“The low gravity of rubble-pile asteroids such as Bennu weakens its near-subsurface by not compressing the upper layers, minimizing the influence of particle cohesion,” said SwRI’s Dr. Kevin Walsh, lead author of a paper about this research published in the journal Science Advances. “We conclude that a low density, weakly bound subsurface layer should be a global property of Bennu, not just localized to the contact point.”

Fitting its designation as a “rubble-pile asteroid,” Bennu is a spheroidal collection of rock fragments and debris 1,700 feet in diameter and held together by gravity. It is thought to have been formed after a collision involving a larger main-asteroid-belt object. Rocks are scattered across its heavily cratered surface, indicating that it has had a rough-and-tumble existence since being liberated from its much larger parent asteroid some millions or billions of years ago.

The goal of OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission is to collect and return at least 60 grams of surface material from Bennu and deliver it to Earth in 2023. Sample collection activities provided additional insights.

According to Walsh, researchers involved in the OSIRIS-REx mission have so far measured Bennu’s thermal properties and craters to estimate the strength and porosity of discrete particles of rubble-pile asteroids. The ensemble of particles, or regolith, at an asteroid’s surface controlling and influencing long-term evolution have not yet been probed directly until now.

Before, during, and after the sampling event, the Sample Acquisition Verification Camera (SamCam) of the OSIRIS-REx Camera Suite captured images looking at the Touch-and-Go Sample Acquisition Mechanism (TAGSAM) robotic arm.

“The SamCam images bracketing the moment of contact show the contact caused considerable disturbance at the sample site,” said Dr. Ron Ballouz, a co-author from Johns Hopkins University’s Applied Physics Laboratory. “Nearly every visible particle is moved or re-oriented at all points along the circumference of TAGSAM up to a 15-inch radius.”

These SamCam images showed the downward force of TAGSAM lifted a nearly 16-inch rock. Though strong enough to withstand breaking, the rock was re-oriented and small debris lofted off its surface. The mobility of these millimeter-scale particles under relatively weak forces suggests minimal cohesive bonding with the surface of the larger rock.

Scientists have theorized that the average regolith particle size increases as asteroid size decreases, because larger bodies retain smaller materials due to a higher surface gravity. The team then compared Bennu to similar rubble-pile asteroids.

“We discovered a dichotomy between the rough, boulder-covered surfaces of Bennu and Ryugu versus Itokawa, which includes ponds of smaller particles across 20% of its surface,” Walsh said. “This could have several explanations, including that the latter’s near-surface has compressed enough to frustrate these microparticles percolating into the interior or perhaps the granular deposits are subsurface layers revealed by a recent disruptive reorganization of the body.”

A companion paper in the journal Science and co-authored by Walsh characterized the 30-foot-long elliptical crater excavated by the TAGSAM arm when it collected the sample. The event mobilized rocks and dust into a debris plume, exposing material that is darker, redder and more abundant in fine particulates than the original surface. The displaced subsurface material’s bulk density is about half that of the asteroid as a whole.

Video: https://youtu.be/wCO1y_GNo98

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Hypothyroidism occurs when the thyroid gland doesn’t make enough thyroid hormones. This can slow metabolism. Symptoms include feeling tired, weight gain and sensitivity to cold.

“In some cases, thyroid disorders have been associated with dementia symptoms that can be reversible with treatment,” said study author Chien-Hsiang Weng, MD, MPH, of Brown University in Providence, Rhode Island. “While more studies are needed to confirm these findings, people should be aware of thyroid problems as a possible risk factor for dementia and therapies that could prevent or slow irreversible cognitive decline.”

For the study, researchers looked at the health records of 7,843 people newly diagnosed with dementia in Taiwan and compared them to the same number of people who did not have dementia. Their average age was 75. Researchers looked to see who had a history of either hypothyroidism or hyperthyroidism. Hyperthyroidism, which is also called overactive thyroid, is when the thyroid produces too much hormone. This can increase metabolism. Symptoms include unintended weight loss, rapid or irregular heartbeat and nervousness or anxiety.

A total of 102 people had hypothyroidism and 133 had hyperthyroidism.

The researchers found no link between hyperthyroidism and dementia.

Of the people with dementia, 68 people, or 0.9%, had hypothyroidism, compared to 34 of the people without dementia, or 0.4%. When researchers adjusted for other factors that could affect the risk of dementia, such as sex, age, high blood pressure and diabetes, they found that people over age 65 with hypothyroidism were 80% more likely to develop dementia than people the same age who did not have thyroid problems. For people younger than 65, having a history of hypothyroidism was not associated with an increased risk of dementia.

When researchers looked only at people who took medication for hypothyroidism, they found they were three times more likely to develop dementia than those who did not take medication. “One explanation for this could be that these people are more likely to experience greater symptoms from hypothyroidism where treatment was needed,” Weng said.

Weng noted that the observational study does not prove that hypothyroidism is a cause of dementia; it only shows an association.

A limitation of the study was that researchers were not able to include information about how severe the hypothyroidism was for participants.

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“We know a lot about pathways involved in image-forming vision, but until now it remained unknown if and how non-image-forming visual behaviors rely on these same pathways in the eye,” said Johan Pahlberg, Ph.D., head of the Photoreceptor Physiology Group at NEI and a senior author of the study.

Vision begins when light travels into the eye and hits the retina’s light-sensing photoreceptors. The photoreceptors transfer signals through several layers of retinal neuron before those signals are sent to the brain. Light also triggers certain non-vision functions, such as controlling how much light enters the eye through the pupil (pupillary light reflex) and regulating the wake/sleep cycle (circadian rhythm). Circadian rhythm disruption has been linked to sleep problems, obesity, and other health issues.

To investigate pathways used by image-forming versus non-image-forming functions in the retina, Pahlberg and colleagues studied groups of mice that had been genetically modified to turn off one or more pathway links, or synapses, between photoreceptors and their next downstream neuronal neighbors, called bipolar cells. The group investigated the roles of rod photoreceptors, which are sensitive to low light levels; cone photoreceptors, which see color; as well as three types of bipolar cells: rod bipolar cells, “on” cone bipolar cells, and “off” cone bipolar cells.

“On” cone bipolar cells react to increases in light, and “off” cone bipolar cells react to decreases in light. Cone photoreceptors can only communicate with cone bipolar cells, while rod photoreceptors have pathways to communicate with each of the bipolar cell types, depending on the level of light. Bipolar cells then communicate with other neurons in the retina, passing information to the optic nerve and on to the brain. Some mice in the study had no functional connections between rods and “on” bipolar cells, for example, or connections between cones and any bipolar cells, or lacked connections between rod and cone photoreceptors.

The researchers compared the mice’s responses to visual stimuli while assessing pupillary light responses and monitoring their nocturnal wake/sleep cycle. They determined that while image-forming vision can use rod and cone photoreceptors, as well as all the types of bipolar cells, the same was not true for non-image forming functions. The pupil response relies exclusively on rod photoreceptors, while cones are unable to control this behavior. Meanwhile, both circadian rhythm regulation and the pupil reflex only use “on” bipolar cells pathways, relying on rod bipolar cells and “on” cone bipolar cells, but not “off” cone bipolar cells.

“We were really surprised to find that animals with only ‘off’ bipolar cells can’t adjust to changes in the day/night cycle, but can still see and respond to visual events, meaning they have functional image-forming vision. It was really interesting to us that the non-imaging forming functions completely ignore information from the ‘off’ pathway,” said Pahlberg. “We were equally surprised that rod photoreceptors, which are optimized for low light conditions, were still being used for the pupillary response even when light levels were high. We really thought the rods would be maxed out at that point.”

Pahlberg expects many of these findings in mice will hold true for humans, since the retinal circuitry is similar across mammals. Moving forward, he intends to explore other non-image-forming functions of the retina, like mood regulation, and see how else these different retinal circuits are being used.

The research was funded by the intramural programs of NEI, NIMH, the National Institute of Dental and Craniofacial Research, and the National Institute of Neurological Diseases and Stroke.

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In a study published in the journal PLOS ONE, University of Florida scientists found that gardening activities lowered stress, anxiety and depression in healthy women who attended twice-weekly gardening classes. None of study participants had gardened before.

“Past studies have shown that gardening can help improve the mental health of people who have existing medical conditions or challenges. Our study shows that healthy people can also experience a boost in mental wellbeing through gardening,” said Charles Guy, principal investigator on the study and a professor emeritus in the UF/IFAS environmental horticulture department.

The study was co-authored by an interdisciplinary team of researchers with the environmental horticulture department, the UF College of Medicine, the UF Center for Arts in Medicine and the UF Wilmot Botanical Gardens, which also hosted all the study treatment sessions.

Thirty-two women between the ages of 26 and 49 completed the study. All were in good health, which for this experiment meant screening for factors such as chronic health conditions, tobacco use and drug abuse, and having been prescribed medications for anxiety or depression. Half of the participants were assigned to gardening sessions, while the other half were assigned to art-making sessions. Both groups met twice a week for a total eight times. The art group served as a point of comparison with the gardening group.

“Both gardening and art activities involve learning, planning, creativity and physical movement, and they are both used therapeutically in medical settings. This makes them more comparable, scientifically speaking, than, for example, gardening and bowling or gardening and reading,” Guy explained.

In the gardening sessions, participants learned how to compare and sow seeds, transplant different kinds of plants, and harvest and taste edible plants. Those in the art making sessions learned techniques such as papermaking, printmaking, drawing and collage.

Participants completed a series of assessments measuring anxiety, depression, stress and mood. The researchers found that the gardening and art making groups experienced similar improvements in mental health over time, with gardeners reporting slightly less anxiety than art makers.

Given the relatively small number of participants and the length of the study, the researchers were still able to demonstrate evidence of what medical clinicians would call the dosage effects of gardening — that is, how much gardening someone has to do to see improvements in mental health.

“Larger-scale studies may reveal more about how gardening is correlated with changes in mental health,” Guy explained. “We believe this research shows promise for mental wellbeing, plants in healthcare and in public health. It would be great to see other researchers use our work as a basis for those kinds of studies.”

The idea of using gardening to promote better health and wellbeing — called therapeutic horticulture — has been around since the 19^th century.

But why does being around plants make us feel good? The answer might be found in the important role of plants in human evolution and the rise of civilization, the study’s authors explain. As a species, we may be innately attracted to plants because we depend on them for food, shelter and other means of our survival.

Whatever the deeper reasons might be, many of the study participants left the experiment with a newly discovered passion, the researchers noted.

“At the end of the experiment, many of the participants were saying not just how much they enjoyed the sessions but also how they planned to keep gardening,'” Guy said.

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Materials provided by University of Florida. Original written by Samantha Murray. Note: Content may be edited for style and length.