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Shuttle to Be Launched in July Without Tank Fix

NASA has decided to fly the space shuttle Discovery in July without making all potential modifications to its external fuel tank that might reduce damaging foam debris, a move that concerns some agency engineers, officials said today.

Engineers have removed two large sections of insulating foam from the tank and are still evaluating the effects of that action, they said. Work will continue on redesigning or removing all or some of 34 smaller, potentially hazardous foam wedges in the future, but they will fly "as is" on the upcoming flight, they said.

Reducing falling fuel tank debris has been a priority for NASA since the loss of the shuttle Columbia on Feb. 1, 2003. Foam insulation falling from the tank during the launching damaged Columbia’s heat shield, causing the destruction of the craft and the deaths of seven astronauts as the ship attempted to return through the atmosphere from a science mission.

When Discovery flew last July on the first mission since Columbia, a greatly reduced but hazardous amount of foam still fell from its redesigned tank during the launching. Afterward, engineers removed more than 37 pounds of foam that formed two air ramps, or deflectors, that protected pressurized fuel lines and a tray guiding cables down the side of the tank, places from which the biggest pieces of foam fell in the last mission.

NASA wants to fly the shuttle three times before the end of the year to get back on schedule for building the International Space Station before the shuttle fleet’s mandatory retirement in 2010. Officials hope to then fly four per year to finish the station with 16 flights, plus send a shuttle to repair the Hubble Space Telescope, before the deadline.

posted by: kyawoo at 04:10 | link | comments |
space shuttle

Early gravitational pull tilted the big planets

WASHINGTON - An early gravitational dance made the giant planets tilt the way they do — which is different from the way Earth and the other smaller planets tilt, an astronomer reported on Wednesday.

The shift probably happened billions of years ago when the bigger planets in our solar system were closer together than they are now, and the gravity of each one exerted a pull on the others, said Adrian Brunini of the Facultad de Ciencias Astronomicas y Geofisicas in Buenos Aires.

This "neutral gravitational interaction" caused Jupiter, Saturn, Uranus and Neptune to have tilted axes that were determined as they moved through the solar system to take their current positions far from the sun, Brunini said in a telephone interview.

This is a departure from an earlier theory that holds that the massive planets' tilts — or obliquities, as astronomers call them — were caused by collisions with Earth-sized space rocks during the early period of the solar system.

"This model has some problems that were not clear how to solve," Brunini said. "For example, we believe that such a big object never existed in the outer solar system."

In research published in the current edition of the journal Nature, Brunini used numerical models to show that the outer planets' obliquities could have been created by gravitational interactions.

All the planets in our solar system have tilted axes but the bigger ones have axes that lean at a constant angle, while the smaller ones like Earth have obliquities that can change.

Despite the potential for change, Earth's axis has been leaning about 23 degrees for millions of years and is almost completely stabilized by the moon's gravitational pull, Brunini said, but Mars' axis might change over tens of millions of years.

For humans, the reliability of Earth's tilted axis is important since it is responsible for the change of seasons. At the point in its annual orbit where Earth's northern hemisphere leans away from the sun, it's winter; when the southern hemisphere tilts away, it's winter there.

While the more massive planets have stable obliquities, they range in size from a nearly perpendicular 3 degrees for Jupiter to about 97 degrees for Uranus. Brunini said.

Source msnbc

posted by: kyawoo at 14:01 | link | comments |
astronomy

Breaking the myths of meteorites

The term meteor comes from the Greek meteoron, meaning phenomenon in the sky. It is used to describe the streak of light produced as matter in the solar system falls into Earth’s atmosphere creating temporary incandescence resulting from atmospheric friction. This typically occurs at heights of 80 to 110 kilometers (50 to 68 miles) above Earth’s surface. The term is also used loosely with the word meteroid referring to the particle itself without relation to the phenomena it produces when entering the Earth’s atmosphere. A meteoroid is matter revolving around the sun or any object in interplanetary space that is too small to be called an asteroid or a comet. Even smaller particles are called micrometeoroids or cosmic dust grains, which includes any interstellar material that should happen to enter our solar system. A meteorite is a meteoroid that reaches the surface of the Earth without being completely vaporized.

Meteorites are an explosive phenomenon credited with such things as ending the age of dinosaurs, altering our planet, stimulating the beginning of life and daily threatening our very existence. Many of our myths about meteors come from a complete lack of understanding and sensationalized movies like Armageddon, Deep Impact, and Meteor.

The Myths:

1. Meteorites can be highly radioactive.

Actually meteorites are no more likely to be radioactive than ordinary terrestrial rocks.

2. Meteorites sometimes contain rare elements and exotic materials like Kryptonite.

Scientists report that no meteorite yet has been found to contain any element not occurring naturally on Earth.

3. Meteorites are rare and account for a very small amount of material reaching the earth.

Actually the Earth accumulates approximately 100 tons of extraterrestrial material every year. The current rate of fall for meteorites greater than 100g is approximately 27 per year. Meteorites as large as a basketball strike the Earth approximately once a month with nearly 75% of the impacts landing in water.

4. There are just a few known impact sites in the world.

The latest scientific count has 174 documented craters (impact structures) and the list is growing as detection technology and awareness continues to spread quickly worldwide. Other research groups have documented 543 suspected Earth impact craters.

This map documents the known and suspected Earth impacts. What is particularly amazing is that if nearly 75% of all meteorites land in the water the count would be many times higher than what is primarily evidenced by land impacts.

5. No one is looking for a Doomsday asteroid.

A large and growing network of scientists are tracking an astoundingly large list of dangerous asteroids. NASA maintains a current list of potentially hazardous asteroids. Consulting the list reveals hundreds of near earth asteroids being closely monitored by scientists the world over.

6. The odds of a significantly sized asteroid striking the Earth are too small to calculate.

Actually scientists place the odds of a significant, life altering, meteorite event at 1 in 40 by 2029. More specifically scientists expect the recently detected asteroid Apophis MN4 2004 to have a surprisingly high impact probability on April 13, 2029 with a near Earth pass as close as 3,380km.

Other close calls include asteroid 1989 FC with a diameter about 0.3 miles and a kinetic energy of over 1,000 one-megaton hydrogen bombs, which on March 23, 1989 passed within 430,000 miles of the Earth. This asteroid was not discovered until it had already passed its point of closest approach, and only after calculating backwards its orbital path. Since then several other celestial bodies of similar sizes have been measured as coming within 62,000 miles of Earth.

7. Meteorites are meaningless except as threats to our existence.

Actually, besides the known effect they have had on life and dinosaurs, meteorites have revealed or contributed through impact a tremendous volume of natural resources to our planet. Extraterrestrial objects colliding with Earth can cause dramatic changes to the planet and affect the course of evolution.

An impact in the region around Popigai, Siberia created a 60-mile-diameter crater and industrial-grade diamonds. When the diamonds were discovered in modern times, the area was closed to outsiders in the event the diamonds might prove valuable some day.

Another impact site called the Alamo Breccia, a fragmented carbonate rock now found in the mountains about 100 miles north of Las Vegas, Nev., is composed of pieces of lagoon sediments and fossils, typical of an ancient shallow ocean. The Breccia contains shocked quartz from the impact, carbonate spherules from the vapor cloud that was created, and iridium from the projectile itself.

The historical impacts to the terrain have revealed or contributed to mines, oil reserves, natural springs, silica, iron in places they would not ordinarily be revealed. Much more is still being learned about the wide variety of impact sites and the resulting wide range of mineral resources not ordinarily found in these locations.

Another such example is the Carswell crater of Saskatchewan which benefited from a meteor impact in the Cluff Lake area, where the impact created an uplift of the Athabascan sandstone revealing a number of large unconformity-type uranium deposits.

The above sea level portion of the rim of a huge meteorite impact crater known as the Chicxulub impact crater, located in Mexico has been studied amongst others by Glamis Gold.

The Vredefort crater of South Africa well-known for its gold-uranium deposits is intensively mined by different companies.

Lately, Great Australian Resources started investigating the South African Morokweng impact crater, where drilling intercepted high-grade nickel sulphide mineralization.

posted by: kyawoo at 21:46 | link | comments (1) |
meteorites

Early days on Mars

Mineral maps based on data from Europe’s Mars Express probe are helping scientists piece together a detailed picture of the Red Planet’s history.

Life on Mars was most likely during the planet’s infancy, the data suggest.

Ancient clays bearing telltale signs of standing water indicate the most likely time for life to have developed on Mars was about four billion years ago, before a cataclysmic global change left the planet cold, dry and plagued with acid water, researchers said.

The first era began with the planet’s formation about 4.6 billion years ago and lasted for about 600 million years. Rock from this period lies exposed on the planet’s surface due to meteorite strikes, erosion and underground shifts that formed cracks or faults in the planet’s crust.

This ancient Mars terrain contains clay minerals, such as chamosite and nontronite, which form when water is abundant, temperatures are moderate and acidity is low, conditions that may have been suitable for life.

The planet’s golden years did not last long. Between four billion and 3.5 billion years ago, Mars underwent a dramatic change. The shift may have been triggered by massive volcanic eruptions that spewed sulfur into the atmosphere, which then rained down on the planet’s surface.

Researchers found that minerals formed during this period, such as gypsum and grey hematite, are marked by sulfates, which indicate a dry and acidic environment, one that is not believed to be suitable for life as we know it to form.

The changes stripped away most of Mars’ atmosphere, leaving the world vulnerable to radioactive assaults from the sun, as well as freezing temperatures.

Between 3.2 billion and 3.5 billion years ago, the planet transitioned to its third epoch, one that exists now. Minerals dating to this time were not formed with or altered by liquid water. They are dominated by ferric oxides and other iron-rich minerals and they cover most of the planet.

Scientists plan to refine their mineral maps of Mars with a more powerful instrument aboard the newly arrived Mars Reconnaissance Orbiter. The spacecraft is maneuvering into an orbit suitable for science operations and is scheduled to begin surveys this fall.

posted by: kyawoo at 22:41 | link | comments |
mars

ASteroids and Comets

Comets have been known, and often feared, since ancient times. Their spectacular appearance in the night sky, with wide bright tails, has inspired awe and even been considered an omen.

Comets, asteroids and other cosmic debris have also had a fundamental impact on the development of planet Earth and the life on it, by bombarding it constantly at first, and periodically since. Future impacts pose a significant threat to human civilisation.

Comets are incredibly numerous - astronomers predict as many as one trillion could exist in the outer reaches of our solar system. Bright comets, however, appear in our skies just once a decade on average. The brightest recent ones were comets Hale-Bopp in 1996 and Hyakutake in 1997. Perhaps the most interesting recent comet was Shoemaker-Levy 9. This broke apart into dozens of pieces which then crashed into Jupiter in 1994.

The most famous comet of all, Halley’s Comet, was the first one recognised to reappear in the sky at regular intervals. Sir Edmond Halley studied records of past appearances and suggested that one comet followed a similar track through the sky roughly every 76 years, appearing in 1531, 1607, and 1682. He then predicted that it should pass by again in 1759. Though Halley did not live to see the reappearance, the successful prediction proved these bodies orbited the Sun, and were not atmospheric phenomena.

Comets and asteroids are now understood to be leftover debris from the formation of the solar system. Astronomers currently think the solar system’s planets and minor bodies - including asteroids, comets and moons - all formed from the same cloud of dust and gas that initially condensed to form the Sun.

As the Sun grew, its gravitational field condensed the remaining matter into a large, swirling, flattened disc. Particles of dust collided to form bigger particles, and soon, until they built up into large chunks of rock and ice called planetesimals.

The small bodies that formed far from the Sun were rich in ice and other volatile materials, and billions of them orbit our star in a distant halo called the Oort Cloud. This is the source of "long-period" comets, those with orbits longer than 200 years.

In the inner solar system, many of these icy planetesimals coalesced to form the giant planets, while others were ejected out into the Kuiper Belt, beyond the orbit of Pluto but closer than the Oort Cloud. Pluto has been considered the ninth planet but some a stronomers believe it should really be considered a Kuiper Belt Object. Objects whose orbits are disturbed from the Kuiper Belt form the short-period comets.

The leftover planetesimals that remained within the inner solar system were largely contained in a region between the orbits of Mars and Jupiter, known as the asteroid belt.

Though the distinction can be fuzzy, asteroids are smaller than comets, are made up of less ice and volatile compounds, and have more regular orbits. Unlike comets, asteroids can usually only be observed with telescopes, so the first one, Ceres, was not discovered until 1801, by Italian astronomer Giovanni Piazza. It orbits in the asteroid belt and remains the largest known asteroid, at 930 kilometres (580 miles) across, about the size of Texas.

Other similar objects were found in rapid succession - Pallas in 1802, Juno in 1804 and Vesta in 1807 - leading to the realisation that there was a whole family of objects forming the asteroid belt.

It was not until 1979, however, that scientists began to realise that comets and asteroids can catastrophically impact the Earth.

The theory was initially proposed by physicist Luis Alvarez and others. It was based on evidence of a massive impact at the time of one of Earth’s greatest mass extinctions of life, when the last dinosaurs became extinct. The 65-million-year-old evidence included anomalous amounts of the element iridium - common in meteorites - in sediments deposited at the Cretaceous/Tertiary boundary.

Since then, astronomers have become increasingly aware of the risk of future impacts, and major efforts are underway to discover and calculate the orbits for all asteroids larger than 1 km wide. A scale for comparing the potential risks of newly-found asteroids, the Torino scale, was proposed in 1999.

Since then, a number of asteroids have presented a future risk of impact, but in most cases those were quickly ruled out by further observations which refined the calculation of their orbits. The main exceptions so far have been 1950 DA, which has a possible collision course with Earth in the year 2880, and 2004 MN4, now renamed Apophis, which has a slight possibility of impact in 2036. An earlier possible impact path for Apophis, in 2029, has been ruled out, but will be the closest known miss ever predicted for a large asteroid, and will be visible to the naked eye from some parts of the Earth.

While no large impacts have been recorded in historical times, a mysterious blast in the skies over the Tunguska region of Siberia in 1908 has now been identified as a comet that exploded at high altitude as it entered Earth’s atmosphere.

Rather than only waiting for comets and asteroids to arrive on Earth, astronomers have also been sending probes into space to chase down the objects. The first close-up views of a comet’s nucleus were obtained in 1986 by ESA’s Giotto mission, which passed within 20,000 km of the nucleus of Halley’s Comet. Flying through its tail of dust and gas - the coma - it obtained good images of the irregular, potato-shaped nucleus. The USSR’s twin spacecraft Vega 1 and 2 also made close flybys of Halley’s nucleus in 1986.

The next close encounter came in 2001, when NASA’s Deep Space 1 spacecraft flew by comet Borrelly, coming within 2200 km of the nucleus.

Then, on 2 January 2004, NASA’s Stardust mission flew by Comet Wild 2. It survived and obtained high-resolution images that showed large, deep steep-sided circular depressions, which were initially interpreted as craters. Later analysis showed they are more likely collapsed vents caused by jets of gas bursting out from deeper layers of ice. Stardust returned to Earth in January 2006 with precious samples comet dust.

The most spectacular comet encounter came on 4 July 2005, when NASA’s Deep Impact craft deliberately struck Comet Tempel 1, creating a controlled impact that was studied by cameras and spectrometers on a separate section of the spacecraft, and also by hundreds of telescopes on Earth and in orbit.

The next cometary encounter will be the European Space Agency’s Rosetta mission, which will go into orbit around comet Churyumov-Gerasimenko in 2014.

Asteroids were first observed close-up by the Galileo probe on its way to Jupiter, which passed Gaspra in 1991 and Ida in 1993, discovering its tiny moon Dactyl. Then came the first dedicated asteroid mission, NEAR Shoemaker, which visited Mathilde in 1998 and then went into orbit around Eros in 2001 and eventually crash-landed on it.

The Japanese Hayabusa probe visited the asteroid Itokawa in 2005, hoping to scoop up some samples to be returned to Earth, but the sampling probe is thought to have failed in this goal and will probably return to Earth empty in 10 years.

Most attention today is focused on the Near-Earth Asteroids (NEAs), which are the ones that may someday collide with Earth. As an attempt to prove methods that might someday be used to deflect an asteroid from a collision course, a private group called the B612 Foundation hopes to change a non-threatening asteroid’s course slightly, using rocket motors or perhaps the gravitational pull of a spacecraft close to it. Giant mirrors and "cosmic airbags" have even been suggested.

Perhaps the most ambitious asteroid mission yet, NASA’s Dawn, was supposed to be launched in 2006, but has now been delayed for at least a year.

(Source: New Scientists)

posted by: kyawoo at 22:24 | link | comments |
asteroids, comets

Outermost ring of Uranus is blue

The recently discovered outermost ring of gas giant Uranus is a bright blue, scientists said Thursday. The rare blue hue is probably created by a small moon called Mab that orbits just inside the ring The ring and the moon Mab were only discovered in 2005 by the Hubble Space Telescope.

Saturn is the only other planet with an identified blue outer ring in the solar system. All other rings — such as those around Jupiter, Saturn, Uranus and Neptune — sport a reddish color because they are composed of larger particles that reflect red light. The particles themselves may also be reddish, possibly from iron.

The color of Saturn’s blue ring has been credited to the tiny particles spewed into space by Enceladus as it orbits around the planet. But the same probably isn’t true for Uranus, scientists say. Uranus’ moon, Mab, is a small, dead, rocky ball only about 15 miles (24 kilometers) across — one-twentieth the diameter of Enceladus.

The scientists, however, suspect that both of these rings are subject to forces acting on dust in the rings, which allow the tiny particles to survive while the larger ones are captured by their moons.

The team’s explanation is that the outer ring is made of very fine water ice particles, mostly less than a tenth of a micrometre across. They are too small to scatter long-wavelength infrared light, but visible wavelengths can bounce off the particles - especially at the shorter blue end of the spectrum.

The view of Uranus will soon be clearer because, as seen from the Earth, the rings are changing their angle. In 2007 the ring will be edge on, and 100 times brighter. Then it should be possible to obtain a better image and confirm the curious colour of Uranus’ outermost ring.

posted by: kyawoo at 22:37 | link | comments |
uranis

Comet ejected tons of water

The Nasa Deep Impact spacecraft that slammed into Comet Tempel 1 last year kicked out at least 250,000 tonnes of water; observed on the Swift telescope.

The orbiting Swift’s "day job" is to hunt down the colossal bursts of gamma-ray radiation that flash randomly across the cosmos. However, on 4 July last year, it was among a fleet of space and ground-based telescopes asked to watch what happened when Nasa’s Deep Impact probe released a 370kg projectile into the path of the 14km-wide Comet Tempel 1.

But whilst the other observatories made relatively quick studies and then turned away, Swift continued to look at the impacted "ice mountain" on and off for more than 60 days. Its patience paid off.

Swift’s X-ray Telescope (XRT) saw the comet continue to release water for some 13 days after the initial event, with a peak five days on from the collision. X-rays provide a direct measurement of the colossal amount of water thrown out as a result of the impact - the Earth-equivalent volume of about 100 Olympic sized swimming pools.

The question is why the comet continued to eject material for so long after the initial impact.

posted by: kyawoo at 22:51 | link | comments |
comets

Millions of tiny satelllites orbiting Saturn

As many as 10 million tiny satellites, some up to 100 meters in diameter, are orbiting Saturn within its rings, scientists with NASA’s Cassini mission reported on Wednesday.

Careful analysis of these pictures revealed four faint, propeller-shaped double streaks in an otherwise bland part of the mid-A Ring, a bright section in Saturn’s main rings. The researchers believe the "propellers" provide the first direct observation of how moonlets of 100 meters in diameter affect nearby particles.

Previous measurements, including those made by NASA’s Voyager spacecraft in the early 1980s, have shown that Saturn’s rings contain mostly small water-ice particles ranging in size from less than 1 centimeter across to the size of a small house.

Scientists knew about two larger embedded ring moons, 30-kilometer-wide Pan and 7-kilometer-wide Daphnis. The latest findings mark the first evidence of objects of about 100 meters in diameter.

These moonlets are likely to be chunks of the ancient body whose break-up produced Saturn’s glorious rings.

posted by: kyawoo at 05:30 | link | comments |
saturn