What’s the News: Looking at images of odd undulations in the rings of Saturn and Jupiter, astronomers have discovered that comets are to blame. The finding means that a planet’s rings act as a historical record of passing comets, possibly leading to a better understanding of comet populations. “We now know that collisions into the rings are very common—a few times per decade for Jupiter and a few times per century for Saturn,” Mark Showalter, from the SETI Institute in Mountain View, California, told the Daily Mail. “Now scientists know that the rings record these impacts like grooves in a vinyl record, and we can play back their history later.”

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What’s the News: While the Kepler spacecraft is busy finding solar system-loads of new planets, other astronomers are expanding our idea where planets could potentially be found. One astronomer wants to look for habitable planets around white dwarfs, arguing that any water-bearing exoplanets orbiting these tiny, dim stars would be much easier to find than those around main-sequence stars like our Sun. Another team dispenses with stars altogether and speculates that dark matter explosions inside a planet could hypothetically make it warm enough to be habitable, even without a star. “This is a fascinating, and highly original idea,” MIT exoplanet expert Sara Seager told Wired, referring to the dark matter hypothesis. “Original ideas are becoming more and more rare in exoplanet theory.”

How the Heck:

• Because white dwarfs are much smaller than our Sun, an Earth-sized planet that crossed in front of it would block more of its light, which should make these planets easier to spot. So astronomer Eric Agol suggests survey the 20,000 white dwarfs closest to Earth with relatively meager 1-meter ground telescopes.
• And because white dwarfs are so cool, a planet in a white dwarfs habitable zone would be very close, meaning its transit would happen very fast. Agol says we’d only need to watch a star for 32 hours to pick up on any transiting, habitable planets.
• One leading theory about dark matter is that it’s made of theoretical particles called WIMPS (weakly interacting massive particles). It’s thought that when WIMPs collide (if, of course, they exist), they would explode. Astronomers think that these WIMP explosions could possibly heat a planet enough to make it habitable.
• There are no immediate plans to test the dark matter hypothesis, which is quite theoretical, and any plan to find dark matter-fueled planets would need to look far from here: our part of the universe doesn’t have nearly enough dark matter to bring a planet to habitability.

What’s the Context:

• In other white dwarf news, astronomers have discovered a red dwarf in an extremely tight orbit with a white dwarf.
• And others are still wrangling over what dark matter really is.
• As for exoplanets, astronomers have actually seen one—as in, with visible light—orbiting its star.

Not So Fast:

• It’s not at all clear if white dwarfs have any planets, and if so, whether any of them could possibly support water or life as we know it. For one thing, planets in the habitable zone would be tidally locked with the star—permanent scalding daylight on one side; permanent frozen nighttime on the other.
• Taking 32 hours to find a planet orbiting a white dwarf may seem like a short time, but when you’re looking at tens of thousands of stars, it adds up. Agol told UW Today, “This could take a huge amount of time, even with [a network of telescopes].”
• And just like star-orbiting planets have their Goldilocks zones (not to hot or too cold), dark matter-containing planets would need the right amount of dark matter to be habitable. “It’s not something that’s likely to produce a lot of habitable planets,” Fermilab researcher Dan Hooper told Wired. “But in very special places and in very special models, it could do the trick.” 

References: Eric Agol. “TRANSIT SURVEYS FOR EARTHS IN THE HABITABLE ZONES OF WHITE DWARFS.” doi: 10.1088/2041-8205/731/2/L31

Dan Hooper and Jason H. Steffen. “Dark Matter And The Habitability of Planets.” arXiv:1103.5086v1

Image: NASA/European Space Agency

What’s the News: Based on early Kepler data, astronomers say that the Milky Way galaxy may house at least two billion Earth-like planets—one for every several dozen sun-like stars. As NASA researcher Joseph Catanzarite told Space.com, “With that large a number, there’s a good chance life and maybe even intelligent life might exist on some of those planets. And that’s just our galaxy alone — there are 50 billion other galaxies.” But while 2 billion sounds like a lot, it’s actually far below many scientists’ expectation; Catanzarite says his teams’ findings actually show that Earth-like planets are “relatively scarce.”

How the Heck:

• Using mathematical models to plot the size and orbital distance for all the potential planets spotted during four months’ worth of Kepler data, astronomers extrapolated the data and calculated that 1.4 to 2.7% of the Milky Way’s sun-like stars may have an Earth analog.
• Two percent of the Milky Way’s roughly one hundred billion sun-like stars means that “you have two billion Earth analog planets in the galaxy,” Catanzarite told National Geographic.

What’s the Context:

• The Kepler team recently announced a mother lode of 1,200 potential alien worlds (68 of them about Earth size), a tightly scrunched-up mini solar system, and a bizarro “styrofoam” world; unfortunately, the “most Earth-like planet” planet it found so far got a major demotion: it’s not actually habitable.

Not So Fast:

• MIT astronomer Sara Seager says that the team “completely underestimates the frequency of Earths.” The calculations are based on only four months of Kepler data—too early to be making an accurate projection.
• There’s also the fact that Kepler can only detect the size and orbital distance (and occasionally the masses) of planets, which doesn’t tell you whether life as we know it could actually live there; Venus, for example, would roughly like Earth to aliens peering at us from many light-years away, but because of its atmosphere’s runaway greenhouse effect, it’s way too hot to be habitable.

Next Up: The astronomers plan on calculating an even more accurate number once all of Kepler’s data is in.

Reference: Joseph Catanzarite and Michael Shao. “The Occurrence Rate of Earth Analog Planets Orbiting Sunlike Stars.” arXiv:1103.1443v1 Image: Kepler/NASA

What’s the News: Images sent back from NASA’s Cassini spacecraft depict storm clouds and methane rain puddles, the first solid evidence of modern rainfall on Titan, Saturn’s largest moon. “We’re pretty confident that it has just rained on Titan,” lead author Elizabeth Turtle, from Johns Hopkins University Applied Physics Laboratory, told Wired. Astronomers have previous evidence of sulfuric-acid precipitation on Venus, but it doesn’t count as rainfall because it never reaches the surface.

What’s the Olds:

• Launched in 1997, Cassini arrived at Saturn’s orbit in 2004, where it started studying several of the planet’s moons.
• As covered in 80beats, this wasn’t the first time scientists have thought about whether it rains on Titan.
• 80beats covered the 2008 discovery of the “ingredients of life” on Saturn’s moon Enceladus.
• And the spacecraft has also caught the changing seasons on Titan’s surface.
• Images reveal that these seasonal changes are so drastic that they affect the methane levels on Titan’s lakes.

Not So Fast: Don’t read too much into these showers: Methane rain doesn’t mean life. The search continues.

Reference: “Rapid and Extensive Surface Changes Near Titan’s Equator: Evidence of April Showers.” E.P. Turtle, J.E. Perry, A.G. Hayes, R.D. Lorenz, J.W. Barnes, A.S. McEwen, R.A. West, A.D. Del Genio, J.M. Barbara, J.I. Lunine, E.L. Schaller, T.L. Ray, R.M.C. Lopes, E.R. Stofan. Science, Vol 331, March 18, 2011. DOI: 10.1126/science.1201063

Image: NASA/JPL/Space Science Institute

What’s the News: After firing its thrusters for about 15 minutes on Thursday, NASA’s MESSENGER spacecraft lost enough speed to be pulled in by Mercury’s gravitational field, making it the first probe to orbit the Swift Planet. “Mercury’s secrets, and the implications they hold for the formation and evolution of Earth-like planets, are about to be revealed,” MESSENGER principal investigator Sean Solomon told Slate.

What’s the Olds:

• Launched on 3 August 2004, MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging spacecraft) has clocked 4.9 billion miles since day one—a trek that includes three Mercury fly-bys as it eased its way into orbit.
• 80beats published an image gallery of the stunning photos already sent back during the fly-bys and has covered such findings as ancient magma oceans and magnetic volcanoes.
• In 2008, MESSENGER imaged most of the never-before-seen swaths of Mercury’s surface.
• As Phil Plait points out, it’s not just Mercury that MESSENGER has photographed: It’s also sent long shots of Earth.

Not So Fast: Don’t expect any stunning images by this weekend: MESSENGER’s first pictures in orbit are slated to arrive toward the end of the month.

The Future Holds: Engineers will continue checking how well the probe is withstanding Mercury’s hot temperatures, with plans of turning on equipment on March 23, and starting scientific studies on April 4. The spacecraft will carry out a one-year survey of Mercury in hopes of using close-up mapping to settle long-held debates, such as whether ice is hiding at the poles.

Image: Science/AAAS, Carnegie Inst.Washington/ Arizona State Univ. / Johns Hopkins Univ. Appl. Phys. Lab. / NASA

Planetar. Substar. Failed star. Sub-stellar object. Astronomers have pinned each of these monikers on brown dwarfs, a category that has always perplexed scientists because it raises questions about what it means to be a star or a planet. And if that wasn’t enough, now they’ve discovered the coldest brown dwarf yet, blurring the line between planet and star even further.

It’s name is CFBDSIR J1458+1013B, and may be cooler than the boiling point of water (at the pressure of Earth’s atmosphere). This strange body is about 75 light-years from us, where it orbits its binary partner, another brown dwarf. Using the infrared capabilities of the 10-meter Keck II Telescope on Mauna Kea, University of Hawaii researcher Michael Liu and his team estimated the brown dwarf’s temperature, and have a ballpark range for its mass: between 6 and 15 times the mass of Jupiter.

It’s special because it may be a class Y dwarf (temperature less than 225 degrees Celsius (440 F)), a type of object whose existence astronomers had predicted but never actually found. Before this candidate arose, the coolest known brown dwarf was in the T spectral class; while there have been a few Y-class candidates in the past, scientists have a better grasp on the temperature of this one: 97 degrees Celsius, plus or minus 40C.

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Last month, when astronomers with the Kepler space telescope released a list of 1,235 possible planets orbiting other stars, one particular candidate, KOI 326.01, especially stood out. Scientists, journalists, and the general public couldn’t help it: In a population of planetary candidates dominated by sizzling, Jupiter-sized gas giants—which are much easier to spot—here was the closest thing yet to our very own planet. It was just about the size of Earth, even a little smaller, and had a temperature around 138 degrees—rather warm for human tastes, but still a place where liquid water could rain down from clouds into oceans, and where life as we know it could possibly exist. A clever but perhaps overambitious monetary calculation valued the planet at exactly $223,099.93.

Alas, KOI 326.01’s 15 minutes of fame must now end. Additional analysis of the planet’s star now suggests that the planet is a lot larger, and most likely a lot hotter, than previously thought. “The details of the planet need to be hammered out, but this certainly means that this is not an Earth-size planet in the habitable zone,” where liquid water could exist, says Natalie Batalha, a Kepler team member.

The road to demotion began when a DISCOVER fact-checker, Mara Grunbaum, asked for some additional information about the planet. In response, Batalha and her colleagues dug up images of the sky near KOI 326.01—and almost immediately found a problem. The planet’s sun, known as KIC 9880467, is located close to another star (see above). In a reference catalog characterizing the stars in the probe’s field of view, KIC 9880467 is listed as brighter than its neighbor. But as you can easily see in the above image, that is not the case.

That simple error messes up the calculations of the planet’s temperature and size. Kepler finds planets by detecting tiny dips in a star’s brightness during transits—when a planet crosses in front of it. When the Kepler team analyzed the combined light from the two stars, they assumed KIC 9880467 accounted for most of the brightness. Now they have to chalk up almost all that light to the neighboring star. In fact, while Batalha is still confident KOI 326.01 exists, she is no longer sure which of the two nearby stars it is orbiting. In either case, the calculations indicate that the planet is somewhat warmer and a lot larger than the previous estimate. And if it is orbiting the bright, neighboring star, as Batalha suspects, the planet’s temperature will soar. More analysis is required, but it’s safe to say that KOI 326.01 should no longer be considered potentially habitable.

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Humankind’s experience visiting worlds beyond our own begins and ends with the dozen Apollo astronauts who skipped about on tiny swaths of the moon. But that doesn’t mean we can’t experiment with how and where we might visit (or live) on the extreme surfaces of other worlds. A few studies out recently are doing just that.

Radiation? Big deal

Our planet provides a protective shield from the most damaging radiation produced by the sun—a shield not available on the moon or Mars. It’s a hazard for any human leaving the planet, and it’s a hazard for plants, too.

However, a new study of the Chernobyl area in the Ukraine, site of the famous nuclear accident, is actually raising hopes for space farming.

Even 25 years after the catastrophic nuclear accident at Chernobyl, the area around the site harbors radioactive soil. But researchers working there have found that oil-rich flax plants can adapt and flourish in that fouled environment with few problems. Exactly how the flax adapted remains unclear, but what is clear is that two generations of flax plants have taken root and thrived there, and that could have big implications for growing plants aboard spacecraft or on other planets at some point in the future. [Popular Science]

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• While modeling plasma flows deep inside the sun, scientists may have found an explanation for why some sunspots cycles (like the most recent one) are weaker than others. “It’s the flow speed during the cycle before that seems to dictate the number of sunspots. Having a fast flow from the poles while a cycle is ramping up, followed by a slow flow during its decline, results in a very deep minimum.”
• Risky business: In defending President Obama’s vision for space exploration that relies upon commercial space companies, NASA administrator Charles Bolden says the country must “become unafraid of exploration. We need to become unafraid of risks.”
• Bad timing: Just as Apple unveils its new iPad—and Steve Jobs uses the opportunity to gloat about his company’s superiority in apps compared to Google’s Android system—Google had to take 21 apps off the Android Market because they were infected with malware.
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One nitrogen atom, three hydrogen atoms. That’s all it takes to make the basic ammonia molecule. This simple compound was one of the most important building blocks for the origin of life, scientists believe, providing the nitrogen that is crucial to many organic compounds. They just don’t know for sure how so much of it could form under the conditions of the early Earth.

In a new study this week, Sandra Pizzarello and colleagues tie the ammonia surplus to one of the more fascinating theories about the rise of life—that some of its basic components seeded the Earth from space on board meteorites that pounded the planet’s surface.

Pizzarello’s team analyzed a particular meteorite found in Antarctica. Its name is Graves Nunataks (GRA) 95229, and it was discovered in 1995. But its important characteristic is that the it belongs to a class of meteorites called carbonaceous chondrites that are full of organic materials. In the lab, the researchers tried to simulate how those materials in GRA 95299 might have reacted when they reached the younger Earth.

Pizzarello and her co-authors subjected a sample of the meteorite … to temperatures of 300 degrees Celsius at high pressures in the presence of water to simulate hydrothermal conditions on the meteorite’s parent asteroid or on Earth. Under heat and pressure, GRA 95229 released almost nothing but ammonia, in amounts that constitute roughly 1 percent by mass of the type of meteoritic material examined. Its parent asteroid, the authors speculate, must have been rich in ammonia. [Scientific American]

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• Who needs a vomit comet? The Southwest Research Institute (SwRI) in Colorado reached a deal with Virgin Galactic to send some of its scientists up on SpaceShipTwo’s suborbital flights, allowing them to conducts tests in weightlessness.
• Fire ants may have originated in South America, but their home base for invading the world at large is right here in the United States. So says a new study of more than 2,000 fire ant colonies spread around the globe.
• Gone in a flash: About 150,000 Gmail users woke up to find their mailboxes wiped clean—messages, folders, and all. Google is racing to recover the lost correspondences. In the meantime, this is a reminder of two things. First, you should back up your email. And second, Google is really, really big. Those 150,000 people represent just .08 percent of Gmail users.
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Young. Old. Scalding hot. Icy cold. Terrestrial midgets. Gas giants. As the cavalcade of planets spotted beyond our solar system continues to grow, we get to see worlds of all sorts—and we get to speculate on the staggering number of exoplanets that might inhabit just our own galaxy.

Today’s first piece of otherworldly news involves baby exoplanets. Astronomer Christian Thalmann says his team may have spotted planets in the process of forming around three different stars, the first time scientists have spotted the process in action.

An infant star forms from a collapsing cloud of dust and gas and gathers a dense, flat disk of material that rotates with the star like a record album. The material in the disk will eventually clump up into nascent planets. Theoretical models of planet formation predicted that those protoplanets should suck up more gas and dust with their gravity, clearing a wide gap in the otherwise solid disk. [Wired]

Peering at young stars like T Chamaeleontis (T Cha) LkCa15 and AB Auriga, Thalmann and colleagues saw those telltale gaps in the dusty rings (their study is forthcoming in the Astrophysical Journal Letters). The stars are much like our own sun, so these pictures of infant solar systems could resemble what our own looked like as a baby. But though the stars are nearby in cosmic terms—T Cha lies just 350 light years away—the gaps are faint enough that it’s difficult to tell for certain if newly forming planets, and not the influence of binary stars or other objects, are creating them.

If Thalmann’s team is right, catching the birth of new worlds would be a great scientific coup. Our galaxy, however, isn’t exactly hurting for planets.

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For NASA, this was a week of launches and lack of launches. The space shuttle Discovery successfully blasted off yesterday on its final mission, but NASA’s climate-watching Glory satellite, which was scheduled to launch on Wednesday, is still stuck on the ground.

With an estimated 40,000 viewers at the Kennedy Space Center, Discovery launched at 4:53:24 p.m. ET on Thursday. Its crew of six is bound for the International Space Station, after four months of delay due to fuel tank repairs.

“Discovery now making one last reach for the stars,” the Mission Control commentator said once the shuttle cleared the launch tower. [CBS News]

Also on board is the first ever space-bound humanoid robot: Robonaut 2, or R2. This robot resembles a human from the waist up, and may eventually take on tedious chores and complete station repairs that are too dangerous for humans. At it entered space the robot tweeted (via its earthly handlers): “I’m in space! HELLO UNIVERSE!!!”

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Starting this week, NASA will have a new eye in the sky to better sort out the way that greenhouse gases, air pollution, and solar activity interact to affect the climate of our planet. The Glory satellite, currently set to launch on Friday, will spy on changes both in our atmosphere and in the sun.

Its main job will be to study fine airborne particles known as aerosols. Smaller than the diameter of a human hair, these specks can move great distances across the globe and are largely responsible for hazy skies. [The New York Times]

Greenhouse gases and their contribution to climate change have been the subject of much research, of course, but aerosols remain murkier. Climate scientist James Hansen, a member of the Glory team, says researchers must use an uncertainty range for modeling aerosols that’s three to four times greater than what they use with greenhouse gases, simply because the contribution of aerosols is much less understood.

The Glory mission will, if all goes according to plan, collect data on the micro-physical, chemical and optical properties of aerosols using two instruments—an Aerosol Polarimetry Sensor (ARS) and a Total Irradiance Monitor (TIM)—that will monitor the climate system and provide new data for scientists working on the issue of climate change. The APS will collect visible and near-infrared data scattered from aerosols and clouds and the TIM, mounted on a special track that allows it move independent of the satellite, should record total electromagnetic radiation given off by the sun that hits the top of Earth’s atmosphere. [The Atlantic]

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With the space shuttles soon bound for retirement homes, NASA is dreaming up the future of U.S. human space flight. Recently, NASA has divulged its interest in two new gadgets: rockets launched via lasers and reusable, manned, deep-space crafts. Now, all the agency needs is a plan to get more money from the government to actually build these things.

The lasers (or possibly microwaves) would be ground-based, and would shoot through the air to energize a rocket’s heat exchanger; elevating the rocket’s fuel to over 3,100 degrees Fahrenheit would give it more thrust.

“The objective is to reduce the cost of getting into space. The way this rocket works, it has a more energetic propulsive system than one where you have fuel and oxidizer that release energy,” Carnegie Mellon University’s Kevin Parkin, head of the Microwave Thermal Rocket project at NASA’s Ames Research Center in California, told Discovery News. [Discovery News]

Although the laser-powered rocket system would be expensive to build, it would reduce launch costs in the long haul.

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