Tag Archives: planetary

Passion, Persistence and Pluto

New Horizons Pluto Flyby

Alliterations aside this is a great story of how passion, persistence and persuasiveness can make a real impact. This is especially significant when you look at the triumphant climax to NASA’s unlikely New Horizons mission to Pluto. Over 20 years in the making and fraught with budget cuts and political infighting — NASA is known for its bureaucracy — the mission reached its zenith last week. While thanks go to the many hundreds engineers and scientists involved from its inception, the mission would not have succeeded without the vision and determination of one person — Alan Stern.

In a music track called “Over the Sea” by the 1980s (and 90s) band Information Society there is a sample of Star Trek’s Captain Kirk saying,

“In every revolution there is one man with a vision.”

How appropriate.

From Smithsonian

On July 14 at approximately 8 a.m. Eastern time, a half-ton NASA spacecraft that has been racing across the solar system for nine and a half years will finally catch up with tiny Pluto, at three billion miles from the Sun the most distant object that anyone or anything from Earth has ever visited. Invisible to the naked eye, Pluto wasn’t even discovered until 1930, and has been regarded as our solar system’s oddball ever since, completely different from the rocky planets close to the Sun, Earth included, and equally unlike the outer gas giants. This quirky and mysterious little world will swing into dramatic view as the New Horizons spacecraft makes its closest approach, just 6,000 miles away, and onboard cameras snap thousands of photographs. Other instruments will gauge Pluto’s topography, surface and atmospheric chemistry, temperature, magnetic field and more. New Horizons will also take a hard look at Pluto’s five known moons, including Charon, the largest. It might even find other moons, and maybe a ring or two.
It was barely 20 years ago when scientists first learned that Pluto, far from alone at the edge of the solar system, was just one in a vast swarm of small frozen bodies in wide, wide orbit around the Sun, like a ring of debris left at the outskirts of a construction zone. That insight, among others, has propelled the New Horizons mission. Understand Pluto and how it fits in with those remnant bodies, scientists say, and you can better understand the formation and evolution of the solar system itself.
If all goes well, “encounter day,” as the New Horizons team calls it, will be a cork-popping celebration of tremendous scientific and engineering prowess—it’s no small feat to fling a collection of precision instruments through the frigid void at speeds up to 47,000 miles an hour to rendezvous nearly a decade later with an icy sphere about half as wide as the United States is broad. The day will also be a sweet vindication for the leader of the mission, Alan Stern. A 57-year-old astronomer, aeronautical engineer, would-be astronaut and self-described “rabble-rouser,” Stern has spent the better part of his career fighting to get Pluto the attention he thinks it deserves. He began pushing NASA to approve a Pluto mission nearly a quarter of a century ago, then watched in frustration as the agency gave the green light to one Pluto probe after another, only to later cancel them. “It was incredibly frustrating,” he says, “like watching Lucy yank the football away from Charlie Brown, over and over.” Finally, Stern recruited other scientists and influential senators to join his lobbying effort, and because underdog Pluto has long been a favorite of children, proponents of the mission savvily enlisted kids to write to Congress, urging that funding for the spacecraft be approved.
New Horizons mission control is headquartered at Johns Hopkins University’s Applied Physics Laboratory near Baltimore, where Stern and several dozen other Plutonians will be installed for weeks around the big July event, but I caught up with Stern late last year in Boulder at the Southwest Research Institute, where he is an associate vice president for research and development. A picture window in his impressive office looks out onto the Rockies, where he often goes to hike and unwind. Trim and athletic at 5-foot-4, he’s also a runner, a sport he pursues with the exactitude of, well, a rocket scientist. He has calculated his stride rate, and says (only half-joking) that he’d be world-class if only his legs were longer. It wouldn’t be an overstatement to say that he is a polarizing figure in the planetary science community; his single-minded pursuit of Pluto has annoyed some colleagues. So has his passionate defense of Pluto in the years since astronomy officials famously demoted it to a “dwarf planet,” giving it the bum’s rush out of the exclusive solar system club, now limited to the eight biggies.
The timing of that insult, which is how Stern and other jilted Pluto-lovers see it, could not have been more dramatic, coming in August 2006, just months after New Horizons had rocketed into space from Cape Canaveral. What makes Pluto’s demotion even more painfully ironic to Stern is that some of the groundbreaking scientific discoveries that he had predicted greatly strengthened his opponents’ arguments, all while opening the door to a new age of planetary science. In fact, Stern himself used the term “dwarf planet” as early as the 1990s.
The wealthy astronomer Percival Lowell, widely known for insisting there were artificial canals on Mars, first started searching for Pluto at his private observatory in Arizona in 1905. Careful study of planetary orbits had suggested that Neptune was not the only object out there exerting a gravitational tug on Uranus, and Lowell set out to find what he dubbed “Planet X.” He died without success, but a young man named Clyde Tombaugh, who had a passion for astronomy though no college education, arrived at the observatory and picked up the search in 1929. After 7,000 hours staring at some 90 million star images, he caught sight of a new planet on his photographic plates in February 1930. The name Pluto, the Roman god of the underworld, was suggested by an 11-year-old British girl named Venetia Burney, who had been discussing the discovery with her grandfather. The name was unanimously adopted by the Lowell Observatory staff in part because the first two letters are Percival Lowell’s initials.
Pluto’s solitary nature baffled scientists for decades. Shouldn’t there be other, similar objects out beyond Neptune? Why did the solar system appear to run out of material so abruptly? “It seemed just weird that the outer solar system would be so empty, while the inner solar system was filled with planets and asteroids,” recalls David Jewitt, a planetary scientist at UCLA. Throughout the decades various astronomers proposed that there were smaller bodies out there, yet unseen. Comets that periodically sweep in to light up the night sky, they speculated, probably hailed from a belt or disk of debris at the solar system’s outer reaches.
Stern, in a paper published in 1991 in the journal Icarus, argued not only that the belt existed, but also that it contained things as big as Pluto. They were simply too far away, and too dim, to be easily seen. His reasoning: Neptune’s moon Triton is a near-twin of Pluto, and probably orbited the Sun before it was captured by Neptune’s gravity. Uranus has a drastically tilted axis of rotation, probably due to a collision eons ago with a Pluto-size object. That made three Pluto-like objects at least, which suggested to Stern there had to be more. The number of planets in the solar system would someday need to be revised upward, he thought. There were probably hundreds, with the majority, including Pluto, best assigned to a subcategory of “dwarf planets.”
Just a year later, the first object (other than Pluto and Charon) was discovered in that faraway region, called the Kuiper Belt after the Dutch-born astronomer Gerard Kuiper. Found by Jewitt and his colleague, Jane Luu, it’s only about 100 miles across, while Pluto spans 1,430 miles. A decade later, Caltech astronomers Mike Brown and Chad Trujillo discovered an object about half the size of Pluto, large enough to be spherical, which they named Quaoar (pronounced “kwa-war” and named for the creator god in the mythology of the pre-Columbian Tongva people native to the Los Angeles basin). It was followed in quick succession by Haumea, and in 2005, Brown’s group found Eris, about the same size as Pluto and also spherical.
Planetary scientists have spotted many hundreds of smaller Kuiper Belt Objects; there could be as many as ten billion that are a mile across or more. Stern will take a more accurate census of their sizes with the cameras on New Horizons. His simple idea is to map and measure Pluto’s and Charon’s craters, which are signs of collisions with other Kuiper Belt Objects and thus serve as a representative sample. When Pluto is closest to the Sun, frozen surface material evaporates into a temporary atmosphere, some of which escapes into space. This “escape erosion” can erase older craters, so Pluto will provide a recent census. Charon, without this erosion, will offer a record that spans cosmic history. In one leading theory, the original, much denser Kuiper Belt would have formed dozens of planets as big or bigger than Earth, but the orbital changes of Jupiter and Saturn flung most of the building blocks away before that could happen, nipping planet formation in the bud.
By the time New Horizons launched at Cape Canaveral on January 19, 2006, it had become difficult to argue that Pluto was materially different from many of its Kuiper Belt neighbors. Curiously, no strict definition of “planet” existed at the time, so some scientists argued that there should be a size cutoff, to avoid making the list of planets too long. If you called Pluto and the other relatively small bodies something else, you’d be left with a nice tidy eight planets—Mercury through Neptune. In 2000, Neil deGrasse Tyson, director of the Hayden Planetarium in New York City, had famously chosen the latter option, leaving Pluto out of a solar system exhibit.
Then, with New Horizons less than 15 percent of the way to Pluto, members of the International Astronomical Union, responsible for naming and classifying celestial objects, voted at a meeting in Prague to make that arrangement official. Pluto and the others were now to be known as dwarf planets, which, in contrast to Stern’s original meaning, were not planets. They were an entirely different sort of beast. Because he discovered Eris, Caltech’s Brown is sometimes blamed for the demotion. He has said he would have been fine with either outcome, but he did title his 2010 memoir How I Killed Pluto and Why It Had It Coming.
“It’s embarrassing,” recalls Stern, who wasn’t in Prague for the vote. “It’s wrong scientifically and it’s wrong pedagogically.” He said the same sort of things publicly at the time, in language that’s unusually blunt in the world of science. Among the dumbest arguments for demoting Pluto and the others, Stern noted, was the idea that having 20 or more planets would be somehow inconvenient. Also ridiculous, he says, is the notion that a dwarf planet isn’t really a planet. “Is a dwarf evergreen not an evergreen?” he asks.
Stern’s barely concealed contempt for what he considers foolishness of the bureaucratic and scientific varieties hasn’t always endeared him to colleagues. One astronomer I asked about Stern replied, “My mother taught me that if you can’t say anything nice about someone, don’t say anything.” Another said, “His last name is ‘Stern.’ That tells you all you need to know.”
DeGrasse Tyson, for his part, offers measured praise: “When it comes to everything from rousing public sentiment in support of astronomy to advocating space science missions to defending Pluto, Alan Stern is always there.”
Stern also inspires less reserved admiration. “Alan is incredibly creative and incredibly energetic,” says Richard Binzel, an MIT planetary scientist who has known Stern since their graduate-school days. “I don’t know where he gets it.”
Read the entire article here.

Image: New Horizons Principal Investigator Alan Stern of Southwest Research Institute (SwRI), Boulder, CO, celebrates with New Horizons Flight Controllers after they received confirmation from the spacecraft that it had successfully completed the flyby of Pluto, Tuesday, July 14, 2015 in the Mission Operations Center (MOC) of the Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Maryland. Public domain.

Europa Here We Come


With the the European Space Agency’s (ESA) Philae lander firmly rooted to a comet, NASA’s Dawn probe orbiting dwarf planet Ceres and its New Horizon’s spacecraft hurtling towards Pluto and Charon it would seem that we are doing lots of extraterrestrial exploration lately. Well, this is exciting, but for arm-chair explorers like myself this is still not enough. So, three cheers to NASA for giving a recent thumbs up to their next great mission — Europa Multi Flyby — to Jupiter’s moon, Europa.

Development is a go! But we’ll have to wait until the mid-2020s for lift-off. And, better yet, ESA has a mission to Europa planned for launch in 2022. Can’t wait — it looks spectacular.

From ars technica:

Get ready, we’re going to Europa! NASA’s plan to send a spacecraft to explore Jupiter’s moon just passed a major hurdle. The mission, planned for the 2020s, now has NASA’s official stamp of approval and was given the green light to move from concept phase to development phase.

Formerly known as Europa Clipper, the mission will temporarily be referred to as the Europa Multi Flyby Mission until it is given an official name. The current mission plan would include 45 separate flybys around the moon while orbiting Jupiter every two weeks. “We are taking an exciting step from concept to mission in our quest to find signs of life beyond Earth,” John Grunsfeld, associate administrator for NASA’s Science Mission Directorate, said in a press release.

Since Galileo first turned a spyglass up to the skies and discovered the Jovian moon, Europa has been a world of intrigue. In the 1970s, we received our first look at Europa through the eyes of Pioneer 10 and 11, followed closely by the twin Voyager satellites in the 1980s. Their images provided the first detailed view of the Solar System’s smoothest body. These photos also delivered evidence that the moon might be harboring a subsurface ocean. In the mid 1990s, the Galileo spacecraft gave us the best view to-date of Europa’s surface.

“Observations of Europa have provided us with tantalizing clues over the last two decades, and the time has come to seek answers to one of humanity’s most profound questions,” Grunsfeld said. “Mainly, is there life beyond Earth?”

Sending a probe to explore Jupiter’s icy companion will help scientists in the search for this life. If Europa can support microbial life, other glacial moons such as Enceladus might as well.

Water, chemistry, and energy are three components essential to the presence of life. Liquid water is present throughout the Solar System, but so far the only world known to support life is Earth. Scientists think that if we follow the water, we may find evidence of life beyond Earth.

However, water alone will not support life; the right combination of ingredients is key. This mission to Europa will explore the moon’s potential habitability as opposed to outright looking for life.

When we set out to explore new worlds, we do it in phases. First we flyby, then we send robotic landers, and then we send people. This three-step process is how we, as humans, have explored the Moon and how we are partly through the process of exploring Mars.

The flyby of Europa will be a preliminary mission with four objectives: explore the ice shell and subsurface ocean; determine the composition, distribution, and chemistry of various compounds and how they relate to the ocean composition; map surface features and determine if there is current geologic activity; characterize sites to determine where a future lander might safely touch down.

Europa, at 3,100 kilometers wide (1,900 miles), is the sixth largest moon in the Solar System. It has a 15 to 30 kilometer (9 to 18 mile) thick icy outer crust that covers a salty subsurface ocean. If that ocean is in contact with Europa’s rocky mantle, a number of complex chemical reactions are possible. Scientists think that hydrothermal vents lurk on the seafloor, and, just like the vents here on Earth, they could support life.

The Galileo orbiter taught us most of what we know about Europa through 12 flybys of the icy moon. The new mission is scheduled to conduct approximately 45 flybys over a 2.5-year period, providing even more insight into the moon’s habitability.

Read the article here.

Image: Europa. Europa is Jupiter’s sixth-closest moon, and the sixth-largest moon in the Solar System. Courtesy of NASA.

Philae: The Little Lander That Could


What audacity! A ten year journey, covering 4 billion miles.

On November 12, 2014 at 16:03 UTC, the Rosetta spacecraft delivered the Philae probe to land on a comet; a comet the size of New York’s Manhattan Island, speeding through our solar system at 34,000 miles per hour. What utter audacity!

The team of scientists, engineers, and theoreticians at the European Space Agency (ESA), and its partners, pulled off an awe-inspiring, remarkable and historic feat; a feat that ranks with the other pinnacles of human endeavor and exploration. It shows what our fledgling species can truly achieve.

Sadly, our species is flawed, capable of such terrible atrocities to ourselves and to our planet. And yet, triumphant stories like this one — the search for fundamental understanding through science —  must give us all some continued hope.

Exploration. Inspiration. Daring. Risk. Execution. Discovery. Audacity!

From the Guardian:

These could be the dying hours of Philae, the device the size of a washing machine which travelled 4bn miles to hitch a ride on a comet. Philae is the “lander” which on Wednesday sprung from the craft that had carried it into deep, dark space, bounced a couple of times on the comet’s surface, and eventually found itself lodged in the shadows, starved of the sunlight its solar batteries needed to live. Yesterday, the scientists who had been planning this voyage for the past quarter-century sat and waited for word from their little explorer, hoping against hope that it still had enough energy to reveal its discoveries.

If Philae expires on the hard, rocky surface of Comet 67P the sadness will be felt far beyond mission control in Darmstadt, Germany. Indeed, it may be felt there least of all: those who have dedicated their working lives to this project pronounced it a success, regardless of a landing that didn’t quite go to plan (Philae’s anchor harpoons didn’t fire, so with gravity feeble there was nothing to keep the machine anchored to the original, optimal landing site). They were delighted to have got there at all and thrilled at Philae’s early work. Up to 90% of the science they planned to carry out has been done. As one scientist put it, “We’ve already got fantastic data.”

Those who lacked their expertise couldn’t help feel a pang all the same. The human instinct to anthropomorphise does not confine itself to cute animals, as anyone who has seen the film Wall-E can testify. If Pixar could make us well up for a waste-disposing robot, it’s little wonder the European Space Agency has had us empathising with a lander ejected from its “mothership”, identifiable only by its “spindly leg”. In those nervous hours, many will have been rooting for Philae, imagining it on that cold, hard surface yearning for sunlight, its beeps of data slowly petering out as its strength faded.

 But that barely accounts for the fascination this adventure has stirred. Part of it is simple, a break from the torments down here on earth. You don’t have to go as far as Christopher Nolan film Interstellar, which fantasises about leaving our broken, ravaged planet and starting somewhere else – to enjoy a rare respite from our earthly woes. For a few merciful days, the news has featured a story remote from the bloodshed of Islamic State and Ukraine, from the pain of child abuse and poverty. Even those who don’t dream of escaping this planet can relish the escapism.

But the comet landing has provided more than a diversion: it’s been an antidote too. For this has been a story of human cooperation in a world of conflict. The narrow version of this point focuses on this as a European success story. When our daily news sees “Europe” only as the source of unwanted migrants or maddening regulation, Philae has offered an alternative vision; that Germany, Italy, France, Britain and others can achieve far more together than they could ever dream of alone. The geopolitical experts so often speak of the global pivot to Asia, the rise of the Bric nations and the like – but this extraordinary voyage has proved that Europe is not dead yet.

Even that, as I say, is to view it too narrowly. The US, through Nasa, is involved as well. And note the language attached to the hardware: the Rosetta satellite, the Ptolemy measuring instrument, the Osiris on-board camera, Philea itself – all imagery drawn from ancient Egypt. The spacecraft was named after the Rosetta stone, the discovery that unlocked hieroglyphics, as if to suggest a similar, if not greater, ambition: to decode the secrets of the universe. By evoking humankind’s ancient past, this is presented as a mission of the entire human race. There will be no flag planting on Comet 67P. As the Open University’s Jessica Hughes puts it, Philea, Rosetta and the rest “have become distant representatives of our shared, earthly heritage”.

That fits because this is how we experience such a moment: as a human triumph. When we marvel at the numbers – a probe has travelled for 10 years, crossed those 4bn miles, landed on a comet speeding at 34,000mph and done so within two minutes of its planned arrival – we marvel at what our species is capable of. I can barely get past the communication: that Darmstadt is able to contact an object 300 million miles away, sending instructions, receiving pictures. I can’t get phone reception in my kitchen, yet the ESA can be in touch with a robot that lies far beyond Mars. Like watching Usain Bolt run or hearing Maria Callas sing, we find joy and exhilaration in the outer limits of human excellence.

And of course we feel awe. What Interstellar prompts us to feel artificially – making us gasp at the confected scale and digitally assisted magnitude – Philae gives us for real. It is the stretch of time and place, glimpsing somewhere so far away it is as out of reach as ancient Egypt.

All that is before you reckon with the voyage’s scholarly purpose. “We are on the cutting edge of science,” they say, and of course they are. They are probing the deepest mysteries, including the riddle of how life began. (One theory suggests a comet brought water to a previously arid Earth.) What the authors of the Book of Genesis understood is that this question of origins is intimately bound up with the question of purpose. From the dawn of human time, to ask “How did we get here?” has been to ask “Why are we here?”

It’s why contemplation of the cosmic so soon reverts to the spiritual. Interstellar, like 2001: A Space Odyssey before it, is no different. It’s why one of the most powerful moments of Ronald Reagan’s presidency came when he paid tribute to the astronauts killed in the Challenger disaster. They had, he said, “slipped the surly bonds of Earth to touch the face of God”.

Not that you have to believe in such things to share the romance. Secularists, especially on the left, used to have a faith of their own. They believed that humanity was proceeding along an inexorable path of progress, that the world was getting better and better with each generation. The slaughter of the past century robbed them – us – of that once-certain conviction. Yet every now and again comes an unambiguous advance, what one ESA scientist called “A big step for human civilisation”. Even if we never hear from Philae again, we can delight in that.

Read the entire article here.

Image: Philae lander, detached from the Rosetta spacecraft, on its solitary journey towards the surface of comet P67. Courtesy of ESA.

A Subsurface Anomaly


Researchers published details of this “subsurface anomaly” in the journal Science, on April 4, 2014. The summary reads as follows:

Our results indicate the presence of a negative mass anomaly in the south-polar region, largely compensated by a positive subsurface anomaly compatible with the presence of a regional subsurface sea at depths of 30 to 40 kilometers and extending up to south latitudes of about 50°. The estimated values for the largest quadrupole harmonic coefficients (106J2 = 5435.2 ± 34.9, 106C22 = 1549.8 ± 15.6, 1?) and their ratio (J2/C22 = 3.51 ± 0.05) indicate that the body deviates mildly from hydrostatic equilibrium. The moment of inertia is around 0.335MR2, where M is the mass and R is the radius, suggesting a differentiated body with a low-density core.

In effect this means that the researchers are reasonably confident that an ocean of water lies below the icy surface of Enceladus, one of Saturn’s most intriguing moons.

From NYT:

Inside a moon of Saturn, beneath its icy veneer and above its rocky core, is a sea of water the size of Lake Superior, scientists announced on Thursday.

The findings, published in the journal Science, confirm what planetary scientists have suspected about the moon, Enceladus, ever since they were astonished in 2005 by photographs showing geysers of ice crystals shooting out of its south pole.

“What we’ve done is put forth a strong case for an ocean,” said David J. Stevenson, a professor of planetary science at the California Institute of Technology and an author of the Science paper.

For many researchers, this tiny, shiny cue ball of a moon, just over 300 miles wide, is now the most promising place to look for life elsewhere in the solar system, even more than Mars.

“Definitely Enceladus,” said Larry W. Esposito, a professor of astrophysical and planetary sciences at the University of Colorado, who was not involved in the research. “Because there’s warm water right there now.”

Enceladus (pronounced en-SELL-a-dus) is caught in a gravitational tug of war between Saturn and another moon, Dione, which bends its icy outer layer, creating friction and heat. In the years since discovering the geysers, NASA’s Cassini spacecraft has made repeated flybys of Enceladus, photographing the fissures (nicknamed tiger stripes) where the geysers originate, measuring temperatures and identifying carbon-based organic molecules that could serve as building blocks for life.

Cassini has no instruments that can directly detect water beneath the surface, but three flybys in the years 2010-12 were devoted to producing a map of the gravity field, noting where the pull was stronger or weaker.

During the flybys, lasting just a few minutes, radio telescopes that are part of NASA’s Deep Space Network broadcast a signal to the spacecraft, which echoed it back to Earth. As the pull of Enceladus’s gravity sped and then slowed the spacecraft, the frequency of the radio signal shifted, just as the pitch of a train whistle rises and falls as it passes by a listener.

Using atomic clocks on Earth, the scientists measured the radio frequency with enough precision that they could discern changes in the velocity of Cassini, hundreds of millions of miles away, as minuscule as 14 inches an hour.

They found that the moon’s gravity was weaker at the south pole. At first glance, that is not so surprising; there is a depression at the pole, and lower mass means less gravity. But the depression is so large that the gravity should actually have been weaker.

“Then you say, ‘A-ha, there must be compensation,’ ” Dr. Stevenson said. “Something more dense under the ice. The natural candidate is water.”

Liquid water is 8 percent denser than ice, so the presence of a sea 20 to 25 miles below the surface fits the gravity measurements. “It’s an ocean that extends in all directions from the south pole to about halfway to the equator,” Dr. Stevenson said.

The underground sea is up to six miles thick, much deeper than a lake. “It’s a lot more water than Lake Superior,” Dr. Stevenson said. “It may even be bigger. The ocean could extend all the way to the north pole.”

The conclusion was not a surprise, said Christopher P. McKay, a planetary scientist at NASA Ames Research Center in Mountain View, Calif., who studies the possibility of life on other worlds, but “it confirms in a really robust way what has been sort of the standard model.”

It also makes Enceladus a more attractive destination for a future mission, especially one that would collect samples from the plumes and return them to Earth to see if they contain any microbes.

Read the entire article here.

Image: View of Saturn’s moon Enceladus on July 14, 2005, from the Cassini spacecraft. Courtesy of NASA / JPL / Space Science Institute.

Mars Emigres Beware

MRO-Mars-impact-craterThe planners behind the proposed, private Mars One mission to Mars are still targeting 2024 for an initial settlement on the Red Planet. That’s now a mere 10 years away. As of this writing, the field of potential settlers has been whittled down to around 2,000 from an initial pool of about 250,000 would-be explorers. While the selection process and planning continues, other objects continue to target Mars as well. Large space rocks seem to be hitting the planet more frequently and more recently than was first thought. So, while such impacts are both beautiful and scientifically valuable — they may come as rather unwanted to the forthcoming human Martians.

From ars technica:

Yesterday [February 5, 2014], the team that runs the HiRISE camera on the Mars Reconnaissance Orbiter released the photo shown above. It’s a new impact crater on Mars, formed sometime early this decade. The crater at the center is about 30 meters in diameter, and the material ejected during its formation extends out as far as 15 kilometers.

The impact was originally spotted by the MRO’s Context Camera, a wide-field imaging system that (wait for it) provides the context—an image of the surrounding terrain—for the high-resolution images taken by HiRISE. The time window on the impact, between July 2010 and May 2012, simply represents the time between two different Context Camera photos of the same location. Once the crater was spotted, it took until November of 2013 for another pass of the region, at which point HiRISE was able to image it.

Read the entire article here.

Image: Impact crater from Mars Reconnaissance Orbiter. Courtesy of NASA / JPL.



How to Rendezvous With a Comet


First, you will need a significant piece of space hardware. Second, you will need to launch it having meticulously planned its convoluted trajectory through the solar system. Third, wait 12 years for the craft to reach the comet. Fourth, and with fingers crossed, launch a landing probe from the craft on to the 2.5 mile wide comet 67 P/Churyumov-Gerasimenko, while all are hurtling through space at around 25,000 miles per hour.

So far so good. The Rosetta spacecraft woke up from its self-induced 30-month hibernation on January 20, having slumbered to conserve energy. Now it continues on its final leg of the journey — a year-long trek to catch the comet.

Visit the European Space Agency (ESA) Rosetta mission home page here.

From ars technica:

The Rosetta spacecraft is due to wake up on the morning of January 20 after an 30-month hibernation in deep space. For the past ten years, the three-ton spacecraft has been on a one-way trip to a 4 km-wide comet. When it arrives, it will set about performing a maneuver that has never been done before: landing on a comet’s surface.

The spacecraft has already achieved some success on its long journey through the solar system. It has passed by two asteroids—Steins in 2008 and Lutetia in 2010—and it tried out some of its instruments on them. Because Rosetta’s journey is so protracted, however, preserving energy has been of the utmost importance, which is why it was put into hibernation in June 2011. The journey has taken so long because the spacecraft needed to be “gravity-assisted” by many planets in order to reach the necessary velocity to match the comet’s orbit.

When it wakes up, Rosetta is expected to take a few hours to establish contact with Earth, 673 million km (396 million mi) away. The scientists involved will wait with bated breath. Dan Andrews, part of a team at the Open University who built one of Rosetta’s on-board instruments, said, “If there isn’t sufficient power, Rosetta will go back to sleep and try again later. The wake-up process is driven by software commands already on the spacecraft. It will wake itself up autonomously and spend some time warming up and orienting its antenna toward Earth to ‘phone home.’”

If multiple attempts fail to wake Rosetta, it could mean the end of the mission.

Rosetta should reach comet 67P/Churyumov-Gerasimenko in May 2014, at which point it will decelerate to match the speed of the comet. In August 2014, Rosetta will enter orbit around the comet to scout 67P’s surface in search of a landing spot. Then, in November 2014, Rosetta’s on-board lander, Philae, will be ejected from the orbiting spacecraft onto the surface of the comet. There are a lot of things that need to come together perfectly for this to go smoothly, but space endeavors are designed to charter unknown territories, and Rosetta will be doing just that.

If Rosetta manages this mission successfully, it will make history as the first spacecraft to land on the surface of a comet. Success is by no means assured, as scientists have no idea what to expect when Rosetta arrives at the comet. Will the comet’s surface be icy, soft, hard, or rocky? This information will affect what kind of landing the spacecraft can expect and whether it will sink into the comet or bounce off. Another problem is that comet 67P is small and has a weak gravitational field, which will make holding the spacecraft on its surface challenging, even after a successful landing.

At a cost of €1 billion ($1.36 billion) it’s important that we get some value for our money with this mission. To ensure we do, Rosetta was designed to help answer some of the most basic questions about Earth and our solar system, such as where water and life originated, even if the landing doesn’t work out as well as we hope it will.

Comets are thought to have delivered some of the chemicals needed for life, including water to Earth and possibly other planets. This is why comet ISON, which sadly did not survive its close encounter with the Sun, had created excitement among scientists. If it had survived, it would have been the closest scientists could get to a comet with modern instruments.

Comet ISON’s demise means Rosetta is more important than ever. Without measuring the composition of comets, we won’t fully understand the origin of our planet. Comet 67P is thought to have preserved the very earliest ingredients of the solar system, acting as a small, deep-freeze time capsule. The hope is that it will now reveal its long-held secrets to Rosetta.

Andrews said, “It will be the first time a spacecraft will approach a comet and actually stay with it for a prolonged period of time, studying the processes whereby a comet ‘switches on’ as it approaches the Sun.”

Once on the comet’s surface, the Philae lander will deploy instruments to measure different forms of the elements hydrogen, carbon, nitrogen, and oxygen in the comet ice. This will allow scientists to understand the composition of the water and organic components that were collected by the comet 4.6 billion years ago, at the very start of the Solar System.

Read the entire article here.

Video: Rosetta’s Twelve-Year Journey to Land on a Comet. Courtesy of European Space Agency (ESA) Space Science.


Earth as the New Venus

New research models show just how precarious our planet’s climate really is. Runaway greenhouse warming would make a predicted 2-6 feet rise in average sea levels over the next 50-100 years seem like a puddle at the local splash pool.

From ars technica:

With the explosion of exoplanet discoveries, researchers have begun to seriously revisit what it takes to make a planet habitable, defined as being able to support liquid water. At a basic level, the amount of light a planet receives sets its temperature. But real worlds aren’t actually basic—they have atmospheres, reflect some of that light back into space, and experience various feedbacks that affect the temperature.

Attempts to incorporate all those complexities into models of other planets have produced some unexpected results. Some even suggest that Earth teeters on the edge of experiencing a runaway greenhouse, one that would see its oceans boil off. The fact that large areas of the planet are covered in ice may make that conclusion seem a bit absurd, but a second paper looks at the problem from a somewhat different angle—and comes to the same conclusion. If it weren’t for clouds and our nitrogen-rich atmosphere, the Earth might be an uninhabitable hell right now.

The new work focuses on a very simple model of an atmosphere: a linear column of nothing but water vapor. This clearly doesn’t capture the complex dynamics of weather and the different amounts of light to reach the poles, but it does include things like the amount of light scattered back out into space and the greenhouse impact of the water vapor. These sorts of calculations are simple enough that they were first done decades ago, but the authors note that this particular problem hadn’t been revisited in 25 years. Our knowledge of how water vapor absorbs both visible and infrared light has improved over that time.

Water vapor, like other greenhouse gasses, allows visible light to reach the surface of a planet, but it absorbs most of the infrared light that gets emitted back toward space. Only a narrow window, centered around 10 micrometer wavelengths, makes it back out to space. Once the incoming energy gets larger than the amount that can escape, the end result is a runaway greenhouse: heat evaporates more surface water, which absorbs more infrared, trapping even more heat. At some point, the atmosphere gets so filled with water vapor that light no longer even reaches the surface, instead getting absorbed by the atmosphere itself.

The model shows that, once temperatures reach 1,800K, a second window through the water vapor opens up at about four microns, which allows additional energy to escape into space. The authors suggest that this could be used when examining exoplanets, as high emissions in this region could be taken as an indication that the planet was undergoing a runaway greenhouse.

The authors also used the model to look at what Earth would be like if it had a cloud-free, water atmosphere. The surprise was that the updated model indicated that this alternate-Earth atmosphere would absorb 30 percent more energy than previous estimates suggested. That’s enough to make a runaway greenhouse atmosphere stable at the Earth’s distance from the Sun.

So, why is the Earth so relatively temperate? The authors added a few additional factors to their model to find out. Additional greenhouse gasses like carbon dioxide and methane made runaway heating more likely, while nitrogen scattered enough light to make it less likely. The net result is that, under an Earth-like atmosphere composition, our planet should experience a runaway greenhouse. (In fact, greenhouse gasses can lower the barrier between a temperate climate and a runaway greenhouse, although only at concentrations much higher than we’ll reach even if we burn all the fossil fuels available.) But we know it hasn’t. “A runaway greenhouse has manifestly not occurred on post-Hadean Earth,” the authors note. “It would have sterilized Earth (there is observer bias).”

So, what’s keeping us cool? The authors suggest two things. The first is that our atmosphere isn’t uniformly saturated with water; some areas are less humid and allow more heat to radiate out into space. The other factor is the existence of clouds. Depending on their properties, clouds can either insulate or reflect sunlight back into space. On balance, however, it appears they are key to keeping our planet’s climate moderate.

But clouds won’t help us out indefinitely. Long before the Sun expands and swallows the Earth, the amount of light it emits will rise enough to make a runaway greenhouse more likely. The authors estimate that, with an all-water atmosphere, we’ve got about 1.5 billion years until the Earth is sterilized by skyrocketing temperatures. If other greenhouse gasses are present, then that day will come even sooner.

The authors don’t expect that this will be the last word on exoplanet conditions—in fact, they revisited waterlogged atmospheres in the hopes of stimulating greater discussion of them. But the key to understanding exoplanets will ultimately involve adapting the planetary atmospheric models we’ve built to understand the Earth’s climate. With full, three-dimensional circulation of the atmosphere, these models can provide a far more complete picture of the conditions that could prevail under a variety of circumstances. Right now, they’re specialized to model the Earth, but work is underway to change that.

Read the entire article here.

Image: Venus shrouded in perennial clouds of carbon dioxide, sulfur dioxide and sulfuric acid, as seen by the Messenger probe, 2004. Courtesy of Wikipedia.

The Mother of All Storms

Some regions of our planet are home to violent and destructive storms. However, one look at a recent mega-storm on Saturn may put it all in perspective — it could be much, much worse.

From ars technica:

Jupiter’s Great Red Spot may get most of the attention, but it’s hardly the only big weather event in the Solar System. Saturn, for example, has an odd hexagonal pattern in the clouds at its north pole, and when the planet tilted enough to illuminate it, the light revealed a giant hurricane embedded in the center of the hexagon. Scientists think the immense storm may have been there for years.

But Saturn is also home to transient storms that show up sporadically. The most notable of these are the Great White Spots, which can persist for months and alter the weather on a planetary scale. Great White Spots are rare, with only six having been observed since 1876. When one formed in 2010, we were lucky enough to have the Cassini orbiter in place to watch it from close up. Even though the head of the storm was roughly 7,000 km across, Cassini’s cameras were able to image it at resolutions where each pixel was only 14 km across, allowing an unprecedented view into the storm’s dynamics.

The storm turned out to be very violent, with convective features as big as 3,000 km across that could form and dissipate in as little as 10 hours. Winds of over 400 km/hour were detected, and the pressure gradient between the storm and the unaffected areas nearby was twice that of the one observed in the Great Red Spot of Jupiter. By carefully mapping the direction of the winds, the authors were able to conclude that the head of the White Spot was an anti-cyclone, with winds orbiting around a central feature.

Convection that brings warm material up from the depths of Saturn’s atmosphere appears to be key to driving these storms. The authors built an atmospheric model that could reproduce the White Spot and found that shutting down the energy injection from the lower atmosphere was enough to kill the storm. In addition, observations suggest that many areas of the storm contain freshly condensed particles, which may represent material that was brought up from the lower atmosphere and then condensed when it reached the cooler upper layers.

The Great White spot was an anticyclone, and the authors’ model suggests that there’s only a very narrow band of winds on Saturn that enable the formation of a Great White Spot. The convective activity won’t trigger a White Spot anywhere outside the range of 31.5° and 32.4°N, which probably goes a long way toward explaining why the storms are so rare.

Read the entire article here.

Image: The huge storm churning through the atmosphere in Saturn’s northern hemisphere overtakes itself as it encircles the planet in this true-color view from NASA’s Cassini spacecraft. Courtesy of NASA/JPL.

One Way Ticket to Mars

You would be rightfully mistaken for thinking this might be a lonesome bus trip to Mars, Pennsylvania or to the North American headquarters of Mars, purveyors of many things chocolaty including M&Ms, Mars Bars and Snickers, in New Jersey. This one way ticket is further afield, to the Red Planet, and comes from a company known as Mars One — estimated time of departure, 2023.

From the Guardian:

A few months before he died, Carl Sagan recorded a message of hope to would-be Mars explorers, telling them: “Whatever the reason you’re on Mars is, I’m glad you’re there. And I wish I was with you.”

On Monday, 17 years after the pioneering astronomer set out his hopeful vision of the future in 1996, a company from the Netherlands is proposing to turn Sagan’s dreams of reaching Mars into reality. The company, Mars One, plans to send four astronauts on a trip to the Red Planet to set up a human colony in 2023. But there are a couple of serious snags.

Firstly, when on Mars their bodies will have to adapt to surface gravity that is 38% of that on Earth. It is thought that this would cause such a total physiological change in their bone density, muscle strength and circulation that voyagers would no longer be able to survive in Earth’s conditions. Secondly, and directly related to the first, they will have to say goodbye to all their family and friends, as the deal doesn’t include a return ticket.

The Mars One website states that a return “cannot be anticipated nor expected”. To return, they would need a fully assembled and fuelled rocket capable of escaping the gravitational field of Mars, on-board life support systems capable of up to a seven-month voyage and the capacity either to dock with a space station orbiting Earth or perform a safe re-entry and landing.

“Not one of these is a small endeavour” the site notes, requiring “substantial technical capacity, weight and cost”.

Nevertheless, the project has already had 10,000 applicants, according to the company’s medical director, Norbert Kraft. When the official search is launched on Monday at the Hotel Pennsylvania in New York, they expect tens of thousands more hopefuls to put their names forward.

Kraft told the Guardian that the applicants so far ranged in age from 18 to at least 62 and, though they include women, they tended to be men.

The reasons they gave for wanting to go were varied, he said. One of three examples Kraft forwarded by email to the Guardian cited Sagan.

An American woman called Cynthia, who gave her age as 32, told the company that it was a “childhood imagining” of hers to go to Mars. She described a trip her mother had taken her on in the early 1990s to a lecture at the University of Wisconsin.

In a communication to Mars One, she said the lecturer had been Sagan and she had asked him if he thought humans would land on Mars in her lifetime. Cynthia said: “He in turn asked me if I wanted to be trapped in a ‘tin can spacecraft’ for the two years it would take to get there. I told him yes, he smiled, and told me in all seriousness, that yes, he absolutely believed that humans would reach Mars in my lifetime.”

She told the project: “When I first heard about the Mars One project I thought, this is my chance – that childhood dream could become a reality. I could be one of the pioneers, building the first settlement on Mars and teaching people back home that there are still uncharted territories that humans can reach for.”

The prime attributes Mars One is looking for in astronaut-settlers is resilience, adaptability, curiosity, ability to trust and resourcefulness, according to Kraft. They must also be over 18.

Professor Gerard ‘t Hooft, winner of the Nobel prize for theoretical physics in 1999 and lecturer of theoretical physics at the University of Utrecht, Holland, is an ambassador for the project. ‘T Hooft admits there are unknown health risks. The radiation is “of quite a different nature” than anything that has been tested on Earth, he told the BBC.

Founded in 2010 by Bas Lansdorp, an engineer, Mars One says it has developed a realistic road map and financing plan for the project based on existing technologies and that the mission is perfectly feasible. The website states that the basic elements required for life are already present on the planet. For instance, water can be extracted from ice in the soil and Mars has sources of nitrogen, the primary element in the air we breathe. The colony will be powered by specially adapted solar panels, it says.

In March, Mars One said it had signed a contract with the American firm Paragon Space Development Corporation to take the first steps in developing the life support system and spacesuits fit for the mission.

The project will cost a reported $6bn (£4bn), a sum Lansdorp has said he hopes will be met partly by selling broadcasting rights. “The revenue garnered by the London Olympics was almost enough to finance a mission to Mars,” Lansdorp said, in an interview with ABC News in March.

Another ambassador to the project is Paul Römer, the co-creator of Big Brother, one of the first reality TV shows and one of the most successful.

On the website, Römer gave an indication of how the broadcasting of the project might proceed: “This mission to Mars can be the biggest media event in the world,” said Römer. “Reality meets talent show with no ending and the whole world watching. Now there’s a good pitch!”

The aim is to establish a permanent human colony, according to the company’s website. The first team would land on the surface of Mars in 2023 to begin constructing the colony, with a team of four astronauts every two years after that.

The project is not without its sceptics, however, and concerns have been raised about how astronauts might get to the surface and establish a colony with all the life support and other requirements needed. There were also concerns over the health implications for the applicants.

Dr Veronica Bray, from the University of Arizona’s lunar and planetary laboratory, told BBC News that Earth was protected from solar winds by a strong magnetic field, without which it would be difficult to survive. The Martian surface is very hostile to life. There is no liquid water, the atmospheric pressure is “practically a vacuum”, radiation levels are higher and temperatures vary wildly. High radiation levels can lead to increased cancer risk, a lowered immune system and possibly infertility, she said.

To minimise radiation, the project team will cover the domes they plan to build with several metres of soil, which the colonists will have to dig up.

The mission hopes to inspire generations to “believe that all things are possible, that anything can be achieved” much like the Apollo moon landings.

“Mars One believes it is not only possible, but imperative that we establish a permanent settlement on Mars in order to accelerate our understanding of the formation of the solar system, the origins of life, and of equal importance, our place in the universe” it says.

Read the entire article following the jump.

Image: Panoramic View From ‘Rocknest’ Position of Curiosity Mars Rover. Courtesy of JPL / NASA.

Mars: 2030

Dennis Tito, the world’s first space tourist, would like to send a private space mission to Mars in 2018. He has pots of money and has founded a non-profit to gather partners and donors to get the mission off the ground. NASA has other plans. The U.S. space agency is tasked by the current administration to plan a human mission to Mars for the mid-2030s. However, due to budgetary issues, fiscal cliffs, and possible debt and deficit reduction, nobody believes it will actually happen. Though, many in NASA and lay-explorers at heart continue to hope.

From Technology Review:

In August, NASA used a series of precise and daring maneuvers to put a one-ton robotic rover named Curiosity on Mars. A capsule containing the rover parachuted through the Martian atmosphere and then unfurled a “sky crane” that lowered Curiosity safely into place. It was a thrilling moment: here were people communicating with a large and sophisticated piece of equipment 150 million miles away as it began to carry out experiments that should enhance our understanding of whether the planet has or has ever had life. So when I visited NASA’s Johnson Space Center in Houston a few days later, I expected to find people still basking in the afterglow. To be sure, the Houston center, where astronauts get directions from Mission Control, didn’t play the leading role in Curiosity. That project was centered at the Jet Propulsion Laboratory, which Caltech manages for NASA in Pasadena. Nonetheless, the landing had been a remarkable event for the entire U.S. space program. And yet I found that Mars wasn’t an entirely happy subject in Houston—especially among people who believe that humans, not only robots, should be exploring there.

In his long but narrow office in the main building of the sprawling Houston center, Bret Drake has compiled an outline explaining how six astronauts could be sent on six-month flights to Mars and what they would do there for a year and a half before their six-month flights home. Drake, 51, has been thinking about this since 1988, when he began working on what he calls the “exploration beyond low Earth orbit dream.” Back then, he expected that people would return to the moon in 2004 and be on the brink of traveling to Mars by now. That prospect soon got ruled out, but Drake pressed on: in the late 1990s he was crafting plans for human Mars missions that could take place around 2018. Today the official goal is for it to happen in the 2030s, but funding cuts have inhibited NASA’s ability to develop many of the technologies that would be required. In fact, progress was halted entirely in 2008 when Congress, in an effort to impose frugality on NASA, prohibited it from using any money to further the human exploration of Mars. “Mars was a four-letter dirty word,” laments Drake, who is deputy chief architect for NASA’s human spaceflight architecture team. Even though that rule was rescinded after a year, Drake knows NASA could perpetually remain 20 years away from a manned Mars mission.

If putting men on the moon signified the extraordinary things that technology made possible in the middle of the 20th century, sending humans to Mars would be the 21st-century version. The flight would be much more arduous and isolating for the astronauts: whereas the Apollo crews who went to the moon were never more than three days from home and could still make out its familiar features, a Mars crew would see Earth shrink into just one of billions of twinkles in space. Once they landed, the astronauts would have to survive in a freezing, windswept world with unbreathable air and 38 percent of Earth’s gravity. But if Drake is right, we can make this journey happen. He and other NASA engineers know what will be required, from a landing vehicle that could get humans through the Martian atmosphere to systems for feeding them, sheltering them, and shuttling them around once they’re there.

The problem facing Drake and other advocates for human exploration of Mars is that the benefits are mostly intangible. Some of the justifications that have been floated—including the idea that people should colonize the planet to improve humanity’s odds of survival—don’t stand up to an economic analysis. Until we have actually tried to keep people alive there, permanent human settlements on Mars will remain a figment of science fiction.

A better argument is that exploring Mars might have scientific benefits, because basic questions about the planet remain unanswered. “We know Mars was once wet and warm,” Drake says. “So did life ever arise there? If so, is it any different than life here on Earth? Where did it all go? What happened to Mars? Why did it become so cold and dry? How can we learn from that and what it may mean for Earth?” But right now Curiosity is exploring these very questions, firing lasers at rocks to determine their composition and hunting for signs of microbial life. Because of such robotic missions, our knowledge of Mars has improved so much in the past 15 years that it’s become harder to make the case for sending humans. People are far more adaptable and ingenious than robots and surely would find things drones can’t, but sending them would jack up the cost of a mission exponentially. “There’s just no real way to justify human exploration solely on the basis of science,” says Cynthia Phillips, a senior research scientist at the SETI Institute, which hunts for evidence of life elsewhere in the universe. “For the cost of sending one human to Mars, you could send an entire flotilla of robots.”

And yet human exploration of Mars has a powerful allure. No planet in our solar system is more like Earth. Our neighbor has rhythms we recognize as our own, with days slightly longer than 24 hours and polar ice caps that grow in the winter and shrink in the summer. Human explorers on Mars would profoundly expand the boundaries of human experience—providing, in the minds of many space advocates, an immeasurable benefit beyond science. “There have always been explorers in our society,” says Phillips. “If space exploration is only robots, you lose something, and you lose something really valuable.”

The Apollo Hangover

Mars was proposed as a place to explore even before the space program existed. In the 1950s, scientists such as Wernher von Braun (who had developed Nazi Germany’s combat rockets and later oversaw work on missiles and rockets for the United States) argued in magazines and on TV that as space became mankind’s next frontier, Mars would be an obvious point of interest. “Will man ever go to Mars?” von Braun wrote in Collier’s magazine in 1954. “I am sure he will—but it will be a century or more before he’s ready.”

Read the entire article after the jump.

Image: Artist’s conception of the Mars Excursion Module (MEM) proposed in a NASA Study in 1964. Courtesy of Dixon, Franklin P. Proceeding of the Symposium on Manned Planetary Missions: 1963/1964, Aeronutronic Divison of Philco Corp.

Exoplanet Exploration

It wasn’t too long ago that astronomers found the first indirect evidence of a planet beyond our solar system. They inferred the presence of an exoplanet (extrasolar planet) from the periodic dimming or wiggle of its parental star, rather than much more difficult direct observation. Since the first confirmed exoplanet was discovered in 1995 (51 Pegasi b), researchers have definitively  catalogued around 800, and identified another 18,000 candidates. And, the list seems to now grow daily.

If that wasn’t amazing enough researchers now have directly observed several exoplanets and even measured their atmospheric composition.

[div class=attrib]From ars technica:[end-div]

The star system HR 8799 is a sort of Solar System on steroids: a beefier star, four possible planets that are much bigger than Jupiter, and signs of asteroids and cometary bodies, all spread over a bigger region. Additionally, the whole system is younger and hotter, making it one of only a few cases where astronomers can image the planets themselves. However, HR 8799 is very different from our Solar System, as astronomers are realizing thanks to two detailed studies released this week.

The first study was an overview of the four exoplanet candidates, covered by John Timmer. The second set of observations focused on one of the four planet candidates, HR 8799c. Quinn Konopacky, Travis Barman, Bruce Macintosh, and Christian Marois performed a detailed spectral analysis of the atmosphere of the possible exoplanet. They compared their findings to the known properties of a brown dwarf and concluded that they don’t match—it is indeed a young planet. Chemical differences between HR 8799c and its host star led the researchers to conclude the system likely formed in the same way the Solar System did.

The HR 8799 system was one of the first where direct imaging of the exoplanets was possible; in most cases, the evidence for a planet’s presence is indirect. (See the Ars overview of exoplanet science for more.) This serendipity is possible for two major reasons: the system is very young, and the planet candidates orbit far from their host star.

The young age means the bodies orbiting the system still retain heat from their formation and so are glowing in the infrared; older planets emit much less light. That makes it possible to image these planets at these wavelengths. (We mostly image planets in the Solar System using reflected sunlight, but that’s not a viable detection strategy at these distances). A large planet-star separation means that the star’s light doesn’t overwhelm the planets’ warm glow. Astronomers are also assisted by HR 8799’s relative closeness to us—it’s only about 130 light-years away.

However, the brightness of the exoplanet candidates also obscures their identity. They are all much larger than Jupiter—each is more than 5 times Jupiter’s mass, and the largest could be 35 times greater. That, combined with their large infrared emission, could mean that they are not planets but brown dwarfs: star-like objects with insufficient mass to engage in hydrogen fusion. Since brown dwarfs can overlap in size and mass with the largest planets, we haven’t been certain that the objects observed in the HR 8799 system are planets.

For this reason, the two recent studies aimed at measuring the chemistry of these bodies using their spectral emissions. The Palomar study described yesterday provided a broad, big-picture view of the whole HR 8799 system. By contrast, the second study used one of the 10-meter Keck telescopes for a focused, in-depth view of one object: HR 8799c, the second-farthest out of the four.

The researchers measured relatively high levels of carbon monoxide (CO) and water (H2O, just in case you forgot the formula), which were present at levels well above the abundance measured in the spectrum of the host star. According to the researchers, this difference in chemical composition indicated that the planet likely formed via “core accretion”— the gradual, bottom-up accumulation of materials to make a planet—rather than a top-down fragmentation of the disk surrounding the newborn star. The original disk in this scenario would have contained a lot of ice fragments, which merged to make a world relatively high in water content.

In many respects, HR 8799c seemed to have properties between brown dwarfs and other exoplanets, but the chemical and gravitational analyses pushed the object more toward the planet side. In particular, the size and chemistry of HR 8799c placed its surface gravity lower than expected for a brown dwarf, especially when considered with the estimated age of the star system. While this analysis says nothing about whether the other bodies in the system are planets, it does provide further hints about the way the system formed.

One final surprise was the lack of methane (CH4) in HR 8799c’s atmosphere. Methane is a chemical component present in all the Jupiter-like planets in our Solar System. The authors argued that this could be due to vigorous mixing of the atmosphere, which is expected because the exoplanet has higher temperatures and pressures than seen on Jupiter or Neptune. This mixing could enable reactions that limit methane formation. Since the HR 8799 system is much younger than the Solar System—roughly 30 million years compared with 4.5 billion years—it’s uncertain how much this chemical balance may change over time.

[div class=attrib]Read the entire article after the jump.[end-div]

[div class=attrib]One of the discovery images of the system obtained at the Keck II telescope using the adaptive optics system and NIRC2 Near-Infrared Imager. The rectangle indicates the field-of-view of the OSIRIS instrument for planet C. Courtesy of NRC-HIA, C. Marois and Keck Observatory.[end-div]

Planets From Stardust

Stunning images captured by Atacama Millimetre-submillimetre Array (ALMA) radio telescope in Chile show the early stages of a planet forming from stardust around a star located 450 light-years from Earth. This is the first time that astronomers have snapped such a clear picture of the process, confirming long-held theories of planetary formation.

[div class=attrib]From Independent:[end-div]

The world’s highest radio telescope, built on a Chilean plateau in the Andes 5,000 metres above sea level, has captured the first image of a new planet being formed as it gobbles up the cosmic dust and gas surrounding a distant star.

Astronomers have long predicted that giant “gas” planets similar to Jupiter would form by collecting the dust and debris that forms around a young star. Now they have the first visual evidence to support the phenomenon, scientists said.

The image taken by the Atacama Millimetre-submillimetre Array (ALMA) in Chile shows two streams of gas connecting the inner and outer disks of cosmic material surrounding the star HD 142527, which is about 450 light-years from Earth.

Astronomers believe the gas streamers are the result of two giant planets – too small to be visible in this image – exerting a gravitational pull on the cloud of surrounding dust and gas, causing the material to flow from the outer to inner stellar disks, said Simon Casassus of the University of Chile in Santiago.

“The most natural interpretation for the flows seen by ALMA is that the putative proto-planets are pulling streams of gas inward towards them that are channelled by their gravity. Much of the gas then overshoots the planets and continues inward to the portion of the disk close to the star, where it can eventually fall onto the star itself,” Dr Casassus said.

“Astronomers have been predicting that these streams exist, but this is the first time we’ve been able to see them directly. Thanks to the new ALMA telescope, we’ve been able to get direct observations to illuminate current theories of how planets are formed,” he said.

[div class=attrib]Read the entire article following the jump.[end-div]

[div class=attrib]Image: Observations (left) made with the ALMA telescope of the young star HD 142527. The dust in the outer disc is shown in red. Dense gas in the streams flowing across the gap, as well as in the outer disc, is shown in green. Diffuse gas in the central gap is shown in blue. The gas filaments can be seen at the three o’clock and ten o’clock positions, flowing from the outer disc towards the centre. And (right) an artist’s impression. Courtesy of Independent.[end-div]

Rivers of Methane

The image shows what looks like a satellite picture of a river delta, complete with tributaries. It could be the Nile or the Amazon river systems as seen from space.

However, the image is not of an earthbound river at all. It’s a recently discovered river on Titan, Saturn’s largest moon. And, the river’s contents are not even water, but probably a mixture of liquid ethane and methane.

[div class=attrib]From NASA:[end-div]

This image from NASA’s Cassini spacecraft shows a vast river system on Saturn’s moon Titan. It is the first time images from space have revealed a river system so vast and in such high resolution anywhere other than Earth. The image was acquired on Sept. 26, 2012, on Cassini’s 87th close flyby of Titan. The river valley crosses Titan’s north polar region and runs into Ligeia Mare, one of the three great seas in the high northern latitudes of Saturn’s moon Titan. It stretches more than 200 miles (400 kilometers).

Scientists deduce that the river is filled with liquid because it appears dark along its entire extent in the high-resolution radar image, indicating a smooth surface. That liquid is presumably ethane mixed with methane, the former having been positively identified in 2008 by Cassini’s visual and infrared mapping spectrometer at the lake known as Ontario Lacus in Titan’s southern hemisphere. Though there are some short, local meanders, the relative straightness of the river valley suggests it follows the trace of at least one fault, similar to other large rivers running into the southern margin of Ligeia Mare (see PIA10008). Such faults may lead to the opening of basins and perhaps to the formation of the giant seas themselves.

North is toward the top of this image.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The RADAR instrument was built by JPL and the Italian Space Agency, working with team members from the US and several European countries. JPL is a division of the California Institute of Technology in Pasadena.

[div class=attrib]Read the entire article following the jump.[end-div]

[div class=attrib]Image courtesy of NASA/JPL-Caltech/ASI.[end-div]