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B1BLancer
Joined: 11 Jul 2003
Posts: 92
Location: SC |
HUYGENS LANDS ON TITAN!!
 Sun Jan 16, 2005 7:27 am
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The updates have been coming hot and heavy since Huygens successfully
entered Titan's atmosphere, and made it alive all the way down to the
surface. The only problem was a loss of telemetry channel "A", which has been traced to a software error. Huygens survived on the surface of Titan well after Cassini had dropped below the horizon, as evidenced by Huygen's carrier signal being received here on Earth. The carrier did not, however, contain any data. It was a simple tone. All scientific data was received by the Cassini orbiter and relayed to Earth.
Here's the latest update.
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CBS NEWS STATUS REPORT
05:45 p.m., 01/15/05, Update: ESA minimizes photo loss; new pictures,
science update
A missing computer command - apparently the result of human error -
caused the loss of half the pictures taken by Europe's Huygens probe as it descended to the surface of Saturn's moon Titan. But project officials said today the 350 pictures that made it back, along with high-quality data from the spacecraft's other instruments and unexpected measurements by Earth-based radio telescopes, should fulfill all of the mission's primary objectives.
"I'm very, very happy to report that we have received a very good data
set that will surely allow us to achieve all of our objectives and probably more than what we had initially set out," said Jean-Pierre Lebreton, the European Space Agency's Huygens project scientist. "We can now start to seea clearer picture of Titan emerging."
Researchers today unveiled a dramatic 360-degree panorama shot by
Huygens descent imager showing the probe's path across the moon as it
descended toward touchdown. The mosaic put in context three photos
released Friday showing channels, an apparent shoreline, an unusual
heart-shaped feature and what appeared to be ice blocks at the landing
site itself.
The mosaic shows the channels and shoreline behind Cassini with the
landing site, near the heart-shaped feature, dead ahead. The channels in light-shaded, elevated terrain flow down toward what look like a shoreline along large expanses of dark, smooth-looking areas. It's not yet known whether ethane, methane or other hydrocarbons exist in liquid form in these areas, but additional data analysis may resolve the matter in the weeks and months ahead.
"It's almost impossible to resist the speculation that this flat, dark
material is some kind of drainage channel, that we're seeing some kind of a shoreline," said University of Arizona researcher Martin Tomasko, principal investigator with the descent imager team. "We don't know if this still has liquid in it or whether the liquid has drained away or drained into the surface. You have the feeling maybe this was wet not so long ago."
Tomasko also unveiled a color version of a photo released Friday that
showed what appeared to be ice boulders strewn across the surface near the Huygens landing site. The boulders, Tomasko said today, were actually closer in size to pebbles, based on additional data analysis. But he said depressions in the surface material around the small rock-like chunks of ice indicated possible erosion patterns due to the flow of some as-yet-unseen liquid.
Huygens entered Titan's thick nitrogen atmosphere around 5:13 a.m. Friday. John Zarnecki, principal investigator of the surface science package, said it took the spacecraft two hours 27 minutes and 50 seconds to complete its parachute descent to the surface. It hit that surface at a velocity of 10.1 mph and experienced a very brief impact deceleration of 15 Gs. The jolt knocked one sensor off line, but it came back to life on its own a few minutes later.
A "penetrometer" on the bottom of the probe extended six inches into the frigid soil. That data, coupled with the deceleration experienced by Huygens as it hit the ground, provided new insights into the nature of the surface material at the landing site.
"What we're seeing is, we think, a material which might have a thin crust followed by a region of relatively uniform consistency," said Zarnecki. "In terms of this (impact) force, the closest analog that I can give you - and remember, this is not suggesting these are the materials we hit, but that the mechanical consistency is similar - then I would say wet sand or clay are materials which give a similar sort of trace."
Huygens sampled the atmosphere as it floated toward the surface in winds measured at about 16 mph between six and 12 miles altitude. A microphone even recorded the sound of the wind rushing past. On-board
instruments detected a thick methane haze, or cloud deck, 11 to 12 miles above the ground where atmospheric pressure measured about 7.3 pounds per square inch.
The outside temperature when the descent began was 70.5 Kelvin, or minus 332.8 degrees Fahrenheit, while the temperature on the surface was slightly warmer: 93.8 Kelvin, or minus 290.8 degrees Fahrenheit.
Huygens was programmed to transmit telemetry and scientific data to NASA's Cassini Saturn orbiter for relay to Earth using two redundant S-band radio systems. Channel A was the sole path for an experiment to measure wind speeds by studying tiny frequency changes caused by Huygens' motion. In one other deliberate departure from full redundancy, pictures from Tomasko's descent imager were split up, with each channel carrying 350 pictures.
As it turned out, Cassini never listened to channel A because of a software commanding error. The receiver on the orbiter was never commanded to turn on, according to officials with the European Space Agency.
"We should remember we're human and we should learn lessons, so I will
institute an ESA inquiry on how the command came to be missing," David
Southwood, director of science for the European Space Agency, told
reporters today. "I'm not going to say any more about that, I'm not going to speculate (about blame)."
In an obvious reference to NASA and earlier news reports, he did say "there have been some erroneous messages implicating one of the other space agencies involved. No. It's an ESA responsibility."
According to published reports, an ESA official said earlier that the missing command was part of a software load developed by ESA for the Huygens mission and that it was executed by Cassini as delivered.
"There isn't any doubt that the command was missing," Southwood said
today. "But I'm not going to say any more because the point of an inquiry is to find out. We will certainly have NASA representation on the inquiry, but I don't want to make a big thing about it."
Tomasko said that before the mission began, his team debated whether to send all pictures and spectral data in two independent sets using channels A and B to ensure full redundancy. In the end, they decided to send spectral data through both channels but to double their picture output by sending different photos through each radio. The loss of channel A means the team only gathered 350 pictures instead of the 700 planned.
"So we do have some holes in our panoramic mosaics, but we have a lot of overlap in our coverage and I think we can still do a fine job," he said. "I think the quality of the images will continue to get better ... as we assemble these mosaics in the days and weeks ahead."
Even the lost wind measurement data will be made up, thanks to a remarkable effort on the ground to monitor a faint carrier signal broadcast by Huygens - the equivalent of a cell phone call at a distance of 751 million miles - using a network of 18 radio telescopes around the world. That data, which not as precise as the Doppler information that was lost, should fill in the blanks.
Leonid Gurvits, a researcher with the Netherlands-based Joint Institute for Very Long Baseline Interferometry in Europe, said his team achieved wind speed accuracy levels of one meter per second, or 2.2 mph even though Huygens was three-quarters of a billion miles away.
"Just as there are malign gods, there are benign gods and with an
extraordinary effort that i still frankly can't believe, the radio astronomers of the world gathered together to look at the little telephone-level signal coming from the other side of the solar system and we're expecting that will be able, with an enormous amount of work ... we will get back wind profiles as we need to get our full picture of the Titan atmosphere." |
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Swamp Gas
Joined: 06 Jun 2001
Posts: 4254
Location: On a Hill in the Lowlands |
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Mon Jan 17, 2005 4:27 pm
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Excellent! This really gives a bit of hope for eventual space migration, but with the military controlling space research in the US, we'll have to go to Europe of China for that. The follwing is some thoughts on Jupiter, Saturn's neighbor.
Years ago, I remember the theory that a mini-balck hole, or white hole was forming near Jupiter. The force that disrupted a star in RX J1242-11 is an extreme example of the tidal force caused by differences in gravity acting on the front and back of an object. The tidal force from the Moon causes tides in Earth's oceans. A tidal force from Jupiter pulled Comet Shoemaker-Levy apart, before it plunged into the giant planet.
Black holes aren't the only things that cause strong tides. Jupiter can do it, too. Comet Shoemaker/Levy crashing into Jupiter in 1994, after the comet was torn apart by the giant planet's tides. Although on a very different scale, the physical mechanism for the breakup of Shoemaker/Levy also caused the disruption of the star in RX J1242-11.
The odds of a stellar tidal disruption in a typical galaxy are low, about one in 10,000 annually. If it happened at the center of the Milky Way Galaxy, 25,000 light-years from Earth, the resulting X-ray outburst would be about 50,000 times brighter than the brightest X-ray source in our galaxy, but it would not pose a threat to Earth.
Other dramatic flares have been seen from galaxies, but this is the first one studied with the high-spatial resolution of Chandra and the high-spectral resolution of XMM-Newton. Both instruments made a critical advance. Chandra showed the RX J1242-11 event occurred in the center of a galaxy, where the black hole lurks. The XMM-Newton spectrum revealed the fingerprints expected for the surroundings of a black hole, ruling out other possible astronomical explanations.
Supermassive black holes in the centers of galaxies are familiar to astronomers. There are many of them, including one at the heart of our own Milky Way. Now astronomers have a way to find more: look for x-ray outbursts when stars are ripped apart by black-hole tides. Observations like these are needed, say researchers, to determine how quickly black holes can grow by swallowing neighboring stars.
Jupiter has always been an unusual planet. The counter modulations of Io and Europa have intrigued radio astronomers for years. One wonders whether Jupiter is a young sun.
_________________
Heard it from a pilot who spoke real gooooood! |
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B1BLancer
Joined: 11 Jul 2003
Posts: 92
Location: SC |
| Methane rain
Sun Jan 23, 2005 4:38 am
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CBS NEWS STATUS REPORT
10:45 a.m., 01/21/05, Update: Huygens data shows liquid methane on, or
just below, Titan's surface
Liquid methane apparently falls like rain on Saturn's smog-shrouded moon Titan, washing down icy channels that ultimately spill into broad lakebeds dotted with ice islands and shoals, according to the latest data from Europe's Huygens probe. While the spacecraft did not detect any standing pools of liquefied natural gas in its immediate area, the data indicate rainfall is common on Titan and that liquid methane is present within a few inches of its surface.
"This isn't Mars, where the liquid that's done the erosion is buried underneath a solid," said Toby Owen, an interdisciplinary scientist with the Cassini-Huygens mission. "This is a planet where the liquids are right there. It might have rained yesterday. This is really a very active situation. That's the important news about detecting methane. It isn't that we think methane is there. It's really there in the liquid state."
Said Martin Tomasko, principal investigator with the Huygens descent imager instrument: "What we know is the place we landed is dry at the
moment. But the liquid is not 200 meters underground, the liquid was within a few centimeters of the surface, indicating that it must have rained not very long ago. Does that mean yesterday or the day before, the week before? We don't really know. But the feeling is, in the place we landed, it must rain fairly frequently. But we can't be more precise than that."
NASA's Cassini Saturn orbiter released the Huygens probe on Christmas
Eve. The small spacecraft, built by the European Space Agency, slammed
into Titan's thick nitrogen atmosphere Jan. 14 and descended by parachute to the moon's frozen surface, snapping pictures and sampling the atmosphere as it fell.
Hitting the surface at about 11 mph, Huygens broke through a thin
crust-like material and settled several inches into a spongy hydrocarbon "soil" with the consistency of loose sand. Nearby chunks of dirty water ice show clear signs of fluid erosion, indicating the spacecraft landed in a zone that at least occasionally experiences flowing liquids.
At a news conference early today to unveil the latest data from Huygens, Owen said pre-landing predictions that liquid methane should exist on the surface of the ultra-cold world - minus 290 degrees Fahrenheit at the surface - were pretty much correct.
"What we've learned is that our speculation is really pretty good," Owen said. "The main difference, the main new thing that we have is that indeed, we can detect liquid methane on the surface. It's not seas of liquid ethane, it's really liquid methane, liquid natural gas."
Tomasko provided a fresh interpretation of a picture released last week showing what appeared to be channels in elevated terrain bordered by an apparent shoreline.
Stereo images show a ridge system in the image is more than 300 feet above he surrounding terrain. Dark channels can be seen in the light-colored elevated terrain leading to larger river bed-like features that empty into a basin.
After studying the images for a week, Tomasko said his team believes
the channels "really are evidence of rain."
"These branching, dendritic channels are evidence of rain and the dark
material in the bottoms of the channels is very likely this photochemical smog that falls out of the atmosphere, coats the whole terrain and gets preferentially washed off the top of the ridges," he said.
"The top of the ridges are ... not really very bright, they're relatively dark, but the dark material is definitely concentrated in the bottom of these drainage channels. And these ridges, we think, are made not of silicate rocks as on the Earth, but frozen, hard water ice. So we think we're seeing water ice ridges washed off by rainfall with a liquid and a concentration of these organic materials in the bottom of the (channels).
Looking at a larger mosaic that included the original picture, Tomasko said "we see this river system which flows down into this delta, into this low-lying terrain. We see this ridge draining from the back and these dendritic structures and then coming down from the front draining also into this broad, low-lying terrain."
In a new picture released today, Tomasko described additional features
that indicate flowing liquids, including short, stubby channels that could indicate methane springs and areas that might be extrusions of water ice. Another photo showed a thin ridge in one of the pool-like basins that had multiple channels cut through it, presumably from erosion, giving the appearance of a chain of islands.
"So there's lots of evidence of fluid flow, there's lots of evidence of this dark material, there's some evidence of water ice extrusion as well," Tomasko said. "We don't think we see liquids in these areas, but we do think there's plenty of evidence that there was flowing fluids on the surface of Titan."
For methane be present in the atmosphere today, it must be constantly
replenished. Owen said the source of the methane was Titan itself.
"The photochemistry is happening up above, breaking methane apart,
fragments are combining, making more complex things, making these smog particles and they're precipitating down to the surface," he said. "The methane, as we expected from the beginning, must condense because it's so cold on the surface of Titan that we would expect liquid natural gas to be present there. And now the question is, is it really there?"
Data from Huygens shows nitrogen is the dominant gas in the upper
atmosphere of Titan. But as the probe descended, methane concentrations shot up.
"This is just like what happens on the Earth with water vapor," Owen said. "Water on Earth is confined to the lower atmosphere. The reason is, there's a very low temperature point in the atmosphere and there's the same thing on Titan, there's a kind of cold trap that forces the methane to be down below so that the methane increases more rapidly than the nitrogen as you go down into the lower atmosphere. That's where it is.
"Now, when you come to the surface, you would expect everything to be
stable and that's what the nitrogen indeed does. However, the methane
suddenly jumps up by about 30 percent. Boom, in three minutes, up it goes. That methane must be coming out of the ground and that's the
exciting part. It means there's liquid methane very near the surface, maybe right on the surface."
Tomasko said it's possible Huygens landed in Titan's equivalent of an arid region on Earth.
"We don't think we have open pools of liquid methane, but the methane kind of sinks down into the surface material," he said. "It's more like Arizona or someplace like that where the river beds are dry most of the time but after rain, you might have open flowing liquids and pools. These pools gradually dry out, the liquid sinks down into the surface. Perhaps it's very seasonal."
No one yet knows. But Jean-Pierre Lebreton, the Huygens mission scientist for the European Space Agency, said Titan would make an ideal target for some future robot lander. |
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