Pity poor Mercury. The tiny planet endures endless assaults by intense sunlight, powerful solar wind and high-speed miniature meteoroids called micrometeoroids. The planet's flimsy covering, the exosphere, nearly blends in with the vacuum of space, making it too thin to offer protection. Because of this, it's tempting to think of Mercury's exosphere as just the battered remains of ancient atmosphere.

Really, though, the exosphere is constantly changing and being renewed with sodium, potassium, calcium, magnesium and other species that are liberated from Mercury's soil by barrages of particles. Because both these particles and Mercury's surface materials respond to sunlight, the solar wind, Mercury's own magnetic sheath (the magnetosphere) and other dynamic forces, the exosphere may not look the same from one observation to the next. Far from being dead, Mercury's exosphere is a place of amazing activity that can tell astronomers a lot about the planet's surface and environment.

Three related papers written by scientists at NASA's Goddard Space Flight Center in Greenbelt, Md., and their colleagues offer insight into the details of how the exosphere gets replenished and show that new modeling of the magnetosphere and exosphere can explain some intriguing observations of the planet. These papers are published as part of Icarus's September 2010 special issue devoted to observations of Mercury during the first and second flybys of the MESSENGER (short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft.

1. Mercury's substitute. No spacecraft have been able to land on Mercury, so astronomers have to figure out indirectly what's in the planet's soil. One approach is to study Earth's moon. Like Mercury, the moon has a very thin exosphere, and on both bodies, the same processes drive species from the surface and into the exosphere. So when Goddard's Rosemary Killen, an expert on both exospheres, and her colleagues wanted to find out what kind of soil could give rise to the concentrations of sodium and potassium found in Mercury's exosphere, they looked at lunar samples. Their best match? Samples brought back by Russia's Luna 16 spacecraft.

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With a brilliant, finely tuned spark of ultraviolet (UV) light, a physicist at the National Institute of Standards and Technology helped NASA scientists successfully position a crucial UV sensor inside a space-borne instrument to observe a "hidden" layer of the Sun where violent space weather can originate.

Dark spots on the Sun release particles and electromagnetic fields into space. As these particles and fields pass through the Sun's "transition region," 5,000 kilometers above the surface, they can gather considerable steam, resulting in violent episodes of "space weather" that can damage Earth-orbiting satellites and disrupt electronic communications.

The powerful magnetic fields in the transition region can be studied indirectly, by observing the UV light emanating from that region. The fields slightly shift the colors (wavelengths) of UV light released by charged atoms (ions) in their vicinity. Measuring how much these wavelengths shift can yield information on the magnetic field's strength.

The catch is you can't do it from Earth, where the atmosphere absorbs the UV light, so a team at NASA Marshall Space Flight Center in Huntsville, Ala., constructed a rocket-borne instrument, known as the Solar Ultraviolet Magnetograph Investigation (SUMI), designed to take pictures of these magnetic fields from space.

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 ESA's (European Space Agency) Herschel infrared space observatory has discovered that ultraviolet starlight is a key ingredient for making water in the atmosphere of some stars. It is the only explanation for why a dying star is surrounded by a gigantic cloud of hot water vapour. These new results will be published tomorrow in Nature. 

Every recipe needs a secret ingredient. When astronomers discovered an unexpected cloud of water vapour around the old star CW Leonis in 2001, they immediately began searching for the source. Water is known to be present around several types of stars, but CW Leonis is a “carbon star” and therefore thought not to produce water. Initially they suspected the star’s heat must be evaporating comets or even dwarf planets to produce the water.

Now, Herschel’s PACS (Photodetector Array Camera and Spectrometer) and SPIRE instruments have revealed that the secret ingredient is ultraviolet light, because the water vapour is too hot to have come from the destruction of icy celestial bodies and is distributed throughout the stellar wind, including deep down near the surface of the star itself. This suggests that the water is being created by a previously unsuspected chemical process where ultraviolet radiation from interstellar space is breaking up the carbon monoxide and releasing oxygen atoms that can then react with hydrogen to form water molecules.

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(PhysOrg.com) — Astronomers at the University of Hawaii have measured the temperature of a young gas-giant planet around another star using the W. M. Keck Observatory, and the results are puzzling. They have found that its atmosphere is unlike that of any previously studied extrasolar planet.

By obtaining a spectrum of its emitted light, the astronomers determined the temperature of the planet. As a result, they found that current theoretical models of gas-giant planets did a poor job of explaining all the data. The team suspects that the reason is dust in the planet’s atmosphere. Models with normal amounts of dust do not resemble this planet, but models with exceptionally thick dust clouds do a much better job. It therefore appears that young gas-giant planets are extremely cloudy.

“We are at a point where not only can we directly image planets around other stars, but we can begin to study the properties of their atmospheres in detail. Direct spectroscopy of exoplanets is the future of this field,” said Mr. Brendan Bowler, a graduate student at the University of Hawaii and the lead author of the study.

The planet, known as HR 8799 b, is one of three gas-giant planets orbiting the star HR 8799, located 130 light-years away from Earth in the constellation Pegasus. (For reference, the distance to the nearest nighttime star from Earth is about four light-years.) HR 8799 b is the lowest-mass planet around the star, about seven times the mass of Jupiter. This multiplanet system was discovered by direct imaging in 2008, and now, only a year and a half later, astronomers have obtained a spectrum of one of its planets. The spectrum of a planet contains much more information than a single image: it can reveal the temperature, chemical composition, and cloud properties of the planet.

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ScienceDaily (Sep. 1, 2010) — Side-by-side comparisons of organic and conventional strawberry farms and their fruit found the organic farms produced more flavorful and nutritious berries while leaving the soil healthier and more genetically diverse.

"Our findings have global implications and advance what we know about the sustainability benefits of organic farming systems," said John Reganold, Washington State University Regents professor of soil science and lead author of a paper published in the peer-reviewed online journal, PLoS ONE. "We also show you can have high quality, healthy produce without resorting to an arsenal of pesticides."

The study is among the most comprehensive of its kind, analyzing 31 chemical and biological soil properties, soil DNA, and the taste, nutrition and quality of three strawberry varieties on more than two dozen commercial fields — 13 conventional and 13 organic.

"There is no paper in the literature that comprehensively and quantitatively compares so many indices of both food and soil quality at multiple sampling times on so many commercial farms," said Reganold. Previous Reganold studies of "sustainability indicators" on farms in the Pacific Northwest, California, British Columbia, Australia, and New Zealand have appeared in the journals Science, Nature, and Proceedings of the National Academy of Sciences.

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ScienceDaily (Sep. 1, 2010) — NASA and NOAA's latest Geostationary Operational Environmental Satellite, GOES-15, has successfully completed five months of on-orbit testing and has been accepted into service. The satellite has demonstrated operational readiness of its subsystems, spacecraft instruments and communications services. GOES-15 is the third and final spacecraft in the GOES N-P Series of geostationary environmental weather satellites.

The GOES fleet help NOAA forecasters track life-threatening weather and solar activity that can impact the satellite-based electronics and communications industry. During the checkout period, GOES-15 delivered high-resolution images from space, including the first visible and infrared images of Earth taken by its imager instrument, and the first image of the sun taken by its solar X-ray imager instrument.

"NASA is ecstatic that we were able to deliver on our promise to provide NOAA and this Nation with three geosynchronous weather satellites," said Andre Dress, GOES Deputy Project Manager at NASA's Goddard Space Flight Center, Greenbelt, Md. "From the very beginning, we set the bar high and we have attained all our goals. It is something that NASA and its contractors (Boeing Space & Intelligence Systems, Lockheed Martin, ITT and United Launch Alliance) can be very proud of."

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EMPTY space may really be empty. Though quantum theory suggests that a vacuum should be fizzing with particle activity, it turns out that this paradoxical picture of nothingness may not be needed. A calmer view of the vacuum would also help resolve a nagging inconsistency with dark energy, the elusive force thought to be speeding up the expansion of the universe.

A space-time continuum of calm (Image: Ralf Hiemisch/Getty)

Quantum field theory tells us that short-lived pairs of particles and their antiparticles are constantly being created and destroyed in apparently empty space. A branch of the theory, called quantum chromodynamics (QCD) – which explains how gluons and quarks, the particles that make up protons and neutrons, behave – predicts that a vacuum should be awash with an interacting sea or "condensate" of quarks and gluons. This picture helps to explain how particles made of quarks get most of their mass.

This condensate carries energy, so it might be thought to be a candidate for the mysterious source of dark energy, which can be described by a parameter called the cosmological constant. The trouble is that when physicists use QCD to estimate the condensate's energy density, their calculations suggest it would pack a punch that is 10⁴⁵ times the cosmological constant that we measure from observations of the universe's expansion.

Now Stanley Brodsky of the SLAC National Accelerator Laboratory in Menlo Park, California, and colleagues have found a way to get rid of the discrepancy. "People have just been taking it on faith that this quark condensate is present throughout the vacuum," says Brodsky. Instead, his team have assumed that the condensate exists only inside protons, neutrons, pions and all other quark-containing particles, collectively known as hadrons (Physical Review C, DOI: 10.1103/PhysRevC.82.022201).

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A lonely island in the middle of the South Atlantic conceals Charles Darwin's best-kept secret.

In his twenties, Charles Darwin explored the world aboard HMS Beagle.

Two hundred years ago, Ascension Island was a barren volcanic edifice.

Today, its peaks are covered by lush tropical "cloud forest".

What happened in the interim is the amazing story of how the architect of evolution, Kew Gardens and the Royal Navy conspired to build a fully functioning, but totally artificial ecosystem.

By a bizarre twist, this great imperial experiment may hold the key to the future colonisation of Mars.

The tiny tropical island of Ascension is not easy to find. It is incredibly remote, located 1,600km (1,000 miles) from the coast of Africa and 2,250km (1,400 miles) from South America.

Its existence depends entirely on what geologists call the mid-Atlantic ridge. This is a chain of underwater volcanoes formed as the ocean is wrenched apart.

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A NASA astronaut on the Space Shuttle Endeavor brought space back down to Earth. Astronaut Don Pettit took over 85 time-lapsed videos of Earth from his stint on the International Space Station to highlight features of the changing planet.

"There is phenomenology that happens on a timescale that you can't see in real time," he said. "It occurred to me that making time-lapse movies on the space station would bring out things that you normally don't observe."

Pettit also wanted to capture what it feels like to be in space. "You feel like you're on a frontier," he says. "I like to define a frontier as a place where your intuition does not apply. It's a place where the answers are not in the back of the book. As a result, a frontier is a place that's rich in discovery."

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Edward Cheung, long-time principal engineer for the Hubble Space Telescope Development Project was recently dubbed Knight of the Royal Order of the Netherlands Lion. In this picture, the Governor of Aruba, Fredis Refunjol, fastens the royal decoration to Cheung’s jacket. Credit: Edward Cheung

A long-time NASA engineer working on the Hubble Space Telescope  is now a full-fledged knight in the Netherlands due to his work to help keep the renowned 20-year-old space observatory in working order.

Edward Cheung, an engineer who develops electrical systems and solutions for the Hubble Space Telescope, was knighted on June 12 by Queen Beatrix of the Netherlands, in recognition of his accomplishments on Hubble and his work in educating the youth of his native Aruba (an island country belonging to the Kingdom of the Netherlands).

Cheung now lives in Greenbelt, Md., where he works at NASA's Goddard Space Flight Center. He joined the Royal Order of the Netherlands Lion – the highest civilian order in the Dutch kingdom.

The Hubble Space Telescope was launched in 1990, and has been visited by astronauts five times in 20 years for repairs or upgrades to its systems.

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