Space.com : Missing Matter Caught in Tangled Cosmic Webs

By SPACE.com Staff posted: 10 December 2007 06:33 am ET

Cosmologists are always complaining about their inability to find the dark matter in the universe, invisible stuff that's supposedly more prevalent than regular matter. They don't even know what it is, so of course they can't see it.

Meantime, a whole bunch of normal matter is missing, too.

A new computer model at least suggests where some of that missing normal matter might be.

Regular vs. dark

Regular matter—the "visible" atoms and molecules of dirt, people, stars, gas and dust—makes up only about 5 percent of the universe. Scientists call it baryonic matter, or baryons.

Dark matter is the term used to describe the invisible stuff that's holding galaxies together. Some 25 percent of the universe is dark matter, and it's all missing in action. The rest is even more mysterious, a sort of anti-gravity force called dark energy.

While scientists have no clue when they'll actually find dark matter, they'd really like to square the cosmic ledger a bit by tallying up all the regular matter that theory holds should exist. Only about 40 percent of it is in the books yet.

The rest, according to the new simulation, is gas that's caught in a tangled web of cosmic filaments that are hundreds of millions of light-years long. The filaments connect clusters of galaxies, and the gas within the filaments is hidden by huge gas clouds.

This conclusion is based on a new computer model that took nearly 10 years to make. It models a region of space equal to 2.5 percent of the visible universe and showed how matter collapsed due to gravity and became dense enough to form the cosmic filaments, galaxy structures and the clouds that hide the filaments.

"We see this as a real breakthrough in terms of technology and in scientific advancement," said Jack Burns of the University of Colorado at Boulder. "We believe this effort brings us a significant step closer to understanding the fundamental constituents of the universe."

The research will be detailed in the Dec. 10 issue of the Astrophysical Journal.

Let's look

Burns predicts that future telescopes will be able to spot the filaments.

The 10-meter South Pole Telescope in Antarctica and the 25-meter Cornell-Caltech Atacama Telescope, or CCAT, being built in Chile's Atacama Desert, will aim to do so, Burns said.

The CCAT telescope will observe radiation in sub-millimeter wavelengths, which are longer than infrared waves but shorter than radio waves. It will probe galaxies in their infancy shortly after the universe was born.

"We think that as we begin to see these filaments and understand their nature, we will learn more about the missing baryons in the universe," Burns said.

HubbleSite : Hubble Finds that Extrasolar Planet Has a Hazy Sunset

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A team of astronomers, led by Frederic Pont from the Geneva University Observatory in Switzerland, has detected for the first time strong evidence of hazes in the atmosphere of a planet orbiting a distant star. The new Hubble Space Telescope observations were made as the extrasolar planet, dubbed HD 189733b, passed in front of its parent star in an eclipse. As the light from the star briefly passes through the exoplanet's atmosphere, the gases in the atmosphere stamp their unique spectral fingerprints on the starlight. Where the scientists had expected to see the fingerprints of sodium and potassium, there were none; implying that high-level hazes (with an altitude of nearly 2,000 miles) are responsible for blocking the light from these elements.

Universe Today : Water or Land: The Orion Landing Choice

Written by Nancy Atkinson

Work is progressing on designing the new Orion Crew Exploration Vehicle (CEV), the next generation of NASA spacecraft that will take humans to the International Space Station, back to the Moon, and hopefully on to Mars. But one major question about the spacecraft has yet to be answered. On returning to Earth, will the CEV splash down in water, or land on terra firma?

NASA officials discussed various aspects of development that is currently underway for the Constellation program at a media briefing on December 10. The mobile launch platform for the Ares rocket is being built, landing parachutes have been tested and the first capsule structure of the new CEV will be constructed starting in early 2008. Design requirements for the booster rockets have been completed and just ahead are final design definitions for operational capabilities such as ground procedures at Kennedy Space Center, mission control in Houston and other areas such as spacesuit design.

Additionally research on the International Space Station has begun to help prepare for long duration spaceflights such as a measurements of microbe growth, a study of the formation of kidney stones, and a nutritional study to help understand what is ‘normal’ for the human body in space.

But questions from the media focused mainly on the yet unmade decision of whether the CEV will land in the water or on land.

NASA originally explored multiple options for landing in both water and land. After initial studies, the first assessment by NASA and the contractor for the CEV, Lockheed Martin, was that landing on land was preferred in terms of total life cycle costs for the vehicles. But now a splashdown in water seems to be favored.

“There are a couple of aspects that pop out at us,” said Jeff Hanley, Manager for the Constellation Program. “One is the safety and the risks involved in landing. Looking at the landing itself, the event of actually touching down, water comes out to be preferable as less risk.” Another aspect is the performance of the Orion vehicle as it is sent to the moon. “In looking at what it takes to get a pound of spacecraft to low lunar orbit in terms of the cost, every pound that you send toward the moon is precious. From an efficiency and performance point of view, carrying 1500 lbs of landing bags to the moon and back when we have a perfectly viable mode of landing in the water near a US coastal site didn’t seem like a good trade in performance. We’ve tended toward updating our point of departure concept to now be a nominal US coastal water landing.”

The Constellation program has always considered that for the first few missions, the spacecraft would land in water until the guidance system had been tested thoroughly and proven in actual landings.

But NASA is continuing to look at landing on land as a possibility for future flights. “We want to be able to land on land in a contingency and have the crew be able to get out and walk away….There’s limitation of what you can do on land but by the time we get done really looking at what the minimal capability of landing on land and having the crew walk away, we’ll see what the design looks like, and if the design is robust enough we could return to having nominal land landings.”

One challenge for the Constellation program has been getting the CEV light enough for the Ares rockets to be able to launch it, and therefore eliminating the 1500 lb airbags for landing has its appeal.

“The predominant design philosophy for Orion and Ares 1 has been that we are designing for lunar missions,” continued Hanley. “We will service the International Space Station within that set of capabilities. From that perspective, designing a lot of mass into the spacecraft just to enable land landings has not traded out to be an effective use of our performance. That’s the major consideration in play. Right behind that are life cycle costs.”

Making the decision of land vs. water is the goal for 2008 for the Constellation program. “We’ve studied and have cost estimates for water landings against the infrastructure costs of having multiple landing sites on land and they are comparable,” said Hanley. Right now, NASA is looking at a single target landing zone off the coast of California with one or two recovery vessels.

But they are keeping their options open for a land landing. “If the Orion team is able to come in at the preliminary design review later this next year with a concept for be able to land on land that is fairly robust but not cost a lot of mass to have to hurl to the moon and back, then it becomes an operational decision,” said Hanley.

There’s been much debate about what type of landing would be best. “There’s been a lot of assumptions made that landing on land is going to be better, but there are lot of people in the technical community that do not buy into that,” said Hanley. “There’s been a lot of debate surrounding whether or not land landing truly is better from a life cycle cost perspective and there isn’t a lot of quantitative data to really pull from.”

Hanley feels there are assumptions being made but not a lot of substantive date to clarify what the right answer is. So the next steps are to get the spacecraft to a detailed preliminary design and really interrogate the water vs. land issue. That includes further developing the operational concepts , such as how long does the capsule stay in the water, and what loads does the spacecraft see from landing on water and land. Those are all questions that need to be answered in order to make a final decision on the type of landing that will be used. Stay tuned, as 2008 should be a year of decision for many details about Constellation and the CEV.

Original News Source: NASA News Audio

ESA : Mars Express watches a dust storm engulf Mars

A dust storm on Mars

11 December 2007
This summer, Mars suffered a titanic dust storm that engulfed the entire planet. The dust storm contributed to a temporary warming effect around Mars, which raised the temperature of the atmosphere by around 20-30°C.

However, the surface temperature of the planet itself dropped.

Imagine a dust cloud on Earth that started in the Sahara desert and grew to encompass our whole planet. Such a catastrophe would block sunlight from reaching the surface and plunge us into twilight for months. It happens on Mars on a regular basis. Planetary scientists watched the latest dust storm take shape at the end of June. By mid July it had covered the Red Planet, dispersing gradually over the next few months.

Whereas some of the spacecraft’s instruments, such as the Visible and Infrared Mineralogical Mapping Spectrometer (known as OMEGA) and the High Resolution Stereo Camera (HRSC), which both rely on a clear view of the surface have to wait until the dust subsides, the Planetary Fourier Spectrometer (PFS) instrument was able to work throughout the event and has gained new insights into the effects of the dust storms on the atmosphere of Mars.

	Temperatures in the Martian atmosphere

“Once the atmosphere becomes full of dust, only 20% of the solar radiation can reach the surface of the planet,” says Vittorio Formisano, Istituto Fisica Spazio Interplanetario, Rome, Italy, and the principal investigator of the PFS instrument.

The dust absorbs the solar radiation which directly heats the atmosphere, creating a strong warming effect. This year, PFS saw the temperature of the Martian atmosphere rise by between 20-30°C. As the atmosphere heats up, the atmosphere inflates around the planet. Formisano estimates that this increase was probably by about 20 km and hopes that a fuller analysis of the PFS data will give a precise figure.

PFS determines the composition of the Martian atmosphere from both the wavelengths of sunlight absorbed by the various molecules in the atmosphere and from the infrared radiation they absorb and emit. It collects infrared radiation in the range of 1.2–45 micrometres (microns).

Mars - thermal radiation spectra

There is still a lot to understand about Martian dust storms. They begin during summer in Mars’s southern hemisphere. Southern summer is hotter than the northern summer because Mars’s orbit is elliptical and draws the planet closer to the Sun during southern summer than during northern summer.

The Hellas Basin obviously plays a very important role as the dust storms usually begin in its vicinity. Hellas is a vast impact structure, 9 km deep and about 2300 km across. It is so large that it disrupts the circulation of the atmosphere. “How the dust propagates into the whole atmosphere is still a complete mystery,” says Formisano.

One puzzle is that the dust storms reach the poles of Mars. Polar regions on planets are usually distinct atmospheric pockets that prevent warm air from the equatorial regions from entering. On Mars, however, the dust reaches everywhere and smaller particles remain suspended for a long time. “The micron sized particles fall back to the surface in a few months, the sub-micron sized particle can remain up there for years,” says Formisano.

	Mars Express

“Another mystery is why such large dust storms happen some years and not others,” says Francois Forget, Université Paris, France, and Mars Express Interdisciplinary Scientist.

Interestingly, whereas the atmosphere of the planet heats up, the surface of the planet cools down because it receives much less solar heat. This poses an additional problem for Martian landers, which rely on solar arrays for power. They have to hibernate during the storms. It also presents a clear challenge to potential visiting astronauts.

“We have beautiful data from PFS of this dust storm and we now intend to analyse this fully,” says Formisano.

ESA : Envisat captures South Korea’s crude oil leak

11 December 2007
Crude oil from the wrecked 146 000-ton tanker, Hebei Spirit, is seen polluting the sea off South Korea in this Envisat image.

More than 10 000 tons of oil from the tanker is reported to have leaked into the sea since colliding with another vessel on Friday 7 December. The South Korean government has declared the coastal regions, located southwest of Seoul, where oil is washing onto their beaches disaster areas.

This image was acquired today at 01:40 UTC by the Advanced Synthetic Aperture Radar (ASAR) aboard ESA’s Envisat, while operating in its wide-swath mode covering an area approximately 400 km by 400 km.

The presence of oil on the sea surface damps down smaller wind generated waves. It is these waves that reflect the radar signal back in the direction of the source. When they are damped, the reflected power measured by the radar is reduced, causing oil slicks to be seen as dark areas on an otherwise brighter sea.

ASAR, like other space-based radar systems, essentially provide its own source of illumination and operates at longer wavelengths than optical sensors. This enables it to observe the Earth’s surface at night and through thick cloud cover.