Tuesday, October 21, 2008
Astronomers have long talked about a "habitable zone" around a star as being a confined and predictable region where temperatures were not to cold, not to hot, so that a planet could retain liquid water and therefore support life as we know it.
The zone may not be so fixed, it turns out. Some extrasolar planets that one might assume are too cold to host life could in fact be made habitable by a squishing effect from their stars, a new study found.
A planet's midsection gets stretched out by its star's gravity so that its shape is slightly more like a cigar than a sphere. Some planets travel non-circular, or elongated paths around their stars. As such a world moves closer to the star, it stretches more, and when it moves farther away, the stretching decreases.
When a planet's orbit is particularly oblong, the stretching changes are so great that its interior warms up in a process called tidal heating.
"It's basically the same effect as when you bend a paper clip, and it gets hot inside," said researcher Brian Jackson of the University of Arizona's Lunar and Planetary Laboratory.
Jackson and colleagues created a computer model to simulate this effect on exoplanets, and found that the process could shift the range and distance of the "habitable zone" around a star in which planets would have the right temperatures needed to harbor life.
"It could be that planets close to the edge of the habitable zone get way too much tidal heating, and they'd be too hot," Jackson told SPACE.com. It also could be that planets just beyond the outer edge, which according to previous models would be too cold, might undergo enough heating that their surfaces would be warm enough for life and water, Jackson said.
Tidal heating could in fact affect many planets in the galaxy, because the oblong orbits that cause the phenomenon are quite common.
"Most of the extrasolar planets we've found so far are in pretty elongated orbits, which is surprising because most of the planets in our solar system have orbits that are roughly circular," Jackson said.
Scientists aren't sure why our solar system is unique in this way, but the difference could significantly affect the hunt for life beyond Earth.
In some cases it would suggest that it's going to be little bit harder, Jackson said, because worlds that looked habitable may experience too much tidal heating. On the other hand, some planets that were thought to be too cold might in fact be warmed up enough for life, and that might improve our odds.
Tidal heating could further boost some planets' habitability by warming them enough to spur volcanism, which in turn drives plate tectonics, the process that recycles rock through a planet's surface layers.
Plate tectonics is a definite boon for life, because stirring up the surface layers helps to regulate the amount of carbon dioxide in the atmosphere, since rock absorbs CO2 from the air. And having the perfect balance of carbon dioxide in the atmosphere helps a planet maintain that "just right" temperature range.
An organism that was discovered in a South African gold mine, nearly 3km beneath the Earth's surface, has scientists "buzzing with excitement" because it offers fascinating evidence that life could exist on other planets, say reports.
A community of the organisms was found by researchers in water extracted from a rock fissure in the Mponeng gold mine on the Witwatersrand near Johannesburg.
The rod-shaped bacterium, named Desulforudis audaxviator, exists in total darkness, with no oxygen and in 60°C heat. But, most importantly, it is the first known species to live in isolation in its own ecosystem, say researchers in a report by the Lawrence Berkley National Laboratory in California, one of a number of institutions involved in the research.
"One question that has arisen when considering the capacity of other planets to support life is whether organisms can exist independently, without access even to the sun," says Dylan Chivian, the bioinformatics lead scientist at the Joint BioEnergy Institute in Berkeley, California, who studied the gene samples found in the fissure water.
"The answer is yes, and here's the proof. It's sort of philosophically exciting to know that everything necessary for life can be packed into a single genome."
This could be the kind of organism that could survive below the surface of Mars, say scientists. The bacterium gets its energy from hydrogen and sulphate produced by the radioactive decay of uranium, say the researchers. And because it lives alone, they believe that it builds its organic molecules by itself out of water, inorganic carbon, and nitrogen from ammonia in the surrounding rocks and fluid.
A team of scientists reportedly made the discovery that there were microbes in the Mponeng fissure two years ago. "We knew from previous work in these mines, using molecular biology techniques, that there seemed to be very simple communities living down there," says Fred Brockman of the biology department of Pacific Northwest National Laboratory, where the DNA was extracted from the filtered cells.
"We expected we'd have a good chance of assembling one entire genome of the most dominant species, or perhaps 70 to 80 percent of several species."
But, to the researchers' surprise, only one organism was present. Even before the analysis was complete it was evident the lone species's genome was remarkable, the researchers say.
It contained everything needed for the organism to survive and reproduce, including the ability to incorporate the elements necessary for life from inorganic sources, move freely, and protect itself from viruses, harsh conditions, and nutrient-poor periods by becoming a spore.
About the only thing D audaxviator can't do is live in oxygen, which suggests it hasn't been exposed to pure oxygen for a very long time - perhaps millions of years - the researchers say. The water the bacterium lives in, they believe, has not seen the light of day for more than 3 million years, which could be a clue to how old the species is.
D audaxviator's name comes from Jules Verne's Journey to the Centre of the Earth, in which a message in Latin deciphered by Professor Lidenbrock, Verne's protagonist, reads in part, "descende, Audax viator, et terrestre centrum attinges". It means "descend, Bold traveller, and attain the centre of the Earth".
FedEx Express, a subsidiary of FedEx Corp, broke ground on its first - and largest - international solar energy facility on Monday. The facility near the Cologne, Germany airport will house over 16,000 square meters of solar panels.
The new solar panel installation is slated for completion by 2010; a 1.4-megawatt (MW) solar power system that will generate 1.3 GWhs of electricity/year. That is equivalent to the annual consumption of 370 homes!
The hub which is located in Cologne, Germany will about double FedEx’s on-site solar energy production.
Back in 2005, FedEx’s Oakland hub was California’s biggest rooftop solar system installation; the panels provide 20% of the facilities electrical needs. In its first three years online it offset more than 1,000 tons of CO2 emissions! FedEx also has solar facilities in Whittier and Fontana, California - together all three facilities offset 2.9 M pounds of C02 emissions every year.
In Geneva, Switzerland, a FedEx station uses a geothermal system to provide heating in the winter and cooling in the summer. Looks like FedEx is trying to clean up its environmental record, starting with energy.Original here
Print collections are known elsewhere but the scale here is impressive
Scientists have identified an amazing collection of dinosaur footprints on the Arizona-Utah border in the US.
There are so many prints - more than 1,000 - that geologists have dubbed the site "a dinosaur dance floor".
Located within the Vermilion Cliffs National Monument, the marks were long thought simply to be potholes gouged out of the rock by years of erosion.
A paper describing the 190-million-year-old footprints is published in the palaeontology journal Palaios.
"Get out there and try stepping in their footsteps, and you feel like you are playing the game 'Dance Dance Revolution' that teenagers dance on," says Professor Marjorie Chan from the University of Utah.
"This kind of reminded me of that - a dinosaur dance floor - because there are so many tracks and a variety of different tracks."
"There must have been more than one kind of dinosaur there," she adds. "It was a place that attracted a crowd, kind of like a dance floor."
The site covers about a third of a hectare and records dinosaur movements around what was probably a watering hole during the Early Jurassic Period, when the US south-west was covered with a field of sand dunes larger than the Sahara Desert.
The prints will eventually erode away
Investigation of the site reveals at least four dinosaur species were present, with the animals ranging from adults to youngsters.
"The different size tracks [2.5-50cm] may tell us that we are seeing mothers walking around with babies," says Winston Seiler, who worked on the project.
As well as footprints, the site also records tail-drag marks - which are up to seven metres in length.
The scientists say the dinosaur prints were locked into sandstone after being covered by shifting dunes.They became exposed through erosion and will eventually disappear through erosion, too.
SOLAR REFRIGERATION: The sun can be used to power refrigerators rather than the electrical compressors common today.
Fishermen in the village of Maruata, which is located on the Mexican Pacific coast 18 degrees north of the equator, have no electricity. But for the past 16 years they have been able to store their fish on ice: Seven ice makers, powered by nothing but the scorching sun, churn out a half ton of ice every day.
There's a global scramble to drive down emissions of carbon dioxide: the electricity to power just refrigerators in the U.S. contributes 102 million tons annually. Solar refrigeration can also be inexpensive and it would give the electric grid much-needed relief. Electricity demand peaks on hot summer days—150 gigawatts more in summer than winter in the U.S. (A gigawatt equals on billion watts.) That's almost 1.5 times the generating capacity of all the coal-fired power plants west of the Mississippi River. Further, solar is plentiful. The solar energy hitting 54 square feet (five square meters) of land each year is the equivalent of all the electricity used by one American household, according to data from the National Renewable Energy Laboratory and Energy Information Administration, both part of the U.S. Department of Energy.
Making cold out of hot is easier than one might think. A group of students last year at San Jose State University built a solar-powered ice maker with $100 worth of plumbing and a four-by-eight-foot (1.2-by-2.4-meter) sheet of reflecting steel. No moving parts, no electricity but give it a couple hours of sunshine and it can make a large bag of ice.
The key is the energy exchanged when liquids turn to vapor and vice versa—the process that cools you when you sweat. By far the most common approach, the one used by the refrigerator in your house, uses an electric motor to compress a refrigerant—say, Freon—turning it into liquid. When the pressure created by the compressor is released, the liquid evaporates, absorbing heat and lowering the temperature.
Absorptive chillers like solar refrigerators use a heat source rather than a compressor to change the refrigerant from vapor to liquid. The two most common combinations are water mixed with either lithium bromide or ammonia. In each case, the refrigerating gas is absorbed until heat is applied, which raises the temperature and pressure. At higher pressure, the refrigerant condenses into liquid. Turning off the heat lowers the pressure, causing that liquid to evaporate back into a gas, thereby creating the cooling effect.
As with most technologies, the efficiency of such absorptive refrigeration depends on the degree of engineering (and expense) brought to bear. Single-effect devices have a coefficient of performance of 0.6 to 0.7—that is, they create 60 to 70 Btus (British thermal units) of cooling for every 100 Btus of input heat. That low level of efficiency can be achieved with something as crude as some pipe, a bucket of water, some calcium chloride (as absorbant), ammonia (as refrigerant), and a sheet of shiny metal (the solar collector).
If what you want to do is heat or cool, using solar energy this way is probably more efficient—and certainly cheaper—than converting it first into electricity. "That approach ought to be comparable to photovoltaics, or a little better," said Tom Mancini, program manager for solar power at the Sandia National Laboratories in Albuquerque, N.M.
It would take a fair-size collector—86 square feet (eight square meters), assuming 40 percent panel efficiency—just to deliver the cooling of a small (6,000 Btu per hour or half-ton) window air conditioner. And central air-conditioning units are often 30,000 Btu or more; few homeowners could spare the space for that.
But concerns over collector area depend on location. In the developing world, solar powered ice makers allow locals to store the village's food or medicine without any electricity. For example, in May charitable organization, Heifer International, set up three solar ice makers in remote areas of Kenya. Each will be able to keep 26.5 gallons (100 liters) of milk chilled. More than 500 members of two dairy cooperatives are expected to benefit directly.
Most of the interest in such solar refrigeration in Western countries comes from the commercial, not residential, sectors. Cost is one reason—absorption chiller systems typically cost $7,000 to $10,000 per ton of cooling; one-ton window air conditioners from big box retailers start around $250—but companies can save on electric bill as well as enjoy a more benign environmental image.
Building occupancy patterns is another; most Americans are not at home during the day. "We don't have as much daytime occupancy in residential buildings as in commercial," says Pat Hale, sales manager for Yazaki Energy Systems, in Plano, Tex. Other problems include the expense of retrofitting homes to add plumbing to the attic. And the high temperatures associated with concentrating solar collectors raise liability concerns.
But some entrepreneurs think a residential market nevertheless is emerging. Walter Ross is CEO of Austin Solar AC, a start-up that is testing 36,000 and 60,000 Btu solar-fired chillers. The units provide cooling in summer and heating during winter by just using the sun's heat directly. "We're getting a lot of interest from people who have been using propane for heating," he said. "The biggest issue we run into with these is siting: Most neighborhood associations won't allow these things on your roof."Original here
Science reporter, BBC News
It's a big white building on Mission Boulevard. You can't miss it; the Art Deco style is really striking. The grass is trimmed and it all looks perfectly inviting, except this is a lock-out.
The first Hayward City Hall in California has long been off-limits to occupants because its foundations sit right atop an earthquake fault and it's gradually splitting in two.
"Look up at the stairwell," says geologist Russ Graymer, as we peer through a window.
"There are huge cracks, several centimetres broad and many metres long - basically showing the evidence that this building is being torn in half."
The Hayward Fault is one of a network of cracks in the Earth's surface running through the San Francisco Bay Area. The San Andreas Fault is probably the best known, but right now the Hayward is the one everyone's talking about.
The records show that the past five large earthquakes on this fault have occurred on average about 140 years apart, and the last was - you've guessed it - 140 years ago. Tuesday is the anniversary.
At 0755 on the morning of 21 October, 1868, the Hayward broke with a Magnitude 6.8 quake.
The San Francisco Bay Area is crossed by a number of faults
The ground lurched some two metres and the cities of Oakland to the north and San Francisco to the west were shattered.
In the context of post-1850 quake history in the Bay Area, the tremor is rivalled in size only by the 1906 "Big One" in San Francisco (7.8), and the 6.9 event of Loma Prieta in 1989.
"The difference with Loma Prieta was that the maximum shaking was 50 miles to the south in the mountains," says Dr Graymer from the US Geological Survey (USGS).
"The squirrels and the redwoods took the brunt of the shaking in 1989. In contrast, this is an urban area and the folks who live here will take the brunt of it if the Hayward decides to go."
Some have now dubbed the Hayward "the most dangerous urban fault in America".
"It's the probability that the Hayward will generate a large earthquake in the next 30 years combined with the fact that it runs right through an urban area. These two facts taken together make it the most dangerous right now," says Dr Graymer.
The comparison is often made with Kobe, Japan, which suffered a Magnitude 6.9 earthquake in 1995.
Kobe, like Hayward and Oakland, sits on the east side of a bay - Osaka Bay - and the Nojima Fault running through Kobe mirrors the Hayward in type (strike-slip) and in length.
More than 5,000 people died in the 1995 Kobe event.
When scientists assessed the probabilities of a big quake occurring in the San Francisco Bay Area in the coming decades, they pointed to the Hayward and its northern extension, the Rodgers Creek Fault, as being the most likely locations for the tremor.
"There's a 63% chance of a Magnitude 6.7 or greater in the next 30 years across the entire Bay Area," says USGS seismologist Tom Brocher.
"That's roughly two out of three odds, and about half of that falls on the Hayward/Rodgers Creek Fault. That's why we're focussing on the Hayward and why we're so concerned about it."
The concern has been heightened in recent years by research which indicates that the Hayward and the parallel Calaveras Fault might actually be connected at depth, and, as such, could produce, in effect, a single, even more powerful event.
Between two and four million people would experience shaking strong enough to cause damage if the Hayward lets go in a similar fashion to 1868. Economic losses could exceed $200bn, says the USGS.
The apparent risks have authorities across the Bay racing hard to shore up local infrastructure. In excess of $30bn has been spent since Loma Prieta.
Roads, rail, bridges, buildings, hospitals, water and other utility systems are all being "retro-fitted", which involves suspect engineering being swapped out for structures thought more likely to ride out immense shaking.
"The local power company, Pacific Gas and Electric, has been replacing old cast-iron gas pipes with new flexible piping. A lot of work is being done but we have more to do," Dr Brocher tells BBC News.
Hayward is now on its third City Hall. While the first is not expected to survive a big quake, the latest incarnation will rock back and forth on a "pendulum" system fitted to its foundations. This should see it come through a Magnitude 7 event without major damage.