Five years ago, the Cassini spacecraft first detected plumes of water ice emanating from Saturn’s moon Enceladus, making the moon one of the best hopes for finding life somewhere else in the solar system. Astronomers have argued over whether or not those jets come from a subsurface ocean of liquid water, but new findings by Cassini provide evidence that water could indeed be sloshing around beneath the frozen surface of this small moon.

During a 2008 pass through the plumes, the spacecraft found negatively charged water molecules. Back home this short-lived type of ion is produced where water is moving, such as in waterfalls or crashing ocean waves [Scientific American]. Researcher Andrew Coates led the study, which is coming out in the journal Icarus.

Besides the water ions, the team also found negatively charged hydrocarbons—huge ions that could result from Saturn’s magnetic field and the sun’s ultraviolet rays interacting with the atmosphere of Enceladus. Researchers find the combination of ions enticing. “While it’s no surprise that there is water there, these short-lived ions are extra evidence for sub-surface water and where there’s water, carbon and energy, some of the major ingredients for life are present,” said Dr Coates [BBC News]. Previous studies have shown that the Enceladus plumes contain ammonia, which could act as an antifreeze to keep an ocean in liquid state, and others have argued that the plumes are spewing sodium, which would indicate that liquid water had been in contact with rocks that leach salt.

Cassini’s new ion findings make Enceladus look a little more like its big brother, the huge and also hugely interesting Saturnian moon of Titan. In fact, the same plasma spectrometer on board Cassini has been used to confirm the presence of large negative hydrocarbon ions high in the atmosphere of Titan, indicating the presence of an organic mix of chemicals called “tholins” on Titan’s surface [Discovery News]. NASA just extended Cassini’s mission by seven more years, giving it time to learn even more about both of these marvelous moons.

Related Content:
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80beats: Does Enceladus, Saturn’s Geyser-Spouting Moon, Have Liquid Oceans?
80beats: New Evidence of Hospitable Conditions for Life on Saturn’s Moons
80beats: Geysers From Saturn’s Moon May Indicate Liquid Lakes, and a Chance for Life
80beats: Cassini Spacecraft Snaps Pictures of Saturn’s Geyser-Spouting Moon

Image: NASA / Cassini

You might not be a smoker yourself, but hanging around people who are smoking can cause you to inhale noxious cigarette fumes. For years, scientists have cautioned against the ill-effects of such second-hand smoke. Now they’re warning about the dangers of “third-hand smoke”—the chemical traces that cling to a smoker, and that are left behind in a room where someone has been smoking.

A team of researchers at the Lawrence Berkeley National Laboratory found that remnants of a smoke don’t just inertly settle onto surfaces, they can react with a common gas (nitrous acid, which is emitted from gas appliances and vehicles, among other sources) to create carcinogenic compounds known as tobacco-specific nitrosamines (TSNAs) [Scientific American]. The study (pdf) was published in Proceedings of the National Academy of Sciences.

The study suggests that even if a smoker puffs outside, some smoke swirls and settles in clothing and hair and is brought back into the building. With smoking inside, the left-over nicotine residue settles on surfaces like furniture, carpets, and curtains, where it can mix with common gas and turn into the carcinogenic TSNAs. Says study coauthor Hugo Destaillats: “It’s this third-hand smoke residue that is the source of the smells that we all easily perceive in a room or a car where cigarettes have been smoked, as a consequence of such places being coated with cigarette emissions…. And we found that such emissions do give rise to new pollutants when they react with non-cigarette compounds found indoors” [BusinessWeek].

To study how the carcinogenic compounds were created, scientists used samples from the glove compartment of a pick-up truck whose driver smoked in the truck regularly. They also studied a cellulose-containing paper similar to a carpet or drape and let it absorb nicotine from cigarette smoke. They then put this paper in a chamber containing nitrous acid and studied the reaction between nicotine and the nitrous acid. In both the lab and in the truck, the reaction between nicotine and nitrous acid produced substantial amounts of three types of toxic compounds…. All three compounds belonged to a group called nitrosamines, which are known to prompt tumor growth [Discovery News].

The researchers say with so many toxic compounds, young infants could be at a risk as they crawl around on rugs and come into contact with dust. However, they also caution that there needs to be more research into third-hand smoke, and note that the study doesn’t indicate that homes and couches that smell of smoke could potentially cause cancer. To deal with third-hand smoke, researchers recommend avoiding smoking in closed spaces like homes and cars. Also, in enclosed spaces that have seen plenty of puffs over the years, they suggest replacing furniture, carpet and even wallboard to cut down on the amount of TSNA exposure [Scientific American].

Related Content:
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80beats: Electronic Cigarettes Not a Safe Alternative to Conventional Cigs
DISCOVER: Smoking and Ethnicity
DISCOVER: By The Numbers: Smoke Gets in Your Hair
DISCOVER: 54: R-Rated Films Tempt Teenagers to Smoke

Image: flickr/SuperFantastic

Under the Microscope is a cool website ‘where women and science connect.’ It’s the online component of the Women Writing Science project at The Feminist Press featuring stories from women about science, technology, engineering, and math, and aimed to inspire the next generation of STEM pioneers. Last week I was delighted to chat with one of the hosts, Kristina Necovska. Here’s an excerpt from our Q&A:

UTM: I’m curious whether you’ve found that the public’s ability to distinguish credibility and sound arguments is going out the window?

SK: I’m very concerned. We just saw this hack into e-mails of climate change. Most people made very quick judgments without fully understanding the context of what they were reading. [There is] a survey just released by George Mason University and Yale Center for Climate Change Communication. It’s a dismal report, people more than ever don’t “believe” in climate change.

The big point here is that pseudoscience is on the rise. … It’s dangerous and I’m not sure what it means for the future of science and it’s a big red flag in terms of where we’re going. Science needs a better platform. It’s certainly not about PR in a traditional sense but we have to think about how we’re represented when we’re working against so many other forces that have a certain vested interest. We’re trying to emphasize the best research and [research] is very dynamic. There’s no black and white in the way that the pseudo-scientific [groups] want to represent things.

UTM: Can you give us just a few examples of what ordinary people can do to benefit science literacy?

SK: I think just being engaged and being interested is a big part of it. Looking for sources that you should be able to trust like universities. More and more young scientists are creating their own websites in order to counter the rubbish that’s out there. I’d love to see more young people engaged in their communities — like those that have a [bachelor of science] but are unsure whether they want to go to graduate school — writing op-eds or working with local politicians or schools.

Read the full interview here and stick around to check out other featured stories and interviews at Under The Microscope.

Welcome to this week’s installment of the From Eternity to Here book club. This week we’re tackling two chapters at once: Chapter Four, “Time is Personal,” and Chapter Five, “Time is Flexible.” That’s just because these chapters are relatively short; next time we’ll return to one chapter per week.

Excerpt:

Starting from a single event in Newtonian spacetime, we were able to define a surface of constant time that spread uniquely throughout the universe, splitting the set of all events into the past and the future (plus “simultaneous” events precisely on the surface). In relativity we can’t do that. Instead, the light cone associated with an event divides spacetime into the past of that event (events inside the past light cone), the future of that event (inside the future light cone), the light cone itself, and a bunch of points outside the light cone that are neither in the past nor the future.

It’s that last bit that really gets people. In our reflexively Newtonian way of thinking about the world, we insist that some far away event either happened in the past, the future, or at the same time as some event on our own world line. In relativity, for spacelike separated events (outside one another’s light cones), the answer is “none of the above.” We could choose to draw some surfaces that sliced through spacetime, and label them “surfaces of constant time,” if we really wanted to. That would be taking advantage of the definition of time as a coordinate on spacetime, as discussed in Chapter One. But the result reflects our personal choice, not a real feature of the universe. In relativity, the concept of “simultaneous faraway events” does not make sense.

These two chapters take on a task that is part of the responsibility of any good book on modern cosmology or gravity: explaining Einstein’s theory of relativity. Both special relativity and general relativity, hence two chapters. In retrospect they are pretty short, so an argument could be made that I should have just combined them into a single chapter.

The special challenge of these chapters is precisely that many readers — but not all — will already have read numerous other popular-level expositions of relativity. But you have to do it. Fortunately, my favorite way of talking about relativity is a little bit different from the standard one, and lines up well with the overarching goal of understanding the meaning of “time.” In particular, I try to make the point that the secret to relativity is to think locally — to compare things happening right next to each other in spacetime, not events that are widely separated. You’re allowed to compare separated events, of course, but the answers are necessarily dependent on arbitrary choices of coordinates, and that leads to endless confusion. So you won’t read a lot about “length contraction” or “time dilation,” but you will read a lot about the actual amount of time measured along a trajectory.

Unfortunately, a search for vivid examples of the maxim “freely-falling paths through spacetime experience the longest amount of proper time” led me directly to the most embarrassing mistake in the book. (At least, “most embarrassing mistake so far uncovered.”) Sordid details below the fold!

The mistake is the claim that a clock that sits stationary on a tower will experience less proper time than a clock that orbits the Earth at the same height above ground. That’s wrong: the orbiting clock will measure less time. This appears in the paragraph at the bottom of page 85 and top of 86, and is elevated from “unfortunate” to “a real doozy” by being illustrated in graphic detail by the figure on page 86. Not really any way I can claim it was just a typo.

The subtle issue underlying the mistake is illustrated in this figure, which shows two paths connecting two points on a sphere. Both paths are great circles. The shortest distance between two points on a sphere is a great circle; but it certainly doesn’t follow that any path following a great circle gives us the shortest distance between two points. If you go more than half the way around the sphere, you end up with a pretty long path!

The same kind of thing happens in spacetime. The trajectory of longest proper time between two events will always be a freely-falling trajectory (a geodesic). But not every freely-falling path gives us the longest time, and that’s exactly the case in this example. Given two events at the same position above the Earth, the actual path of longest time is a radial freely-falling orbit. If you want your clock to experience the longest time it can, you throw it straight up in the air to where the gravitational field is weaker (and clocks run more quickly with respect to time measured at infinity) and let it fall back down. A circular orbit actually loses time by staying at the same altitude but zipping around the Earth. I relied on my affection for the general underlying principle, and didn’t bother to sit down and work out the actual numbers in this case, so I never found the mistake. Pretty sure my membership in the general relativists’ guild is going to be permanently revoked for this one.

If you’re still not convinced of the wrongness of my example, here’s an equation, the line element along a circular trajectory in the equatorial plane in the Schwarzschild metric:

On the left we have a small interval (squared) of the proper time τ, what a clock would measure along some path. The first term on the right is the contribution from our motion with respect to t, the time measured at infinity; for any given amount of t, we experience less proper time τ as our height r decreases and the coefficient (1-2GM/r) becomes smaller. The second term on the right is the contribution from our angular motion φ. Taking the square root of the whole thing and integrating along a path gives you the proper time.

We don’t have to go through the entire calculation to convince ourselves that staying stationary on the tower has a longer proper time than the circular orbit does. Both trajectories get the same contribution from the first term on the right side, while the second term is zero for the clock on the tower (it’s not moving, so dφ=0), but it’s negative for the orbit. So the orbit is definitely less time. To be corrected in the next printing.

The deep point, of course, remains true: the time measured by clocks in general relativity depends on their path through spacetime, and the way to maximize that time is to take a freely-falling path. Just not that one.

Whether your fear is panicked, like in a life-or-death situation, or deliberative, like a decision about whether to take a big risk on game show, it all comes back to the amygdala. And a new study of patients with lesions on the amygdala, reported by Caltech scientists in the Proceedings of the National Academy of Sciences, suggests that damage to our brain’s fear center might turn people into reckless gamblers.

The researchers found two women with Urbach-Wiethe disease, which results in damage to the almond-shaped amygdala. Benedetto De Martinoa and his team paired those two with 12 people with undamaged brains, and presented everyone with a series of gambling tests. The study found that healthy volunteers would only opt to gamble if the potential gains were one and a half to two times the size of the potential losses [BBC News]. The women with Urbach-Wiethe, however, would keep rolling the dice as the odds got worse, and in some cases would even play if the potential loss was greater than the potential gain.

Two, of course, is a pretty small sample size. But that problem is unavoidable, the researchers say. They noted this kind of study usually involves only a few people as it is not possible or ethical to deliberately damage a person’s brain to see what happens [Reuters]. So Urbach-Wiethe patients are particularly valuable to science, showing how damage to one particular area of the brain can change a person’s behavior.

The PNAS findings also back up what some of the same researchers have documented in previous studies, that the amygdala might be responsible not only for more primal fears, but also for social fears and inhibitions. Last year study coauthor Ralph Adolphs led a separate study of a patient with amygdala damage and found that her understanding of personal space was far different from most people’s (she stood much closer during conversation), and she struggled to pick up signs of fear or aggression in other people. Says Adolphs of the newer work: “A fully functioning amygdala appears to make us more cautious. We already know that the amygdala is involved in processing fear, and it also appears to make us ‘afraid’ to risk losing money” [Reuters].

Related Content:
80beats: An Acidic Brain Leads to Panic; A Deep Breath Can Fix That
80beats: Jell-O Shots in Adolescence Lead to Gambling Later in Life
DISCOVER: Conquering Your Fears, One Synapse at a Time
DISCOVER: Emotions and the Brain: Fear

Image: flickr / Morberg