(Note - Methane in the atmosphere is a good indicator of life)
The glow of methane has been detected in the atmosphere of Jupiter-sized alien planet orbiting close to its parent star.
Because the signature of glowing methane, which might be triggered in a similar way to Earth's auroras, is so strong, it could help scientists better understand the atmospheres of exoplanets, if it turns out to be a common feature among them.
The detection was also made from a ground-based telescope and not space-based one, suggesting that many more detailed measurements of exoplanet atmospheres will be made in the coming years, possibly even the signatures of biological activity, researchers said.
Methane is belched out by certain kinds of microbes on Earth (as well as by big animals, such as cows), and scientists think this is one form that potential alien life could take. (Methane is also created through geophysical and chemical processes on Earth that have nothing to do with life.)
"That's not where we are today, but that's where we're going," said Mark Swain of NASA's Jet Propulsion Laboratory in Pasadena, Calif., who led the team that made the methane discovery.
Glowing methane
Scientists detected this particular signature of methane in the atmosphere of an extrasolar planet dubbed HD 189733b, which was one of the first exoplanets to have its atmosphere "sniffed" my spectrometers, which measure the range of light given off by a particular object and show the light signatures that are peculiar to different elements and molecules.
Water vapor, carbon dioxide, and methane have already been detected in HD 189733b's atmosphere, though that first methane detection had a different signature than the new one.
The new detection seems to be from the fluorescence of methane in the atmosphere of the planet. (An Earth analogue to this phenomenon would be something like the aurora borealis, Swain said.)
The finding, detailed in the Feb. 4 issue of the journal Nature, was unexpected if not a total surprise, as similar signatures have been seen in the atmospheres of bodies in our own solar system.
"It's not particularly surprising since we have seen fluorescent methane in Jupiter, Saturn and even Titan," said Seth Redfield of Wesleyan University in Middletown, Conn., who was not involved with the finding, but has previously made detections of sodium in the same exoplanet's atmosphere. Redfield wrote an opinion article about the new discovery in the same issue of Nature.
Understanding atmospheres
For the atmospheric signatures collected for exoplanets so far, astronomers have assumed that heat is what is causing the emission of various atmospheric constituents, as most are so-called hot Jupiters, which orbit very close to their stars and are bathed in large amounts of stellar radiation.
But heat can't explain the fluorescence of methane. "The light is being generated by something other than heat," Swain told SPACE.com.
But the energy source driving the emission is still a mystery.
"We don't know the answer for that today," Swain said, but he added that two possible sources where collisions with photons or charged particles from the stellar wind. The solar wind from our sun is not known to cause methane fluorescence in any planets in our solar system.
But the fluorescence does tell astronomers something about the atmosphere of the planet: that the part where the fluorescence is happening is likely "very tenuous layers in the atmosphere of the planet," Swain said.
This is because fluorescence is what in physics is called a non-locally thermodynamic equilibrium process.
So in an atmosphere that is in locally thermodynamic equilibrium, energy moves between particles primarily through collisions – this can happen because the atmosphere is thick and the molecules are relatively close together. This is the case in the lower portions of Earth's atmosphere.
But when the atmosphere thins out, its molecules can become far enough apart that the time between collisions is long enough that energy can get to molecules through other means. A similar process occurs in the upper portions of Earth's atmosphere, where things like the solar wind can collide with particles — this is what creates the auroras that flash over Earth's poles.
So it's possible that the signature of methane fluorescence from HD 189733b is coming from a different part of the atmosphere than the previous methane signature, though Swain cautions that it will take more observations and new atmospheric models to really characterize the exoplanet's atmosphere.
Future detections
Swain and his team are already at work looking for this fluorescent signature in other exoplanets. If it turns out to be a common feature, "it could change how detectable these exoplanets are," because the signature is strong and unique, Swain said.
Redfield said the finding is exciting because it adds to the list of known exoplanet atmospheric components, which are building up at a time when "we're just getting use to finding exoplanets." In a decade, exoplanet atmosphere detections will likely be as routine as exoplanet detections now are, he said.
Making more detections of methane in particular could be helpful because it can be a by-product of biological processes. Building a better understanding of what kinds of methane are out there and where in exoplanet atmospheres the gas occurs could help scientists determine which signatures are most likely to be related to alien biology.
"This is one step on a much longer journey," Redfield said.
The finding is also exciting, both Swain and Redfield said, because it was made with a relatively modest-sized ground-based telescope, NASA's Infrared Telescope Facility (IRTF) in Hawaii, whereas most other atmospheric detections were made with space-based telescopes, such as Hubble and the Spitzer Space Telescope.
The detections of atmospheres from the Earth's surface can only be made in particular wavelengths of light that aren't absorbed or scattered by the Earth's atmosphere, but ground-based detections are an important complement to space-based ones because ground-based telescopes are much bigger — while Hubble is 2.4-m telescope, the Keck telescopes (also in Hawaii) are 10 meters in diameter. This means that atmospheres could be observed with more detail or at fainter objects.
This capability "is going to prove really, really critical to understanding these exoplanet atmospheres," Redfield said.
Swain already has plans to use some bigger Earth-based telescopes in the future.
Thursday, 11 February 2010
Slam! Two Asteroids Suspected in Space Collision
A mysterious trail of debris spotted in space suggests two asteroids recently slammed into each other.
Though such space rock collisions are thought to be common, direct evidence of the cosmic smashups has never been seen before. New images from NASA's Hubble Space Telescope, however, have caught the suspected collision on camera.
An X-shaped debris pattern was observed by Hubble on Jan. 25 and 29. The pictures, released today, show a comet-like object, dubbed P/2010 A2, with the X-pattern of filamentary structures near the nucleus.
"This is quite different from the smooth dust envelopes of normal comets," said study leader David Jewitt of the University of California at Los Angeles. "The filaments are made of dust and gravel, presumably recently thrown out of the nucleus. Some are swept back by radiation pressure from sunlight to create straight dust streaks. Embedded in the filaments are co-moving blobs of dust that likely originated from tiny unseen parent bodies."
The two asteroids likely smashed into each other with an average impact speed of more than 11,000 miles per hour, or five times faster than a rifle bullet.
The Hubble photos show that the main nucleus of P/2010 A2 lies outside its own halo of dust. This pattern has never been seen before in a comet-like object. The nucleus is estimated to be about 460 feet (140 meters) in diameter.
Scientists think this nucleus is the surviving remnant of the collision, and the tail is the rubble left over from the crash.
"If this interpretation is correct, two small and previously unknown asteroids recently collided, creating a shower of debris that is being swept back into a tail from the collision site by the pressure of sunlight," Jewitt said.
P/2010 A2 orbits in the warm, inner regions of the asteroid belt between Mars and Jupiter. When the object was observed, it was approximately 180 million miles (290 million km) from the sun and 90 million miles (145 million km) from Earth.
The Hubble images were captured by its new Wide Field Camera 3, which was installed during the May 2009 space shuttle servicing trip. The camera can spot house-sized fragments at the distance of the asteroid belt
A Star is Born in Nearby Cosmic Nursery
A new panorama of a cosmic nebula offers an up-close glimpse of baby stars being born.
The nebula, dubbed NGC 3603, is called a starburst region because stars are coming into being in feverish bursts of activity. It lies about 22,000 light-years away from the sun, making it the closest region of the kind known in our galaxy. This near view offers astronomers a relatively local test bed for studying intense star formation processes that are usually hard to observe in detail because of their great distance from us.
The new view was captured by the European Southern Observatory's Very Large Telescope in the Atacama desert of Chile. The cosmic panorama displays the rich texture of the surrounding clouds of gas and dust in the area, with many of the hot newborn stars dotting the scene with blue light.
This nebula is also home to the most massive star ever to be "weighed" so far. This behemoth, part of a binary system called A1, is estimated to be roughly 116 times the mass of the sun.
NGC 3603 owes its shape to the intense light and winds coming from the young, massive stars that push out against the curtains of gas and clouds. The central cluster of stars inside the nebula harbors thousands of stars of all sorts: the majority have masses similar to or less than that of our sun, but most spectacular are several of the very massive stars that are close to the end of their lives.
Several blue supergiant stars crowd into a volume of less than a cubic light-year, along with three so-called Wolf-Rayet stars — extremely bright and massive stars that are ejecting vast amounts of material before finishing off in glorious explosions known as supernovae
Tuesday, 2 February 2010
This image shows the galaxy density in the COSMOS field surveyed by the Hubble Space Telescope, with colors representing the distance of the galaxies. The X-ray contours (in pink) show the extended X-ray emission as observed by the XMM-Newton spacecraft. Credit: ESA
To weigh the universe, scientists use two kinds of cosmic scales: one to measure all the regular matter out there, and another to deduce how much invisible dark matter remains hidden underneath.
These calculations have been taken further than ever before by a new study that tallied both types of mass in smaller and more distant groups of galaxies than any previous projects. The project found that these faraway galactic clusters have roughly the same proportion of dark matter to regular matter as the closer galaxy groups do.
The findings could help astronomers understand more about dark matter, as well as its even stranger sibling – dark energy.
Invisible universe
Dark matter is a form of stuff that does not interact with light, so cannot be seen, but makes its presence felt by exerting a gravitational pull on normal matter.
Astronomers measure how much dark matter lies in galaxies by a fluke of physics called gravitational lensing. This phenomenon, predicted by Einstein's theory of general relativity, causes light to curve as it flies through space-time that has been dented by the gravity of large bodies of mass.
For example, groups of massive galaxies will gravitationally warp the space-time around them, forcing light to bend as it passes through, and causing them to look distorted when their light reaches our telescopes. Scientists can tell how much total mass there is by how much of this distortion occurs.
Next, researchers calculate how much normal matter is in a cluster of galaxies by looking at its X-ray light, since the light must be coming from only the regular stars and gas that make up the cluster.
Comparing these two calculations — the total matter to just the regular matter — gives a ratio astronomers call the mass-luminosity relation. So far, the mass-luminosity relation has been measured well for nearby, large galaxy clusters, but there has not been good enough X-ray data to probe farther or smaller, dimmer clusters of galaxies.
"We can map out the big cities, but no one's been able to map out the villages yet," said Alexie Leauthaud of the Lawrence Berkeley National Laboratory in Berkeley, Calif., leader of the new study.
New ranges
Astronomers used observations from the European Space Agency's XMM-Newton satellite and from NASA's Chandra satellite, as well as data from the Hubble Space Telescope's Cosmic Evolution Survey (COSMOS). These ultra-high resolution photos allowed the scientists to extend the mass-luminosity relation further than ever before.
With such dim objects, the gravitational lensing wasn't immediately apparent. So researchers used a statistical analysis to measure the orientation and shape of the galaxies to find small distortions due to so-called weak lensing.
They found that the same general ratio of dark matter to normal matter prevailed in these distant, small clusters as for nearby, larger clusters.
"We didn't know what to expect going down to lower masses or [farther distances], and we find this nice simple relationship," Leauthaud told SPACE.com. "Now the aim is to find out why we find this nice, simple relationship."
Dark energy enigma
The finding may help shed light on an even more bizarre aspect of the universe — dark energy. Dark energy is the name given to whatever mysterious force is causing the universe to accelerate as it expands.
"We want to try to understand the properties of dark energy," Leauthaud said. "One way to measure properties of dark energy is to measure the number of structures that have formed for a given amount of dark matter."
Dark energy basically works against gravity in a tug-of-war. While gravity constantly pulls mass inward, encouraging things to clump together and condense into smaller space, dark energy does the opposite. This force somehow pulls everything apart, causing everything in the universe to move away from everything else at ever-increasing speeds.
When mass clumps together enough to form galaxies, it means that gravity has won on those scales, helping things to stick together despite the pull of dark energy. So the more astronomers can measure when and how structures formed in the universe, the better they can understand just how far dark energy's pull reaches
Weird Rock Offers Glimpse Deep Inside Mars
NASA's Opportunity rover has discovered a peculiar rock on Mars that scientists think originated deep within the red planet.
The stone could reveal new secrets about the makeup of Mars' interior.
Dubbed "Marquette Island," the rock is a dark boulder not much bigger than a basketball that sits on a rippled Martian plain.
"Marquette Island is different in composition and character from any known rock on Mars or meteorite from Mars," said Opportunity principal investigator Steve Squyres of Cornell University in Ithaca, N.Y. "It is one of the coolest things Opportunity has found in a very long time."
Opportunity and its twin rover, Spirit, landed on Mars in 2004, and have drastically outlived their original 90-day mission plan. While Spirit is currently stuck in a sand trap with two broken wheels, Opportunity is still roving free.
In all of its 11 miles worth of traveling, Opportunity has found only one other rock of comparable size to Marquette Island and scientists think it was ejected from a distant crater. Called "Bounce Rock," that stone closely matched the composition of a meteorite that landed on Earth, but was thought to have originated on Mars.
The coarse-grained texture and basalt composition of Marquette Island indicates that it cooled slowly from molten rock, allowing crystals time to grow. That means that it likely originated deep in the crust, not at the surface where it would cool quicker and have finer-grained texture, scientists say.
"It is from deep in the crust and someplace far away on Mars, though exactly how deep and how far we can't yet estimate," Squyres said.
In contrast, most Martian basalt rocks that Spirit and Opportunity have encountered have different textures and composition.
At first, scientists thought Marquette Island could be a meteorite, but it appears to have a much lower nickel content than other meteorites Opportunity has found. And Marquette Island's interior contains more magnesium than typical Martian basalt rocks.
"It's like having a fragment from another landing site," said Ralf Gellert of the University of Guelph, in Ontario, Canada. Gellert is lead scientist for the alpha particle X-ray spectrometer on Opportunity's robotic arm. "With analysis at an early stage, we're still working on some riddles about this rock."
The rover team used Opportunity's rock abrasion tool to grind away some of Marquette Island's weathered surface and expose the interior.
This was the 38th rock target Opportunity has ground into, and one of the hardest. The tool was designed to grind into only one Martian rock, and this rock may not be its last.
"We took a conservative approach on our target depth for this grind to ensure we will have enough of the bit left to grind the next hard rock that Opportunity comes across," said Joanna Cohen of Honeybee Robotics Spacecraft Mechanisms Corp., in New York, which built and operates the tool.
While Marquette Island is intriguing, Opportunity couldn't stop too long to investigate — it left the site Jan. 12. The rover is mid-way on a journey toward a much larger crater, Endeavour, that scientists think will offer a host of scientific prospects.
"We're on the road again," said Mike Seibert, a rover mission manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The year ahead will include lots more driving, if all goes well. We'll keep pushing for Endeavour crater but watch for interesting targets along the way where we can stop and smell the roses."
Ganymede & Calisto - Surface Differences Explanation
Each of Jupiter's more than 60 moons has its own unique character, but scientists have often wondered at the striking differences between the surfaces and interiors of two of the gas giant's largest moons, Ganymede and Callisto.
A new study, detailed in the Jan. 24 issue of the journal Nature Geoscience, might have found an explanation for the disparate features of these Galilean moons: Ganymede was pummeled by more and faster comets impacts than its sister moon billions of years ago.
While Ganymede and Callisto are similar in size and both made up of a mixture of ice and rock, data from both the Galileo and Voyager missions show that they sport different looks, both on the inside and outside.
But just why the two moons looked so different is a problem that planetary scientists have been grappling with for 30 years. The solution to the problem could shed light on how our solar system, and planets in general, evolved.
"Similar to Earth and Venus, Ganymede and Callisto are twins, and understanding how they were born the same and grew up to be so different is of tremendous interest to planetary scientists," said Amy Barr of the Southwest Research Institute Planetary Science Directorate.
Ganymede has a surface that shows evidence of resurfacing by tectonic processes — the same forces that continually reshape the surface of the Earth. The moon also has a large rock/metal core, showing that its constituent materials separated out over time, with the heavier stuff settling to the interior of the planet (just as the iron present in Earth settled to the core, while the lighter rocky materials floated to the surface).
The surface of Callisto, on the other hand, shows no signs of resurfacing, and the separation of rock and ice within it seems to be incomplete.
Barr and her colleague Robin Canup created a model that looked at the possible role of comet impacts in the evolution of these two moons. The model simulated the impacts and rocky core formation and found that Ganymede and Callisto's evolutionary paths diverged around 3.8 billion years ago, during a period in the solar system's life called the Late Heavy Bombardment. (The pockmarked surface of Earth's moon shows that this period was dominated by large impacts).
In the model, Jupiter's strong gravity focuses comets that swing into the neighborhood into the paths of Ganymede and Callisto.
When a comet impacted either moon, the mixed ice and rock that made up the surface would have created a pool of liquid water, allowing rock in the melt pool to sink to the moon's center.
Because Ganymede is closer to Jupiter, it was hit by twice the number of impactors as Callisto was. The proximity to Jupiter also meant that the comets colliding with Ganymede were going faster than those that hit Callisto.
The model shows that if the impacts to Ganymede released enough energy, the process of rock sinking and core formation could have become self-sustaining.
"Impacts during this period melted Ganymede so thoroughly and deeply that the heat could not be quickly removed. All of Ganymede's rock sank to its center the same way that all the chocolate chips sink to the bottom of a melted carton of ice cream," Barr said. "Callisto received fewer impacts at lower velocities and avoided complete melting."
These model findings help link the evolution of Jupiter's moons to the overall evolution of the solar system and the history of bombardment of Earth's own moon
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