, but they need a little help to make things happen. Simply adding energy such as heat or light turns a soup of organic molecules into a tarlike substance, Benner said.

That's where oxidized molybdenum comes in. Inserting it or boron, another element, into the mix would help organics make the leap to life, Benner added.
"Analysis of a Martian meteorite recently showed that there was boron on Mars; we now believe that the oxidized form of molybdenum was there, too," he said.

Another point in Mars' favor is the likelihood that the early Earth was completely covered by water while the ancient Red Planet had substantial dry areas, Benner said. All of this liquid would have made it difficult for boron, which is currently found only in extremely dry places, to form in high enough concentrations on Earth when life was first evolving.

Further, Benner added, water is corrosive to RNA, which most researchers think was the first genetic molecule (rather than DNA, which came later).

No indigenous Red Planet organisms have ever been discovered. But it is possible that life on Mars — if it ever existed — may have made its way to Earth at some point, many scientists say.

Some microbes are incredibly hardy, after all, and may be able to survive an interplanetary journey after being blasted off their home world by an asteroid impact. And orbital dynamics show that it's much easier for rocks to travel from Mars to Earth than the other way around.

Wherever Earth life originated, Benner is glad it put down roots on our blue planet.
"It’s lucky that we ended up here nevertheless, as certainly Earth has been the better of the two planets for sustaining life," Benner said. "If our hypothetical Martian ancestors had remained on Mars, there might not have been a story to tell."

Source of Article: Space.com

Mars Landslides Spawned By Weird Double-Layered Craters

Scientists are a step closer to solving a 40-year-old mystery about some unusual looking craters on Mars.

These features are called double-layered ejecta (DLE) craters, and attracted research attention because their debris patterns do not match the typical understanding of how craters are formed.

Craters are pockmarks that form on the surface of a planet or moon when a high-speed rock smashes into the surface. The fast-moving collision sprays out dirt and other debris in a ring. There are more than 600 craters on Mars that have two layers of this debris, however. A new study suggests a glacial landslide would have created the second layer.

The study by Brown University geology researchers David Weiss and James Head is detailed in the Aug. 7 edition of the journal Geophysical Research Letters.

Landslides on ice

The first DLEs came into view during NASA's Viking missions to Mars in the 1970s. The twin spacecraft each carried an orbiter and a lander. While the landers made the first footfalls on Mars, the orbiters remained above for years and mapped much of the planet with their cameras.

In the decades since, scientists then uncovered extensive evidence that water and ice covered much of Mars in the distant past.
The only large deposits of ice on the Red Planet today are at the north and south poles, although icy traces linger in other areas. The DLEs, however, were formed while the Martian surface was covered by a huge sheet of glacial ice, the researchers concluded after examining past climactic studies.

At maximum, this ice sheet reached to the mid-latitudes of Mars and was about 165 feet (50 meters) thick. Ice is slippery, meaning that once the crater was formed and the debris sprayed out, the dirt slid and formed a second layer on top of the first.

Groovy observations
The theory matches up with more detailed observations of DLEs, the authors said. Many of the studied craters have radial striations, or grooves radiating from the crater's epicenter. These are common in Earth landslides, particularly those that take place on glaciers.
Steep slopes are also required to make the scenario work. The scientists calculated that the craters must be smaller than 15.5 miles (25 kilometers) in diameter to form DLEs because anything larger would have too shallow a slope. They next examined hundreds of DLEs on Mars and discovered that almost every one surveyed is that size or smaller. 
DLEs also exhibit few secondary craters, which happen after thicker parts of the debris carve gouges in the surface. Because these ejecta would have landed on ice, these features would have vanished after the ice melted.

Source of Article: Space.com

Planet Labs Unveils Tiny Earth-Observation Satellite Family

The tiny satellites that could change the way humanity views and monitors its home planet are getting their first close-up.

Planet Labs has released photos of its Dove line of spacecraft, 28 of which the San Francisco-based startup plans to launch a few months from now to form the world's largest constellation of Earth-observing satellites.

Planet Labs has been keeping a low profile since its founding in 2010, unveiling its plans for the 28-satellite "Flock 1" constellation just two months ago. But after presenting the findings of its Dove 1 and Dove 2 demonstration missions at the 2013 Small Satellite Conference, which was held Aug. 10-15 in Utah, the company decided it was time to publish some photos of its hardware, officials said. 

Dove 1 and Dove 2 launched two days apart this past April, with Dove 2 hitching a ride on a Russian Soyuz rocket and its sister spacecraft getting to orbit on the first flight of the Antares rocket, which aerospace firm Orbital Sciences Corp. built to make robotic cargo runs to the International Space Station for NASA.

Both Dove 1 and 2 were tiny, measuring just 12 inches long by 4 inches wide by 4 inches tall (30 by 10 by 10 centimeters), yet both beamed home sharp images of Earth's surface. Dove 1 burned up in the atmosphere after less than a week on orbit because of the low altitude of the Antares test flight, but Dove 2 is still zipping around the planet.

The Doves that make up Flock 1 will piggyback on Antares' first launch toward the space station, which may come as early as December. The constellation was designed to enable frequent, high-resolution and low-cost imagery of the globe that could benefit humanity in a number of ways, Planet Labs officials have said.

"To best enable this mission, the company has selected a low orbit for its constellation and an optical resolution of three to five meters — a scale that allows measurement of a tree canopy, but does not compromise individual privacy," officials wrote in a June 26 statement announcing the Flock 1 project. "This will enable monitoring of deforestation, help improve agricultural yields, track natural disasters and many other applications."

Planet Labs, which has raised more than $13 million from venture capital firms, has big dreams, and they're laid out for all to read on the company's website:
"The Blue Marble is a photograph of Earth taken by Apollo 17 astronauts in 1972 and is credited with popularizing the environmental movement. What the Blue Marble did for global awareness, Planet Labs will do for global action."

Source of Article: Space.com

On Giant Blue Alien Planet, It Rains Molten Glass

There's a "blue marble" alien planet just 63 light-years from Earth, but the world is anything but friendly to life. Researchers say the blue color in the atmosphere likely comes from a rain of molten glass.

This super-hot glass rain is just one consequence of the close proximity between the gas giant alien planet HD189733b and its sun. which causes daytime temperatures to soar as high as 1,700 degrees Fahrenheit (930 degrees Celsius), scientists said.

A fresh set of observations of the planet in X-rays also suggest HD189733b has an outer atmosphere that is far larger than expected. 

These surprise finds are all signals that so-called hot Jupiter alien planets are worthy of study on their own, even though they are hostile planets to life, researchers said.

Rewriting planetary formation

Hot Jupiters are large, roughly Jupiter-sized planets that become very hot by circling tight around their stars. These worlds have been described as planetary daredevils because they orbit so close to their parent stars that they risk being consumed. Often, one side of the planet is tidally locked to the star, exposing that side to scorching hot temperatures, while leaving the other side permanently turned away.

Hot Jupiters are easy to spot from a distance because as they pass in front of a star, their disc blots out a large portion of the star's light; HD189733b causes a three per cent drop in its star's light, for example. The planets' gravitational pull often causes their parent stars to wobble, too.

While common in the universe, however, Hot Jupiters are totally different than what denizens of Earth's solar system encounter. In our case, small, rocky planets orbit close to the star and the gas giants are much farther out.

The latest observations of HD189733b are challenging some theories of planetary formation and are just one of the reasons Hot Jupiters are earning more attention from astronomers these days.

"At first considered to be the 'chaff' researchers would have to wade through to get to the fainter Earth-like worlds, hot Jupiters are now attracting their own attention," NASA scientists wrote in a recent Science@NASA post about these planets.

Boiling atmosphere

New attention came to HD189733b, which was discovered in 2005, after two X-ray observatories watched the blue planet pass across the face of its star. Both NASA's Chandra X-Ray Observatory and ESA's XMM Newton saw a drop in X-rays from the star that was three times more than that observed in optical light.

This means the planetary atmosphere is much larger than previously thought. It's also bleeding quickly. HD189733b's atmosphere is fleeing the planet at a rate of 220 million pounds (100 million kilograms) to 1.3 billion pounds (600 million kg) a second, a new study estimated.

"The extended atmosphere of this planet makes it a bigger target for high-energy radiation from its star, so more evaporation occurs," Scott Wolk, an astronomer at the Harvard-Smithsonian Center for Astrophysics, said in a statement.

HD189733b could also have bright planet-wide auroras due to the extensive stellar radiation hitting it, but that's speculation at this point, the study authors said.

Source of Article: Space.com

2013년 8월 25일 일요일

A Fluffy Disk Around a Baby Star

An international team of astronomers that are members of the Strategic Exploration of Exoplanets and Disks with Subaru Telescope (SEEDS) Project has used Subaru Telescope's High Contrast Instrument for the Subaru Next Generation Adaptive Optics (HiCIAO) to observe a disk around the young star RY Tau (Tauri). The team's analysis of the disk shows that a "fluffy" layer above it is responsible for the scattered light observed in the infrared image. Detailed comparisons with computer simulations of scattered light from the disk reveal that this layer appears to be a remnant of material from an earlier phase of stellar and disk development, when dust and gas were falling onto the disk.

Since 2009, the five-year SEEDS Project (Note) has focused on direct imaging of exoplanets, i.e., planets orbiting stars outside of our Solar System, and disks around a targeted total of 500 stars. Planet formation, an exciting and active area for astronomical research, has long fascinated many scientists. Disks of dust and gas that rotate around young stars are of particular interest, because astronomers think that these are the sites where planets form--in these so-called "protoplanetary disks." Since young stars and disks are born in molecular clouds, giant clouds of dust and gas, the role of dust becomes an important feature of understanding planet formation; it relates not only to the formation of rocky, Earth-like planets and the cores of giant Jupiter-like planets but also to that of moons, planetary rings, comets, and asteroids.
As a part of the SEEDS Project, the current team of researchers used HiCIAO mounted on the Subaru Telescope to observe a possible planet-forming disk around the young star RY Tau. This star is about 460 light years away from Earth in the constellation Taurus and is around half a million years old. The disk has a radius of about 70 AU (10 billion kilometers), which is a few times larger than the orbit of Neptune in our own Solar System.
Astronomers have developed powerful instruments to obtain images of protoplanetary disks, and Subaru Telescope's HiCIAO is one of them. HiCIAO uses a mask to block out the light of the central star, which may be a million times brighter than its disk. They can then observe light from the star that has been reflected from the surface of the disk. The scattered light will reveal the structure of the surface of the disk, which is very small in scale and difficult to observe, even with large telescopes. Observers use HiCIAO with a 188 element adaptive optics system to reduce the blurring effects of Earthʼs atmosphere, making the images significantly sharper.
This team succeeded in capturing a near-infrared image (1.65 μm) associated with the RY Tau disk. Unlike many other protoplanetary disks, the disk emission is offset from the centre of the star. In contrast to longer wavelength observations, which are associated with the midplane of the disk, near-infrared, scattered light coming from the surface of the disk produced this offset, which provides information about the vertical structure of the disk.
Changes in structure perpendicular to the surface of a disk are much harder to investigate because there are few good examples to study. Therefore, the information about vertical structure that this image provides is a contribution to understanding the formation of planets, which depends strongly on the structure of the disk, including structures such as spirals and rings, as well as height.
The team performed extensive computer simulations of the scattered light, for disks with different masses, shapes, and types of dust. They found that the scattered light is probably not associated with the main surface of the disk, which is the usual explanation for the scattered light image. Instead, the observed infrared emission can be explained if the emission is associated with a fluffy upper layer, which is almost transparent and not completely transparent. The team estimated the dust mass in this layer to be about half the mass of Earthʼs Moon.
Why is this fluffy layer observed in this disk, but not in many other possible planet-forming disks? The team suspects that this layer is a remnant of the dust that fell onto the star and the disk during earlier stages of formation. In most stars, unlike RY Tau, this layer dissipates by this stage in the formation of the star, but RY Tau may still have it because of its youth. It may act as a special comforter to warm the inside of the disk for baby planets being born there. This may affect the number, size, and composition of the planets being born in this system.

Source of Article: Science Daily

Space Slinky: Jet of Superheated Gas -- 5,000 Light-Years Long -- Ejected from Supermassive Black Hole

More than thirteen years of observations from NASA's Hubble Space Telescope have allowed astronomers to assemble time-lapse movies of a 5,000-light-year-long jet of superheated gas being ejected from a supermassive black hole in the center of the giant elliptical galaxy M87.

The movies promise to give astronomers a better understanding of how active black holes shape galaxy evolution. While matter drawn completely into a black hole cannot escape its enormous gravitational pull, most infalling material drawn toward it first joins an orbiting region known as an accretion disk encircling the black hole. Magnetic fields surrounding the black hole are thought to entrain some of this ionized gas, ejecting it as very high-velocity jets.
"Central supermassive black holes are a key component in all big galaxies," said Eileen T. Meyer of the Space Telescope Science Institute (STScI) in Baltimore, Md., the Hubble study's lead author. "Most of these black holes are believed to have gone through an active phase, and black-hole-powered jets from this active phase play a key role in the evolution of galaxies. By studying the details of this process in the nearest galaxy with an optical jet, we can hope to learn more about galaxy formation and black hole physics in general."
The Hubble movies reveal for the first time that the jet's river of plasma travels in a spiral motion. This motion is considered strong evidence that the plasma may be traveling along a magnetic field, which the team thinks is coiled like a helix. The magnetic field is believed to arise from a spinning accretion disk of material around a black hole. Although the magnetic field cannot be seen, its presence is inferred by the confinement of the jet along a narrow cone emanating from the black hole.
"We analyzed several years' worth of Hubble data of a relatively nearby jet, which allowed us to see lots of details," Meyer said. "The only reason you see the distant jet in motion at all over just a few years is because it is traveling very fast."
Meyer found evidence for the magnetic field's suspected helical structure in several locations along the jet. In the outer part of the M87 jet, for example, one bright gas clump, called knot B, appears to zigzag, as if it were moving along a spiral path. Several other gas clumps along the jet also appear to loop around an invisible structure. "Past observations of black hole jets couldn't distinguish between radial motion and side-to-side motion, so they didn't provide us with detailed information of the jet's behavior," Meyer explained.
M87 resides at the center of the neighboring Virgo cluster of roughly 2,000 galaxies, located 50 million light-years away. The galaxy's monster black hole is several billion times more massive than our Sun.
In addition, the Hubble data provided information on why the jet is composed of a long string of gas blobs, which appear to brighten and dim over time.
"The jet structure is very clumpy. Is this a ballistic effect, like cannonballs fired sequentially from a cannon?" Meyer asked. "Or, is there some particularly interesting physics going on, such as a shock that is magnetically driven?"
Meyer's team found evidence for both scenarios. "We found things that move quickly," Meyer said. "We found things that move slowly. And, we found things that are stationary. This study shows us that the clumps are very dynamic sources."
The research team spent eight months analyzing 400 observations from Hubble's Wide Field Planetary Camera 2 and Advanced Camera for Surveys. The observations were taken from 1995 to 2008. Several team members, however, have been observing M87 for 20 years. Only Hubble's sharp vision allowed the research team to measure the jet's slight motion in the sky over 13 years. Meyer's team also measured features in the hot plasma as small as 20 light-years wide.
It's too soon to tell whether all black-hole-powered jets behave like the one in M87. That's why Meyer plans to use Hubble to study three more jets. "It's always dangerous to have exactly one example because it could be a strange outlier," Meyer said. "The M87 black hole is justification for looking at more jets."

Source of Article: Science Daily

2013년 8월 20일 화요일

Student Contest Launches to Aid Private Manned Mission to Mars

A private manned Mars mission may get some help from students on its way to the launch pad in 2018.

A newly announced contest asks students to propose design concepts for the Inspiration Mars mission, a private effort that aims to launch two astronauts on a flyby of the Red Planet in January 2018.

"Inspiration Mars is looking for the most creative ideas from engineers all over the world," Dennis Tito, executive director of the nonprofit Inspiration Mars Foundation, said in a statement Friday (Aug. 16).

"Furthermore, we want to engage the explorers of tomorrow with a real and exciting mission, and demonstrate what a powerful force space exploration can be in inspiring young people to develop their talent," added Tito, a multimillionaire who in 2001 became the first space tourist when he paid his own way to the International Space Station aboard a Russian Soyuz spacecraft. "This contest will accomplish both of those objectives." 

The competition, which is organized by the nonprofit Mars Society, challenges teams of university students from around the world to design a two-person 2018 Mars flyby mission as cheaply and safely as possible.

Teams — which can include university faculty and staff members, but not in a leading role — must submit their proposals by March 15, 2014. The top 10 concepts will be presented to a panel of judges a month later during a public event at NASA's Ames Research Center in Moffett Field, Calif., Mars Society officials said.

First prize is $10,000, along with an all-expenses-paid trip to the Mars Society's 2014 conference. The second- through fifth-place teams will receive $5,000, $3,000, $2,000 and $1,000, respectively.

"The Mars Society is delighted to lead this effort," Mars Society president Robert Zubrin said in a statement. "This contest will provide an opportunity for legions of young engineers to directly contribute their talent to this breakthrough project to open the space frontier." 
Inspiration Mars seeks to launch one man and one woman — preferably a married couple — on a 501-day roundtrip journey, punctuated by a close flyby of the Red Planet in August 2018. The mission would not land on Mars but would zip within 100 miles (160 kilometers) of the planet's surface, officials say.

Tito has committed to provide two years of funding for the mission, which was announced in February. Inspiration Mars officials hope to foot the bill the rest of the way by soliciting donations and securing media and naming rights, among other strategies.

Source of Article: Space.com

New Nova In the Night Sky: A Star Explosion Explained

Stargazers are thrilled over the surprise appearance of a star explosion, known as a nova, in the night sky last week, but there is more to this cosmic event than meets the eye.

The new Nova Delphinus 2013 was first spotted in the constellation Delphinus (The Dolphin) by Japanese amateur astronomer Koichi Itagaki on Aug. 14 and quickly confirmed by other skywatchers soon after. Novas are stars that are undergoing a powerful eruption, causing them to brighten significantly, so that they appear suddenly in the night sky where previously no star was visible.

Since its discovery, this nova has brightened rapidly to become an object visible to the naked eye, though stargazers will need to be away from city lights in order to see it clearly.

Just how frequently does a nova become bright enough to be seen without the use of binoculars or a telescope? 

On average, new novas are detected about once every four or five years. Over the last 112 years, there have been 47 novas that have flared into naked-eye view. The majority of these — 26 — were quite dim and could only be positively identified by using a star chart or sky atlas. 

Novas that become as bright as Nova Delphini are more readily visible. Since 1901 there have been 13 novas in this category, which occur about once every 10 years.
Even brighter objects, which shine about as much as Polaris the North Star and the other brightest stars in the sky, have been few. In fact, only six have appeared since 1901, meaning one occurs about every 20 years. However, we have not had one of these bright nova since 1975, so it seems we are overdue for another.

Then there are those novas that are super-bright, attaining a magnitude of zero or even brighter. In 112 years, we have had only two that have become as brilliant as that; on average, we get one about every 60 years. However, we have not had a nova in this category since 1918, so certainly we are long overdue for a bright new star.

The brightest nova in recent years was Nova Scorpii, also known as V1280 Scorpii. It attained a peak brightness of magnitude +3.9 on Feb. 4, 2007. The brightest nova in the last 70 years was Nova Cygni, also known as V1500 Cygni. This star attained a peak brightness of magnitude +1.7 on Aug. 30, 1975. And since 1901, the brightest nova ever — landing in the super-bright category — was Nova Aquilae, also known as V603 Aquilae. It attained a peak brightness of magnitude -1.4 on June 9, 1918, virtually matching Sirius, the brightest star in the sky!

Source of Article: Space.com

Once in a Blue Moon Event Is Not Really Blue

The moon can sometimes appear reddish, especially during eclipses. But what we call a "Blue Moon" has nothing to do with its color. Normally there are 12 fully lit, or full, moons per year. A season of three months should therefore contain three full moons.

Thought to be called "blue" after an old English term meaning "betrayer," a Blue Moon is an extra full moon that occurs in that span, due to a quirk of the calendar. 

On occasions where there are four full moons in a season instead of three, the third of the full moons is traditionally called a Blue Moon. A Blue Moon happens on average about once every 2.7 years.

Occasionally two full moons will fall within the same month. The second full moon is also often called a Blue Moon, but this is not the term's original meaning.
The moon can actually appear blue under certain circumstances, such as when ash is present in the atmosphere from fires or volcanic eruptions. This type of Blue Moon cannot be predicted in advance, however.

Source of Article: Space.com

2013년 8월 17일 토요일

Cosmic Turbulences Result in Star and Black Hole Formation

Just how stars and black holes in the Universe are able to form from rotating matter is one of the big questions of astrophysics. What we do know is that magnetic fields figure prominently into the picture. However, our current understanding is that they only work if matter is electrically well conductive -- but in rotating discs this isn't always the case. Now, a new publication by Helmholtz-Zentrum Dresden-Rossendorf physicists in the scientific journal Physical Review Letters shows how magnetic fields can also cause turbulences within "dead zones," thus making an important contribution to our current understanding of just how compact objects form in the cosmos.

When Johannes Kepler first proposed his laws of planetary motion in the early days of the 17th century, he could not have foreseen the central role cosmic magnetic fields would play in planetary system formation. Today, we know that in the absence of magnetic fields, mass would not be able to concentrate in compact bodies like stars and black holes. One prominent example is our solar system, which formed 4.6 billion years ago through the collapse of a gigantic cloud of gas, whose gravitational pull concentrated particles in its center, culminating in the formation of a large disc. "These accretion discs are extremely stable from a hydrodynamic perspective as according to Kepler's laws of planetary motion angular momentum increases from the center towards the periphery," explains HZDR's own Dr. Frank Stefani. "In order to explain the growth rates of stars and black holes, there has to exist a mechanism, which acts to destabilize the rotating disc and which at the same time ensures mass is transported towards the center and angular momentum towards the periphery."

As early as 1959, Evgenij Velikhov conjectured that magnetic fields are capable of prompting turbulences within stable rotating flows. Although it wasn't until 1991 that astrophysicists Steven Balbus and John Hawley fully grasped the fundamental significance of this magneto rotational instability (MRI) in cosmic structure formation. Balbus and Hawley will be this year's recipients of the one million Dollar Shaw Prize for astronomy, which will be given in September 2013. However, în order to ensure the MRI actually works, the discs have to exhibit a minimum degree of electrical conductivity. In areas of low conductivity like the "dead zones" of protoplanetary discs or the far-off regions of accretion discs that surround supermassive black holes, the MRI's effect is numerically difficult to comprehend and is thus a matter of dispute. HZDR scientists, who to date have been mostly concerned with an experimental study of the MRI, have now offered a new theoretical explanation for this phenomenon.
Rivalry between physicists and astrophysicists
If you try and simulate the MRI in a liquid metal experiment with an exclusively vertically oriented magnetic field this field has to be rather strong. At the same time, since the rotational speed has to be very high, these types of experiments are extremely involved and thus far success has eluded them. Back in 2005, for the first time ever, Dr. Stefani and his colleagues at the HZDR and the Leibniz Institute for Astrophysics Potsdam managed to successfully simulate the cosmic process in the lab. By adding a circular magnetic field to a vertical one, they were able to observe the MRI at substantially smaller magnetic fields and rotational speeds. According to Steven Balbus and Hantao Ji per the current August edition of the magazinePhysics Today, one of the blemishes of this "helical MRI" is the fact that it only acts to destabilize rotational profiles that are relatively precipitous towards the periphery, which for now does not include rotation profiles obeying Kepler's law.
Magnetic fields and rotating flows reinforce each other
The HZDR scientists are now countering this weighty astrophysics argument with their latest insights. The calculations by Dr. Oleg Kirillov and Dr. Frank Stefani have shown that the helical MRI very much applies to the Keplerian rotation profile if only the circular magnetic field is produced not entirely from the outside but at least partly from within the accretion disc. "This is in fact a much more realistic scenario. In the extreme case that there does not exist a vertical field, we're looking at a problem of what came first -- the chicken or the egg. A circular magnetic field acts to destabilize the disc and the resulting turbulence generates components of vertical magnetic fields. They in turn reproduce the circular magnetic field because of the special form of the disc's rotational movement." Regardless of whether with or without a vertical magnetic field, current calculations show that the MRI is possible even in areas of low conductivity like the "dead zones" -- something astrophysicists had not previously thought possible.
The HZDR scientists were driven by their long-standing experience with cosmic magnetic field experiments in the lab, from a model of Earth's dynamo to magneto-rotational instability all the way to Tayler instability. The latter is being debated by astrophysicists with reference to cosmic jets and the formation of neutron stars, among others, but also has to be considered in the construction of large liquid metal batteries, for example. At this time, the scientists are planning a large-scale experiment using liquid sodium, which they are hoping to realize over the next few years as part of the DRESDYN Project. "Once we get this experiment, which for the first time ever will combine the MRI with Tayler instability, up and running, we will much improve our understanding of the interaction between various magnetic cosmic phenomena," says a happy Stefani. Regardless of who is the one to push the envelope in this amicable competition -- the experimental physicists or the theoretical astrophysicists -- the angular momentum transport in astrophysics and in the lab will continue to be a hotly contested topic.

Source of Article: Science Daily

2013년 8월 16일 금요일

Galaxy Anatomy In Early Universe Was a 'Cosmic Zoo'

The diversity of galaxies in the early universe was as varied as the many galaxy types seen today, a massive Hubble Space Telescope photos survey reveals.
The Hubble photo survey found that the assorted range of galaxy types seen today were also present about 11 billion years ago, meaning that the types of galaxies seen today, which astronomers described as a "cosmic zoo," have been around for at least 80 percent of the universe’s lifespan. The universe is estimated to be 13.82 billion years old.

At the heart of the new study is a galaxy classification system known as the Hubble Sequence. The research team found that this system still applied to galaxies 11 billion years ago. The research will appear upcoming edition of the Astrophysical Journal.

"This is a key question: when and over what timescale did the Hubble Sequence form?" study lead author BoMee Lee of the University of Massachusetts, said in a statement. "To do this you need to peer at distant galaxies and compare them to their closer relatives, to see if they too can be described in the same way."

The new study is part of the Hubble Space Telescope Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey, or CANDLES.

"The largest project in the history of Hubble, it aims to explore galactic evolution in the early universe and the very first seeds of cosmic stracture at less than 1 billion years after the Big Bang," Hubble officials said in a statement.

The Hubble Sequence divides galaxies into three types based on their appearance. Spiral galaxies in the prime of their lives are full of gas used in star formation. Once that gas runs out, they can transition into a somewhat blob-like elliptical galaxy.

A third type of galaxy in the sequence, known as a lenticular galaxy, represents a transitional phase between a middle aged spiral galaxy and an older elliptical galaxy. These kinds of galaxies have a bright bulge like an elliptical galaxy; yet maintain some spiral-like structure as their star-forming gas runs out.
Scientists observed these kinds of galaxies in the early universe.

"This is the only comprehensive study to date of the visual appearance of the large, massive galaxies that existed so far back in time," co-author Arjen van der Wel of the Max Planck Institute for Astronomy in Heidelberg, Germany said in a statement. "The galaxies look remarkably mature, which is not predicted by galaxy formation models to be the case that early on in the history of the universe."

While past research showed that these distinct types of galaxy morphology existed as early as 8 billion years ago, the new study extends that understanding back another 2.5 billion years.
"The Hubble Sequence underpins a lot of what we know about how galaxies form and evolve — finding it to be in place this far back is a significant discovery," Lee said.

Source of Article: Space.com

Planet-Hunting Days of NASA's Kepler Spacecraft Likely Over

The revolutionary planet-hunting activities of NASA's prolific Kepler space telescope have come to an end.

NASA has given up hope of restoring the Kepler spacecraft to full health and is now attempting to determine what the observatory can accomplish in its compromised state, agency officials announced today (Aug. 15).

"We are now moving on to the next phase of Kepler's mission, because that's what the data requires us to do," Paul Hertz, director of NASA's astrophysics division, told reporters during a press conference today. "This is not the last you'll hear from Kepler. There's a huge amount of data collected that we'll continue to analyze."

Balky wheels

The $600 million Kepler mission launched in March 2009 on a 3.5-year prime mission to determine how commonly Earth-like planets occur around the Milky Way galaxy.
Kepler detects exoplanets by noting the tiny brightness dips caused when these worlds cross in front of, or transit, their parent stars. The observatory needs three working reaction wheels — gyroscope-like devices that maintain Kepler's position in space — to do this precision work.

Kepler had four of these wheels when it launched — three for immediate use and one spare. But one wheel, known as number 2, failed in July 2012. And then wheel four conked out on May 11 of this year, halting the spacecraft's planet hunt.

Mission engineers have since managed to get those two malfunctioning wheels spinning again, but both of them still exhibit too much friction to support Kepler's fine-pointing work. So the observatory's original mission is over, officials said today.
"We do not believe that we can recover three-wheel operations, or Kepler's original science mission," Hertz said.

Sending astronauts out to fix Kepler, as was done five times with NASA's Hubble Space Telescope, is not an option. That's because Kepler orbits the sun rather than Earth and is currently millions of miles from our planet.

Looking ahead

The focus has now shifted to examining what Kepler can accomplish with just two healthy wheels and its thrusters, Hertz added.

To that end, NASA is conducting two separate studies: an engineering assessment to see what the spacecraft is capable of, and a science study to determine if a modified mission is worth funding. (It currently costs about $18 million per year to operate the telescope.)
Both studies are due in the fall, Hertz said.

"NASA may use a senior review to help us prioritize a two-wheel Kepler mission against the continued operation of other NASA astrophysics missions," he said. "Only after weighing these considerations will NASA be in a position to make a decision on the future of Kepler operations."

There are a variety of possible uses for Kepler in the future, mission scientists say. The observatory could scan the heavens for asteroids, comets and supernova explosions, for example. And it may still be able to detect huge alien planets using a technique called gravitational microlensing. (In this method, astronomers watch what happens when a massive object passes in front of a star; the closer object's gravitational field bends and magnifies the star's light, acting like a lens.)

But it's still to soon to tell which, of any, of these missions will pan out.

"Until we have analyzed the full capability of the mission and we have looked at what the requirements are in terms of guidance, we really have no way no way of knowing which of these missions would be practical," said Kepler principal investigator Bill Borucki, of NASA's Ames Research Center in Moffett Field, Calif.

Lots of discoveries to come

Kepler has detected 3,548 candidate planets to date, 135 of which have been confirmed by follow-up observations. Mission scientists expect more than 90 percent of the observatory's finds will end up being the real deal.

And there will be more discoveries to come, whatever Kepler ends up doing in the future. It will take several more years to pore through all of the observatory's data, Borucki said.

"We expect hundreds, maybe thousands of new planet discoveries, including the long-awaited Earth-size planet orbiting a star as hot as our sun — so a very sun-like star," he said.
Kepler outlasted its prime mission lifespan of 3.5 years, and it should be able to accomplish its main goal despite the reaction-wheel failures, Borucki added.

"In the next two years, when we complete this analysis, we'll be able to answer the question that inspired the Kepler mission: Are Earths common or rare in our galaxy?" he said.

Source of Article: Space.com

Voyager 1 Spacecraft Left Solar System Last Year, Study Suggests

While the handlers of NASA's venerable Voyager 1 spacecraft are still waiting for it to depart the solar system, a new study argues that the probe actually popped free into interstellar space last year.

Voyager 1 left the sun's sphere of influence on July 27, 2012, according to the study, which employs a new model to explain and interpret the probe's data. The new model is different from NASA's take, which suggests Voyager 1 remains within the solar system, though just barely.

"It's a somewhat controversial view, but we think Voyager has finally left the solar system, and is truly beginning its travels through the Milky Way," lead author Marc Swisdak of the University of Maryland said in a statement.

Swisdak and co-authors James Drake and Merav Opher — of the University of Maryland and Boston University, respectively — are not Voyager mission scientists. Their findings contrast with recent papers by the mission team and other researchers, which have concluded that the spacecraft is likely plying a strange transition zone at the edge of the solar system.

A long journey

Voyager 1 and its twin, Voyager 2, launched a few weeks apart in 1977 to study Saturn, Jupiter, Uranus and Neptune. The duo completed this "grand tour" and then kept right on flying toward interstellar space.

Voyager 1 will get there first. It's about 11.6 billion miles (18.7 billion kilometers) from Earth, making it the farthest-flung manmade object in the universe. Voyager 2, for its part, is now 9.4 billion miles (15.2 billion km) from home.

Both spacecraft are exploring the outer layers of the heliosphere, the huge bubble of charged particles and magnetic fields emanating from the sun. But things are really getting interesting for Voyager 1; it has detected a dramatic drop in solar particles and a simultaneous jump in high-energy galactic cosmic rays, which originate from outside the solar system.

NASA's Voyager mission scientists don't think the probe has left the heliosphere yet, however, because it hasn't measured a shift in the direction of the ambient magnetic field. (The team thinks the observed magnetic field will change orientation from roughly east-west within the solar system to north-south outside of it.)

A different interpretation

But Swisdak and his colleagues present a different view in a paper published online today (Aug. 15) in The Astrophysical Journal Letters. They devised a new model, which envisions the heliosphere boundary not as a relatively homogeneous surface but rather as a porous and multilayered structure.

Magnetic reconnection — the breaking and rejoining of field lines — creates a complex set of nested "magnetic islands" in the solar system's outer reaches, allowing the mixing of interstellar and solar material near the heliosphere's edge, the researchers say.

This model provides a better explanation of Voyager 1's data, Swisdak and his team say, and it suggests that the probe cruised into interstellar space on July 27, 2012.
Voyager mission chief scientist Ed Stone, a physicist at the California Institute of Technology in Pasadena, said he and his team will keep the new model in mind as they continue to study the data Voyager 1 beams home.

"Their model would mean that the interstellar magnetic field direction is the same as that which originates from our sun," Stone said in statement released by NASA today. "Other models envision the interstellar magnetic field draped around our solar bubble and predict that the direction of the interstellar magnetic field is different from the solar magnetic field inside. By that interpretation, Voyager 1 would still be inside our solar bubble."

"The fine-scale magnetic connection model will become part of the discussion among scientists as they try to reconcile what may be happening on a fine scale with what happens on a larger scale," Stone added. "The Voyager 1 spacecraft is exploring a region no spacecraft has ever been to before. We will continue to look for any further developments over the coming months and years as Voyager explores an uncharted frontier."

Source of Article: Space.com

2013년 8월 14일 수요일

NASA's Juno Spacecraft Is Halfway to Jupiter

A NASA spacecraft has hit the halfway mark of its five-year voyage to the solar system's largest planet: Jupiter.

The odometer on NASA's Juno probe clicked over to 880 million miles (1.415 billion kilometers) on Monday (Aug. 12), space agency officials said. That means the spacecraft is halfway to Jupiter, at least in terms of distance traveled, they added.

The $1.1 billion Juno mission launched in August 2011 and will arrive at the Jovian system in July 2016. The probe is taking an indirect, looping path to its destination, with a close Earth flyby scheduled two months from now to provide a dramatic speed boost.

"On Oct. 9, Juno will come within 347 miles (559 km) of Earth," Juno project manager Rick Nybakken, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. (Juno was 34.46 million miles, or 55.46 million km, from Earth when the halfway milestone was reached on Monday morning, officials said.)

"The Earth flyby will give Juno a kick in the pants, boosting its velocity by 16,330 mph (26,280 km/h)," Nybakken added. "From there, it's 'Next stop, Jupiter.'"

Once Juno reaches Jupiter, it will circle the planet for a full Earth year, making 33 orbits from pole to pole. The spacecraft will use its eight science instruments to study the gas giant's atmosphere, gravitational field and magnetic field.

Juno's observations should reveal a great deal about Jupiter's origins, structure and composition, including whether or not it possesses a solid core, researchers said.

The mission is named after the goddess Juno in Greek and Roman mythology.In the myth, the god Jupiter (or Zeus, in the Greek version) used clouds to hide his acts of mischief, but his wife Juno was able to peer through the veil to see her husband's antics, according to a NASA description.

The 8,000-pound (3,267 kilograms) Juno probe is the first solar-powered spacecraft ever to visit the outer solar system.Juno has three huge solar arrays, each of which is the size of a tractor-trailer.

Source of Article: Space.com

Manned Missions to Mars: Is the Moon Really a Stepping Stone?

The moon may be more of a stumbling block than a stepping stone on humanity's path to the Red Planet, one prominent researcher says.

The perceived need to develop lunar infrastructure and resources first could push a manned Mars mission far off into the future, said Harley Thronson, senior scientist for advanced concepts in the Astrophysics Science Division at NASA's Goddard Space Flight Center in Greenbelt, Md.

And if putting boots on the Red Planet in the next few decades is indeed the top priority of the international human spaceflight community, then making a prolonged stopover on the moon beforehand runs counter to the spirit and history of exploration, he added.

"In the 19th century, the American West was explored for decades by trappers, frontiersmen and occasional minimal expeditions sent by the central government," Thronson wrote in an essay in The Space Review, which was published online Aug. 5.

"Only later was the elaborate national infrastructure established to support sustained development of the West," Thronson continued. "In contrast, widely popular 'moon first, then Mars' architectures are a reverse of the historical experience of human exploration on Earth."

Discussions about how to send astronauts to Mars often center on "stepping stones" — for example, whether to go to a near-Earth asteroid or the moon first. But mission architects must keep in mind that focusing too much on intermediate destinations could significantly delay or doom a manned Mars effort, especially in this era of tight budgets, Thronson said.

Indeed, the best approach may be to work toward heading straight to the Red Planet with a bare-bones mission.

"Let's just go — prove that it is doable, prove that it is feasible and then examine how you do it on a regular basis that's affordable," Thronson told SPACE.com.

The success of that first mission, however stripped-down it may be, would generate a great deal of excitement and momentum that would pave the way for future, more sustained Red Planet efforts, he added.

The exploitation of lunar or asteroid resources could eventually play a large role in humanity's Red Planet plan, but it may be unwise to wait for this step. It could take hundreds of billions of dollars and many decades to build up enough infrastructure to make a difference, Thronson said.

Thronson said his thinking on this issue has been influenced by Inspiration Mars, a private mission that aims to launch two astronauts on a Red Planet flyby in 2018.
"They have obviously adopted the philosophy of, 'Let's just do it,'" he said.

The Space Review piece is meant to stimulate productive discussion and debate about the future of human spaceflight, Thronson said. And it may also help scientists, engineers and policymakers view the term "stepping stone" in a new light.

"Stepping stones don't have to be measured by distance; they could be measured by capabilities," Thronson said.

"The successful space station program is stepping stone number one," he added. "Going to Mars in a minimal or reduced-capabilities mission is stepping stone two. And then setting up the support system for subsequent missions to Mars — say, on the moon — is stepping stone three."

Humans haven't been on the moon, or anywhere else in deep space, since NASA's Apollo 17 mission returned to Earth in 1972. NASA is currently working to get astronauts to a near-Earth asteroid by 2025, then on to the vicinity of Mars by the mid-2030s, as directed by President Barack Obama in 2010.

Source of Article: Space.com

Alien Life on Europa? Funding Gap Means We May Never Know

Is there life on Europa, Jupiter's moon? Perhaps — but researchers may not know for years, or even decades, depending on the outcome of wars over NASA's budget that broke out before Congress went home for its August recess.

Scientists know very little about Europa, one of Jupiter's largest moons. NASA's Voyager 2 and Galileo spacecraft together flew by the moon a dozen times and took some of the most captivating pictures of it from space. But the Galileo mission was nearly 20 years ago, and Voyager 2 was in 1979. Still, the pictures those and other missions sent home were enough to keep scientists guessing about what might lie beneath Europa's fractured, ice-covered exterior.

In fact, an all-star NASA science team recently speculated that there are signs of a liquid-water ocean under Europa's icy surface, and this could potentially be a home for microbial life. Their work appeared Aug. 7 in a new study published in the journal Astrobiology.

Newer research, funded by both NASA and the National Science Foundation, has shown that microbes can survive in even the harshest environments — near the edge of underwater volcanoes in the deep oceans or in the iciest of conditions on Antarctica. So if there's a liquid ocean on Europa, there might also be microbial life.

When NASA sets out on a planetary science mission, it starts with the big science questions that need to be answered. That's what a NASA "science definition" research team, drawn from the agency's various centers, did in the recent Astrobiology study. The scientists laid out the biggest questions that need to be answered if NASA is going to land a spacecraft on Europa.

"If one day humans send a robotic lander to the surface of Europa, we need to know what to look for and what tools it should carry," said the study's lead author, Robert Pappalardo, from NASA's Jet Propulsion Laboratory in California. "Europa is the most likely place in our solar system beyond Earth to have life today, and a landed mission would be the best way to search for signs of life."

A number of scientists contributed to the Astrobiology article, hailing from a number of NASA centers and university-supported facilities: the Jet Propulsion Laboratory, Goddard Space Flight Center, Ames Research Center, Johns Hopkins University-based Applied Physics Lab, University of Colorado and University of Texas.

In perhaps its first activity, a NASA mission to Europa would look for a marker of microbial life near fissures on the moon's surface. "The hope would be that surface materials, possibly near the linear crack features, include biomarkers carried up from the ocean," said Ames researcher Chris McKay, a senior editor for Astrobiology.

Just as NASA did with the Mars rover, the agency would have a lander on Europa take a large number of pictures up close — providing a human-scale context vastly different from the pictures Voyager 2 and Galileo captured from space. The rover would also look for geological activity and the presence of liquid water.

The American public is fascinated with planetary science, and such a mission would capture public support. More than 30,000 Americans have now paid a small fee for a one-way trip to Mars a decade from now, sponsored by a start-up foundation called the Mars One project. More than 100,000 people worldwide have signed up to spend the rest of their lives on the Red Planet, the project's founder announced recently.

Life-threatening details — like whether people will be exposed to lethal space radiation during the one-way trip to Mars or how the settlement will be permanently funded — are a long way from being answered. In spite of that, the response has been strong, clearly showing that the public wants to explore the rest of the Earth's solar system. People are inspired by space travel and planetary science.

However, the White House — and to a lesser extent, parts of the House of Representatives — have not shown the same enthusiasm. There is currently a three-way fight — amongst the House, the Senate and the White House — raging in Washington, D.C., over NASA's planetary science future, and this fight was on full display as the space agency's budget was debated in July.

The battle began when the White House submitted its fiscal year 2014 NASA budget to Congress. While the overall number was unchanged from last year's budget, the White House proposed to significantly cut the planetary-science and space-exploration portions of NASA's budget to make way for other priorities.

Then, the House Appropriations Committee weighed in, proposing to cut NASA's overall budget deeply, below President Barack Obama's request. NASA has argued against the deep cuts. "This proposal would challenge America's preeminence in space exploration," NASA Associate Administrator David Weaver wrote in a blog on the eve of the House panel vote. "We are especially concerned [that] the bill cuts funding for space technology, the 'seed corn' that allows the nation to conduct ever more capable and affordable space missions."

Next, the House Committee on Science, Space and Technology proposed cutting NASA's budget even further, in line with sequestration guidelines. The House's Senate counterpart restored those cuts, setting the stage for a budget shootout when Congress returns in September. NASA's fiscal 2014 budget has to be finalized by the end of September.

So what's the future of a proposed mission to Europa that would check for life beneath that moon's icy surface? It depends. The White House's Office of Management and Budget (OMB) doesn't see a need for such a mission. House appropriators, from both parties, clearly do — because they approved nearly $100 million more for planetary science in NASA's budget (with cuts elsewhere to offset the increase) than the White House did. The Senate has yet to state its priorities.

"The nation's planetary science program has been under sustained attack from the White House budget cutters, and remains in jeopardy," Rep. Adam Schiff (D-Calif.) wrote recently in an unusually critical opinion piece attacking the White House for its NASA budget. "Time and again, deficit hawks in the Office of Management and Budget have targeted specific parts of the NASA portfolio for disproportionate cuts, and none more so than arguably the most successful of all NASA's recent achievements — planetary science."

Schiff explained why the House appropriators restored the money for planetary science in NASA's budget, moves which would allow NASA to begin planning for a Europa mission.

"Some in Washington have questioned why funding these missions is such a priority in an era of austerity and deficits. Plainly, the bureaucrats at OMB think the search for life on other planets to be an expensive, quixotic and dispensable activity," wrote Schiff, who sits on the Appropriations committee. "Profoundly important research and development and all the economic benefits it brings will be forsaken if we abandon the field," he said.

"Planetary science is about seeking the answers to questions as old as mankind — and perhaps older. Are we alone? What is the nature of the universe and our place in it? Americans come from a long line of explorers. Are we really content to take a back seat now?"
f there is microbial life on Europa, finding it will depend on human life in Congress.

Source of Article: Space.com