Posted on by Fraser Cain

Tethys Glides Past Saturn

Saturn’s moon Tethys glides past in its orbit. Image credit: NASA/JPL/SSI Click to enlarge
The majesty of Saturn overwhelms in this image from Cassini. Saturn’s moon Tethys glides past in its orbit, and the icy rings mask the frigid northern latitudes with their shadows. Tethys is 1,071 kilometers (665 miles) across.
The image was taken in visible green light with the Cassini spacecraft wide-angle camera on June 10, 2005, at a distance of approximately 1.4 million kilometers (900,000 miles) from Saturn. The image scale is 80 kilometers (50 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Return to Flight Launch Pushed Back at Least a Week

The Space Shuttle sits on the Mobile Launcher Platform. Image credit: NASA/KSC. Click to enlarge
Space Shuttle managers now say the launch of NASA’s Space Shuttle Return to Flight mission, STS-114, will take place no earlier than late next week. At 1 p.m. EDT today, managers officially stopped the current launch countdown for Space Shuttle Discovery at Kennedy Space Center, Fla. Space Shuttle managers are optimistic that Discovery can lift off by July 31, the end of this launch window.

This weekend, managers and engineers will continue troubleshooting the problem with a liquid hydrogen low-level fuel sensor inside the External Tank. The sensor failed a routine prelaunch check during the launch countdown Wednesday, causing mission managers to postpone Discovery’s first launch attempt. A dozen teams, with hundreds of engineers across the country, are working on the issue.

Once the problem is resolved and the countdown can be restarted, it will take about four days to launch. A countdown from this point will be a complete start over at T-43 (time minus 43) hours. Currently, there are no plans to roll Discovery back from the launch pad.

For now, Commander Eileen Collins and her six Discovery crew mates will stay at Kennedy Space Center while engineers work on the solution.

For the latest information about the STS-114 mission, visit:
http://www.nasa.gov/returntoflight

Original Source: NASA News Release

Posted on by Fraser Cain

Canada’s Humble Space Telescope

Artist illustration of Canada’s Most Telescope. Image credit: MOST. Click to enlarge.
Canada’s first space telescope, MOST, looks for minute variations in the brightness of nearby stars. As Jaymie Matthews, of the University of British Columbia, explains in this talk given at a recent symposium on extrasolar planets, MOST can provide scientists with a unique perspective on how distant worlds interact with their host stars.

I’d like to describe a powerful new small instrument in space called MOST, which stands for Microvariability and Oscillations of Stars (and because it’s Canadian, it stands for Microvariabilit? et Oscillations Stellaire as well). MOST is Canada’s first space telescope. It is literally a suitcase in space: 60 by 60 by 30 centimeters (24 by 24 by 12 inches), 54 kilos, about 124 pounds. I weigh more than the MOST satellite; I think I’m the only mission scientists that out-masses his space satellite. And you can check it on the plane; they can lose it for you.

MOST was actually designed to do seismology of stars, to probe the interiors and histories of stars. That’s relevant to the exoplanets search, because the more we know about parent stars, the more we know about their planetary systems. But we realized, once MOST was underway, that we could actually do some additional exciting things in the exoplanet field. One of the things that MOST can do that nobody else can do at the moment is to stare at stars for up to 2 months at a time, putting stars on a stakeout, to detect variations in the brightnesses of stars or the brightnesses of the planets orbiting those stars, down to a level of 1 part per million, 1 ten-thousandth of a percent.

Just to emphasize to you how small that is, if you were to go to New York City and look at the Empire State Building at night, all the lights were on, all the office window blinds were open and you wanted to make the Empire State Building darker by 1 part per million, you would lower one shade by 3 centimeters, by a little more than an inch. That’s the level of signal that we are looking for in stars. And there is no other instrument on Earth or in space right now that’s capable of doing this. And I should point out that this whole mission has an end-to-end budget of $10 million Canadian, or $7 million US. So we’re the Wal-Mart of space telescopes.

MOST has a unique vantage point in space. It has a very different orbit from the Hubble Space Telescope, or from Spitzer, a pole-to-pole orbit. We communicate with it with our own little custom ground-station network in Toronto, Vancouver and Vienna, and we got into that orbit on the top of a former Soviet Intercontinental Ballistic Missile. A honest-to-goodness weapon of mass destruction. So not only did we put up a scientific instrument, but we destroyed a weapon of mass destruction in the bargain. MOST launched from northern Russia on June 30, 2003, so we’re approaching our second anniversary in space.

Being able to give a star that kind of intense long-term coverage is really important for astronomers to understand what’s going on in systems that have exoplanets. To give an analogy, we’re trying to read the messages that stars and exoplanets are telling us, but from the ground, we only get part of that message. If you have a network of telescopes on the ground, spread in a longitude, you can start to fill in some of the gaps, you can start to recognize some things that look like words. If you have some theories and expectations ahead of time, you might be able to infer a bit of the story, but you could very well get the completely wrong story if you’ve made the wrong assumptions. Having this kind of continuous coverage of a star allows us to really see what stars are doing, and in the case of exoplanets systems, what the exoplanets around them are doing.

MOST is primarily intended to study very tiny variations in stars’ output light. We’re trying to put our own Sun in context by looking at other sunlike stars, looking at some of the senior citizens our galactic city, trying to put some limits on the age of the universe. But the point that’s most important for us today is the fact that MOST also does exoplanet science. What we are looking for is reflected light, the same kind of wavelengths that you see with your eye, from close-in giant planets that have become known as hot Jupiters.

We’re not an exoplanets hunter. We’re too small a telescope to have a statistical chance of finding new planets. We would have to be very lucky. But we are an exoplanet explorer. We take advantage of the work of Drs. Mayor and Brown, and Geoff Marcy, and other groups, who find the planets with their Doppler surveys, and then we can go in and take a closer look. We’ve examined 3 known exoplanet systems already, Tau Bootis, HD 209458 – the telephone-book numbers that astronomers love for stars – and 51 Pegasi, the very first exoplanet around a normal star, which Dr. Mayor and his colleague, Didier Queloz, discovered 10 years ago.

When we looked at Tau Bootis, in a trial run last year, for 11 days, continuously, we saw a signal that very closely matched the planet’s orbital period. But it was far too large to be associated with the planet. It’s about .25 percent, and this is almost certainly originating in the star itself. Tau Bootis, the star, is far more active and variable than we imagined. And we’ve now been able to combine the Doppler data with the data from MOST and the light cures line up, beautifully. The star’s brightness is varying with exactly the same period as the planet orbiting around it.

We’re accustomed to bodies tidally locking each other through their gravitational influence if they’re close enough. The Earth has locked the Moon into a rotation period related to its orbit, so the Moon always keeps the same face to us. We’re convinced that these exoplanets close to their parent stars are tidally locked, so that they always keep one face to the star. But it’s almost counter-intuitive, like the tail wagging the dog, that a planet should be able to tidally lock the star. Now, in this case, it’s probably not locking the entire star, but rather its outer envelope, but there may be a kind of a spot complex, like a super-sunspot, on the surface of Tau Bootis, which has been somehow triggered by the influence of the planet, Tau Bootis b, and tracks it in its orbit. This was suspected by some of the ground-based data, but MOST has been able to confirm that these things are in perfect lockstep.

The good news is that we’re learning a lot about the star that we didn’t know before, and maybe about the interactions between the planet and the star. Possibly their magnetic fields are interacting. Usually rapidly rotating stars are young, but we don’t really know anything about the age of Tau Bootis other than information based on its rotation rate and its activity. It’s hard for us to tell: Is it genuinely young, or maybe it’s an older star, and when the planet migrated in the star was spun up and rejuvenated, kind of going through a second childhood. The bad news is that this stellar activity is going to make it hard to see reflected light from the planet, although we’re not going to give up on that, and we’re going to continue to observe Tau Bootis.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

What’s Up This Week – July 18 – July 24, 2005

Omicron Cygni. Image credit: Simone Bolzoni. Click to enlarge.
Monday, July 18 – Twenty five years ago today, India launched its first satellite. Tonight about 45 minutes after sunset, watch as Venus and Regulus begin their dance over the week. Tonight the pair will appear about half a fist apart, with Regulus to the south (left) and slightly east (above) sparkling Venus. While magnitude 1 Regulus is the brightest star in Leo, you may initially need binoculars to pick it out of the bright twilight. Be sure to monitor the pair each night as they make their closest appearance on Friday.

While the Moon will dominate tonight’s sky, we can still take a very unusual and beautiful journey to a bright and very colorful pair of stars known as Omicron 1 Cygni. Easily located about halfway between Alpha (Deneb) and Delta on the western side, this is a pure delight in binoculars or any size telescope. The striking gold color of 3.7 magnitude 31 Cygni (Omicron 1) is easily highlighted against the blue of same field companion, 5th magnitude 30 Cygni. Although this wide pairing is only an optical one, the K-type giant is a double star – an eclipsing variable around 150 times larger than or own Sun – and is surrounded by a gaseous corona more than double the size as the star itself. If you are using a scope, you can easy spot the blue tinted, 7th magnitude B star about one third the distance as between the two giants. Although our true pair are some 1.2 billion miles apart, they are oriented nearly edge-on from our point of view – allowing the smaller star to be totally eclipsed during each revolution. This total eclipse lasts for 63 days and happens about every 10.4 years, but don’t stay up too late… We’ve still got 7 years to wait!

Tuesday, July 19 – Today in 1846, Edward Pickering was born. Although his name is not well known, he became a pioneer in the field of spectroscopy. Pickering was the Harvard College Observatory Director from 1876 to 1919, and it was during his time there that photography and astronomy began to merge. Known as the Harvard Plate Collection, these archived beginnings still remain a valuable source of data.

Tonight bright, fat Selene will hold court directing in the middle of the constellation of Saggitarius. Can you still make out the “teapot” pattern? The tip of the “spout” – Al Nasl – will be a little less than a fist width to the Moon’s northwest and the top of the “lid” – Kaus Borealis will be half a fist above it. Can you see than “handle” a half a fist away to the east? For viewers in most of Australia, you will have the chance to see the Moon occult 3.3 magnitude Tau and you will find locations and times on this IOTA webpage.

Wednesday, July 20 – Today is a busy day in astronomy history! In 1969, the world held its breath as the Apollo 11 lander touched down and Neil Armstong and Edwin Aldrin became the first humans to touch the lunar surface. We celebrate our very humanity because even Armstrong was so moved that he messed up his lines! The famous words were meant to be “A small step for a man. A giant leap for mankind.” That’s nothing more than one small error for a man, and mankind’s success continued on July 20, 1976 when Viking 1 landed on Mars – sending back the first images ever taken from that planet’s surface.

For most of us, tonight the Moon will be about as full as it’s going to get, but it is great fun just to trace its bright ray systems. In the northeast quarter, look for a faded ray which cuts its way diagonally from Menelaus, across Mare Crisium and all the way to Atlas and Hercules. Notice how bright the ejecta blankets around Copernicus, Keplar and Aristarchus are. Who cannot be amazed at Tycho and its broad system that covers the entire southern region?

Thursday, July 21 – The Moon will become officially full at 11:00 UT. Sometimes known as the Summer Moon or Thunder Moon, at 20:00 UT, it will reach perigee and the second closest Earth-Moon separation of the year.

With only a short time until Luna rises tonight, let’s take a look at a pair of stars who also have a close separation – Epsilon Lyrae. Known to most of us as the “Double Double”, look about a finger width northeast of Vega. Even the slightest optical aid will reveal this tiny star as a pair, but the real treat is with a telescope – for both components are double stars! Both sets of stars appear as primarily white and both are very close to each other in magnitude. What is the lowest power that you can use to split them?

Friday, July 22 – Be sure to watch the western horizon about 45 minutes after sunset to catch Venus dancing by Regulus tonight. Just barely more than a degree (a finger width) separates the two pair, with the stately star having moved west (below) and slightly south (left) of the bright planet. If you continue your observations, you will note the pair continues to move apart about a degree a day until Regulus is lost.
Tonight we will note the work of Friedrich Bessel, who was born on this day in 1784. Bessel was a German astronomer and mathematician whose functions still carry his name in many areas of mathematical physics. But, you may put away your calculator, because Bessel was also the very first person to measure a star’s parallax. In 1837, he chose 61 Cygni and the measurement was no more than a third of an arc second. His work ended a debate that had stretched back two millenia to Aristotle’s time and the Greek’s theories about the distances to the stars.

With the slightly later rise of the Moon, this would be a great evening to check out 61 Cygni for yourself. Like finding Omicron earlier in the week, you’ll easily locate 61 between Deneb and Zeta on the eastern side. Look for a small trio of just visible stars and choose the westernmost. Not only is it famous because of Bessel’s work, but it is one of the most noteworthy of double stars for a small telescope. Of the unaided visible stars in the constellation of Cygnus, 61 is the fourth closest star to Earth, with only Alpha Centauri, Sirius, and Epsilon Eridani closer. Just how close is it? Try right around 11 light years.

Visually, the two components have a slightly orange tint, are less than a magnitude apart in brightness and a nice separation of around 30″ to the south/southeast. Back in 1792, Piazzi first noticed its abnormally large proper motion and dubbed it “The Flying Star”. At that time, it was only separated by around 10″ and the B star was to the northeast. It takes nearly 7 centuries for the pair to orbit each other, but there is another curiosity here. Orbiting the A star around every 4.8 years is an unseen body that is believed to be about 8 times larger than Jupiter. A star – or a planet? With a mass considerably smaller than any known star, chances are good that when you view 61 Cygni, you’re looking toward a distant world!

If you are up late enough tonight, you can also see the lunar crater named for Bessel as a small, bright ring located just slightly southwest of the center of Mare Crisium.

Saturday, July 23 – Tonight we have awhile to enjoy early dark skies, so let’s head toward an outstanding globular cluster that can be seen in anything from small binoculars to a huge telescope. It’s as easy as finding Antares, so slide 1.3 degrees west and behold the M4.

To binoculars, this huge, very loose globular cluster will look much like a “gone to seed” dandelion with its soft, white round form – yet even the smallest of telescopes can begin to resolve out individual stars in this 5700 light year distant system. As you step up in aperture, you step up in resolution and individual chains and bars of stars begin to swim forward from its more than 10,000 members. Enjoy it tonight!

Sunday, July 24 – If you have the chance to arise before dawn, be sure to look for Mars about halfway up the southeast skies. Now cruising through Pices at around a half a degree a day, most observers will see 4th magnitude Omicron about a finger width above the Red Planet this morning. Just as we’ve watched the motions of Saturn, Venus and Mercury over the last few weeks, use this star to judge Mars’ motion over the next few mornings. Which way is it heading?

Tonight let’s just enjoy a little stargazing and revel in the beauty of our own galaxy’s spiral arm – the Milky Way. For those living in the city, you owe it to yourself to get away to a dark location to enjoy this veritable “river of stars” which spans out of the galactic center south and runs overhead. Almost directly behind you from the galactic anti-center stretches the Perseus arm, and the sight is a beautiful one. If skies are fine, you can easily see the dark dust rift where the arm separates and the billows of light of unresolved stars. It’s the most glorious sight of summer! While we have many days yet before the Aquarid meteor shower officially reaches its peak, you will be pleasantly surprised at this year’s high activity. They’ve been flying out of the night sky for almost two weeks now, and it would not surprise me if you saw ten or more per hour of these quick, bright visitors.

In the mean time? Ask for the Moon, but keep reaching for the stars! May all your journeys be at Light Speed… ~Tammy Plotner

Posted on by Fraser Cain

Pandora and Prometheus

Prometheus and Pandora above the dark side of Saturn’s rings. Image credit: NASA/JPL/SSI. Click to enlarge
Saturn’s moons Prometheus and Pandora are captured here in a single image taken from less than a degree above the dark side of Saturn’s rings. Pandora is on the right, and Prometheus is on the left. Prometheus is 102 kilometers (63 miles) across. Pandora is 84 kilometers (52 miles) across.
The two moons are separated by about 69,000 kilometers (43,000 miles) in this view.

The F ring, extending farthest to the right, contains a great deal of fine, icy material that is more the size of dust than the boulders thought to comprise the dense B ring. These tiny particles are particularly bright from this viewing geometry, especially at right near the ansa, or edge.

At left of center, a couple of ringlets within the Encke gap (325 kilometers, or 200 miles wide) can also be easily seen due to their fine dust-sized material. The other dark features in the rings are density waves and bending waves.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 20, 2005, when Cassini was a mean distance of 1.85 million kilometers (1.15 million miles) from the moons. The image scale is about 11 kilometers (7 miles) per pixel on both moons.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Strange White Streak on Titan

Unusual bright spot offers Titan mystery. Image credit: NASA/JPL/SSI. Click to enlarge
During a recent pass of Saturn’s moon Titan, one of more than 40 during Cassini’s planned four-year mission, the spacecraft acquired this infrared view of the bright Xanadu region and the moon’s south pole. Titan is 5,150 kilometers (3,200 miles) across.

Southeast of Xanadu (and above the center in this view) is a peculiar semi-circular feature informally referred to by imaging scientists as “the Smile.” This surface feature is the brightest spot on Titan’s surface, not only to the imaging science subsystem cameras, but also to the visual and infrared mapping spectrometer instrument, which sees the surface at even longer wavelengths. The Smile is 560 kilometers (345 miles) wide.

At the landing site of the successful Huygens probe mission, brighter regions correspond to icy upland areas, while the darker regions are lowlands that possess a higher proportion of the organic byproducts of Titan’s atmospheric photochemistry. Those results seem to confirm the long-standing hypothesis that Xanadu is a relatively high region of less contaminated ice. However, the cause of the even brighter Smile is a mystery that is still under study.

Farther south, a field of bright clouds arcs around the pole, moving at a few meters per second. Around the limb (edge), Cassini peers through Titan’s smoggy, nitrogen-rich atmosphere.

North in this image is toward the upper left.

The image was taken with the Cassini spacecraft narrow-angle camera on June 4, 2005, at a distance of approximately 1.2 million kilometers (700,000 miles) from Titan using a spectral filter sensitive to wavelengths of infrared light centered at 938 nanometers. The image scale is 7 kilometers (4 miles) per pixel.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

APEX Telescope Sees First Light

The APEX Telescope at Chajnantor. Image credit: ESO. Click to enlarge
The Atacama Pathfinder Experiment (APEX) project has just passed another major milestone by successfully commissioning its new technology 12-m telescope, located on the 5100m high Chajnantor plateau in the Atacama Desert (Chile). The APEX telescope, designed to work at sub-millimetre wavelengths, in the 0.2 to 1.5 mm range, has just performed its first scientific observations. This new front-line facility will provide access to the “Cold Universe” with unprecedented sensitivity and image quality.

Karl Menten, Director of the group for Millimeter and Sub-Millimeter Astronomy at the Max-Planck-Institute for Radio Astronomy (MPIfR) and Principal Investigator of the APEX project is excited: ” Among the first observations, we have obtained wonderful spectra, which took only minutes to take but offer a fascinating view of the highly complex organic chemistry in star-forming regions. In addition, we have also obtained exquisite images from the Magellanic Clouds and observed molecules in the active nuclei of several external galaxies. Traditionally, telescopes turn to weak extragalactic sources only after they are well in operation. With APEX, we could pick them amongst our first targets!”

Because sub-millimetre radiation from space is heavily absorbed by water vapour in the Earth’s atmosphere, APEX is located at an altitude of 5100 metres in the high Chilean Atacama desert on the Chajnantor plains, 50 km east of San Pedro de Atacama in northern Chile. The Atacama desert is one of the driest places on Earth, thus providing unsurpassed observing opportunities – at the costs of the demanding logistics required to operate a frontier science observatory at this remote place.

Along with the Japanese 10-m ASTE telescope, which is operating at a neighbouring, lower altitude location, APEX is the first and largest sub-millimetre facility under southern skies. With its precise antenna and large collecting area, it will provide, at this exceptional location, unprecedented access to a whole new domain in astronomical observations. Indeed, millimetre and sub-millimetre astronomy opens exciting new possibilities in the study of the first galaxies to have formed in the Universe and of the formation processes of stars and planets. APEX will, among other things, allow astronomers to study the chemistry and physical conditions of molecular clouds, that is, dense regions of gas and dust in which new stars are forming.

APEX follows in the footsteps of the 15m Swedish-ESO Submillimetre Telescope (SEST) which was operated at ESO La Silla from 1987 until 2003 in a collaboration between ESO and the Onsala Space Observatory. SEST operated in the wavelength range from 0.8 to 3 mm. Says Catherine Cesarsky, ESO’s Director General: “SEST was for a long time the only instrument of its kind in the southern hemisphere. With it, ESO and our collaborators have gained valuable operational experience with regard to ground-based observations in the non-optical spectral domain. With APEX, we offer the ESO community a most exciting new facility that will pave the way for ALMA.”

As its name implies, APEX is the pathfinder to the ALMA project. It is indeed a modified ALMA prototype antenna and is located at the future site of the ALMA observatory. ALMA is planned to consist of a giant array of 12-m antennas separated by baselines of up to 14 km and is expected to start operation by the end of the decade. It will bring to sub-millimetre astronomy the aperture synthesis techniques of radio astronomy, enabling precision imaging to be done on sub-arcsecond angular scales, and will so nicely complement the ESO VLT/VLTI observatory.

In order to operate at the shorter sub-millimetre wavelengths, APEX presents a surface of exceedingly high quality: after a series of high precision adjustments, the APEX project team was able to adjust the surface of the mirror with remarkable precision: over the 12m diameter of the antenna, the deviation from the perfect parabola is now less than 17 thousandths of a millimetre. This is smaller than one fifth of the average thickness of a human hair!

“From the engineering point of view, APEX is already a big success and its performance surpasses our expectations”, says APEX Project Manager Rolf G?sten. “This could only be achieved thanks to the highly committed teams from the constructor, from the MPIfR and from the APEX project whose endless hours of work, often at high altitudes, made this project become reality.”

In parallel to the construction and commissioning of the APEX telescope, a demanding cutting-edge technology program has been launched to provide the best possible detectors for this outstanding facility. For its first observations, APEX was equipped with state-of-the-art sub-millimetre spectrometers developed by MPIfR’s Division for Sub-Millimetre Technology and, more recently, with the first facility receiver built at Chalmers University (OSO).

APEX is a collaboration between the Max-Planck-Institute for Radio Astronomy (MPIfR), Onsala Space Observatory (OSO), and the European Organisation for Astronomical Research in the Southern Hemisphere (ESO). The telescope was designed and constructed by VERTEX Antennentechnik GmbH (Germany), under contract by MPIfR, and is based on a prototype antenna constructed for the ALMA project. Operation of APEX in Chajnantor is entrusted to ESO.

Background information on sub-millimetre astronomy and on the first APEX results can be found as PDF files on the APEX Fact Sheets page.

Original Source: ESO News Release

Posted on by Fraser Cain

Nicholson Crater on Mars

Perspective view of Nicholson Crater central peak. Image credit: ESA. Click to enlarge
This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA?s Mars Express spacecraft, shows Nicholson Crater, located at the southern edge of Amazonis Planitia on Mars.

The HRSC obtained this image during orbit 1104 with a ground resolution of approximately 15.3 metres per pixel. The scene shows the region around Nicholson Crater, at approximately 0.0? South and 195.5? East.

Nicholson Crater, measuring approximately 100 kilometres wide, is located at the southern edge of Amazonis Planitia, north-west of a region called Medusae Fossae.

Located in the centre of this crater is a raised feature, about 55 kilometres long and 37 kilometres wide, which extends to a maximum height of roughly 3.5 kilometres above the floor of the crater.

At present, it is still unclear how this central feature was shaped and what kind of processes led to its formation. It is thought that the remnant hill could be composed of material from underground or was built as a result of atmospheric deposition.

The tall feature in the centre of this hill is the central peak of the crater, which forms when the surface material ?rebounds? after being compressed during the formation of an impact crater.

However, it is clear that this feature has been heavily sculpted after its creation, by the action of wind or even water.

Original Source: ESA Mars Express

Posted on by Fraser Cain

Martian Dust Devils Will Plague Astronauts

Dust devil tracks. Image credit: NASA/JPL. Click to enlarge
Ah, Martian summer! Finally, the days are long, just like on dear old Earth. And daytime highs rocket all the way up to a balmy 20?C (68?F) from the summer nighttime low of -90?C (-130?F), meaning you and your fellow astronauts can warm up your machinery earlier to get a good start on mining operations.

Dust devils on Mars form the same way they do in deserts on Earth. “You need strong surface heating, so the ground can get hotter than the air above it,” explains Lemmon. Heated less-dense air close to the ground rises, punching through the layer of cooler denser air above; rising plumes of hot air and falling plumes of cool air begin circulating vertically in convection cells. Now, if a horizontal gust of wind blows through, “it turns the convection cells on their sides, so they begin spinning horizontally, forming vertical columns–and starting a dust devil.”

Hot air rising through the center of the column powers the whirling air ever faster–fast enough to begin picking up sand. Sand scouring the ground then dislodges flour-fine dust, and the central column of hot rising air buoys that dust high aloft. Once prevailing horizontal winds begin pushing the dust devil across the ground, look out!

“If you were standing next to the Spirit rover right now [in Gusev Crater] in the middle of the day, you might see half a dozen dust devils,” says Lemmon. Each Martian spring or summer day, dust devils begin appearing about 10 AM as the ground heats, and start abating about 3 PM as the ground cools (Mars’s solar day of 24 hours 39 minutes is only 39 minutes longer than Earth?s). Although the exact frequency and duration of Martian dust devils is unknown, photographs from Mars Global Surveyor in orbit reveal innumerable wandering tracks at all latitudes on the planet. These tracks crisscross the surface where dust devils have scoured away loose surface material to reveal different-colored soil beneath.

Moreover, actual dust devils have been photographed from orbit–some of them as large as 1 to 2 kilometers across at their base and (from their shadows) clearly towering 8 to 10 km high.

What intrigues Farrell from having chased dust devils in the Arizona desert, however, is the strange fact that terrestrial dust devils are electrically charged–and Martian dust devils might be, too.

Dust devils get their charge from grains of sand and dust rubbing together in the whirlwind. When certain pairs of unlike materials rub together, one material gives up some of its electrons (negative charges) to the other material. Such separation of electric charges is called triboelectric charging, the prefix “tribo” (pronounced TRY-bo) meaning “rubbing.” Triboelectric charging makes your hair stand on end when you rub a balloon against your head. Dust and sand, like plastic and hair, form a tribolelectric pair. (Dust and sand aren’t necessarily made of the same stuff, notes Lemmon, because “dust can be blown in from anywhere.”) Smaller dust particles tend to charge negative, taking away electrons from the larger sand grains.

Because the rising central column of hot air that powers the dust devil carries the negatively-charged dust upward and leaves the heavier positively-charged sand swirling near the base, the charges get separated, creating an electric field. “On Earth, with instruments we’ve measured electric fields on the order of 20 thousand volts per meter (20 kV/m),” Farrell says. That’s peanuts compared to the electric fields in terrestrial thunderstorms, where lightning doesn’t flash until electric fields get 100 times greater–enough to ionize (break apart) air molecules.

But a mere 20 kV/m “is very close to the breakdown of the thin Martian atmosphere,” Farrell points out. More significantly, Martian dust devils are so much bigger than their terrestrial counterparts that their stored electrical energy may be much higher. “How would those fields discharge?” he asks. “Would you have Martian lightning inside the dust devils?” Even if lightning wouldn’t ordinarily occur naturally, the presence of an astronaut or rover or habitat might induce filamentary discharges, or local arcing. “The thing you’d really have to watch out for is corners, where electric fields can get very strong,” he adds. “You might want to make your vehicle or habitat rounded.”

Another consideration for astronauts on Mars would be “radio static as charged grains hit bare-wire antennas,” Farrell warns. And after the dust devil passed over and was gone, a lasting souvenir of its passage would be an increased adhesion of dust to spacesuits, vehicles, and habitats via electrostatic cling–the same phenomenon that causes socks to stick together when pulled out of a clothes dryer–making cleanup difficult before reentering a habitat.

Because Martian dust devils can tower 8 to 10 kilometers high, planetary meteorologists now think the devils may be responsible for throwing so much dust high into the Martian atmosphere. Importantly for astronauts, that dust may be carrying negative charges high into the atmosphere as well. Charge building up at the storm top could pose a hazard to a rocket taking off from Mars, as happened to Apollo 12 in November 1969 when it lifted off from Florida during a thunderstorm: the rocket exhaust ionized or broke down the air molecules, leaving a trail of charged molecules all the way down to the ground, triggering a lightning bolt that struck the spacecraft.

“Early sea navigators, like Columbus, understood that their ships had to be designed for extreme weather conditions,” Farrell points out. “To design a mission to Mars, we need to know the extremes of Martian weather–and those extremes appear to be in the form of dust storms and devils.”

Original Source: NASA News Release

Posted on by Fraser Cain

Discovery Won’t Launch Before Sunday

Space Shuttle Discovery on the launch pad. Image credit: NASA. Click to enlarge
NASA announced the earliest the Return to Flight Space Shuttle mission (STS-114) could launch is 2:14 p.m. EDT, Sunday, July 17. Mission Management Team and engineering meetings took place last night and today at NASA’s Kennedy Space Center.

Team members reviewed data and possible troubleshooting plans for the liquid hydrogen tank low-level fuel cut-off sensor. The sensor failed a routine pre-launch check during the launch countdown Wednesday, causing mission managers to scrub Discovery’s first launch attempt.

The sensor protects the Shuttle’s main engines by triggering shutdown if fuel runs unexpectedly low. The sensor is one of four inside the liquid hydrogen section of the External Tank (ET).

A new official launch date will be scheduled once a troubleshooting plan is complete and engineers are working on a solution. Space Shuttle Program managers plan meetings tomorrow to discuss the problem and finalize the troubleshooting plan.

The launch control team began troubleshooting while the liquid oxygen and liquid hydrogen was drained from the ET last night. The No. 2 liquid hydrogen sensor in the ET’s liquid hydrogen tank continued to read ‘wet’ and did not transition to a ‘dry’ indication once the tank was completely drained.

Following de-tanking operations, the same commands that were sent during the launch countdown were repeated while draining. While going through commands, sensor No. 2 continued to show ‘wet’ instead of ‘dry.’ The firing room reissued commands, and the sensor went to ‘dry’ as it should. Another round of commands was sent and sensor No. 2 performed as expected, with all sensors in the ‘dry’ state. Space Shuttle Discovery remains at Launch Pad 39B. The Rotating Service Structure was put back around the vehicle last night.

The STS-114 crew, led by Commander Eileen Collins, remains at Kennedy Space Center while engineers assess the problem. During their 12-day Return to Flight mission to the International Space Station, Discovery’s seven crew members will test new techniques and equipment designed to make Space Shuttle missions safer. They’ll also deliver supplies and make repairs to the Space Station.

For the latest information about the STS-114 mission, visit: http://www.nasa.gov/returntoflight

Original Source: NASA News Release