Artist's impression of a solar sail. Image credit: NASA
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Last week we talked about rockets. How they work and their limitations. This week we’re going to look at the future of propulsion systems. From the ion engines that are already working to explore the Solar System to the prototype solar sails to futuristic technologies like magnetic sails, and bussard ramjets. This is how we’ll travel to other stars.
Are you seeing a ghost? It could be. When most people think of the Trifid nebula they think of the wild colored fantasy images they’ve seen taken with filtered, long exposure photography. But what happens when you combine science with imagery? Just ask Toni Heidemann. Toni may have made his living in Grenoble, France by studying cold neutron backscattering in a spectrometer, but when he retired in 2002 he did the world a favor by turning his interest in h-alpha celestial photography into works of art.
The Trifid Nebula is also known as Messier 20 and NGC 6514. But what is it? Behold a three-lobed, glowing cloud of gas and plasma where star formation is taking place. In the case of our ghostly apparition, this is a remarkable collection of open cluster, emission nebula and Barnard dark nebula (B85) combined. Buried in here are hot, young blue stars which formed from the gas itself and they are emitting unfathomable amounts of ultraviolet light and ionizing the nebulous sheath around them.
Is M20 the ghost of the past – or the ghost of the future? The huge cloud of ionized molecular hydrogen may have already given birth to thousands of stars and may yet be the home of an eventual supernova. In a few more million years, the driving force of the stellar winds from the more massive stars will disperse the cloud, leaving only the cluster. But, for now, recent Hubble studies have shown NGC 6514 to be home to an EGG – an evaporating gaseous globule – a clump of gas so dense that not even the Trifid’s fueling star can destroy it.
Perhaps it is M20’s varying nature that makes its distance so hard to distinguish as a single object. Many times we disregard history’s teachers, such as Sir William Herschel, who instinctively chose to label the Trifid as four separate objects. Of course, why he did so may remain open to debate, but as a devotee of Herschel’s work, I’ve often found his assumptions have often remarkably been proved accurate. There is a star cluster in the center, surrounded by an emission nebula, enfolded in a reflection nebula and divided by a dark nebula. No wonder science can’t decide if its 2200 light years away or 7600! Some figures place it at 5200, others at 3140, and even recent Hubble studies can only say “about 9000 light years away”.
So why are images like Toni’s M20 really more exciting than the colorful Trifid renditions? By using h-alpha, he’s blocking most of the visible spectrum and centering on collecting specific photons. The h-alpha wavelength is a wonderful resource for studying the ionized hydrogen content of gas clouds like NGC 6514. Because it requires as much energy to excite the hydrogen atom’s electron as it does to ionize it, chances are slim that it will be removed from the equation. Once ionized, the electron and proton recombine to form a new hydrogen atom – perhaps emitting hydrogen alpha wavelengths and photons.
Want to know more? According to studies done by Yushef-Zadeh (et al), “Radio continuum VLA observations of this nebula show free-free emission from three stellar sources lying close to the O7 V star at the center of the nebula. We argue that neutral material associated with these stars is photoionized externally by the UV radiation from the hot central star. We also report the discovery of a barrel-shaped supernova remnant at the northwest rim of the nebula, and two shell-like features.” More features? “We also note a remarkable complex of filamentary and sheetlike structures that appear to arise from the edge of a protostellar condensation. These observations are consistent with a picture in which the bright massive star HD 164492A is responsible for the photoevaporation of protoplanetary disks of other less massive members of the cluster, as well as the closest protostellar condensation facing the central cluster.”
There is such a huge amount of information packed into what appears to be such a small area of space. According to Lefloch (et al), “The Trifid Nebula is a young H II region undergoing a burst of star formation.” Their far-infrared studies took a deeper look at the protostars surrounding the Trifid’s exciting star hiding behind the ionization front. “Inspection of their physical properties suggest that they are similar to the dust protostellar cores observed in Orion, although at an earlier evolutionary “pre-Orion” stage. The cores are embedded in a compressed layer of dense gas. Based on comparison with the models, we find that the cores could have formed from the fragmentation of the layer and that the birth of the protostars was triggered by the expansion of the Trifid Nebula.”
From studies that examine the internal dust which absorbs and scatters radiation from the H II region and central star to polarization studies which show the continuum is higher in emission lines for three regions in the southern part of the nebula, the M20 is still a wonderful, delightful and mysterious “Ghost Of Summer”… and meant to be enjoyed in exactly the color in which we see it.
Many thanks to Toni Heidemann and his outstanding h-alpha imaging work. Merci.
The space-time bubble. Unfortunately, quantum physics may have the final word (Michael Alcubierre)
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Standard in almost every Star Trek episode are warp drives and cloaking devices. But in reality these science fiction gadgets defy the laws of physics. Or do they? Different scientists have been working on developing these two devices and they say they are getting closer to actually creating working prototypes. While warp drive won’t be available anytime soon, scientists are gaining a better understanding of how faster-than-light speed could possibly be achieved. And as for cloaking devices, don’t look now, but researchers recently cloaked three-dimensional objects using specially engineered materials that redirects light around objects.
Previously, scientists at the University of California, Berkley were only able to cloak very thin, two dimensional objects. But now, using meta-materials, which are mixtures of metal and circuit board materials such as ceramic, Teflon or fiber composite, scientists have deflected light waves around an object, like water flowing around a smooth rock in a stream. Objects are visible because they scatter the light that strikes them, reflecting some of it back to the eye. But the meta-materials would ward off light, radar or other waves. In effect, it would be a type of optical camouflage.
The research group, led by Xiang Zhang say they are a step closer to being able to render people and objects invisible. Their findings will be released later this week in the journals Nature and Science. The path that light rays would take through a theoretical cloaking device. Credit: John Pendry
Another scientist and one of the leaders in cloaking research is John Pendry, a theoretical physicist at Imperial College, London. It was he who first worked out how a cloak could be built in theory, and then he helped build the first working cloak. Pendry recently submitted an abstract that discusses what he says is a new type of cloak, one that gives all cloaked objects the appearance of a flat conducting sheet. Pendry says this type of cloak has the advantage in that nothing remarkable is required to create the cloak. Pendry said the device could be “made isotropic. It makes broadband cloaking in the optical frequencies one step closer.” This type of cloak seemingly creates a mirage to render an object invisible to the eye. Pendry’s own website says information on his new cloak will be available soon.
While cloaking devices would have military applications, a group of scientists researching warp drives say they just want to have the ability to travel to Earth-like exoplanets, like Gliese 581c to better understand the origin and development of life. “The only way we could realistically visit these worlds in time-frames on the order of a human lifespan would be to develop what has been popularly termed a `warp drive,'” said researchers Gerald Cleaver and Richard Obousy from Baylor University in Texas.
Their work expands on research done by theoretical physicist Michael Alcubierre from the University of Mexico, who in 1994 demonstrated space could be made to move around a spacecraft by `stretching’ space so that space itself would expand behind a hypothetical spacecraft, while contracting in front of the craft, creating the effect of motion. So, the ship itself doesn’t move, but space moves around it.
Their new research tries to take advantage of advances in understanding dark energy and why our universe is ever-expanding in every direction. Comprehending that might give us a leg up in being able to generate an asymmetric bubble around a spacecraft. “If we can understand why spacetime is already expanding, we may be able to use this knowledge to artificially generate an expansion (and contraction) of spacetime,” said Cleaver and Obousy in their abstract.
They propose manipulating the 11th dimension, a special theoretical part of an offshoot of string theory called the “m-theory” to create a bubble of dark energy by shrinking the 11th dimension in front of the ship and expanding it behind.
Obviously, this is highly theoretical, but if it leads researchers to a better understanding of dark energy, so much the better.
There’s one hitch, however. Cleaver and Obousy calculated that the energy needed to distort the space around a spacecraft-sized object is about 10^45 Joules or the total energy of an object the size of Jupiter if all its mass were converted into energy.
This creates a chicken and the egg type of conundrum. Which comes first: understanding dark energy or having the ability to create huge amounts of energy?
But Cleaver and Obousy are upbeat about it all. “This is a hypothetical propulsion device that could theoretically circumvent the traditional limitations of special relativity which restricts spacecraft to sub-light velocities. Any breakthrough in this field would revolutionize space exploration and open the doorway to interstellar travel.”
Hubble's 100,000th Orbit Celebration Image. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
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This morning at 7:42 EDT, the Hubble Space Telescope completed it’s 100,000th orbit around the Earth. That’s about 4.38 billion kilometers (2.72 billion miles), as it clicks along at 8 km per second (5 miles/s), orbiting Earth once every 90 minutes. Hubble’s been in orbit for over 18 years now, since its launch on the space shuttle Discovery on April 24, 1990. To commemorate occasion, scientists at the Space Telescope Science Institute in Baltimore, Md., released a special image taken with Hubble’s Wide Field Planetary Camera 2 of a nebula near the star cluster NGC 2074 (upper, left) , showing a dazzling region of celestial birth and renewal. And soon, Hubble will have a little renewal of its own, with the upcoming fifth and final servicing mission in October.
In preparation for the STS-125 servicing mission to Hubble, on Friday engineers mated the external tank (ET-127) to the two solid rocket boosters. Things are going well with getting Atlantis ready to go, and NASA is looking at actually moving up the launch date for the mission a few days, from the currently scheduled October 8 to October 2. Read more about the mission here, and interviews with the seven astronauts who will be part of the mission are available to read on that page, or you can watch them on NASA TV this week.
The above image released today shows a firestorm of raw stellar creation, perhaps triggered by a nearby supernova explosion. It lies about 170,000 light-years away near the Tarantula nebula, one of the most active star-forming regions in our Local Group of galaxies. This representative color image was taken just yesterday on August 10, 2008. Red shows emission from sulfur atoms, green from glowing hydrogen, and blue from glowing oxygen.
Hubble remains in orbit without any fuel; it just uses its speed and Earth’s gravity to maintain its circular orbit, and gyroscopes to maintain the correct attitude. The astronauts on Atlantis will make one final mechanic’s check to replace worn gyroscopes, batteries and a fine guidance sensor and to install new instruments to extend Hubble’s vision. These include a new Wide Field Camera 3 and a Cosmic Origins Spectrograph, to observe the light put out by extremely faint, far-away quasars.
Hubble has been an incredible spacecraft that has changed our view of the universe. Happy 100,000th orbit Hubble!
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If you thought Pluto was going quietly and giving up its planetary status without a fight, think again. Leading astronomers have spoken out against the International Astronomical Union (IAU) decision to classify the dwarf planet as a “Plutoid,” described by some critics as a “celestial underclass.” The IAU decision was made after it was deemed that Pluto cannot be called a “planet.” Although the spherical rocky body can tick most attributes of being a “planet,” the IAU pointed out that Pluto is too small to be capable of gravitationally clearing its own orbit (plus it periodically crosses the path of Neptune’s orbit); it should therefore be called a “dwarf planet.” Back in June however, the IAU gloriously announced that Pluto should be now be re-classified as a “Plutoid” and any other Pluto-like planets should follow suit. But on Thursday, at a major conference in Maryland, leading astronomers will refute the Plutoid classification saying the IAU re-naming is confusing and unworkable…
It may be the smallest planet in the Solar System a Plutoid, but this little spherical rock is causing a lot of noise down here on Earth. In 2006, the IAU re-classified the definition of a planet to distinguish between the differences between the larger known planets with the smaller rocky bodies (such as the increasing number of observed Kuiper Belt objects). There are three defining characteristics of what a planet should be:
It is in orbit around the Sun.
It has sufficient mass so that it assumes a hydrostatic equilibrium (nearly round) shape.
It has “cleared the neighbourhood” around its orbit.
Pluto fulfils #1 and #2, but fails on #3, it is simply too small to gravitationally clear its own orbit. So Pluto was caught right in the middle of the “planetary classification debate ’06” and incidentally failed on one count. If any object fulfils the first two planetary criteria, but fails on the last, the IAU would classify the celestial body as a “dwarf planet.” To complicate matters, Pluto also travels inside the orbit of the gas giant Neptune periodically, giving it the extra classification of being a Trans-Neptunian Object (TNO). Although Pluto is a “dwarf” by Solar System standards, it is one of the largest Kuiper Belt Objects (KBO) in the outer Solar System; a true King amongst dwarfs.
Pluto has had a hard few months after getting kicked out of the planetary club.
So, for two years, Pluto was stuck in no-man’s land. It had been re-classified as a dwarf planet and astronomy teachers had to re-write their teaching material. Websites like NinePlanets.org had to scrub the 9 and replace it with an 8; but also had the foresight to buy “EightPlanets.org.” Times were a little messy for Pluto. Then, in June this year, the IAU seemed to want Pluto to feel a little better. Not only was it the King of the Kuiper Belt, it would have an entire army of Pluto-like dwarf planets named after it. The IAU created the “Plutoid,” and as if to avoid any more confusion, it gave the classification a no-nonsense definition:
Plutoids are celestial bodies in orbit around the Sun at a semi major axis greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighbourhood around their orbit. Satellites of plutoids are not plutoids themselves. – The IAU definition of a Plutoid (June 11th 2008).
Got that? Good. But not everyone was happy, least of all Pluto. T-shirts have even been printed with the quote: “It’s okay Pluto, I’m not a planet either” (and yes, I have one), for anyone wanting to show their support for the struggling rocky body.
So this Thursday, some very prominent astronomers will take their case to the “The Great Planet Debate: Science as Process” conference at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. To cut a long story short, they want Pluto to be reinstated as a planet, thereby abandoning the term “Plutoid.”
Dr David Morrison, director of the NASA Lunar Science Institute in California, makes the point that if the largest planets in our Solar System can be called Gas “Giants” then it should be fine to call Pluto a “Dwarf” Planet. But in the current IAU classification, Pluto cannot be called a planet.
“It has never before been necessary for any organisation to define a word that has been in common every day use so I see no reason why it was necessary on this occasion. Astronomers use adjectives such as giant and dwarf to describe different subclasses of objects like planets, stars and galaxies, so why could Pluto not remain as a dwarf planet just as Jupiter is a giant planet. Also, around 90 per cent of the planets we know now are outside our solar system, but under the International Astronomical Union’s definition, they cannot be classed as planets.” – Dr David Morrison
So it would seem the classification of “planet” will remain a very exclusive club of eight under the IAU rules; only Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune will have this honour unless the scientists at the Great Planet Debate conference can convince the IAU otherwise. Mark Sykes, from the Planetary Science Institute, argues that only #2 of the IAU planet definition need be applied; it is therefore the shape, or roundness, of the object that defines whether it can be called a planet or not. If this definition were applied, the Solar System would expand to include 12 planets. This worries some traditional thinkers at the IAU. As our observational techniques improve, more planet candidates will be discovered, therefore making the Solar System wildly different than what it is now.
But if there are more “planets” out there, why shouldn’t more planets be added to the official eight we currently have? It sounds like the Pluto debate is far from over and it will be interesting to hear what the delegates have to say on Thursday…
An early parachute drop test for the Constellation Project (NASA)
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At the end of last month, the Orion crew module and the Ares I rocket parachute systems underwent a series of drop tests. The “drogue parachute” that will gently slow the descent of the spent first-stage motor of the Ares vehicle appeared to function as expected over the Arizona skies. However, an Orion test failed, “programmer parachute” failing to correct the orientation of the test crew module, allowing the module to drop through the sky upside-down. The programmer parachute is intended to inflate before the main three parachutes are deployed to bring the re-entering Orion astronauts to land safely. This news has come from an internal memo referring to the Orion test drop back on July 31st; the successful Ares I drogue parachute drop was carried out on July 24th. So what went wrong with the Orion test-drop?
NASA engineers are continuing a series of parachute tests on Orion and Ares. The first parachute system to be employed in any given launch will be the Ares parachute recovery system (assuming the emergency jettison motor isn’t fired before then). At approximately 126 seconds into flight and at an altitude of 189,000 feet (58,000 m), the first Ares I stage will separate, letting the spent booster drop through the atmosphere. To ensure the engine can be re-used by subsequent Constellation launches, the booster’s nose cap will be jettisoned at 15,740 feet (4800 m), releasing a small pilot parachute, dragging a larger drogue parachute out to slow down the rapidly falling first stage.
The Ares I components (NASA)
The drogue is smaller than a conventional parachute and it is intended to slow the booster from 402 mph (647 km/hr) to 210 m/hr (338 km/hr), positioning the cylinder vertically. Only when this slowdown is achieved that the main three cluster of parachutes can be deployed to complete the descent and plunge into the Atlantic Ocean for retrieval.
It would appear that the essential drogue testing of the first stage Ares I booster worked flawlessly when tested by NASA at the U.S. Army’s Yuma Proving Ground near Yuma, Arizona on July 24th. The next drogue test is scheduled for October.
However, during the July 31st Orion parachute test-run, there was a slight technical hitch that gave the Parachute Test Vehicle (PTV) a violent spin and then thud into the ground. The “programmer” parachute is intended to “right” the orientation of the re-entering crew module as it descends, an essential task before the drogue parachutes can be deployed to rapidly slow the module (in a similar way to the Ares I system). Unfortunately, during this PTV test-drop, problems arose very quickly. As soon as the programmer parachute was deployed, it failed to inflate and therefore did not cause any drag. This happened as the programmer parachute was being buffeted by the turbulence in the wake of the PTV and stabilization parachutes. The PTV was therefore allowed to fall ungracefully, upside-down.
The Orion crew module (HowStuffWorks.com)
Continuing to drop, the programmer and stabilization parachutes were jettisoned (having not done their job very well), and drogue parachutes were deployed. As the PTV was falling out of control, the drogue parachutes were put under immediate strain and wrapped around the PTV, dynamic pressure causing the drogue to be cut away.
Having suffered some major whiplash, the PTV’s main bag retention system was damaged and failed. Continuing to fall, the main parachutes were deployed, two were ripped from the vehicle, forcing the PTV to hit the ground with only one parachute open. There are no details as to what damage was caused by this failed test, but I think we can assume the PTV’s bodywork will be dented (and I wonder if human cadavers were used on this particular drop. If they were, I wouldn’t want to be the first engineer on the scene!).
Although an obvious set-back for the Orion parachute system, the NASA memo highlights that it was a “test technique failure” and not a failure of the technology itself. Regardless, I am sure this issue will be ironed out soon enough as the Constellation Program continues to push ahead with development…
Fireworks at the 2008 Olympics Opening Ceremony. Credit: Clive Rose, Getty Images
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Space and the Olympics might not be synonymous in most people’s minds — although this image of the Opening Ceremony fireworks makes it look like Olympic Stadium is going supernova — but there are a few connections between the two for this year’s Summer Olympics in Beijing, China. Google Earth recently updated the satellite imagery it uses for the Beijing area to provide users with better maps. They also used satellite imagery to create a 3-D tour of all the facilities for the 2008 Olympics (see video below). Other space connections include several space explorers who carried the Olympic torch on its running tour around the world, and NASA space spinoff technology used in some of the clothing and equipment for Olympic use.
The first woman in space, Russian cosmonaut Valentina Tereshkova, one of 80 Russian runners, carried the Olympic torch during its tour of that country in early April. Sheikh Muszaphar Shukor, the first Malaysian in space, ran with the torch along the top of Kuala Lumpur Tower on April 21, just six months after his visit as a “spaceflight participant” to in International Space Station. Fittingly, several Chinese taikonauts carried the torch: Fei Junlong and Nie Haisheng, the two-man crew from China’s second spaceflight, Shenzou 6 ran with the torch when it arrived in China in May. China’s first space explorer, Yang Liwei who flew solo on Shenzou 5 in 2003, carried the torch when it first arrived in Beijing on August 6.
While no US astronauts carried the torch, NASA astronaut Scott Parazynski was at Base Camp when Chinese climbers carried the torch to the summit of Mt. Everest on May 8.
NASA developed “riblet” technology to aid in the aerodynamic properties of airplanes. Riblets are V-shaped grooves with angles that point in the direction of the air flow. They are no bigger than a scratch, and they look like very tiny ribs. Riblets help reduce “skin-friction” drag. But it also helps reduce friction from water, and riblets have been used in rowing shells in the four-oar-with-coxswain category. Swimsuits with riblets have also been used in competition at the Pan American games.
And of course, everyone is probably familiar with the lore that today’s athletic shoes use the same cushioning technology that was developed for the moon boots used in the Apollo missions to the moon.
The Perseids are coming! The Perseids are coming! I’m sure you’re already hearing the cry around the world… But what will be the best place to watch and when will be the best date to see the most “shooting stars”? Follow along and let’s find out…
The Perseid meteor shower has a wonderful and somewhat grisly history. Often referred to as the “Tears of St. Lawrence” this annual shower coincidentally occurs roughly about the same date as the saint’s death is commemorated on August 10. While scientifically we know the appearance of the shooting stars are the by-products of comet Swift-Tuttle, our somewhat more superstitious ancestors viewed them as the tears of a martyred man who was burned for his beliefs. Who couldn’t appreciate a fellow who had the candor to quip “I am already roasted on one side and, if thou wouldst have me well-cooked, it is time to turn me on the other.” while being roasted alive? If nothing else but save for that very quote, I’ll tip a wave to St. Lawrence at the sight of a Perseid!
While the fall rate – the number of meteors seen per hour – of the Perseids has declined in recent years since Swift-Tuttle’s 1992 return, the time to begin your Perseid watch is now. While the peak of activity will not occur until August 12 at approximately 11:00 GMT, this will leave many observers in daylight. For those who wish only to observe during the predicted maximum rate, the place to be is western North America and the time is around 4:00 a.m. However, let’s assume that not all of us can be in that place and be up at that time… So let’s take a more practical look at observing the Perseid Meteor Shower.
For about the last week or so, I’ve noticed random activity has picked up sharply and traceable Perseid activity begins about midnight no matter where you live. Because we are also contending with a Moon which will interfere with fainter meteors, the later you can wait to observe, the better. The general direction to face will be east around midnight and the activity will move overhead as the night continues. While waiting for midnight or later to begin isn’t a pleasant prospect, by then the Moon has gone far west and we are looking more nearly face-on into the direction of the Earth’s motion as it orbits the Sun, and the radiant – the constellation of the meteor shower origin – is also showing well. For those of you who prefer not to stay up late? Try getting up early instead!
How many can you expect to see? A very average and cautiously stated fall rate for this year’s Perseids would be about 30 per hour, but remember – this is a collective estimate. It doesn’t mean that you’ll see one every two minutes, but rather you may see four or five in quick succession with a long period of inactivity in between. You can make your observing sessions far more pleasant by planning for inactive times in advance. Bring a radio along, a thermos of your favorite beverage, and a comfortable place to observe from. The further you can get away from city lights, the better your chances will be.
Will this 2000 year-old meteor shower be a sparkling success or a total dud? You’ll never know unless you go out and try yourself. I’ve enjoyed clear skies here for the last week and without even trying caught at least 15 per hour each night I’ve gone out. One thing we do know is the Perseids are one of the most predictable of all meteor showers and even an hour or so of watching should bring a happy reward!
Images and data from the Mars Reconnaissance Orbiter (MRO) have revealed layers of clay-rich rock that suggests abundant water was once present on Mars. Scientists from the SETI Institute, the Jet Propulsion Laboratory and several universities have been studying data focused on the Mawrth Vallis area on Mars’ northern highland region. This is a heavily cratered, ancient area of the Red Planet whose surface geology resembles a dried-up, river valley through which water may have flowed. While their findings don’t provide evidence for life, it does suggest widespread and long-term liquid water in Mars’ past.
The researchers used the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard MRO to examine infrared light reflected from clays situated in the many-kilometer wide channel of Mawrth Vallis.
The infrared spectra from CRISM show an extensive swath of phyllosilicate-bearing material. This is a type of iron and magnesium-rich clay that forms in liquid water, and can be found on Earth in oceans and river beds. It is familiar to anyone who’s nearly broken a shovel while trying to plant a tree. There is also evidence in the spectra for hydrated silica, which in its pure, clean form is known as opal.
The researchers combined their data on the composition of soils in this region with topographic information collected by MOLA, the Mars Orbiter Laser Altimeter, on board the Mars Global Surveyor spacecraft. They found layered aluminum clays lying on top of hydrated silica and iron/magnesium clays. These clays were likely formed when water came in contact with basalt – which is the dominant component of the Martian highlands, and probably was produced from volcanic ash, which once blanketed the planet.
CRISM image overlayed with MOLA data of Mawrth Vallis. This covers an area about 10 kilometers (6.2 miles) wide. Fe/Mg-phyllosilicate is shown in red, Al-phyllosilicate is shown in blue, hydrated silica and an Fe2+ phase are shown in yellow/green.
“We were surprised by the variety of clay minerals in this region,†says Janice Bishop of the SETI Institute. “But what’s interesting is that we find the same ordering of the clay materials everywhere in Mawrth Vallis. It’s like a layer-cake of clays, one on top of another. All these layers are topped with a ‘frosting’ of lava and dust. We can see the clay layers where an impact crater has carved a hole through the surface or where erosion has exposed them.â€
Since phyllosilicates have been found in a number of outcrops on Mars in CRISM images, these new data suggest that whatever mechanism formed clays at Mawrth Vallis has probably operated over much greater areas of the Red Planet. Alteration by liquid water may have been widespread on early Mars.
Bishop is careful to note that this work is part of the long-term effort to establish just how widespread, and for what period of time, liquid water may have existed on Mars.
“This is not evidence for life,†she notes. “But it does suggest the long-term and common presence of liquid water – and concomitant active chemistry – on the Red Planet in the distant past.â€
Greetings, fellow SkyWatchers! Are you ready for another weekend? As the seasons slowly begin to change for both hemispheres and the Moon grows more full, look for an optical phenomena known as a “nimbus” – or halo around the Moon. While it’s nothing more than a thin layer of ice crystals in the upper troposphere, it is a wonderfully inspiring sight and was once used as a means of weather forecasting. If you see a nimbus, try counting the number of stars visible inside the halo and see if it matches the number of days before bad weather arrives! In the meantime, follow me as we head out on our next weekend journey into the night…
HipparchusFriday, August 8, 2008 – Our first order of business for the weekend will be to pick up a Lunar Club challenge we haven’t noted so far this year – Hipparchus. Located just slightly south of the central point of the Moon and very near the terminator, this is not truly a crater – but a hexagonal mountain-walled plain. Spanning about 150 kilometers in diameter with walls around 3320 meters high, it is bordered just inside its northern wall by crater Horrocks. This deep appearing “well” is 30 kilometers in diameter, and its rugged interior drops down an additional 2980 meters below the floor. To the south and just outside the edge of the plain is crater Halley. Slightly larger at 36 kilometers in diameter, this crater named for Sir Edmund Halley is a little shallower at 2510 meters – but it has a very smooth floor. To the east you’ll see a series of three small craters – the largest of which is Hind.
On this date in 2001, the Genesis Solar Particle Sample Return mission was launched on its way toward the Sun. On September 8, 2004, it returned with its sample of solar wind particles – unfortunately a parachute failed to deploy, causing the sample capsule to plunge unchecked into the Utah soil. Although some of the specimens were contaminated, many did survive the mishap. So what is “star stuff?” Mostly highly charged particles generated from a star’s upper atmosphere flowing out in a state of matter known as plasma.
Despite tonight’s Moon, let’s study one of the grandest of all solar winds as we seek out an area about three fingerwidths above the Sagittarius teapot’s spout as we have a look at the magnificent M8.
Visible to the unaided eye as a hazy spot in the Milky Way, fantastic in binoculars, and an area truly worth study in any size scope, this 5200 light-year diameter area of emission, reflection, and dark nebulae has a rich history. Its involved star cluster – NGC 6530 – was discovered by Flamsteed around 1680, and the nebula by Le Gentil in 1747. Cataloged by Lacaille as III.14 about 12 years before Messier listed it as number 8, its brightest region was recorded by John Herschel, and dark nebulae were discovered within it by Barnard.
Tremendous areas of starbirth are taking place in this region, while young, hot stars excite the gas in a region known as the “Hourglass” around the stars Herschel 36 and 9 Sagittarii. Look closely around cluster NGC 6530 for Barnard Dark Nebulae B 89 and B 296 at the nebula’s southern edge…and try again on a darker night. No matter how long you choose to swim in the “Lagoon” you will surely find more and more things to delight both the mind and the eye!
ArchimedesSaturday, August 9, 2008 – Today in 1976, the Luna 24 mission was launched on a return mission of its own – not to retrieve solar wind samples, but lunar soil! When we begin our observations tonight, we’ll start by having a look at another great study crater – Archimedes. You’ll find it located in the Imbrium plain north of the Apennine Mountains and west of Autolycus.
Under this lighting, the bright ring of this class V walled plain extends 83 kilometers in diameter. Even though it looks to be quite shallow, it still has impressive 2150 meter high walls. To its south is a feature not often recognized – the Montes Archimedes. Though this relatively short range is heavily eroded, it still shows across 140 kilometers of lunar topography. Look for a shallow rima that extends southeast across Palus Putredinus toward the Apennines. Mark your challenge notes!
Now let’s go have a look at a star buried in one of the spiral arms of our own galaxy – W Sagittarii…
Located less than a fingerwidth north of the tip of the teapot spout (Gamma), W Sagittarii (RA 18 05 01 Dec -29 34 48) is a Cepheid variable that’s worth keeping an eye on. While its brightness only varies by less than a magnitude, it does so in less than eight days! Normally holding close to magnitude 4, nearby field stars will help you correctly assess when minimum and maximum occur. While it’s difficult for a beginner to see such changes, watch it over a period of time. At maximum, it will be only slightly fainter than Gamma to the south. At minimum, it will be only slightly brighter than the stars to its northeast and southwest.
While you watch W go through its changes – think on this. Not only is W a Cepheid variable (a standard for the cosmic distance scale), but it is also one that periodically changes its shape. Not enough? Then think twice… Because W is also a Cepheid binary. Still not enough? Then you might like to know that recent research points toward the W Sagittarii system having a third member as well!
Sunday, August 10, 2008 – Today in 1966 Lunar Orbiter 1 was successfully launched on its mission to survey the Moon. In the days ahead, we’ll take a look at what this mission sent back! Tonight keep a very close watch on Selene as Antares is less than a degree away. Check for an occultation event!
WalterOur lunar mission for tonight is to move south, past the crater rings of Ptolemaeus, Alphonsus, Arzachel and Purbach, until we end up at the spectacular crater Walter. Named for Dutch astronomer Bernhard Walter, this 132 by 140 kilometer wide lunar feature offers up amazing details at high power. It is perhaps most fascinating to take the time to study the differing levels, which drop to a maximum of 4130 meters below the surface. Multiple interior strikes abound, but the most fascinating of all is the wall crater Nonius. Spanning 70 kilometers, Nonius would also appear to have a double strike of its own – one that’s 2990 meters deep!
Eta SgrAlthough it will be tough to locate with the unaided eye thanks to the Moon, let’s take a closer look at one of the most unsung stars in this region of sky – Eta Sagittarii (RA 18 17 37 Dec -36 45 42). This M-class giant star will display a wonderful color contrast in binoculars or scopes, showing up as slightly more orange than stars in the surrounding field. Located 149 light-years away, this irregular variable is a source of infrared radiation and is a little larger than our own Sun – yet is 585 times brighter. At around three billion years old, Eta has either expended its helium core or just began to use it to fuse carbon and oxygen – creating an unstable star capable of changing its luminosity by about 4%. But have a closer look…for Eta is also a binary system with an 8th magnitude companion.
Keep an eye out for the beginnings of the Perseid meteor shower and a futher report! Wishing you clear skies and a great weekend…
This week’s awesome images are: Nimbus – Credit: Shevill Mathers, Hipparchus: Credit: Tammy, M8 – Credit: NOAO/AURA/NSF, Archimedes – Credit: Wes Higgins, Walter – Credit: West Higgins and Eta Sagittarii – Credit: Palomar Observatory courtesy of Caltech. Thank you for sharing!
