New instrument reveals recipe for other Earths

How do you make an Earth-like planet? The 'test kitchen' of Earth has given us a detailed recipe, but it wasn't clear whether other planetary systems would follow the same formula. Now, astronomers have found evidence that the recipe for Earth also applies to terrestrial exoplanets orbiting distant stars.

How do you make an Earth-like planet? The "test kitchen" of Earth has given us a detailed recipe, but it wasn't clear whether other planetary systems would follow the same formula. Now, astronomers have found evidence that the recipe for Earth also applies to terrestrial exoplanets orbiting distant stars.

"Our solar system is not as unique as we might have thought," says lead author Courtney Dressing of the Harvard-Smithsonian Center for Astrophysics (CfA). "It looks like rocky exoplanets use the same basic ingredients."

Dressing presented the research today at a meeting of the American Astronomical Society.

The key to the discovery was the HARPS-North instrument on the 3.6-meter Telescopio Nazionale Galileo in the Canary Islands. (HARPS stands for High-Accuracy Radial velocity Planet Searcher.) It is designed to accurately measure the masses of small, Earth-sized worlds. Those measurements are crucial to determine densities and therefore compositions.

"Our strategy for using HARPS-North over the past year has been to focus on planets less than two times the diameter of Earth and to study a few planets really well," explains Harvard astronomer David Charbonneau (CfA), who currently heads up the HARPS-North Science Team.

Most recently the team targeted Kepler-93b, a planet 1.5 times the size of Earth in a tight, 4.7-day orbit around its star. The mass and composition of this world were uncertain. HARPS-North nailed the mass at 4.02 times Earth, meaning that the planet has a rocky composition.

The researchers then compared all ten known exoplanets with a diameter less than 2.7 times Earth's that had accurately measured masses. They found that the five planets with diameters smaller than 1.6 times Earth showed a tight relationship between mass and size. Moreover, Venus and Earth fit onto the same line, suggesting that all these worlds have similar rock-iron compositions.

As for the larger and more massive exoplanets, their densities proved to be significantly lower, meaning that they include a large fraction of water or other volatiles, hydrogen and/or helium. They also showed more diverse compositions rather than fitting into a single group like the smaller terrestrial worlds.

The team also noted that not all planets less than six times the mass of Earth are rocky. Some low-mass worlds with very low densities are known (such as the planets in the Kepler-11 system). But for typical close-in small planets, the chances are high that they share an Earth-like composition.

"To find a truly Earth-like world, we should focus on planets less than 1.6 times the size of Earth, because those are the rocky worlds," recommends Dressing.

Making Other Earths

Makes one small model planet

Ingredients:

• 1 cup magnesium
• 1 cup silicon
• 2 cups iron
• 2 cups oxygen
• 1/2 teaspoon aluminum
• 1/2 teaspoon nickel
• 1/2 teaspoon calcium
• 1/4 teaspoon sulfur
• dash of water delivered by asteroids

Blend well in a large bowl, shape into a round ball with your hands and place it neatly in a habitable zone area around a young star. Do not over mix. Heat until mixture becomes a white hot glowing ball. Bake for a few million years. Cool until color changes from white to yellow to red and a golden-brown crust forms. It should not give off light anymore. Season with a dash of water and organic compounds. It will shrink a bit as steam escapes and clouds and oceans form. Stand back and wait a few more million years to see what happens. If you are lucky, a thin frosting of life may appear on the surface of your new world.

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Super-Earths have long-lasting oceans

This artist's depiction shows a gas giant planet rising over the horizon of an alien waterworld. New research shows that oceans on super-Earths, once established, can last for billions of years.

For life as we know it to develop on other planets, those planets would need liquid water, or oceans. Geologic evidence suggests that Earth's oceans have existed for nearly the entire history of our world. But would that be true of other planets, particularly super-Earths? New research suggests the answer is yes and that oceans on super-Earths, once established, can last for billions of years.

"When people consider whether a planet is in the habitable zone, they think about its distance from the star and its temperature. However, they should also think about oceans, and look at super-Earths to find a good sailing or surfing destination," says lead author Laura Schaefer of the Harvard-Smithsonian Center for Astrophysics (CfA).

Schaefer presented her findings today in a press conference at a meeting of the American Astronomical Society.

Even though water covers 70 percent of Earth's surface, it makes up a very small fraction of the planet's overall bulk. Earth is mostly rock and iron; only about a tenth of a percent is water.

"Earth's oceans are a very thin film, like fog on a bathroom mirror," explains study co-author Dimitar Sasselov (CfA).

However, Earth's water isn't just on the surface. Studies have shown that Earth's mantle holds several oceans' worth of water that was dragged underground by plate tectonics and subduction of the ocean seafloor. Earth's oceans would disappear due to this process, if it weren't for water returning to the surface via volcanism (mainly at mid-ocean ridges). Earth maintains its oceans through this planet-wide recycling.

Schaefer used computer simulations to see if this recycling process would take place on super-Earths, which are planets up to five times the mass, or 1.5 times the size, of Earth. She also examined the question of how long it would take oceans to form after the planet cooled enough for its crust to solidify.

She found that planets two to four times the mass of Earth are even better at establishing and maintaining oceans than our Earth. The oceans of super-Earths would persist for at least 10 billion years (unless boiled away by an evolving red giant star).

Interestingly, the largest planet that was studied, five times the mass of Earth, took a while to get going. Its oceans didn't develop for about a billion years, due to a thicker crust and lithosphere that delayed the start of volcanic outgassing.

"This suggests that if you want to look for life, you should look at older super-Earths," Schaefer says.

Sasselov agrees. "It takes time to develop the chemical processes for life on a global scale, and time for life to change a planet's atmosphere. So, it takes time for life to become detectable."

This also suggests that, assuming evolution takes place at a similar rate to Earth's, you want to search for complex life on planets that are about five and a half billion years old, a billion years older than Earth.

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Stars' spins reveal their ages

It's easier to tell the age of a young star because they rotate more quickly and have larger starspots.

When you're a kid every birthday is cause for celebration, but as you get older they become a little less exciting. You might not want to admit just how old you are. And you might notice yourself slowing down over the years. You're not alone -- the same is true of stars. They slow down as they age, and their ages are well-kept secrets. Astronomers are taking advantage of the first fact to tackle the second and tease out stellar ages.

"Our goal is to construct a clock that can measure accurate and precise ages of stars from their spins. We've taken another significant step forward in building that clock," says Soren Meibom of the Harvard-Smithsonian Center for Astrophysics (CfA).

Meibom presented his team's findings today at a meeting of the American Astronomical Society. Their results mark the first extension of such observations to stars with ages beyond 1 billion years, and toward the 4.6-billion-year age of the Sun.

Being able to tell the ages of stars is the basis for understanding how astronomical phenomena involving stars and their companions unfold over time.

Knowing a star's age is particularly relevant to the search for signs of alien life outside our solar system. It has taken a long time for life on Earth to attain the complexity we find today. With an accurate stellar clock, astronomers can identify stars with planets that are as old as our Sun or older.

A star's spin rate depends on its age because it slows down steadily with time, like a top spinning on a table. A star's spin also depends on its mass; astronomers have found that larger, heavier stars tend to spin faster than smaller, lighter ones. This new work shows that there is a close mathematical relationship between mass, spin, and age so that by measuring the first two, scientists can calculate the third.

"We have found that the relationship between mass, rotation rate and age is now defined well enough by observations that we can obtain the ages of individual stars to within 10 percent," explains co-author Sydney Barnes of the Leibniz Institute for Astrophysics in Germany.

Barnes first proposed this method in 2003, building on prior work, and called it gyrochronology from the Greek words gyros (rotation), chronos (time/age), and logos (study).

To measure a star's spin, astronomers look for changes in its brightness caused by dark spots on its surface -- the stellar equivalent of sunspots. Unlike our Sun, a distant star is an unresolved point of light so astronomers can't directly see a sunspot cross the stellar disk. Instead, they watch for the star to dim slightly when a sunspot appears, and brighten again when the sunspot rotates out of view.

These changes are very difficult to measure because a typical star dims by much less than 1 percent, and it can take days for a sunspot to cross the star's face. The team achieved the feat using data from NASA's Kepler spacecraft, which provided precise and continuous measurements of stellar brightnesses.

For gyrochronology ages to be accurate and precise, astronomers must calibrate their new clock by measuring the spin periods of stars with both known ages and masses. Meibom and his colleagues previously studied a cluster of billion-year-old stars. This new study examines stars in the 2.5-billion-year-old cluster known as NGC 6819, thereby significantly extending the age range.

"Older stars have fewer and smaller spots, making their periods harder to detect," says Meibom.

The team examined stars weighing 80 to 140 percent as much as the Sun. They were able to measure the spins of 30 stars with periods ranging from 4 to 23 days, compared to the present 26-day spin period of the Sun. The eight stars in NGC 6819 most similar to the Sun have an average spin period of 18.2 days, strongly implying that the Sun's period was about that value when it was 2.5 billion years old (about 2 billion years ago).

The team then evaluated several existing computer models that calculate the spin rates of stars based on their masses and ages, and determined which model best matched their observations.

"Now we can derive precise ages for large numbers of cool field stars in our Galaxy by measuring their spin periods," states Meibom. "This is an important new tool for astronomers studying the evolution of stars and their companions, and one that can help identify planets old enough for complex life to have evolved."

This work was first published online on the website of the journal Nature on January 5, 2015. It is part of the broader Kepler Cluster Study, for which Meibom is the principal investigator.

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New analyses of Martian chemical maps suggest water bound to sulfates in soil

Water (above) and sulfur (below) mass fractions found within the martian soil are mapped up to about 30-40 cm deep at hundreds of kilometer regional scales.

A research team led by LSU Geology and Geophysics Assistant Professor Suniti Karunatillake reveals a spatial association between the presence of sulfur and hydrogen found in martian soil. The work by this multi-institutional team of researchers from Georgia Tech (James Wray), Stony Brook University (Scott McLennan and Deanne Rogers), CNRS/ Université Fédérale Toulouse Midi-Pyrénées (Olivier Gasnault), Cornell University (Steve Squyres), and University of Arizona (William Boynton) may in turn identify hydrous iron sulfates as key carriers of H₂O in bulk martian soil. The gamma spectral signature of hydrogen serves as a possible indicator of water, a primary driver of weathering and life processes on Earth. The analyzed elemental data from the Gamma Ray Spectrometer onboard the Mars Odyssey orbiter was published in Geophysical Research Letters on Nov. 22, 2014.

The study indicates that within the southern latitudes of Mars, sulfur compounds are a key hydrated phase. This is revealed in part by water-to-sulfur molar ratios that fall within expected ranges corresponding to hydrated sulfate compounds. Reinforcing the data, hydrogen and sulfur correlate compellingly in the southern latitudes. The molar ratios were observed over 80 percent of Mars' southern hemisphere. Consequently, sulfate compounds, acting as primary contributors of H₂O, may also influence modern water-driven processes on Mars.

"Sulfur variation plays an important role as a control on inferred fluid pH, alteration environments, and water activity while the variation in hydration state reinforces the compelling possibility of H₂O bound primarily in sulfates in the southern hemisphere," Karunatillake said. "This applies specifically to bulk soil at decimeter depths, including the possibility that geochemical processes of iron sulfate-rich Paso Robles soil in Gusev Crater may have been more common at regional scales in ancient martian terrain than previously appreciated."

The team suggests that further observations by the Curiosity rover in Gale Crater could move forward models of aqueous processes on Mars. For example, recent analyses of "Rocknest" soil samples suggest complementary modes of soil hydration in the Gale Crater area.

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Why is Greenland covered in ice?

Watkins Mountains in southern East Greenland, with Greenland's highest peak, Gunbjörn Fjeld (3.7 km above sea level) in the background. The photo was taken at about 2 km above sea level, towards the 1.5 km high Watkins Escarpment cut into basalts erupted at the Paleocene-Eocene transition about 56 million years ago, much closer to sea level at that time.

The ice on Greenland could only form due to processes in the deep Earth interior. Large-scale glaciations in the Arctic only began about 2.7 million years ago; before that, the northern hemisphere was largely free of ice for more than 500 million years. Scientists at the German Research Centre for Geosciences GFZ, Utrecht University, the Geological Survey of Denmark and Greenland (GEUS) and the University of Oslo could now explain why the conditions for the glaciation of Greenland only developed so recently on a geological time scale.

The reason for that is the interaction of three tectonic processes. For one thing, Greenland had to be lifted up, such that the mountain peaks reached into sufficiently cold altitudes of the atmosphere. Secondly, Greenland needed to move sufficiently far northward, which led to reduced solar irradiation in winter. Thirdly, a shift of the Earth axis caused Greenland to move even further northward.

Hot rocks underneath Iceland

These glaciations began in the East of Greenland. The authors found hints in rock samples that the high mountains in the east of Greenland were only uplifted during the last ten million years, whereby this process happened especially fast since about 5 million years ago. At that time, Greenland was still largely free of ice. Seismological investigations indicate that hot rocks rise underneath Iceland from Earth's deep mantle. These observations were used as input in computer models by main author Bernhard Steinberger at the German Research Centre for Geosciences GFZ. "These hot rocks flow northward beneath the lithosphere, that is, towards eastern Greenland," Steinberger explains. "Because the upwelling beneath Iceland −the Iceland plume − sometimes gets stronger and sometimes weaker, uplift and subsidence can be explained."

Greenland migrating

The seismological investigations also showed that the lithosphere in the East of Greenland is especially thin -- only about 90 kilometers thick. Earth scientists Steinberger and colleagues reconstructed the position of the tectonic plates 60 to 30 million years ago, and found that the Iceland plume was exactly beneath this part of Greenland during that time. This explains why the lithosphere is so thin. For that reason, the eastern part of Greenland could also be more easily uplifted: Plume material can flow up to a depth of less than 100 km and therefore lift up the overlying lithosphere comparatively easily.

Whereas the Iceland plume remained in approximately the same position in Earth mantle, Greenland moved as a tectonic plate, with a northward component of six degrees of latitude during the past 60 Million years, towards cooler regions.

Shift of Earth axis

This northward motion was amplified through "True polar wander": "Our computations show that Earth axis shifted about 12° towards Greeland during the last 60 million years" GFZ researcher Steinberger says. Therefore, in combination with the tectonic plate motion, Greenland moved about 18° northward. It was now sufficiently far north, and its mountain tops in the East were sufficiently high, such that glaciations could be initiated.

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Rare rock with 30,000 diamonds examined

Diamonds are beautiful and enigmatic. Though chemical reactions that create the highly coveted sparkles still remain a mystery, a professor from the University of Tennessee, Knoxville, is studying a rare rock covered in diamonds that may hold clues to the gem's origins.

The golf-ball sized chunk of rock contains more than 30,000 diamonds, each less than a millimeter in size (rendering them worthless), along with speckles of red and green garnet and other minerals.

The rock was found in Russia's Udachnaya diamond mine in northern Siberia. The diamond company of Russia, ALROSA, loaned it to Earth and Planetary Sciences Professor Larry Taylor and a team of researchers from the Russian Academy of Sciences so they could study the rock to uncover the diamonds' genesis.

Scientists believe that diamonds form at some 100 miles deep in Earth's mantle and are carried to the surface by special volcanic eruptions. However, most mantle rocks crumble during this journey. This rock is one of only a few hundred recovered in which the diamonds are still in their original setting from within the Earth.

"It is a wonder why this rock has more than 30,000 perfect teeny tiny octahedral diamonds -- all 10 to 700 micron in size and none larger," said Taylor. "Diamonds never nucleate so homogeneously as this. Normally, they do so in only a few selective places and grow larger. It's like they didn't have time to coalesce into larger crystals."

Taylor and his colleagues examined the sparkly chunk using a giant X-ray machine to study the diamonds and their relationships with associated materials. They also beamed electrons at the materials inside the diamonds -- called inclusions -- to study the chemicals trapped inside.

This created two- and three-dimensional images which revealed a relationship between minerals. Analyses of nitrogen indicated the diamonds were formed at higher-than-normal temperatures over longer-than-normal times. The images also showed abnormal carbon isotopes for this type of rock, indicating it was originally formed as part of the crust of Earth, withdrawn by tectonic shifts and transformed into the shimmery rock we see today.

"These are all new and exciting results, demonstrating evidences for the birth mechanism of diamonds in this rock and diamonds in general," said Taylor. The findings were presented at the American Geophysical Union's annual conference in San Francisco in December and will be published in a special issue of Russian Geology and Geophysics this month.

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New research dishes the dirt on the demise of a civilization

The monumental Bronze Age tomb at Nichoria from above.

Two researchers are taking a new twist on long-published research about what an ancient civilization did for a living.

W. Flint Dibble, a University of Cincinnati doctoral student in the Department of Classics, and Daniel J. Fallu, a doctoral student in archaeology at Boston University, will present their new discoveries surrounding a key site from the Greek Dark Age on Jan. 9, at the joint annual meeting of the Archaeological Institute of America (AIA) and Society for Classical Studies (SCS, formerly known as the American Philological Association), in New Orleans.

The Greek village of Nichoria remained standing through both the Late Bronze Age and the Greek Dark Age, and previous research has suggested that Nichoria turned to cattle ranching during the region's collapse in the Dark Age. That's because the remains of cattle bones are prevalent among bone fragments in the soil.

In a presentation titled, "The Good, the Bad and the Ugly at the Dark Age Ranch: Taphonomic Reinterpretations of Pastoralism at Nichoria, Messinia," the UC-led research suggests that soil formation after the abandonment of the site in the Dark Age led to poor preservation of the historic record, and as a result, the thicker, larger bones of animals such as cattle survived the breakdown of other bone fragments. Other possible remains would have been destroyed as a result of the more acidic soil. The researchers report that Dark Age sediments contain few visible calcite formations, indicative of poor site preservation.

The village of Nichoria in Messenia was located near the palace of Pylos during the Greek Bronze Age, when Greece was considered a Superpower of the Mediterranean. The region thrived on its trade and economic stability, culture, and art and architecture, including great monuments, palaces and writings. The collapse of the Bronze Age (beginning around 1200 BC), including the abandonment of cities and the destruction of palaces, is known as the Dark Age.

"There's no monumental architecture and little art, writing disappears and there are considerably fewer sites," says Dibble. He explains that Nichoria is one of the few settlements in Greece that remained occupied during both the Bronze Age and the Greek Dark Age. It's believed that the widespread abandonment of settlements was due to the adoption of pastoralism, making populations more mobile as they herded animals.

The explanations for the sudden collapse of civilization in the Dark Age have ranged from believing it was the result of the invasion of another society to a catastrophic climatic event.

"We were exploring this as evidence for a possible climate event, but the soil samples came back inconclusive," says Dibble. "We actually think that as more of these sites are abandoned in the Dark Age, the landscape becomes very stable, and the weather destroys more of what's in the top upper layers than the archaeological material buried deeper below. At this site, we have no evidence that the destruction of bone was the result of climate change."

Previous research from the first excavation of Nichoria in the late '60s -- an extensive project led by the University of Minnesota -- has suggested that Nichoria survived the Dark Age by turning to cattle ranching, after villagers took control of the herds of the palaces in the wake of their collapse.

Dibble says that the evolution of methods and technology has resulted in new examinations of discoveries from decades ago. "We're using modern biology to understand what is happening to ancient remains and we're finding that the bone is dissolving away. I've found teeth that are hollow because the dense enamel is still there, but the dentin is gone, which also tells me that more porous bone is dissolving away."

Dibble adds that their study is unique in that soil that was collected with the bones was also studied before being washed away to better examine the bones. Fallu conducted the examinations of the soil. Concerning the fact that many bags of bones still had dirt, Dibble says, "We got kind of lucky in a sense."

"I want to see if this kind of soil environment that destroys bones also destroys other types of evidence, because there is bone destruction at other sites being studied from the Dark Age," says Dibble. "Bone is made up of calcium carbonate, so other carbon materials could be destroyed, such as charred plants -- key to understanding agriculture at that time. Also, there are few metal objects from the Dark Age, and the soil environment might be an explanation for that."

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More than 1.5 million cancer deaths averted during 2 decades of dropping mortality

The American Cancer Society's annual cancer statistics report finds that a 22% drop in cancer mortality over two decades led to the avoidance of more than 1.5 million cancer deaths that would have occurred if peak rates had persisted. And while cancer death rates have declined in every state, the report finds substantial variation in the magnitude of these declines, generally with the states in the south showing the smallest decline and in the Northeast the largest decline.

Each year, the American Cancer Society compiles the most recent data on cancer incidence, mortality, and survival based on incidence data from the National Cancer Institute and the Centers for Disease Control and Prevention, and mortality data from the National Center for Health Statistics. The data are disseminated in two reports: Cancer Statistics 2015, published in CA: A Cancer Journal for Clinicians, and its companion, consumer-friendly publication, Cancer Facts & Figures 2015. The reports also estimate the number of new cancer cases and deaths expected in the United States in the current year.

Largely driven by rapid increases in lung cancer deaths among men as a consequence of the tobacco epidemic, the overall cancer death rate rose during most of the 20th century, peaking in 1991. The subsequent, steady decline in the cancer death rate is the result of fewer Americans smoking, as well as advances in cancer prevention, early detection, and treatment.

Mortality

• During the most recent five years for which data are available (2007-2011), the average annual decline in cancer death rates was slightly larger among men (1.8%) than women (1.4%). These declines are driven by continued decreases in death rates for the four major cancer sites: lung, breast, prostate, and colon.
• Lung cancer death rates declined 36% between 1990 and 2011 among males and 11% between 2002 and 2011 among females due to reduced tobacco use.
• Death rates for breast cancer (among women) are down more than one-third (35%) from peak rates, while prostate and colorectal cancer death rates are each down by nearly half (47%).
• The magnitude of the decline in overall cancer mortality between 1991 and 2011 varied by state. The smallest declines were generally in the South, where drops were about 15%. They were largest in the Northeast. For example, there were declines of 25% to 30% in Maryland, New Jersey, Massachusetts, New York, and Delaware. As a result, a total of 29,000 cancer deaths were averted in 2011 in these states.

Estimates for the current year

• The report estimates there will be 1,658,370 new cancer cases and 589,430 cancer deaths in the United States in 2015.
• Prostate, lung, and colorectal cancers will account for about one-half of all cases in men, with prostate cancer alone accounting for about one-quarter of new diagnoses.
• The three most commonly diagnosed types of cancer among women in 2015 will be breast, lung, and colorectal cancer, accounting for one-half of all cases in women. Breast cancer alone is expected to account for 29% of all new cancers among women in the U.S.
• The report estimates that 589,430 Americans will die from cancer this year, corresponding to about 1,600 deaths per day.
• The most common causes of cancer death are lung, prostate, and colorectal cancer in men and lung, breast, and colorectal cancer in women. These four cancers account for almost one-half of all cancer deaths, with more than one-quarter (27%) of all cancer deaths due to lung cancer.

Additional findings

• During the past five years for which there are data (2007-2011), the overall cancer incidence rate remained stable in women and declined by 1.8% per year in men.
• The decrease in incidence in men is driven by the rapid declines in colorectal (3.6% per year), lung (3.0% per year), and prostate (2.1% per year) cancers.
• While women in the U.S. have seen similar drops in colorectal and lung cancers, breast cancer incidence rates have flattened, and there's been a dramatic rise in thyroid cancer incidence rates (an average of 4.5% per year from 2007 to 2011).

"The continuing drops we're seeing in cancer mortality are reason to celebrate, but not to stop," said John R. Seffrin, PhD, chief executive officer of the American Cancer Society. "Cancer was responsible for nearly one in four deaths in the United States in 2011, making it the second leading cause of death overall. It is already the leading cause of death among adults aged 40 to 79, and is expected to overtake heart disease as the leading cause of death among all Americans within the next several years. The change may be inevitable, but we can still lessen cancer's deadly impact by making sure as many Americans as possible have access to the best tools to prevent, detect, and treat cancer."

Each year, Cancer Facts & Figures includes a Special Section that focuses on a specific, timely cancer topic. This year, the report highlights breast carcinoma in situ. An estimated 60,290 new cases of breast carcinoma in situ are expected to be diagnosed in 2015, accounting for about one in five breast tumors diagnosed in women. Although in situ breast cancer is a relatively common diagnosis, it is not as widely known or understood as invasive breast cancer.

The term "carcinoma in situ" describes abnormal cells that have not invaded nearby tissues, but that look very similar to cells of invasive carcinoma when viewed under a microscope. For many years, it was assumed that these cells were potentially able to become invasive, and that in the absence of treatment, they would eventually progress to cancer. More recent research indicates that the transition from normal tissue to carcinoma in situ to invasive carcinoma involves a series of molecular changes that are more complex and subtle than the older view based on microscopic appearances. Long-term follow-up studies of patients with carcinoma in situ also find that even without treatment, not all patients develop invasive cancer.

The vast majority (83%) of in situ breast cancers will be ductal carcinoma in situ (DCIS). DCIS refers to abnormal cells lining the breast duct that appear similar to those of invasive breast cancers, but are still within the tissue layer of origin. It is most often detected by a mammogram. While DCIS cannot spread to other organs and cause serious illness or death, it has the potential if left untreated to evolve into invasive cancer and is considered a true cancer precursor. Studies of women with DCIS that was untreated because it was originally misclassified as benign found that 20 to 53% were eventually diagnosed with an invasive breast cancer.

Lobular carcinoma in situ (LCIS) refers to cells that look like cancer cells growing within the walls of the lobules of the milk-producing glands of the breast. LCIS is not generally thought to be a precursor of invasive cancer, but is considered a marker for increased risk of developing invasive breast cancer.

The authors say they hope that the information in the Special Section will help patients facing the disease, as well as friends, family, and others who can provide support and perspective for women who are newly diagnosed and those living after a diagnosis of DCIS or LCIS.

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Gecko grippers get a microgravity test flight

There are no garbage trucks equipped to leave the atmosphere and pick up debris floating around Earth. But what if we could send a robot to do the job?

Scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, are working on adhesive gripping tools that could grapple objects such as orbital debris or defunct satellites that would otherwise be hard to handle.

The gecko gripper project was selected for a test flight through the Flight Opportunities Program of NASA's Space Technology Mission Directorate. As a test, researchers used the grippers in brief periods of weightlessness aboard NASA's C-9B parabolic flight aircraft in August.

"Orbital debris is a serious risk to spacecraft, including the International Space Station," said Aaron Parness, a JPL robotics researcher who is the principal investigator for the grippers. "This is definitely a problem we're going to have to deal with. Our system might one day contribute to a solution."

The gripping system developed by Parness and colleagues was inspired by geckos, lizards that cling to walls with ease. Geckos' feet have branching arrays of tiny hairs, the smallest of which are hundreds of times thinner than a human hair. This system of hairs can conform to a rough surface without a lot of force. Although researchers cannot make a perfect replica of the gecko foot, they have put "hair" structures on the adhesive pads of the grippers.

The synthetic hairs, also called stalks, are wedge-shaped and have a slanted, mushroom-shaped cap. When the gripping pad lightly touches part of an object, only the very tips of the hairs make contact with that surface.

"The stickiness of the grippers can be turned on and off, by changing the direction in which you pull the hairs," Parness said.

To get the gripper to stick to a surface, force is applied to the adhesive pad material in a manner that makes the hairs bend. This increases the real area of contact between the hairs and the surface, which corresponds to greater adhesion. When the force is relaxed and the hairs go back to being upright, this process turns off the stickiness.

A phenomenon called van der Waals forces, named for Nobel Prize-winning physicist Johannes Diderik van der Waals, explains the non-permanent stickiness of the grippers, as well as gecko feet. These temporary adhesive forces happen because electrons orbiting the nuclei of atoms are not evenly spaced, creating a slight electrical charge. Such forces persist even in extreme temperature, pressure and radiation conditions.

"The reliability of van der Waals forces, even in severe environments, makes them particularly useful for space applications," Parness said.

"The system could grapple objects in space that are spinning or tumbling, and would otherwise be hard to target," he said.

In the recent tests, the grippers were able to grapple a 20-pound cube as it floated. The grippers also were able to grapple a researcher wearing a vest made of spacecraft material panels, representing a 250-pound "object." Members of the research team held the device with adhesive pads during the test, but the eventual idea is to integrate the grippers into a robotic arm or leg.

In total, the grippers have been tested on more than 30 spacecraft surfaces at JPL. They also have been tested successfully in a JPL thermal vacuum chamber, with total vacuum conditions and temperatures of minus 76 degrees Fahrenheit (minus 60 degrees Celsius) to simulate the conditions of space. While Parness was in graduate school at Stanford University in Palo Alto, California, the grippers were tested separately in more than 30,000 cycles of "on" and "off," with the adhesive staying strong. Several prototypes have since been designed.

There are more than 21,000 pieces of orbital debris larger than 3.9 inches (10 centimeters) in Earth's orbit. The U.S. Space Surveillance Network routinely tracks these objects. In 2009, an accidental collision occurred between an operational communications satellite and a large piece of debris, destroying the satellite.

Besides grappling orbital debris, the grippers could help inspect spacecraft or assist small satellites in docking to the International Space Station. The grippers are another example of how technology drives exploration.

The California Institute of Technology manages JPL for NASA.

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Hunt for Big Bang particles offering clues to the origin of the universe

Billions upon billions of neutrinos speed harmlessly through everyone's body every moment of the day, according to cosmologists. The bulk of these subatomic particles are believed to come straight from the Big Bang, rather than from the sun or other sources. Experimental confirmation of this belief could yield seminal insights into the early universe and the physics of neutrinos. But how do you interrogate something so elusive that it could zip through a barrier of iron a light-year thick as if it were empty space?

At the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL), researchers led by Princeton University physicist Chris Tully are set to hunt for these nearly massless Big Bang relics by exploiting a curious fact: Neutrinos can be captured by tritium, a radioactive isotope of hydrogen, and provide a tiny boost of energy to the electrons -- or beta particles -- that are emitted in tritium decay.

Tully has created a prototype lab at PPPL to detect Big Bang neutrinos by measuring the extra energy they impart to the electrons -- and to achieve this with greater precision than has ever been done before. Spotting these neutrinos is akin to "detecting a faint heartbeat in a sports arena filled to the brim" said Charles Gentile, who heads engineering for the project, which Tully has dubbed PTOLEMY for "Princeton Tritium Observatory for Light, Early Universe Massive Neutrino Yield." Ptolemy was an ancient Greek astronomer who lived in Egypt during the first century.

Darkest, coldest conditions achievable

The task calls for measuring the energy of an electron with a precision comparable to detecting the mass of a neutrino, which until recently was thought to have no mass at all. Such measurements require the darkest, coldest conditions achievable in a laboratory and the use of quantum electronics -- a discipline that deals with the effect of quantum mechanics on the behavior of electrons in matter -- to detect the minute extra energy that a Big Bang neutrino would impart. Quantum mechanics describes the motion and direction of subatomic particles.

Why is the energy that a Big Bang neutrino provides so extraordinarily small? What's unique about these relics is that their wavelength has been stretched and cooled as the space-time we live in has expanded over approximately 13.7 billion years. This expansion has cooled a tremendous number of neutrinos to temperatures that are billions of times colder, and therefore less energetic, than those of neutrinos originating from the sun. When tritium captures these cold neutrinos, they create a narrow peak in energy that is just above the maximum energy of an electron from tritium decay.

The difficulty in identifying a Big Bang relic doesn't end there. Since neutrinos can take different forms, the height of the peak could be higher or lower by a factor of two, depending on whether the neutrino is like normal matter with a corresponding particle of antimatter -- an antineutrino -- or whether the neutrino is different and is in fact its own antiparticle. The extra height might not appear at all if neutrinos decay over billions of years into yet unknown, lighter particles.

Cutting-edge technology

Tully aims to show that the prototype for PTOLEMY, which is housed in a basement site at PPPL, can indeed achieve the precision needed to detect Big Bang neutrinos. The cutting-edge technology could then become the basis for a major experiment at PPPL to test long-held assumptions about the density of Big Bang neutrinos throughout the universe.

Confirming the assumptions could validate the standard model of the origin of the universe, Tully says, while refuting them could overturn the model and prompt new ideas about the Big Bang and its aftermath. Finding the neutrinos could also show if they could be a source of the invisible dark matter that scientists say makes up 20 percent of the total mass of the universe.

Such discoveries could be epochal. Could the project "make long-term contributions to the understanding of the universe?" Tully asks in presentations about PTOLEMY. "Absolutely!" he says. "We believe that we live in a sea of 14 billion-year-old neutrinos all around us. But is it true?"

The prototype at PPPL may hold the key to finding out. The device consists of a pair of superconducting magnets connected to opposite ends of a five-foot cylindrical vacuum chamber. A source containing a tiny bit of tritium sits inside one end of the chamber, with a calorimeter that Argonne National Laboratory is providing to measure electron energy set at the other end. The experiment will bind electrons from the tritium decay to magnetic field lines and pass them through filters in the vacuum chamber that will remove all but the highest-energy electrons, which the calorimeter will then measure.

Preventing "noise"

Great care will be taken to keep random thermal "noise" from disrupting the finely tuned equipment at each end of the experiment. Researchers will deposit the tritium on the nanomaterial graphene -- a layer of carbon just one atom thick -- to ensure that the electrons come off cleanly into the vacuum.

The calorimeter at the other end of the chamber will be connected to a dilution refrigerator set at between 70 and 100 millikelvins, a temperature 20 times colder than deep space and less than one-tenth of a degree above absolute zero. This deep-freeze will keep the calorimeter poised between a superconducting state -- one in which electrons can flow with virtually no resistance -- and a non-superconducting state with resistance to the flow of electrons. The delicate balance between these two states, combined with extremely low noise conditions achievable only with quantum electronics, will provide the sensitivity needed to precisely measure the energy of an electron that impinges upon the calorimeter. The setup will produce "the most precise electron-energy measurements ever made using calorimeter techniques," Tully said.

This experiment is "a perfect match for the competencies and capabilities that exist at PPPL," said Adam Cohen, deputy director for operations at PPPL and supervisor of the PTOLEMY project. Such qualities include know-how in handling tritium, a laboratory for synthesizing nanomaterial, decades of experience operating magnets and vacuum vessels, and space for an expanded experiment. "Chris and I talked about collaboration between PPPL and the University about three years ago," Cohen recalled. "Every time we pursue an activity with the campus it strengthens the bridge that exists between us."

Cross-fertilization

Looking ahead, Cohen sees PTOLEMY attracting new students, researchers and visitors, along with experts in high-energy physics, to PPPL. This could produce cross-fertilization with the Laboratory's core mission of advancing fusion and plasma science, he said.

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