The Lagoons of Titan: Oily Liquid Confirmed on Saturn Moon August 18, 2008
Posted by muneeb in Mars, Titan.add a comment
Earthlings might be scrambling to find liquid hydrocarbons buried in our planet, but Saturn’s moon Titan has plenty to spare.
Scientists say that a dark, smooth surface feature spotted on the moon last year is definitely a lake filled primarily with liquid ethane, a simple hydrocarbon.
“This is the first observation that really pins down that Titan has a surface lake filled with liquid,” said the paper’s lead author, University of Arizona professor Robert Brown.
The new observations affirm that Titan is one of the likeliest places to look for life in our solar system. Some astrobiologists have speculated that life could develop in the moon’s hydrocarbon lakes, although it would have to be substantially different from known life on Earth, which requires liquid water.
Mixed in solution with the ethane, the lake is also believed to contain nitrogen, methane, and a variety of other simple hydrocarbons.
The Cassini-Huygens probe determined the chemical composition of the liquid by the way it reflected light, a technique known as spectrometry that has provided most of our knowledge about other planets’ atmospheric compositions.
“It was hard for us to accept the fact that the feature was so black when we first saw it,” Brown said. “More than 99.9 percent of the light that reaches the lake never gets out again. For it to be that dark, the surface has to be extremely quiescent, mirror smooth. No naturally produced solid could be that smooth.”
Further, the scientists saw the specific absorption signature of ethane, which absorbs light at exactly 2-micron wavelengths.
These kinds of measurements are made more difficult by the hydrocarbon haze that engulfs the moon, making it hard to actually see the Titanic ground. Cassini scientists have to take advantage of narrow observation windows. One of these occurred in December 2007, which allowed them to catch this view of the lake, Ontario Lacus. At 7,800 square miles, it’s slightly larger than the Earthbound Lake Ontario
Ethane is the byproduct of a solar-energy-induced reaction that transforms atmospheric methane, aka natural gas. Scientists believe ultrafine particles of ethane fall from the atmosphere to the surface and fill the lake.
Here on earth, ethane is used to create ethylene, which is used as an all-purpose chemical precursor and is the world’s most-produced organic compound.
Brown and his team will publish their results in the July 31 issue of the journal Nature.
[SOURCE: Wired Science http://blog.wired.com/wiredscience/2008/07/lake-of-petrole.html ]
Phoenix lander confirms ice in Martian soil August 18, 2008
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The Phoenix spacecraft has tasted Martian water for the first time, scientists reported Thursday.
By melting icy soil in one of its lab instruments, the robot confirmed the presence of frozen water lurking below the Martian permafrost. Until now, evidence of ice in Mars’ north pole region has been largely circumstantial.
In 2002, the orbiting Odyssey spacecraft spied what looked like a reservoir of buried ice. After Phoenix arrived, it found what looked like ice in a hard patch underneath its landing site and changes in a trench indicated some ice had turned to gas when exposed to the sun.
Scientists popped open champagne when they received confirmation Wednesday that the soil contained ice.
“We’ve now finally touched it and tasted it,” William Boynton of the University of Arizona said during a news conference in Tucson on Thursday. “From my standpoint, it tastes very fine.”
Phoenix landed on Mars on May 25 on a three-month hunt to determine if it could support life. It is conducting experiments to learn whether the ice ever melted in the red planet’s history that could have led to a more hospitable environment. It is also searching for the elusive organic-based compounds essential for simple life forms to emerge.
The ice confirmation earlier this week was accidental. After two failed attempts to deliver ice-rich soil to one of Phoenix’s eight lab ovens, researchers decided to collect pure soil instead. Surprisingly, the sample was mixed with a little bit of ice, said Boynton, who heads the oven instrument.
Researchers were able to prove the soil had ice in it because it melted in the oven at 32 degrees — the melting point of ice — and released water molecules. Plans called for baking the soil at even higher temperatures next week to sniff for carbon-based compounds.
The latest scientific finding is the first piece of good news for a mission that has been dogged by difficulties in recent weeks.
An electrical short on one of Phoenix’s test ovens threatened the instrument, but scientists said the problem has not recurred. The lander, which spent the past several weeks drilling into the hard ice, also had trouble delivering ice shavings into an oven until the success this week.
NASA said Phoenix has achieved minimum success thus far. The space agency on Thursday announced that it would extend the mission for an extra five weeks until the end of September, adding $2 million more to the $420 million price tag, said Michael Meyer, Mars chief scientist at NASA headquarters.
Unlike the twin rovers roaming near the Martian equator, Phoenix’s lifetime cannot be extended much more because it likely won’t have enough power to survive the Martian winter
The science team also released a color panorama of Phoenix’s landing site using more than 400 images taken by Phoenix. The view “was painstakingly stitched together,” said Mark Lemmon of Texas A&M University, who headed the effort.
The portrait revealed a Martian surface that was coated with dust and dotted with rocks.
[SOURCE: http://news.yahoo.com/s/ap/20080731/ap_on_sc/phoenix_mars;_ylt=AhSwPqvNaQtymiudhg9f9f8iANEA ]
By ALICIA CHANG, AP Science Writer
Illusion of the moon this weekend July 1, 2007
Posted by muneeb in Moon.add a comment
This weekend’s full moon hangs lower in the sky than any other full moon of 2007, according to NASA, and it’s a good time to be fooled.
When low on the horizon, the Moon can appear to be larger than when it’s higher in the sky. It’s all an illusion, scientists say, and it does not involve any enlarging effects of the atmosphere. Rather, it’s all in your mind.
Here’s how it works:
Our brains think things on the horizon are farther away than stuff overhead, because we’re used to seeing overhead clouds that are close compared to those on the horizon. In the mind’s eye, the sky is a flattened dome.
With this dome as a reference, we expect something on the horizon (such as the moon) to be father, and because it is actually no farther than when overhead, our brains goof and imagine that it is larger.
Skeptical? You can test this from home.
When the moon first rises, hold something small like the eraser of a pencil at arms length and compare its size to the moon on the horizon. Do the same a couple hours later when the moon is higher. Or try this: Take a picture of the moon in both positions, then cut, paste and compare. Another trick: Make a tube from rolled-up paper so the opening is just slightly larger than the moon when it rises. Tape the tube so the size stays fixed, then check later to see if the moon has changed sizes.
Officially, the moon will be full Saturday June 30 at 9:49 a.m. ET. Of course, you’ll want to do your looking in the evening. Local moonrise times are available from the U.S. Naval Observatory. Keep in mind that mountains and buildings can dramatically alter your actual local moonrise time.
The big-moon-rising effect will be evident Friday, Saturday and Sunday. On each evening, the moon will appear nearly full. Interestingly, the moon is never fully full from our point of view, but that’s another story.
While you’re out, check out Venus and Saturn, which are snuggling close together in the western sky as darkness falls.
So why is one full moon lower in the sky than another? The moon’s orbit around Earth is tilted 5 degrees compared to the plane of Earth’s travels around the Sun, and Earth itself is tilted on its rotational axis. All this accounts for the lunar phases, and it also means the moon’s path through our sky can be higher or lower depending on the angles on any given night.
The complex orbit of the Earth-moon system is constantly evolving, too. Right now, the moon is moving away from us by more than 1.5 inches every year.
The universe is at least 156 billion light-years wide! January 17, 2007
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If you’ve ever wondered how big the universe is, you’re not alone. Astronomers have long pondered this, too, and they’ve had a hard time figuring it out. Now an estimate has been made, and its a whopper.
The universe is at least 156 billion light-years wide.
In the new study, researchers examined primordial radiation imprinted on the cosmos. Among their conclusions is that it is less likely that there is some crazy cosmic “hall of mirrors” that would cause one object to be visible in two locations. And they’ve ruled out the idea that we could peer deep into space and time and see our own planet in its youth.
First, let’s see why the size is a number you’ve never heard of before.
Stretching reality
The universe is about 13.7 billion years old. Light reaching us from the earliest known galaxies has been travelling, therefore, for more than 13 billion years. So one might assume that the radius of the universe is 13.7 billion light-years and that the whole shebang is double that, or 27.4 billion light-years wide.
But the universe has been expanding ever since the beginning of time, when theorists believe it all sprang forth from an infinitely dense point in a Big Bang.
“All the distance covered by the light in the early universe gets increased by the expansion of the universe,” explains Neil Cornish, an astrophysicist at Montana State University. “Think of it like compound interest.”
Need a visual? Imagine the universe just a million years after it was born, Cornish suggests. A batch of light travels for a year, covering one light-year. “At that time, the universe was about 1,000 times smaller than it is today,” he said. “Thus, that one light-year has now stretched to become 1,000 light-years.”
All the pieces add up to 78 billion-light-years. The light has not traveled that far, but “the starting point of a photon reaching us today after travelling for 13.7 billion years is now 78 billion light-years away,” Cornish said. That would be the radius of the universe, and twice that — 156 billion light-years — is the diameter. That’s based on a view going 90 percent of the way back in time, so it might be slightly larger.
“It can be thought of as a spherical diameter is the usual sense,” Cornish added comfortingly.
(You might have heard the universe is almost surely flat, not spherical. The flatness refers to its geometry being “normal,” like what is taught in school; two parallel lines can never cross.)
Hall of mirrors
The scientists studied the cosmic microwave background (CMB), radiation unleashed about 380,000 years after the Big Bang, when the universe had first expanded enough to cool and allow atoms to form. Temperature differences in the CMB left an imprint on the sky that was used last year to reveal the age of the universe and confirm other important cosmological measurements.
The CMB is like a baby picture of the cosmos, before any stars were born.
The focus of the new work, which was published last week in the journal Physical Review Letters, was a search of CMB data for paired circles that would have indicated the universe is like a hall of mirrors, in which multiple images of the same object could show up in different locations in space-time. A hall of mirrors could mean the universe is finite but tricks us into thinking it is infinite.
Think of it as a video game in which an object disappearing on the right side of the screen reappears on the left.
“Several years ago we showed that any finite universe in which light had time to ‘wrap around’ since the Big Bang would have the same pattern of cosmic microwave background temperature fluctuations around pairs of circles,” Cornish explained. They looked for the most likely patterns that would be evident in a CMB map generated by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP).
They didn’t find those patterns.
Don’t look back
“Our results don’t rule out a hall-of-mirrors effect, but they make the possibility far less likely,” Cornish told SPACE.com, adding that the findings have shown “no sign that the universe is finite, but that doesn’t prove that it is infinite.”
The results do render impossible a “soccer ball” shape for the universe, proposed late last year by another team. “However, if they were to ‘pump up’ their soccer ball to make it larger, they could evade our bounds” and still be in the realm of possibility, Cornish said. Other complex shapes haven’t been ruled out.
The findings eliminate any chance of seeing our ancient selves, however, unless we can master time travel.
“If the universe was finite, and had a size of about 4 billion to 5 billion light-years, then light would be able to wrap around the universe, and with a big enough telescope we could view the Earth just after it solidified and when the first life formed,” Cornish said. “Unfortunately, our results rule out this tantalizing possibility.”
——————————————————————————–
Impossible? Cornish Explains Further
Update, 8:25 a.m. Tuesday, May 25
This article generated quite a few e-mails from readers who were perplexed or flat out could not believe the universe was just 13.7 billion years old yet 158 billion light-years wide. That suggests the speed of light has been exceeded, they argue. So SPACE.com asked Neil Cornish to explain further. Here is his response:
“The problem is that funny things happen in general relativity which appear to violate special relativity (nothing traveling faster than the speed of light and all that).
“Let’s go back to Hubble’s observation that distant galaxies appear to be moving away from us, and the more distant the galaxy, the faster it appears to move away. The constant of proportionality in that relationship is known as Hubble’s constant.
“One seemingly paradoxical consequence of Hubble’s observation is that galaxies sufficiently far away will be receding from us at a velocity faster than the speed of light. This distance is called the Hubble radius, and is commonly referred to as the horizon in analogy with a black hole horizon.
“In terms of special relativity, Hubble’s law appears to be a paradox. But in general relativity we interpret the apparent recession as being due to space expanding (the old raisins in a rising fruit loaf analogy). The galaxies themselves are not moving through space (at least not very much), but the space itself is growing so they appear to be moving apart. There is nothing in special or general relativity to prevent this apparent velocity from exceeding the speed of light. No faster-than-light signals can be sent via this mechanism, and it does not lead to any paradoxes.
“Indeed, the WMAP data [on cosmic microwave background radiation] contain strong evidence that the very early universe underwent a period of accelerated expansion in which the distance been two points increased so quickly that light could not outrace the expansion so there was a true horizon — in precise analogy with a black hole horizon. Indeed, the fluctuations we see in the CMB are thought to be generated by a process that is closely analogous to Hawking radiation from black holes.
“Even more amazing is the picture that emerges when you combine the WMAP data with [supernova] observations, which imply that the universe has started inflating again. If this is true, we have started to move away from the distant galaxies at a rate that is increasing, and in the future we will not be able to see as many galaxies as they will appear to be moving away from us faster than the speed of light (due to the expansion of space), so their light will not be able to reach us.”
[SOURCE: http://www.space.com/scienceastronomy/mystery_monday_040524.html ]
Lost lakes of Titan are found at last January 5, 2007
Posted by muneeb in Planets.add a comment
Lakes of methane have been spotted on Saturn’s largest moon, Titan, boosting the theory that this strange, distant world bears beguiling similarities to Earth, according to a new study.
Titan has long intrigued space scientists, as it is the only moon in the Solar System to have a dense atmosphere — and its atmosphere, like Earth’s, mainly comprises nitrogen.
Titan’s atmosphere is also rich in methane, although the source for this vast store of hydrocarbons is unclear.
Methane, on the geological scale, has a relatively limited life. A molecule of the compound lasts several tens of millions of years before it is broken up by sunlight.
Given that Titan is billions of years old, the question is how this atmospheric methane gets to be renewed. Without replenishment, it should have disappeared long ago.
A popular hypothesis is that it comes from a vast ocean of hydrocarbons.
But when the US spacecraft Cassini sent down a European lander, Huygens, to Titan in 2005, the images sent back were of a rugged landscape veiled in an orange haze.
There were indeed signs of methane flows and methane precipitation, but nothing at all that pointed to any sea of the stuff.
But a flyby by Cassini on July 22 last year has revealed, thanks to a radar scan, 75 large, smooth, dark patches between three and 70 kilometers across (two and 42 miles) across that appear to be lakes of liquid methane, scientists report on Thursday.
They believe the lakes prove that Titan has a “methane cycle” — a system that is like the water cycle on Earth, in which the liquid evaporates, cools and condenses and then falls as rain, replenishing the surface liquid.
As on Earth, Titan’s surface methane may well be supplemented by a “table” of liquid methane that seeps through the rock, the paper suggests.
Some of the methane lakes seem only partly filled, and other depressions are dry, which suggests that, given the high northerly latitudes where they were spotted, the methane cycle follows Titan’s seasons.
In winter, the lakes expand, while in summer, they shrink or dry up completely — again, another parallel with Earth’s hydrological cycle.
The study, which appears on Thursday in the British weekly journal Nature, is headed by Ellen Stofan of Proxemy Research in Virginia and University College London.
Titan and Earth are of course very different, especially in their potential for nurturing life. Titan is frigid, dark and, as far as is known, waterless, where as Earth is warm, light and has lots of liquid water.
But French astrophysicist Christophe Sotin says both our planet and Titan have been sculpted by processes that, fundamentally, are quite similar.
The findings “add to the weight of evidence that Titan is a complex world in which the interaction between the inner and outer layers is controlled by processes similar to those that must have dominated the evolution of any Earth-like planet,” Sotin said in a commentary.
“Indeed, as far as we know,” Sotin added, “there is only one planetary body that displays more dynamism than Titan. Its name is Earth.”
[SOURCE: PARIS AFP http://news.yahoo.com/s/afp/20070103/sc_afp/spacesaturntitan_070103193516 ]
HAT-P-1 – Largest and Least Dense Planet found September 15, 2006
Posted by muneeb in Planets.4 comments
Using a network of small, automated telescopes known as HAT, Smithsonian astronomers have discovered a planet unlike any other known world. This new planet, designated HAT-P-1, orbits one member of a pair of distant stars 450 light-years away in the constellation Lacerta.
“We could be looking at an entirely new class of planets,” said Gaspar Bakos, a Hubble fellow at CfA. Bakos designed and built the HAT network and is lead author of a paper submitted to the Astrophysical Journal describing the discovery
With a radius about 1.38 times Jupiter’s, HAT-P-1 is the largest known planet. In spite of its huge size, its mass is only half that of Jupiter.
“This planet is about one-quarter the density of water,” Bakos said. “In other words, it’s lighter than a giant ball of cork! Just like Saturn, it would float in a bathtub if you could find a tub big enough to hold it, but it would float almost three times higher.”
HAT-P-1’s parent star is one member of a double-star system called ADS 16402 and is visible in binoculars. The two stars are separated by about 1500 times the Earth-Sun distance. The stars are similar to the Sun but slightly younger – about 3.6 billion years old compared to the Sun’s age of 4.5 billion years.
Although stranger than any other extrasolar planet found so far, HAT-P-1 is not alone in its low-density status. The first planet ever found to transit its star, HD 209458b, also is puffed up about 20 percent larger than predicted by theory. HAT-P-1 is 24 percent larger than expected.
“Out of eleven known transiting planets, now not one but two are substantially bigger and lower in density than theory predicts,” said co-author Robert Noyes (CfA). “We can’t dismiss HD209458b as a fluke. This new discovery suggests something could be missing in our theories of how planets form.”
IAU 2006 General Assembly: Result of the IAU Resolution votes August 29, 2006
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24 August 2006, Prague: The first half of the Closing Ceremony of the 2006 International Astronomical Union (IAU) General Assembly has just concluded. The results of the Resolution votes are outlined here.
It is official: The 26th General Assembly for the International Astronomical Union was an astounding success! More than 2500 astronomers participated in six Symposia, 17 Joint Discussions, seven Special Sessions and four Special Sessions. New science results were vigorously discussed, new international collaborations were initiated, plans for future facilities put forward and much more.
In addition to all the exciting astronomy discussed at the General Assembly, six IAU Resolutions were also passed at the Closing Ceremony of the General Assembly:
Resolution 1 for GA-XXVI: “Precession Theory and Definition of the Ecliptic”
Resolution 2 for GA-XXVI: “Supplement to the IAU 2000 Resolutions on reference systems”
Resolution 3 for GA-XXVI: “Re-definition of Barycentric Dynamical Time, TDB”
Resolution 4 for GA-XXVI: “Endorsement of the Washington Charter for Communicating Astronomy with the Public”
Resolution 5A: “Definition of ‘planet’ “
Resolution 6A: “Definition of Pluto-class objects”
The IAU members gathered at the 2006 General Assembly agreed that a “planet” is defined as a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
This means that the Solar System consists of eight “planets” Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A new distinct class of objects called “dwarf planets” was also decided. It was agreed that “planets” and “dwarf planets” are two distinct classes of objects. The first members of the “dwarf planet” category are Ceres, Pluto and 2003 UB313 (temporary name). More “dwarf planets” are expected to be announced by the IAU in the coming months and years. Currently a dozen candidate “dwarf planets” are listed on IAU’s “dwarf planet” watchlist, which keeps changing as new objects are found and the physics of the existing candidates becomes better known.
The “dwarf planet” Pluto is recognised as an important proto-type of a new class of trans-Neptunian objects. The IAU will set up a process to name these objects.
Results:
Resolution 5A: “Definition of Planet” was not counted but was passed with a great majority.
Resolution 5B: “Definition of Classical Planet” had 91 votes in favour, but many more against so there was no count.
Resolution 6A: “Definition of Pluto-class objects” was passed with 237 votes in favour, 157 against and 17 abstentions.
Resolution 6B: “Definition of Plutonian Objects” had 183 votes in favour and 186 votes against.
RESOLUTIONS
Resolution 5A is the principal definition for the IAU usage of “planet” and related terms.
Resolution 6A creates for IAU usage a new class of objects, for which Pluto is the prototype. The IAU will set up a process to name these objects.
IAU Resolution: Definition of a Planet in the Solar System
Contemporary observations are changing our understanding of planetary systems, and it is important that our nomenclature for objects reflect our current understanding. This applies, in particular, to the designation “planets”. The word “planet” originally described “wanderers” that were known only as moving lights in the sky. Recent discoveries lead us to create a new definition, which we can make using currently available scientific information.
RESOLUTION 5A
The IAU therefore resolves that “planets” and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:
(1) A “planet”1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
(2) A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2 , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects3 except satellites orbiting the Sun shall be referred to collectively as “Small Solar-System Bodies”.
1The eight “planets” are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
2An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
3These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.
IAU Resolution: Pluto
RESOLUTION 6A
The IAU further resolves:
Pluto is a “dwarf planet” by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.
[SOURCE: http://www.iau.org/iau0603.414.0.html ]
