Early Mars Was All Wet

The delta in Jezero crater, a past lake on Mars. Ancient rivers ferried clay-like minerals (shown in green) into the lake, forming the delta. The clays then were trapped by rocks (purple). Credit: NASA/JPL/JHUAPL/MSSS/Brown University

A lot more Martian rocks were altered by water than scientists originally thought, suggesting that early Mars was a very wet place.

New observations made by NASA's Mars Reconnaissance Orbiter (MRO), currently circling the planet, have revealed evidence that vast regions of the southern highlands of Mars were altered by water in a variety of environments billions of years ago.

Water is a key condition for life as we know it. Though there is no firm evidence that Mars has ever harbored life, knowing that the planet was once wet suggests that it was at least habitable in the past.

The key to the finding is the discovery that rocks called phyllosilicates are widespread on at least the planet's southern hemisphere. The water present on Mars from about 4.6 billion to 3.8 billion years ago transformed some rocks into these phyllosilicates, which include clays rich in iron, magnesium or aluminum, mica, and kaolinite (an ingredient in Kaopectate).

"In a phyllosilicate, the atoms are stacked up into layers, and all of the phyllosilicates have some sort of water or hydroxyl [oxygen and hydrogen group] incorporated into the crystal structure," said study team member Scott Murchie of Johns Hopkins University.

Previous data from an instrument called OMEGA - Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activite on the Mars Express spacecraft had revealed only a few large outcrops of phyllosilicates, suggesting they were a relative rarity on Mars.

"It sort of gave the false impression that rocks that were altered like this were more restricted than they really are," Murchie said.

But the new observations, made with MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and detailed in the July 17 issue of the journal Nature, reveal "thousands and thousands of outcrops that we can now resolve with the higher resolution of the instrument, and they're scattered all over the planet wherever the older rocks occur," Murchie told SPACE.com.

"What that's suggesting to us is that we're seeing a pervasive subsurface layer that goes back in time — it's been altered by water to clays and related minerals, and it's outcropping all over the place," Murchie added.

The layer of water-altered rocks sits below younger, volcanic rocks and the ubiquitous windblown Martian dust and sand in many places. But in craters and scarps, including Valles Marineris, across the terrain of the southern hemisphere, the ancient clays and other minerals have been exposed.

"It's like going to the bottom rock layer in the Grand Canyon," Murchie said, where ancient layers underlie the whole area, but are only exposed in a few places.

This layering gives scientists a dividing line of about 3.7 to 3.5 billion years ago for a transition in Martian geology: "Before that the rocks were altered into clays, since then they're not," Murchie said.

The variety of clays and other minerals formed also tells scientists that rock was altered by water under a variety of conditions.

"There's a variety of environments that are formed where the rock was lightly altered where you see things like chlorite, to where it was altered with water at really high temperature, where you see mica, to where a lot of water must have flowed through the rock in order to dissolve out the iron and magnesium and you're left with kaolinite," Murchie said.

The alteration of later rocks, such as the sulfates found by the Mars Exploration Rovers (MER), Spirit and Opportunity in the northern hemisphere, on the other hand, formed under much more restricted conditions.

One implication of these findings is that some of the environments that formed the phyllosilicates would not have been antagonistic to any potential life, unlike the conditions that formed the sulfates, which formed in a highly acidic environment similar to battery acid, as Murchie put it.

Whether the MER rovers can get a close-up peek at these phyllosilicates while the robots still roam the Martian surface is uncertain, Murchie said, because so far the rocks haven't been detected near the crafts. But they could be there and simply be obscured in the north from the MRO instruments by dust.

"It doesn't take much to hide something from our optical instrument in orbit," he said, just a few micrometers of dust. "So just brushing away the rock surface could be enough," he added.

Whether or not Spirit and Opportunity get a chance to investigate these intriguing rocks up close, future rover missions, such as the Mars Science Laboratory set to launch 2009, could certainly be aimed at known phyllosilicate-rich sites, Murchie said, shedding more light on the mysteries of early Mars.

Original here

To Trust or Not to Trust: Ask Oxytocin

The development of trust is an essential social tool, allowing people to form productive and meaningful relationships, both at a professional and personal level. Bonds of trust are also extremely fragile, however and a single act of betrayal—such as a marital affair—can instantly erase years of trustworthy behavior. The consequences of such breaches in confidence can be disastrous, and not only for a relationship. People who have been betrayed in the past will sometimes start avoiding future social interactions, which is a potential precursor to social phobia. In light of these connections, recent research has attempted to elucidate the neural mechanisms underlying trust behavior. This is the goal of an exciting new study by neuroscientist Thomas Baumgartner and colleagues at the University of Zurich in Switzerland that combines different disciplines (economics and neuroscience) and methodologies (neuroimaging and neuropharmacology) to investigate how the brain adapts to breaches of trust.

The Chemistry of Trust
To study social interactions, economists, and more recently neuroscientists, take advantage of a simple game played between two people called the “trust game.” (For more on greed and altruism, see this.) In a typical trust game, an investor (Player 1) is faced with a decision to keep a sum of money (say, $10) or share it with a trustee (Player 2). If shared, the investment is tripled ($30) and the trustee now faces the decision to repay the trust by sending back a larger amount of the initial investment (for example, $15 for each participant) or to defect and violate trust by keeping the money. In this game, the investor is therefore left with an important social dilemma: to trust or not to trust. Although it is more profitable to trust, doing so leaves the investor at risk of betrayal.

It has been hypothesized that oxytocin, a hormone recognized for its role in social attachment and facilitation of social interactions, is also important in the formation of trust. For instance, application of oxytocin to “investors” in experimental games increases their tendency to engage in social risks and trust someone else with their money (see this and this). The study by Baumgartner and his colleagues highlights the neural mechanisms through which oxytocin acts to facilitate trust behavior by investigating what happens in the brain when trust breaks down.

When Trust Is Broken
The authors used functional magnetic resonance imaging (fMRI) to scan 49 participants who were given either placebo or oxytocin via a nasal spray. Participants were instructed to act as investors during multiple rounds of a trust game with different trustees. They were also told that they would engage in a risk game (similar to the trust game in terms of financial risk, but played against a computer instead of another human being). In order to investigate the role of oxytocin following breaches of trust, the experiment was divided into a pre- and post-feedback phase. In between the two phases, participants received feedback information indicating that roughly 50 percent of their decisions (in both trust and risk games) had resulted in poor investments—that is, their trust had been breached (trust game) or their gamble did not pay off (risk game).

Participants who were given a placebo prior to playing the game decreased their rate of trust (that is, how much money they were willing to invest) after they discovered their trust had been violated. Participants who received oxytocin, however, continued to invest at similar rates regardless of whether or not their trusting behavior had been taken advantage of. These behavioral group differences were accompanied by differences in neural responses, as participants in the oxytocin group showed decreases in responses in the amygdala and caudate nucleus. The amygdala is a region of the brain involved in emotion and fear learning, and is rich in oxytocin receptors, whereas the caudate nucleus has been previously linked to reward-related responses and learning to trust . Thus, the authors hypothesized that oxytocin decreases both fear mechanisms associated with a potential aversion of betrayals (via the amygdala) and our reliance on positive feedback that can influence future decisions (via the caudate). This in turn facilitates the expression of trust even after breaches of trust have occurred. Notably, the behavioral and neural results observed were only apparent when participants played the trust game, but not the risk game, suggesting that oxytocin’s effects on trust are exclusive to interactions with real people.

A Science of Social Phobias?
The study demonstrates how oxytocin can facilitate social interactions after trust has been violated, by potentially lowering defense mechanisms associated with social risks and by overcoming negative feedback that is important for adapting behavior in the future. These intriguing results provide an important step in our understanding of mental disorders where deficits in social behavior are observed. Excessive fear of betrayal, for example, could serve as a precursor to social phobia, a disorder characterized by a disabling fear of social interactions. Over the long-term, this lack of social interaction may lead to serious problems in mental and physical well-being. Thus, to continue forming a bridge between basic and clinical research, future studies may focus on the effects of oxytocin during the sort of betrayals that more commonly occur in real life (such as being betrayed by a loved one or a business partner). It will also be interesting to examine how different genders respond to breaches in confidence following oxytocin administration.

Trust is an adaptive mechanism essential to building social relationships, and breaches of trust have a profound impact on social behavior and mental health. Understanding the balance between levels of oxytocin and appropriate levels of trust will be another important step in the future. Lower levels of oxytocin in some situations may certainly be adaptive, as a person will become more wary of possible harm. Higher levels of oxytocin, however, may also be necessary at times to allow an individual to “forgive and forget,” an imperative step in maintaining long-term relationships and mental well-being.

Original here

Study: When kids become teens, they get sluggish

CHICAGO -- One of the largest studies of its kind shows just how sluggish American children become once they hit the teen years: While 90 percent of 9-year-olds get a couple of hours of exercise most days, fewer than 3 percent of 15-year-olds do.

What's more, the study suggests that fewer than a third of teens that age get even the minimum recommended by the government _ an hour of moderate-to-vigorous exercise, like cycling, brisk walking, swimming or jogging.

The sharp drop raises concerns about inactivity continuing into adulthood, which could endanger kids' health throughout their lives, the study authors said.

"People don't recognize this as the crisis that it is," said lead author Dr. Philip Nader, a pediatrician and professor emeritus at the University of California at San Diego.

Inactivity is linked with greater risks for many health problems, including heart disease, obesity, high blood pressure and diabetes.

The new findings come just a week after an influential pediatricians group recommended that more children have their cholesterol checked and that some as young as 8 should be given cholesterol-lowering drugs. That advice was partly out of concern over future levels of heart disease and other ailments linked to rising rates of childhood obesity.

The latest study, appearing in Wednesday's Journal of the American Medical Association, tracked about 1,000 U.S. children at various ages, from 2000 until 2006.

Special gadgets were used to record their activity. Average levels of moderate-to-vigorous activity fell from three hours a day at age 9 to less than an hour at age 15.

Nader said he was "surprised by how dramatic the decline was," and cited schools dropping recess and gym classes and kids' increasing use of video games and computers as possible reasons.

The National Institute of Child Health and Human Development funded the research, calling it one of the largest, most comprehensive studies of its kind to date.

James Griffin, science officer for the study, said that as children mature, "You would expect somewhat of a decline (in activity), but nothing of this magnitude."

He noted that the study coincided with the rise in popularity of video games, DVDs and Internet use _ "all of the types of things that take children from outside and put them on a couch or in front of a computer."

Griffin said the results send a message to parents that it's important to teach their kids to balance computer time with more active pursuits, like walking the dog or shooting some hoops.

Study participants were children involved in agency research on youth development, recruited from 10 hospitals around the country. Family income, race and ethnic background closely matched the U.S. population.

The researchers tracked the children's activity levels starting at age 9, using an accelerometer _ a device about the size of a small belt buckle that attached to a belt around the waist and recorded movement. Activity levels were counted at ages 9, 11, 12 and 15 during the school week and on weekends.

That method isn't foolproof because the device isn't worn during swimming and contact sports. But the researchers said it's unlikely that such activity happened often enough among the children studied to skew the results.

Through age 12, well over half the children got at least the government-recommended amount of activity every day. By age 15, less than one-third were that active on weekdays, and only about 17 percent were on weekends.

Boys were more active than girls at every age. But by age 15, even boys' average activity levels fell short of recommendations, particularly on weekends.

Dr. Samuel Klein, director of Washington University School of Medicine's human nutrition center in St. Louis, said the research provides a more powerful snapshot than previous studies.

The rapid drop-off in exercise by age 15 shows that the preceding years are "really an area we should target," said Klein, who was not involved in the study.

Mary Lee, 13, said the results ring true.

The suburban Cleveland teen said she spends more time on the computer now than she did a few years ago, particularly with online social networking sites. She also didn't have physical education class every day last year, and will only have it for half the upcoming school year in eighth grade.

Lee recently took part in a health program at Rainbow Babies and Children's Hospital in Cleveland. The classes promote exercise and healthy eating.

She said she stays pretty active with volleyball and track, and has been able to avoid gaining weight with help from the program at the Cleveland hospital.

Making exercise fun is important, because if you do, you won't even realize if you're exercising," she said.

"It really helps and it makes you feel better about yourself," she said.

Original here