Thursday, December 18, 2008

Did Multiple Moons Once Orbit Earth?


The history of planet Earth is a fascinating story, involving catastrophic collisions with other small planets and a veritable plethora of asteroid impacts. The prevailing theory about the formation of the moon is called the giant impact hypothesis: the theory goes that a Mars-sized object, known as Theia, crashed in to the young Earth. What was left was Earth, and its moon.

A new computer model suggests, however, that the Moon may not have been the only reminder of that big collision. Jack J. Lissauera of the Space Science and Astrobiology Division, NASA Ames Research Center, and John E. Chambers of the Department of Terrestrial Magnetism, Carnegie Institution of Washington, have suggested that moonlets called Trojans may have been left behind in the collision.

"The giant impact that likely led to the formation of the Moon launched a lot of material into Earth orbit, and some could well have been caught in the Langrangian points," -points in space where the gravity between two objects cancels the other out, said says study team member Lissauer. Their theory places small moonlets, or Trojans, in Earth’s orbit, for up to 100 million years.

Over time, gravitational tugs from other planets would have eventually altered Earth’s orbit, even if it was only slightly. Thus, the Langrangian points would have altered, leaving the Trojans once again susceptible to gravity. From there, they could be anywhere by now, or destroyed entirely.

"The perturbations from the other planets are very, very tiny," said Lissauer. But they change the shape of Earth's orbit, which subsequently changes the effect that the Sun's gravity has on the moons, that " what ultimately destabilizes the Trojans."

A separate yet similar model created by Matija Cuk, an astrophysicist at the University of British Columbia in Canada has suggested that smaller, asteroid sized objects, only a few tens of kilometers in width, could have lasted longest in those stationary positions. She believes that they could have lasted a lot longer too, up to a billion years or more.

However she noted that “they would have looked more like Jupiter or Venus in the sky than a satellite. They would have resembled very bright stars.”

Posted by Josh Hill.

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Report urges timetable for human mission to Mars

by David Shiga

The Obama administration should set a concrete schedule for human Mars missions, says a new report (Illustration: NASA)

The Obama administration should set a concrete schedule for human Mars missions, says a new report (Illustration: NASA)

The Obama administration should set a concrete schedule for human Mars missions, and make sure new hardware developed for NASA's return to the Moon can be adapted for missions to other destinations, a new report says.

With a new US president set to take charge of the White House and many questions hanging over NASA's future, many have been trying to advise the agency about where it should go from here.

President-elect Barack Obama's transition team has been very tight-lipped, but if the Obama administration takes its cue from the preponderance of advice it's getting, then human missions to Mars may well move up in priority.

Back in November, the Planetary Society, a space advocacy group, released a report called "Beyond the Moon", which called for delaying new missions to the Moon and channelling more resources into paving the way for human missions to Mars instead (see Moon takes a backseat in new space plan).

Now, an independent group of space experts, led by David Mindell of MIT, is calling for a timeline for human Mars missions, and urging that any Moon hardware be designed with other destinations in mind as well.

Moon rethink

On Monday, the panel released its report, called "The Future of Human Spaceflight". It was produced by a group of experts including former shuttle astronaut Jeff Hoffman and John Logsdon, the former director of the Space Policy Institute at George Washington University in Washington, DC.

There are some links between the panel and the Planetary Society - Logsdon is a member of the group's advisory council - but the new report was an independent effort.

While the new report stops short of endorsing the Planetary Society's plan, it does urge a rethink of where and when to send astronauts. "The Obama administration and Congress should examine the Bush vision, assess its limitations . . . [and provide] clarification of the moon/Mars strategy with a timetable for the Mars component," it says.

"Even if it means somewhat easing the 2020 deadline for lunar return, NASA must ensure that the new architecture provides a solid foundation for the next generation of human spaceflight," it adds.

It expresses concern that "critical technologies for long-duration missions and Mars landings are not being actively investigated". Previous reports by the US National Research Council have found that technologies including propulsion, lunar dust mitigation and robot vehicles are being designed for the Moon and not Mars, for example.

Cooperation with China

The report also says the US should consider cooperative space efforts with China. Relations between the US and China have been tense at times, notably in the wake of China's test of an anti-satellite weapon in 2007. But Mindell argues that tensions were higher between the US and the Soviet Union when the two countries docked an Apollo capsule with a Soyuz spacecraft in Earth orbit in 1975.

Though some in the US fear space cooperation could allow China to gain new technologies useful for military applications, Mindell says it should be possible to avoid this. For example, joint space missions might involve sharing information about the design of innocuous items such as docking rings, he says.

"It's possible to ask what of the technologies involved are unique to human spaceflight, and then to say, can you devise a collaboration that involves sharing those technologies and not other kinds of things," he told New Scientist. "Now, we've gone the complete other way . . . and it's not clear that's been in the US interest."

Ironically, the lack of cooperation may be boosting China's international prestige, by reinforcing public perceptions that the two countries are in a closely competitive race to the Moon, the report says.

Mindell says members of the panel met with Obama's transition team last week and gave them a copy of the report.

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Lightning-Storm Gamma Rays Could Harm Air Travelers

By Alexis Madrigal

SAN FRANCISCO, California — The most energetic particles in the electromagnetic spectrum could pose a danger to commercial airline passengers.

About every 3000 hours of flying time, a plane is hit with a bolt of lightning. Recently, spacecraft have found gamma rays can be created by thunder storms, and according to new research presented at the American Geophysical Union annual meeting this week, the rays could be intense enough to cause radiation sickness.

"Everywhere we look, we're seeing x-rays and gamma rays flying out of thunderstorms and lightning," said Joseph Dwyer, a physicist at the Florida Institute of Technology and lead author of the study. "The gamma rays coming out of thunderstorms are so intense we can measure these 600 kilometers away and so bright that it almost blinds the spacecraft."

Finding particles flying around at what physicsts call "ultrarelativistic speeds,," i.e. very close to the speed of light, came as a shocker to physicists. Gamma rays had previously been associated with only the most extreme environments in the universe, like supernovae. Now, scientists believe that about 50 terrestrial gamma ray flashes occur per day on Earth.

It turns out that these highly-energetic particles can be created by thunderstorms at altitudes that airplanes regularly fly. While planes generally avoid thunderclouds, sometimes they get surprised or can't avoid them. And it's those situations that worry Dwyer.

"We just don't know enough. The consequences are bad enough that people could potentially get hurt from this," he said. "This is a call for more research. We really need to find out where we are and how big these things are. Could people be hit by these things and get sick? And how would you know?"

His team and others across the country have measured the number of gamma rays that reach satellite observatories, which has allowed them to back into how many particles are created in the thunderstorms.

What remains unclear is just how large and concentrated the source of the gamma rays is. If it's large — hundreds of meters across — then airplane passengers are probably safe. But if the gamma rays are created in a small area, they could be delivering doses of radiation in one millisecond that are many times beyond what the government sees as safe.

"If the source is a little bit smaller — and there are some arguments you can make that the source should be smaller — then the dose someone would get inside an aircraft, through a quarter inch of aluminum, is getting to the point where we'd be worried."

Dwyer's data shows that as the size of the gamma ray source shrinks under 100 meters across, the dose of radiation accelerates to levels that could cause very serious radiation sickness — and even death.

Dwyer is a leader in the emerging field of terrestrial gamma rays who has refined scientists' notions of how lightning works. Back in 2003, while experimenting with triggering lightning by launching specialized rockets into clouds, his team accidentally triggered a gamma ray flash.

"His stuff is fabulous," Dave Sentman, a physicist at the University of Alaska-Fairbanks, who also studies terrestrial gamma rays.

Sentman noted that Dwyer, trained as a nuclear physicist, has a different perspective on the atmospheric physics than most of their colleagues, which has allowed him to gain insight into the high-energy particles

"He has a different way of thinking," Sentman said.

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Hawking Predicts Discovery of Alien Life: But Asks, Will It be Carbon Based?


On the 50th anniversary of NASA, Stephen Hawking, Newton's heir as the Lucasian Professor of Mathematics at the University of Cambridge, answered the question, “Are we alone?”

His answer was short and simple; probably not!

Hawking presented three options. One, being that there is no life out there, and two – somewhat pessimistically, but subsequently, a little too realistic – being that when intelligent life gets smart enough to send signals in to space, it is also busying itself with making nuclear bombs.

Hawking, known not only for his sharp mind, but his sharp sense of humor, prefers option number three. "Primitive life is very common and intelligent life is fairly rare," he quickly added: "Some would say it has yet to occur on earth."

Alien abductions, in Hawking’s view, are nothing more than claims made by “weirdos,” but we should be careful if we ever happen upon an alien. Because alien life may not have DNA like ours, Hawking warns "Watch out if you would meet an alien. You could be infected with a disease with which you have no resistance."

Other prominent astrobiologists have warned that we humans may be blinded by our familiarity with carbon and Earth-like conditions. In other words, what we’re looking for may not even lie in our version of a “sweet spot”. After all, even here on Earth, one species “sweet spot” is another’s species worst nightmare. In any case, it is not beyond the realm of feasibility that our first encounter with extraterrestrial life will not be a solely carbon-based occasion.

Alternative biochemists speculate that there are several atoms and solvents that could potentially spawn life. Because carbon has worked for the conditions on Earth, we speculate that the same must be true throughout the universe. In reality, there are many elements that could potentially do the trick. Even counter-intuitive elements such as arsenic may be capable of supporting life under the right conditions. Even on Earth some marine algae incorporate arsenic into complex organic molecules such as arsenosugars and arsenobetaines. Several other small life forms use arsenic to generate energy and facilitate growth. Chlorine and sulfur are also possible elemental replacements for carbon. Sulfur is capably of forming long-chain molecules like carbon. Some terrestrial bacteria have already been discovered to survive on sulfur rather than oxygen, by reducing sulfur to hydrogen sulfide.

Nitrogen and phosphorus could also potentially form biochemical molecules. Phosphorus is similar to carbon in that it can form long chain molecules on its own, which would conceivably allow for formation of complex macromolecules. When combined with nitrogen, it can create quite a wide range of molecules, including rings.

So what about water? Isn’t at least water essential to life? Not necessarily. Ammonia, for example, has many of the same properties as water. An ammonia or ammonia-water mixture stays liquid at much colder temperatures than plain water. Such biochemistries may exist outside the conventional water-based "habitability zone". One example of such a location would be right here in our own solar system on Saturn's largest moon Titan.

Hydrogen fluoride methanol, hydrogen sulfide, hydrogen chloride, and formamide have all been suggested as suitable solvents that could theoretically support alternative biochemistry. All of these “water replacements” have pros and cons when considered in our terrestrial environment. What needs to be considered is that with a radically different environment, comes radically different reactions. Water and carbon might be the very last things capable of supporting life in some extreme planetary conditions.

Posted by Josh Hill with Rebecca Sato.

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First-Ever Photo of Liquid on Extraterrestrial World

By Wired Science

Wiredtitan2_2 The Huygens probe has captured an image of what may be the first drop of liquid ever observed on an extraterrestrial surface.

The photo is evidence that liquids may exist on the surface of other planets and moons, not just frozen lakes. And liquid is more likely habitat for extraterrestrial life.

Among the pictures snapped by the Huygens probe after landing on Saturn's moon Titan in 2005, one appears to show a dewdrop made of methane that briefly formed on the edge of the probe itself (indicated by arrow at bottom of image on right). Scientists think heat from the probe caused humid air to rise and condense on the cold edge of the craft.

Though Huygens may have helped produce it, the methane drop is still the first liquid directly detected at a surface anywhere beyond Earth.

Like Earth, Titan has clouds, lakes and river channels, and it may be the only other place in the solar system where liquid evaporates from the surface and returns as rain. "Aside from Earth, it's the most exciting world there is," said lead author Erich Karkoschka of the University of Arizona in Tucson.

The Cassini space probe, which took data from above the moon after separating from the Huygens lander, detected what scientists believe are lakes of liquid methane on Titan's surface. Microbes that eat methane thrive on Earth, and scientists think pools of methane could be comfortable homes for similar organisms on Titan.

Because Titan's current atmosphere is a lot like the early Earth's, the lakes could be a lab for studying the origins and early evolution of life.

Astronomers have speculated since they found methane in the atmosphere in 1983 about whether the moon's methane rain falls in violent thunderstorms, light drizzles or some other form. So far, no one has caught it on camera.

The hundreds of images snapped by Huygens, from the time it hit the atmosphere until its power ran out an hour after it landed, revealed only faint, wispy clouds that looked nothing like rain clouds, Karkoschka said.

None of the images showed evidence that it had rained during the previous few years, according to an analysis to be published in the journal Icarus. And some images suggested that Titan’s lower atmosphere was full of small dust particles, which would have been cleared out by rain.

But the scientists noticed light splotches in some of the pictures that hadn't been there moments before. Some of them had spots that initially looked like raindrops because of their uniform size and smooth edges, but analysis showed they were most likely electronic imprints created by cosmic rays.

However, Karkoschka said, "One of those spots was so big that it really cannot be a cosmic ray." He concluded that it was a real, short-lived dewdrop, so close to the camera that it must have condensed on a cold metal shield designed to protect the camera lens from direct sunlight.

Robert West, a planetary scientist at the Jet Propulsion Lab in Pasadena, California, thinks the dewdrop is "a cute observation," but he's more interested in the lack of rainfall. "There are reports in the literature that concluded there is a drizzle going on near the surface," he said. "The fact that Huygens didn’t find anything is significant."

— Lisa Grossman for

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Ancient armored amphibian had world's oddest bite

By Will Dunham

WASHINGTON (Reuters) - A peculiar amphibian that was clad in bony armor prowled warm lakes 210 million years ago, catching fish and other tasty snacks with one of the most unusual bites in the history of life on Earth.

The creature called Gerrothorax pulcherrimus, which lived alongside some of the early dinosaurs, opened its mouth not by dropping its lower jaw, as other vertebrate animals do.

Instead, it lifted back the top of its head in a way that looked a lot like lifting the lid of a toilet seat.

"It's weird. It's the ugliest animal in the world," Harvard University's Farish Jenkins, one of the scientists who describe the mechanics of its bite in the Journal of Vertebrate Paleontology, said in a telephone interview on Friday.

"You almost can't imagine holding your jaws still and lifting your head back to take a bite," Jenkins said.

"There are some vertebrates that will lift their heads slightly or the upper jaws (when they bite). Some salamanders do it slightly. Some fish do it slightly. But no animal is known to have done it this extensively," Jenkins added.

The scientists think Gerrothorax lurked at the bottom of a lake, then with a sudden movement of the skull created a mouth gape that entrapped any fish unfortunate enough to swim by.

Gerrothorax measured about 3 feet (1 meter) long and was stoutly protected by bony body armor reminiscent of chain mail. It had a very flat body and very flat head, short, stubby limbs and well-developed gills, Jenkins added.

Its jaws were lined with sharp teeth. And the roof of its mouth was studded with large fangs to keep any slippery fish from escaping its chomp.

With a special adaptation of the joint between its skull and first neck vertebra, Gerrothorax could raise its head relative to its lower jaw by as much as 50 degrees, giving it the wide gape necessary to swallow its prey.

Gerrothorax is one of a group of odd amphibians called plagiosaurs with no modern descendants that vanished along with numerous other species 200 million years ago in a mass extinction at the end of the Triassic Period. Its fossils were found in the Fleming Fjord Formation of east Greenland.

"That the same species is found in Greenland as well as Western Europe and Scandinavia suggests that their unique structure was hugely successful," Anne Warren of La Trobe University in Melbourne, Australia, another of the scientists, said in a statement.

It was armored for good reason. It lived alongside massive, crocodile-like reptiles called phytosaurs and larger, predatory amphibians. Other fossils show dinosaurs, flying reptiles called pterosaurs and early mammals lived alongside it.

(Editing by Julie Steenhuysen and Todd Eastham)

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Faulty gene causes some people to become aggressive drunks

by Rebecca Smith, Medical Editor

Alcohol appears to trigger violent behaviour in people who have a particular overactive gene.

The MAOA gene produces an enzyme that breaks down brain chemicals involved with mood.

When alcohol is mixed with high levels of the enzyme it can create a 'dangerous cocktail', according to new research.

The finding raises the possibility that people could be screened for the gene and offered treatment, behavioural therapy or be warned to abstain from alcohol.

The discovery emerged from a study of 174 Finnish alcoholic male offenders with histories of violence. Drinking was found to increase the risk of impulsive violence among individuals born with a highly active version of the MAOA gene.

The effect appears to diminish with age which may explain why younger people are more likely to get into alcohol fuelled fights than older ones.

The research comes as the busiest time of the year is approaching for accident and emergency departments and ambulance workers with office Christmas parties this week, followed by the festive and New Year celebrations.

Roope Tikkanen, one of the researchers from Helsinki University Central Hospital, said: "Alcoholism, alcohol consumption and violence are clearly related.

"Increased alcohol consumption and ageing seem to predict violence, although these risk factors work in opposite directions, and only concern individuals who have been given by nature a high-activity variant of MAOA.

"People react quite differently to acute alcohol exposure. Most individuals become relaxed and talkative, while some – particularly people who are introverted while sober – become expansively extroverted and aggressive."

The research, published is online and will appear in the March issue of the journal Alcoholism: Clinical & Experimental Research.

Mr Tikkanen said violent people with high-activity MAOA could be helped to control their behaviour with coaching and possibly psychopharmacological drug treatments, he said.

"Perhaps we could increase the efficacy of addition rehabilitation by focusing resources particularly on younger heavy-drinking, high-activity MAOA individuals," he said.

Don Shenker, Chief Executive of Alcohol Concern, said: "Clearly, better identification and support for offenders with alcohol problems can help cut reoffending and improve rehabilitation. However, this opportunity seems to be missed, as provision of services to offenders with alcohol problems still falls far short of support received by those with drug problems. With 15 per cent of male prisoners suffering from severe alcohol problems or dependency, inadequate treatment means that most of these are not given a chance to tackle their addiction."

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