Planetary

Saturn Moon May Have Water

Mon, 11 Feb 2008 20:45:39 GMT

"Feb. 6, 2008 -- Astrophysicists in Germany say they can add evidence to bolster theories that water, one of the precious ingredients for life, exists on the Saturnian moon Enceladus.

A tiny satellite measuring just 504 kilometers (315 miles) across, Enceladus has become one of the most fiercely debated objects in the solar system, thanks to close-up pictures taken by the NASA Cassini probe.

Enceladus has a brilliant white shell of ice that is untouched except for some strange-looking grooves and impacts from space rocks.

Cassini revealed plumes of water vapor that gush from surface stripes near its south pole, shooting crystal jets upwards for hundreds of miles into space.

Fuelling discussion about the origin of these strange "cryo-volcanoes" is the fact that icy particles of dust are also mixed in with the eruptions, but beguilingly travel far slower than the vapor.

A team led by Juergen Schmidt of the University of Potsdam, near Berlin, say they can now answer at least this part of the mystery.

Their theory is that water vapor and ice grains are blasted through funnels in the so-called tiger stripes -- and the grains, being heavier, rub against the rough sides of these holes.

The friction slows the particles down, which explains why they travel at a far lower velocity in the void.

For this to happen, though, liquid water would have to exist in equilibrium with ice and vapor beneath the moon's frigid crust, according to the model.

One hypothesis for the cause for Enceladus's cryo-volcanoes is a phenomenon called tidal heating.

The little moon suffers agonising gravitational pull from the giant Saturn and from the nearby satellites of Dione and Janus.

As a result, its interior is squeezed and stretched, causing friction that causes water to warm, this theory goes.

Enceladus has a surface temperature of -193 degrees Celsius (-315 degrees Fahrenheit) and the tiger stripes are -133 C (-207 F), which implies that its interior must be warmer still.

Heat and water are two of the essentials for life as we know it, although anything that exists in Enceladus's presumed sub-surface ocean is likely to be microbial at best, scientists add.

The new study appears on Thursday in Nature, the weekly British science journal."

News Source: Discovery News

How a lunar eclipse (on Feb. 20) saved Columbus

Mon, 11 Feb 2008 20:33:18 GMT

"On the night of Feb. 20, the full moon will pass into Earth's shadow in an event that will be visible across all of the United States and Canada.

The total lunar eclipse will be made even more striking by the presence of the nearby planet Saturn and the bright bluish star, Regulus.

Eclipses in the distant past often terrified viewers who took them as evil omens. Certain lunar eclipses had an overwhelming effect on historic events. One of the most famous examples is the trick pulled by Christopher Columbus.

Shipwrecked

On Oct. 12, 1492, as every schoolchild has been taught, Columbus came ashore on an island northeast of Cuba. He later named it San Salvador (Holy Savior). Over the next ten years Columbus would make three more voyages to the "New World," which only bolstered his belief that he reached the Far East by sailing West.

It was on his fourth and final voyage, while exploring the coast of Central America that Columbus found himself in dire straits. He left Cádiz, Spain, on May 11, 1502, with the ships Capitana, Gallega, Vizcaína and Santiago de Palos. Unfortunately, thanks to an epidemic of shipworms eating holes in the planking of his fleet, Columbus' was forced to abandon two of his ships and finally had to beach his last two caravels on the north coast of Jamaica on June 25, 1503.

Initially, the Jamaican natives welcomed the castaways, providing them with food and shelter, but as the days dragged into weeks, tensions mounted. Finally, after being stranded for more than six months, half of Columbus' crew mutinied, robbing and murdering some of the natives, who, themselves grew weary of supplying cassava, corn and fish in exchange for little tin whistles, trinkets, hawk's bells and other rubbishy goods.

With famine now threatening, Columbus formulated a desperate, albeit ingenious plan.

Almanac to the rescue

Coming to the Admiral's rescue was Johannes Müller von Königsberg (1436-1476), known by his Latin pseudonym Regiomontanus. He was an important German mathematician, astronomer and astrologer.

Before his death, Regiomontanus published an almanac containing astronomical tables covering the years 1475-1506. Regiomontanus' almanac turned out to be of great value, for his astronomical tables provided detailed information about the sun, moon and planets, as well as the more important stars and constellations by which to navigate. After it was published, no sailor dared set out without a copy. With its help, explorers were able to leave their customary routes and venture out into the unknown seas in search of new frontiers.

Columbus, of course, had a copy of the Almanac with him when he was stranded on Jamaica. And he soon discovered from studying its tables that on the evening of Thursday, Feb. 29, 1504, a total eclipse of the moon would take place soon after the time of moonrise.

Armed with this knowledge, three days before the eclipse, Columbus asked for a meeting with the natives Cacique ("chief") and announced to him that his Christian god was angry with his people for no longer supplying Columbus and his men with food. Therefore, he was about to provide a clear sign of his displeasure: Three nights hence, he would all but obliterate the rising full moon, making it appear "inflamed with wrath," which would signify the evils that would soon be inflicted upon all of them.

Bad moon rising

On the appointed evening, as the sun set in the West and the moon started emerging from beyond the eastern horizon, it was plainly obvious to all that something was terribly wrong. By the time the moon appeared in full view, its lower edge was missing!

And, just over an hour later, as full darkness descended, the moon indeed exhibited an eerily inflamed and "bloody" appearance: In place of the normally brilliant late winter full moon there now hung a dim red ball in the eastern sky.

According to Columbus' son, Ferdinand, the natives were terrified at this sight and ".. . with great howling and lamentation came running from every direction to the ships laden with provisions, praying to the Admiral to intercede with his god on their behalf." They promised that they would gladly cooperate with Columbus and his men if only he would restore the moon back to its normal self. The great explorer told the natives that he would have to retire to confer privately with his god. He then shut himself in his cabin for about fifty minutes.

"His god" was a sandglass that Columbus turned every half hour to time the various stages of the eclipse, based on the calculations provided by Regiomontanus' almanac.

Just moments before the end of the total phase Columbus reappeared, announcing to the natives that his god had pardoned them and would now allow the moon to gradually return. And at that moment, true to Columbus' word, the moon slowly began to reappear and as it emerged from the Earth's shadow, the grateful natives hurried away. They then kept Columbus and his men well supplied and well fed until a relief caravel from Hispaniola finally arrived on June 29, 1504. Columbus and his men returned to Spain on Nov. 7.

Another side to the story

In an interesting postscript to this story, in 1889, Mark Twain, likely influenced by the eclipse trick, wrote the novel, A Connecticut Yankee in King Arthur's Court. In it, his main character, Hank Morgan, used a gambit similar to Columbus'.

Morgan is about to be burned at the stake, so he "predicts" a solar eclipse he knows will occur, and in the process, claimed power over the sun. He gladly offers to return the sun to the sky in return for his freedom and a position as "perpetual minister and executive" to the king.

The only problem with this story is that on the date that Mark Twain quoted — June 21, 528 A.D. — no such eclipse took place. In fact, the moon was three days past full, a setup that can't generate an eclipse.

Perhaps he should have consulted an almanac!"

News Source

NASA Spots Mysterious 'Spider' on Mercury

Fri, 01 Feb 2008 02:17:51 GMT

"A whole new side of Mercury has been revealed in pictures taken by NASA's MESSENGER probe, which flew by the tiny planet two weeks ago in the first mission to Mercury in more than three decades.

MESSENGER skimmed only 124 miles (200 kilometers) over Mercury's surface on Jan. 14, in the first of three passes it will make before settling into orbit March 18, 2011.

The photos, released today, include one of a feature the scientists informally call "the spider," which appears to be an impact crater surrounded by more than 50 cracks in the surface radiating from its center.

Scientists are perplexed by this structure, which is unlike anything observed elsewhere in the solar system.

"It's a real mystery, a very unexpected find," said Louise Prockter, an instrument scientist at the Johns Hopkins University Applied Physics Laboratory, which built the probe for the $446 million NASA mission. She said whatever event created the spider "is anybody's guess," but suggested perhaps a volcanic intrusion beneath the planet's surface led to the formation of the troughs.

The last time NASA sent a probe to Mercury was in 1975, when the Mariner 10 spacecraft flew by the planet three times. MESSENGER'S first flyby gave scientists the first glimpses of Mercury's hidden side, the 55 percent of its surface that was left uncharted by Mariner 10.

MESSENGER, short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging, also measured another peculiar element of Mercury — its magnetic field. Earth has a magnetic field surrounding it that acts as a protective bubble shielding the surface from cosmic rays and solar storms. But scientists were shocked when Mariner 10 discovered a magnetic field at Mercury, too.

"The only other example in our solar system of an Earth-like magnetosphere is tiny Mercury," said Sean C. Solomon, MESSENGER Principal Investigator from the Carnegie Institution of Washington.

MESSENGER was able to fly through the magnetic field and take detailed measurements that scientists hope to use to discover the origins of the inexplicable magnetosphere.

Scientists have been poring over more than 1,200 new images sent by seven instruments on the probe, and they are excited to gain new insight into the composition of Mercury's surface, the planet's history, and where its atmosphere comes from.

"On the eve of the encounter I couldn't sleep at all," said Robert Strom, a MESSENGER science team member who also worked on the Mariner 10 mission. "I've waited 30 years for this. It didn't disappoint at all. I was astounded at the quality of these images. It dawned on me that this is a whole new planet that we're looking at."

The satellite will further probe Mercury's mysteries in a second pass over the planet in October, followed by a third flyby in September 2009.

The probe has traveled 4.9 billion miles (7.9 billion-kilometers) since it launched in August 2004. On its journey it soared by Earth once and Venus twice, offering gorgeous views of these planets as well. In 2011 MESSENGER will become the first spacecraft to orbit the closest planet to the Sun. "

News Source Space.com

Risk of Mars impact drops to 1 in 10,000

Sun, 13 Jan 2008 16:15:47 GMT

The risk that an asteroid will hit Mars on 30 January has dropped to 1 in 10,000, essentially ruling out an impact, NASA researchers say.

Transient Lunar Phenomena

Sun, 06 Jan 2008 20:27:46 GMT

The Moon is dominated by gigantic circular structures where unusual luminous discharges have been observed. Are they indicative of past electrical events?

Human beings have long looked up at and wondered about the Moon. Our forebears probably pondered its origin and its influence, perhaps seeking a purpose for the pale, shining orb that now dominates the night sky.

For more than a thousand years, reports have circulated about events on the Moon that should not appear on a "dead" celestial body. Various accounts describe glowing clouds in red and green, or sudden outbursts of yellow flares and intense flashes of light. Such observations do not accord with conventional theories.

Because the Moon is thought to have lost all its heat to space more than a billion years ago and it has no magnetic field to speak of, violent activity should not be taking place on its surface today. For this reason, astronomers and astrophysicists have discounted "transient lunar phenomena". Since most of the sightings by single individuals received no corroboration and no images were recorded until recently, the incidents were said to be apocryphal or deliberately misleading. However, some serious attempts have been made to link historical narratives with physical impacts:

"There was a bright new moon, and as usual in that phase its horns were tilted toward the east; and suddenly the upper horn split in two. From the midpoint of this division a flaming torch sprang up, spewing out, over a considerable distance, fire, hot coals, and sparks. Meanwhile the body of the moon which was below writhed, as it were, in anxiety, and, to put it in the words of those who reported it to me and saw it with their own eyes, the moon throbbed like a wounded snake. Afterwards it resumed its proper state. This phenomenon was repeated a dozen times or more, the flame assuming various twisting shapes at random and then returning to normal. Then after these transformations the moon from horn to horn, that is along its whole length, took on a blackish appearance." (Jack B. Hartung (1976). "Was the Formation of a 20-km Diameter Impact Crater on the Moon Observed on June 18, 1178?" Meteoritics 11:187-194).

Meteors are one hypothesis for the abrupt appearance and disappearance of lunar scintillations, although Hartung's proposal has met with skepticism.

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Is a New Solar Cycle Beginning?

Tue, 18 Dec 2007 21:32:12 GMT

The solar physics community is abuzz this week. No, there haven't been any great eruptions or solar storms. The source of the excitement is a modest knot of magnetism that popped over the sun's eastern limb on Dec. 11th, pictured below in a pair of images from the orbiting Solar and Heliospheric Observatory (SOHO).

It may not look like much, but "this patch of magnetism could be a sign of the next solar cycle," says solar physicist David Hathaway of the Marshall Space Flight Center.

Above: From SOHO, a UV-wavelength image of the sun and a map showing positive (white) and negative (black) magnetic polarities. The new high-latitude active region is magnetically reversed, marking it as a harbinger of a new solar cycle.

For more than a year, the sun has been experiencing a lull in activity, marking the end of Solar Cycle 23, which peaked with many furious storms in 2000--2003. "Solar minimum is upon us," he says.

The big question now is, when will the next solar cycle begin?

"New solar cycles always begin with a high-latitude, reversed polarity sunspot," explains Hathaway. "Reversed polarity " means a sunspot with opposite magnetic polarity compared to sunspots from the previous solar cycle. "High-latitude" refers to the sun's grid of latitude and longitude. Old cycle spots congregate near the sun's equator. New cycle spots appear higher, around 25 or 30 degrees latitude.

The region that appeared on Dec. 11th fits both these criteria. It is high latitude (24 degrees N) and magnetically reversed. Just one problem: There is no sunspot. So far the region is just a bright knot of magnetic fields. If, however, these fields coalesce into a dark sunspot, scientists are ready to announce that Solar Cycle 24 has officially begun.

Below: Solar Cycle 23 is coming to an end. What's next? Image credit: NOAA/Space Weather Prediction Center.

Many forecasters believe Solar Cycle 24 will be big and intense. Peaking in 2011 or 2012, the cycle to come could have significant impacts on telecommunications, air traffic, power grids and GPS systems. (And don't forget the Northern Lights!) In this age of satellites and cell phones, the next solar cycle could make itself felt as never before.

The furious storms won't start right away, however. Solar cycles usually take a few years to build to a frenzy and Cycle 24 will be no exception. "We still have some quiet times ahead," says Hathaway.

Meanwhile, all eyes are on a promising little active region. Will it become the first sunspot of a new solar cycle?

News Source

Earth's Moon is Rare Oddball

Fri, 30 Nov 2007 19:50:37 GMT

The moon formed after a nasty planetary collision with young Earth, yet it looks odd next to its watery orbital neighbor. Turns out it really is odd: Only about one in every 10 to 20 solar systems may harbor a similar moon.

New observations made by NASA's Spitzer Space Telescope of stellar dust clouds suggest that moons like Earth's are—at most—in only 5 to 10 percent of planetary systems.

"When a moon forms from a violent collision, dust should be blasted everywhere," said Nadya Gorlova, an astronomer at the University of Florida in Gainesville who analyzed the telescope data in a new study. "If there were lots of moons forming, we would have seen dust around lots of stars. But we didn't."

Gorlova and her team detail their findings in today's issue of the Astrophysical Journal.

Violent birth

Shortly after the sun formed about 4.5 billion years ago, scientists think a vagrant planet as big as Mars smacked into infant Earth and ripped off a chunk of our home's smoldering mantle. The rocky, dusty leftovers fell into orbit around our wounded planet, eventually coalescing into the moon we see today.

The scenario is unique among other moons in the solar system, which formed side-by-side with their planet or were captured by its gravity. Gorlova and her colleagues looked for the dusty signs of similar smash-ups around 400 stars, all about 30 million years old—roughly the age of our sun when Earth's moon formed.

Only one of all the stars they studied, however, displayed the telltale dust. Considering the frequency of planetary solar systems, the amount of time the dust should stick around and the window for moon-forming collisions to occur, the scientists were able to peg the frequency of extrasolar bodies that formed like our moon.

The estimate, however, is possibly a generous one.

"We don't know that the collision we witnessed around the one star is definitely going to produce a moon," said study co-author George Rieke, an astronomer at the University of Arizona in Tucson, "so moon-forming events could be much less frequent than our calculation suggests."

Odd moon out?

Planetary scientists like Gorlova and Rieke think infant solar systems can form moons between 10 and 50 million years after a star forms. That only a single star with collision-generated dust could be found in their latest research, the astronomers said, indicates that the 30 million-year-old stars in the study have finished making their planets.

"Astronomers have observed young stars with dust swirling around them for more than 20 years now," said Gorlova, noting that the dust could be collision-derived or primitive planet-forming material. "The star we have found is older, at the same age our sun was when it had finished making planets and the Earth-moon system had just formed in a collision."

While most the our type of moon may be rare, astronomers think there are billions of rocky planets out there with plenty of moons orbiting around them. The upshot for lunar lovers? There could be millions—or billions—of Earth-like moons drifting through the cosmos.

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