Posted on by Fraser Cain

Galaxy Clusters Formed Early

Image credit: Subaru Telescope
Galaxies often congregate to form clusters of galaxies. At the present day, clusters have tens and hundreds of member galaxies and are the largest astronomical objects in the Universe. Knowing how they formed is a key to understanding the past and future of the Universe.

To study how the Universe has changed over large scales in space and time, it is essential to observe deeply a wide area of the sky. A large number of researchers are now studying the Subaru-XMM Deep Survey Field (SXDS), an approximately one square degree area of the sky in the direction of the constellation Cetus, the Whale, at many wavelengths using several telescopes. (Note 1)

To understand the origin of galaxy clusters, Masami Ouchi, currently at the Space Telescope Science Institute, decided to study how galaxies approximately 12.7 billion light years away (a red shift of 5.7) were distributed in the SXDS. By using the color of galaxies as a guide to their distance, Ouchi and his collaborators found 515 galaxies in a volume 500 million light years in height and width and 100 million light years in depth in images from Subaru’s prime focus camera (Suprime-Cam). (Note 2)

Figure 1 shows a density map of the galaxies in this volume as seen on the sky. This map represents the physical structures in the Universe at the farthest distances and the earliest times that astronomers have been able to observe to date. The yellow regions are where there are the highest concentration of galaxies. (Note 3)

In the bottom portion of this map, the researchers found a concentration of galaxies that could not be explained by chance. By obtaining accurate distance estimates to these galaxies using Subaru’s Faint Object Camera and Spectrograph (FOCAS), the researchers confirmed that there were six galaxies concentrated in a small volume only 3 million light years in diameter, forming a galaxy cluster. Figure 2 identifies the six member galaxies of the cluster.

The cluster has several properties that reveal its young age. It is one hundred times less massive than present day galaxy clusters and has significantly fewer members. Moreover, its member galaxies are producing stars at one hundred times the rate of galaxies outside the cluster.

The infant galaxy cluster existed at a time when the Universe was only one billion years old. The youngest portraits of galaxy clusters that astronomers previously had were from the Universe at an age of one and a half billion years. As any parent would attest, young children change rapidly. The portrait of a galaxy cluster at a younger age fills a significant gap in our knowledge of the early history of the Universe when stars, galaxies, and clusters were first forming.

“The fact that a cluster is already forming so soon after the Big Bang puts strong constraints on the fundamental structure of the Universe”, says Ouchi. The prevailing theory of cosmology postulates that smaller mass structures form first and then grow into more massive structures. “Our results seem to contradict the prevailing wisdom, but the real challenge is in understanding how well the distribution of visible matter such as galaxies correlates with the distribution of mass in general. As we continue to fill in the gaps in the early history of clusters, we should be able to resolve such ambiguities”, he says.

These results were published in the February 10, 2005, edition of the Astrophysical Journal (ApJ 620, L1-L4) and will be presented at the meeting “The Future of cosmology with clusters of Galaxies” beginning on February 26, 2005, in Waikoloa, Hawaii.

Note 1: For more information on the Subaru/XMM-Newton Deep Survey field, see the June 2004 press release on the SXDS public data release and the SXDS home page.

Note 2 : For more information on how astronomers use colors to look for distant galaxies see the March 2003 press release on the discovery of one the most distant galaxies currently known.

Note 3: Maps of the cosmic microwave background such as those from COBE or WMAP show the unevenness in the heat left over from the Big Bang that eventually led to the physical structures revealed in the new map.

Original Source: Subaru Telescope News Release

Posted on by Fraser Cain

Saturn’s Mysterious Auroras Explained

Scientists studying data from NASA’s Cassini spacecraft and Hubble Space Telescope have found that Saturn’s auroras behave differently than scientists have believed for the last 25 years.

The researchers, led by John Clarke of Boston University, found the planet’s auroras, long thought of as a cross between those of Earth and Jupiter, are fundamentally unlike those observed on either of the other two planets. The team analyzing Cassini data includes Dr. Frank Crary, a research scientist at Southwest Research Institute in San Antonio, Texas, and Dr. William Kurth, a research scientist at the University of Iowa, Iowa City.

Hubble snapped ultraviolet pictures of Saturn’s auroras over several weeks, while Cassini’s radio and plasma wave science instrument recorded the boost in radio emissions from the same regions, and the Cassini plasma spectrometer and magnetometer instruments measured the intensity of the aurora with the pressure of the solar wind. These sets of measurements were combined to yield the most accurate glimpse yet of Saturn’s auroras and the role of the solar wind in generating them. The results will be published in the February 17 issue of the journal Nature.

The findings show that Saturn’s auroras vary from day to day, as they do on Earth, moving around on some days and remaining stationary on others. But compared to Earth, where dramatic brightening of the auroras lasts only about 10 minutes, Saturn’s can last for days.

The observations also show that the Sun’s magnetic field and solar wind may play a much larger role in Saturn’s auroras than previously suspected. Hubble images show that auroras sometimes stay still as the planet rotates beneath, like on Earth, but also show that the auroras sometimes move along with Saturn as it spins on its axis, like on Jupiter. This difference suggests that Saturn’s auroras are driven in an unexpected manner by the Sun’s magnetic field and the solar wind, not by the direction of the solar wind’s magnetic field.

“Both Earth’s and Saturn’s auroras are driven by shock waves in the solar wind and induced electric fields,” said Crary. “One big surprise was that the magnetic field imbedded in the solar wind plays a smaller role at Saturn.”

At Earth, when the solar wind’s magnetic field points southward (opposite to the direction of the Earth’s magnetic field), the magnetic fields partially cancel out, and the magnetosphere is “open”. This lets the solar wind pressure and electric fields in, and allows them to have a strong effect on the aurora. If the solar wind’s magnetic field isn’t southward, the magnetosphere is “closed” and solar wind pressure and electric fields can’t get in. “Near Saturn, we saw a solar wind magnetic field that was never strongly north or south. The direction of the solar wind magnetic field didn’t have much effect on the aurora. Despite this, the solar wind pressure and electric field were still strongly affecting auroral activity,” added Crary. Seen from space, an aurora appears as a ring of energy circling a planet’s polar region. Auroral displays are spurred when charged particles in space interact with a planet’s magnetosphere and stream into the upper atmosphere. Collisions with atoms and molecules produce flashes of radiant energy in the form of light. Radio waves are generated by electrons as they fall toward the planet.

The team observed that even though Saturn’s auroras do share characteristics with the other planets, they are fundamentally unlike those on either Earth or Jupiter. When Saturn’s auroras become brighter and thus more powerful, the ring of energy encircling the pole shrinks in diameter. At Saturn, unlike either of the other two planets, auroras become brighter on the day-night boundary of the planet which is also where magnetic storms increase in intensity. At certain times, Saturn’s auroral ring is more like a spiral, its ends not connected as the magnetic storm circles the pole.

The new results do show some similarities between Saturn’s and Earth’s auroras: Radio waves appear to be tied to the brightest auroral spots. “We know that at Earth, similar radio waves come from bright auroral arcs, and the same appears to be true at Saturn,” said Kurth. “This similarity tells us that, on the smallest scales, the physics that generate these radio waves are just like what goes on at Earth, in spite of the differences in the location and behavior of the aurora.”

Now with Cassini in orbit around Saturn, the team will be able to take a more direct look at the how the planet’s auroras are generated. They will next probe how the Sun’s magnetic field may fuel Saturn’s auroras and learn more details about what role the solar wind may play. Understanding Saturn’s magnetosphere is one of the major science goals of the Cassini mission.

For the latest images and information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

The Cassini-Huygens mission is a cooperative mission 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 Office of Space Science, Washington, D.C.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Giant Crater Discovered on Titan

A giant impact crater the size of Iowa was spotted on Saturn’s moon Titan by NASA’s Cassini radar instrument during Tuesday’s Titan flyby.

Cassini flew within 1,577 kilometers (980 miles) of Titan’s surface and its radar instrument took detailed images of the surface. This is the third close Titan flyby of the mission, which began in July 2004, and only the second time the radar instrument has examined Titan. Scientists see some things that look familiar, along with scenes that are completely new.

The new radar images are available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

“It’s reassuring to look at two parts of Titan and see similar things,” said Dr. Jonathan Lunine, Cassini interdisciplinary scientist from the University of Arizona, Tucson. “At the same time, there are new and strange things.”

This flyby is the first time that Cassini’s radar and the imaging camera overlapped. This overlap in coverage should be able to provide more information about the surface features than either technique alone. The 440-kilometer-wide (273-mile) crater identified by the radar instrument was seen before with Cassini’s imaging cameras, but not in this detail.

A second radar image released today shows features nicknamed “cat scratches”. These parallel linear features are intriguing, and may be formed by winds, like sand dunes, or by other geological processes.

On Thursday, Cassini will conduct its first close flyby of Saturn’s icy moon Enceladus (en-SELL-uh-duss) at a distance of approximately 1,180 kilometers (730 miles). Enceladus is one of the most reflective objects in the solar system, so bright that its surface resembles freshly fallen snow. 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 Cassini mission for NASA’s Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

What Telescope is Right for You?

Image credit: Astro.Geekjoy
Contrary to what might be expected, it’s actually quite easy to select a telescope, followed by another telescope, followed by another. In fact many amateurs have been known to select dozens.

But here’s the real challenge: Try selecting your last telescope first. To do so comes down to just two things: Views and usability. If a scope doesn’t deliver the views, you won’t use it. And if it isn’t usable, you won’t bother with the views. It’s as simple – and as difficult – as that.

For instance, a very compact telescope on a lightweight mount can easily be transported from house to yard and back again. If it fails to show you anything you want to see however, the instrument will quickly become a “conversation piece” – like that brass telescope in the office at work…

Meanwhile a large telescope may require complex setup and dissassembly – not to mention the brute force needed to carry around as parts. Such a scope – despite bright views – may be rendered useless for lack of spontaneous access. But other reasons can also discourage the observer – such as difficulty orienting a large instrument toward certain regions of the sky or having to stand on a pedestal or ladder to engage the eyepiece. Great views – once you bother to set it all up…

The author has used scopes at both these extremes. One telescope of fine optics gave sharp views but – due to extremely small aperture – was unable to show anything worth viewing. (Despite the fact that the entire assembly – scope AND mount – could easily be carried about in one hand.) Meanwhile the author has also watched fellow observers take nearly an hour setting up a large truss-framed Newtonian telescope on a relatively simple (dobsonian) mount. (All the while the sky darkened and stars drifted a full fifteen degrees across the heavens.) Of course once this particular scope was assembled, the author was more than willing to peek through the eyepiece. So setup time and portability are important factors the thoughtful amateur may want to consider when evaluating telescope types and models for purchase and personal use.

Another important issue to consider is observing position. After long hours on the feet you may not prefer to stand equally long hours observing. Additionally, even slight shifts in balance can complicate seeing fine planetary detail or resolving ultra-close double stars. Of course, measures can be taken to offset ergonomic problems such as these, comfortable observing stands and chairs are available from various suppliers. So if you find yourself spending less time at the eyepiece than you might pay some attention to your body and seek out a workable after-market solution.

But ultimately the telescope you want follows from the type celestial studies you prefer to view. And that, of course, has a lot to do with the kind of conditions you observe through. (Ranging from dark rural skies through well-lit city sidewalks.) But it also has to do with the conditions you observe from. (Inside you, the stuff of your own head – and heart…)

The faintest studies visible in amateur telescopes are of a class known as quasars. These objects are extremely remote and – despite their incredible intrinsic luminosity – are very faint. Like most quasars, the brightest – 3C273 varies in brightness but at peak output (when its supermassive black hole core is about to swallow some star or another) it appears as a faint star of the 13th magnitude. To make a study of the dozen or so quasars accessible through amateur telescopes requires all the aperture possible. (Scopes to thirty inches in aperture are available from manufacturers.) An interest in quasars would place you on the very edge of what is visually possible in amateur astronomy.

In contrast to quasars, the brightest celestial study is the Sun. Due to its brilliance, it takes but a few inches of aperture to get decent views of spots, faculae, granularities, and other fine features. (The Sun is so intense that direct inspection without a solar filter will permanently damage the retina!!!) Solar observing is best pursued with small scopes due to the reality of daylight sky conditions. As the Sun heats the atmosphere, super-fine detail is lost. Because of this, three inch instruments deliver all detail possible (except when observing at high elevations). Solar observing can lead to the purchase of some very expensive accessories. (Super narrow band hydrogen alpha filters can reveal prominences even as they leap off Sol’s limb.) Conceivably you could spend tens of thousands of US dollars putting together the high-precision optics needed to mask the Sun and view the corona as well! But in general – due to the low cost of solar rejection filters and small apertures involved – beginning solar observation is an inexpensive alternative for those astronomers who prefer sleep to late night skies.

Quasars and solar observation mark the two extremes of aperture in scope selection. We might call this the “light-gathering axis”. This is the axis most people think of when considering a scope. But there are other extremes to consider as well…

Very slow telescopes (those with focal lengths greater than twelve times greater than aperture-F12+) are limited in terms of how much of the sky they can show in a single field of view. To specialize in observing extended star fields (M24 in Sagittarius for instance) or nebulosity (the North America Nebula) three plus degree fields are desirable. For this reason small scopes of low – but quite usable magnification (20-30x) – with fine flat fields – make excellent choices. Such scopes are pretty much limited to fast achromatic or apochromatic refractors, or Maksutov-Newtonian models of five inches or less aperture. (Although fast newtonian models are available, such scopes often show pronounced coma at wide angles. In general, scopes that include light-handling refractory collector elements (refractors, Maksutovs and Schmidt’s) give superior off-axis image quality to all but the slowest pure reflector models.

Meanwhile some very fast scopes (F7-) can lack the kind of optical quality needed to specialize in lunar-planetary-double star observing. In such cases, scopes of greater focal ratios (F10+) are preferred. However even these slower scopes require well-corrected optics. Because of high power use, lunar-planetary telescopes ride best on stable mounts able to track against the Earth’s rotation. Such scopes also need enough aperture (four inches or greater) to resolve fine detail or distinguish close stars – especially those of widely dissimilar magnitudes. Outfitting scopes of this type is often quite expensive (several to many thousands of US dollars). But despite the cost, these instruments have great appeal to a very discriminating subset of amateurs – “optophiles” – those who prize sharp, high contrast views – even though appreciably “dimmer” compared to much larger and often far-less expensive instruments.

So with this we’ve explored the limits of the “image-scale” axis. At one extreme are scopes that deliver large flat fields ignoring fine structure, and at the other those with small fields of view providing exceedingly fine gradations of low-contrast detail. On one hand context is king and on the other subtlety is found in the details.

Most observers find that their interests lie between the extremes. An observer may want to take in as much of a faint extended study as possible, while also boosting magnification to glean fine details as well. Such observers are interested in views that include the entire Great Nebula in Orion, while also being able to distinctly reveal gradations visible in Saturn’s ring system. The reality is that such scopes are not likely to take in the entire Cygnus Loop as a single field of view but they should resolve numerous components in the Great Hercules Cluster. For intermediate observations of this type, magnifications ranging from 50 to 200x are needed – a range that doesn’t necessarily require a tracking mount but can keep you busy without one. Meanwhile enough light must be gathered to reveal faint structure.

What’s the best scope1 for you?

Perhaps its the one that gets you out week after week exploring the Moon, planets, doubles, clusters, nebulae, or galaxies until you have no choice but to get another – along with the observatory to house it in!

1 The author has found that the Greek aphorism “Know Thyself” is at root of most matters of choice, taste, and aspiration. Selecting an appropriate instrument is a voyage of self-discovery. Enjoy the journey!

About The Author:
Inspired by the early 1900’s masterpiece: “The Sky Through Three, Four, and Five Inch Telescopes”, Jeff Barbour got a start in astronomy and space science at the age of seven. Currently Jeff devotes much of his time observing the heavens and maintaining the website Astro.Geekjoy.

Posted on by Fraser Cain

Titan’s Fourth Flyby

This image was taken during Cassini’s third close approach to Titan on Feb. 15, 2005.

The image was taken with the Cassini spacecraft narrow angle camera, through a filter sensitive to wavelengths of polarized infrared light, centered at 938 nanometers.

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 . For additional images visit the Cassini imaging team homepage http://ciclops.org.

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

SMART-1’s Mission Extended

Illustration credit: ESA
ESA’s SMART-1 mission was extended by one year, pushing back the mission end date from August 2005 to August 2006.

ESA’s Science Programme Committee endorsed unanimously the proposed one-year extension of SMART-1 on 10 February 2005.

The extension by one year of the mission will provide opportunities to extend the global coverage, compared to the original six-month mission, and to map both southern and northern hemispheres at high resolution. The new orbit will also be more stable and require less fuel for maintenance.

The extension also gives the possibility to perform detailed studies of areas of interest by performing stereo measurements for deriving topography, multi-angle observations for studying the surface ‘regolith’ texture, and mapping potential landing sites for future missions.

Implementation of this mission extension will be in two periods of six months that correspond to different orbital parameters and illumination conditions. During the first period, the southern survey study is to be completed and dedicated pointings made for multi-angle, stereo and polar illumination studies.

In the second period, high-resolution coverage of the Moon on the equator and part of the northern hemisphere will take place due to the favourable illumination conditions. High resolution follow-up observations of specific targets will also be made, as well as observations relevant for the preparation of future international lunar exploration missions.

Between 10 January and 9 February, SMART-1’s electric propulsion system (or ‘ion engine’) was not active. This allowed mission controllers to accurately determine the amount of fuel remaining, as well as ensure accurate planning for a mission extension, and obtain reconnaissance data from an orbit at 1000-4500 kilometres above the lunar surface.

All the instruments have been performing well from this orbit. As the ion engine is now active again, SMART-1 will spiral down to arrive at the lunar science orbit by the end of February.

The cruise and lunar approach has permitted the demonstration of a number of technologies, such as spacecraft, navigation, operations and instruments, which will be useful for future missions. The SMART-1 mission has now fulfilled its primary objective ? to demonstrate the viability of solar electric propulsion, or ‘ion drives’.

Original Source: ESA News Release

Posted on by Fraser Cain

The Limit of Black Holes

The very largest black holes reach a certain point and then grow no more, according to the best survey to date of black holes made with NASA’s Chandra X-ray Observatory. Scientists have also discovered many previously hidden black holes that are well below their weight limit.

These new results corroborate recent theoretical work about how black holes and galaxies grow. The biggest black holes, those with at least 100 million times the mass of the Sun, ate voraciously during the early Universe. Nearly all of them ran out of ‘food’ billions of years ago and went onto a forced starvation diet.

Focus on Black Holes in the Chandra Deep Field North Focus on Black Holes in the Chandra Deep Field North
On the other hand, black holes between about 10 and 100 million solar masses followed a more controlled eating plan. Because they took smaller portions of their meals of gas and dust, they continue growing today.

“Our data show that some supermassive black holes seem to binge, while others prefer to graze”, said Amy Barger of the University of Wisconsin in Madison and the University of Hawaii, lead author of the paper describing the results in the latest issue of The Astronomical Journal (Feb 2005). “We now understand better than ever before how supermassive black holes grow.”

One revelation is that there is a strong connection between the growth of black holes and the birth of stars. Previously, astronomers had done careful studies of the birthrate of stars in galaxies, but didn’t know as much about the black holes at their centers.

“These galaxies lose material into their central black holes at the same time that they make their stars,” said Barger. “So whatever mechanism governs star formation in galaxies also governs black hole growth.”

Astronomers have made an accurate census of both the biggest, active black holes in the distance, and the relatively smaller, calmer ones closer by. Now, for the first time, the ones in between have been counted properly.

Growth of the Biggest Black Holes Illustrated Growth of the Biggest Black Holes Illustrated
“We need to have an accurate head count over time of all growing black holes if we ever hope to understand their habits, so to speak,” co-author Richard Mushotzky of NASA’s Goddard Space Flight Center in Greenbelt, Md.

Supermassive black holes themselves are invisible, but heated gas around them — some of which will eventually fall into the black hole – produces copious amounts of radiation in the centers of galaxies as the black holes grow.

This study relied on the deepest X-ray images ever obtained, the Chandra Deep Fields North and South, plus a key wider-area survey of an area called the “Lockman Hole”. The distances to the X-ray sources were determined by optical spectroscopic follow-up at the Keck 10-meter telescope on Mauna Kea in Hawaii, and show the black holes range from less than a billion to 12 billion light years away.

Since X-rays can penetrate the gas and dust that block optical and ultraviolet emission, the very long-exposure X-ray images are crucial to find black holes that otherwise would go unnoticed.

Chandra found that many of the black holes smaller than about 100 million Suns are buried under large amounts of dust and gas, which prevents detection of the optical light from the heated material near the black hole. The X-rays are more energetic and are able to burrow through this dust and gas. However, the largest of the black holes show little sign of obscuration by dust or gas. In a form of weight self-control, powerful winds generated by the black hole’s feeding frenzy may have cleared out the remaining dust and gas.

Other aspects of black hole growth were uncovered. For example, the typical size of the galaxies undergoing supermassive black hole formation reduces with cosmic time. Such “cosmic downsizing” was previously observed for galaxies undergoing star formation. These results connect well with the observations of nearby galaxies, which find that the mass of a supermassive black hole is proportional to the mass of the central region of its host galaxy.

The other co-authors on the paper in the February 2005 issue of The Astronomical Journal were Len Cowie, Wei-Hao Wang, and Peter Capak (Institute for Astronomy, Univ. of Hawaii), Yuxuan Yang (GSFC and the Univ. of Maryland, College Park), and Aaron Steffan (Univ. of Wisconsin, Madison).

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA’s Space Mission Directorate, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

Original Source: Chandra News Release

Posted on by Fraser Cain

Spirit Finds New Rock Affected by Water

NASA’s Spirit rover found a new class of water-affected rock, while its twin, Opportunity, finished inspecting its own heat shield and set a new martian driving record. The rovers successfully completed their three-month primary missions in April 2004 and are working on extended exploration missions.

“This is probably the most interesting and important rock Spirit has examined,” said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the rovers. The rock, dubbed “Peace,” is an exposure of bedrock in the Columbia Hills. The rock is in the Gusev Crater, where Spirit landed 13 months ago. “This may be what the bones of this mountain are really made of; it gives us even more compelling evidence for water playing a major role for altering the rocks here,? Squyres added.

Peace contains more sulfate salt than any other rock Spirit has examined. Dr. Ralf Gellert, of Max-Planck-Institut fur Chemie, Mainz, Germany, said, “Usually when we have seen high levels of sulfur in rocks at Gusev, it has been at the very surface. The unusual thing about this rock is that deep inside; the sulfur is still very high. The sulfur enrichment at the surface is correlated with the amount of magnesium, which points to magnesium sulfate.”

Observations by Spirit show the rock contains significant amounts of the minerals olivine, pyroxene and magnetite, all of which are common in some types of volcanic rock. The rock’s texture appears to be sand-size grains coated with a material loosely binding the rock together. Spirit’s rock abrasion tool dug about 1 centimeter (0.4 inch) deep in two hours.

“It looks as if you took volcanic rocks that were ground into little grains, and then formed a layered rock with them cemented together by a substantial quantity of magnesium-sulfate salt,” Squyres said. “Where did the salt come from? We have two working hypotheses we want to check by examining more rocks. It could come from liquid water with magnesium sulfate salt dissolved in it, percolating through the rock, then evaporating and leaving the salt behind. Or it could come from weathering by dilute sulfuric acid reacting with magnesium-rich minerals that were already in the rock. Either case involves water,” he said.

Opportunity used its microscopic imager last week to examine a cross section of the heat shield that protected the spacecraft as it slammed into Mars’ atmosphere. This is the first time experts have been able to examine a heat shield after it entered another planet’s atmosphere. Engineers expect the findings to aid design for future missions.

“We’ve identified each broken piece of the heat shield. We know there’s a lot of data there, but we still need to analyze it,” said Ethiraj Venkatapathy of NASA’s Ames Research Center, Moffett Field, Calif.

Christine Szalai, a spacecraft engineer at NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., said, “We are examining the images to determine the depth of charring in the heat shield material. In the initial look, we didn’t see any surprises. We will be working for the next few months to analyze the performance of the heat shield,” Szalai said.

Since leaving the heat shield, Opportunity has been traveling south to explore new sites. The rover set a single-day martian driving record, covering 154.65 meters (507.4 feet) on Jan. 28. Two days later, it drove even farther, 156.55 meters (513.6 feet). The first 90 meters (295 feet) of each drive was performed in blind-drive mode, following a route planners created from stereo images from the rover and maps created from orbital imagery. The rest was autonomous driving, with the rover choosing its own route to avoid any hazards it perceived in stereo images taken along the way.

“The terrain we’re crossing is so flat we can see a long way ahead,” said JPL rover planner Frank Hartman, who teamed with Jeff Biesiadecki to plot the drive. “Opportunity has paused for some trenching, but in a few days we’ll put the pedal to the metal again.”

For Images and additional information about the rovers on the Internet, visit:

http://www.nasa.gov/vision/universe/solarsystem/mer_main.html

For information about NASA and agency programs on the Internet, visit:

http://www.nasa.gov

Original Source: NASA News Release

Posted on by Fraser Cain

Centre of Valles Marineris

This image, taken by the High Resolution Stereo Camera (HRSC) on board ESA?s Mars Express spacecraft, shows the central part of the 4000-kilometre long Valles Marineris canyon on Mars.

The HRSC obtained these images during during orbits 334 and 360 with a resolution of approximately 21 metres per pixel for the earlier orbit and 30 metres per pixel for the latter.

The scene shows an area of approximately 300 by 600 kilometres and was taken from an image mosaic that was created from the two orbit sequences. The image is located between 3? to 13? South, and 284? to 289? East.

Valles Marineris was named after the US Mariner 9 probe, the first spacecraft to image this enormous feature in 1971. Here, the huge canyon which runs east to west is at its widest in the north-south direction.

It remains unclear how this gigantic geological feature, unparalleled in the Solar System, was formed. Tensions in the upper crust of Mars possibly led to cracking of the highlands. Subsequently, blocks of the crust slid down between these tectonic fractures.

The fracturing of Valles Marineris could have occurred thousands of millions of years ago, when the Tharsis bulge (west of Valles Marineris) began to form as the result of volcanic activity and subsequently grew to the dimensions of greater than a thousand kilometres in diameter and more than ten kilometres high. On Earth, such a tectonic process is called ?rifting?, presently occurring on a smaller scale in the Kenya rift in eastern Africa.

The collapse of large parts of the highland is an alternative explanation. For instance, extensive amounts of water ice could have been stored beneath the surface and were then melted as a result of thermal activity, most likely the nearby volcanic Tharsis province.

The water could have travelled towards the northern lowlands, leaving cavities beneath the surface where the ice once existed. The roofs could no longer sustain the load of the overlying rocks, so the area collapsed.

Regardless of how Valles Marineris might have formed, it is clear that once the depressions were formed and the surface was topographically structured, heavy erosion then began shaping the landscape.

Two distinct landforms can be distinguished. On one hand, we see sheer cliffs with prominent edges and ridges. These are erosion features that are typical in arid mountain zones on Earth.

Today, the surface of Mars is bone dry, so wind and gravity are the dominant processes that shape the landscape (this might have been much different in the geological past of the planet when Valles Marineris possibly had flowing water or glaciers winding down its slopes).

In contrast, some gigantic ?hills? (indeed, between 1000 and 2000 metres high) located on the floors of the valleys have a smoother topography and a more sinuous outline. So far, scientists have no definitive explanation for why these different landforms exist.

Below the northern scarp, there are several landslides, where material was transported over a distance of up to 70 kilometres. Also seen in the image there are several structures suggesting flow of material in the past. Therefore, material could have been deposited in the valleys, making the present floor look heterogeneous.

In the centre of the image, there are surface features that appear similar to ice flows. These were previously identified in pictures from the US Viking probes of the 1970s; their origin remains a mystery.

Original Source: ESA News Release

Posted on by Fraser Cain

What’s Up This Week – Feb 14 – 20, 2005

Monday, February 14 – Happy Valentine’s Day! One of the more unusual and ephemeral objects for the northern sky is the elusive IC 1805 – known as the “Heart” nebula in Cassiopeia. Thanks to the presence of the Moon and the constellation’s position, viewing the IC 1805 will be next to impossible, but you can still challenge yourself to Mel 15, the 7th magnitude star cluster associated with the “Heart”. Remember its position for a night with clear, dark skies. The IC 1805 will be your “Valentine” for years to come. You see? Even the stars can hold surprises!

And what could be more romantic than a moonlit evening? Why not take out a scope and tonight let’s study dorsa! Along the terminator you will see 75% of Mare Tranquillitatis, joined at its northern edge by the beginnings of Mare Serenitatis. It is here that you will find our “marker” – the ancient walled plain Posidonius. Inside Serenitatis and running parallel with the terminator are the snake-like lines of the Dorsa Smirnov – a beautiful collection of wrinkle ridges known as “dorsa”. To the south look for the “three ring circus” of craters Theophilus, Cyrillus and Catharina. Focus your attention on the sunlit Mare Nectaris. Cutting across it between Theophilus in the north, and shallow open crater Beaumont in the south you will see a thin, bright line. Congratulations! You have just spotted an officially “unnamed” lunar feature that is often referred to as Dorsa Beaumont.

Very cool…

Tuesday, February 15 – Happy 441st Birthday to Galileo Galilei! He was the first scientist to use a telescope for astronomical observation. I wonder if Galileo could have ever dreamed when he first saw the Moon that mankind would one day walk on its surface? Let’s celebrate his achievements by a look into lunar history…

Tonight, all of Mare Tranquillitatis, and the majority of Mare Serenitatis will be revealed just north of the terminator’s mid-point. On the northwestern shore of Serenitatis, you will see the eastern portion Caucasus Mountains emerging in the sunlight. Tonight let us take an historic journey to the southwest edge of Tranquillitatis and visit with the Apollo 11 landing area. Although we can never see the “Eagle” telescopically, we can find where it landed! Tracing along the western wall, look for the small circles of craters Sabine and Ritter. Once you have located them, go to your highest power! To the east in the smooth sands you will see a parallel line of three tiny craters. From west to east, these are Aldrin, Collins and Armstrong – the only craters to be named for the living! It is just south of these three tiny punctuations that Apollo 11 touched down, forever changing our perceptions of space exploration.

Galileo would have been proud!

Sunday, February 26 – Fran?ois Jean Dominique Arago was born on this day in 1786. Arago was the pioneer scientist in the wave nature of light and the inventor of the polarimeter and other optical devices. In February 1948, Gerard Kuiper discovered Uranus’s moon, Miranda. And speaking of moons, did you see Selene during the daylight today? Spectacular, isn’t it? Have you ever wondered if there was any place on the lunar surface that has not seen the light? Then let’s go exploring for one tonight…

Our first order of business will be to identify crater Albategnius. Directly in the center of the Moon is a dark floored area known as the Sinus Medii. South of it will be two conspicuously large craters – Hipparchus to the north and ancient Albategnius to the south. Trace along the terminator toward the south until you have almost reached its point (cusp) and you will see a black oval. This normal looking crater with the brilliant west wall is equally ancient crater Curtius. Because of its high latitude, we shall never see the interior of this crater – and neither has the Sun! It is believed that the inner walls are quite steep and the crater Curtius’ interior has never been illuminated since its formation billions of years ago. Because it has remained dark, we can speculate that there may be “lunar ice” pocketed inside its many cracks and rilles that date back to the Moon’s formation!

Because our Moon has no atmosphere, the entire surface is exposed to the vacuum of space. When sunlit, the surface reaches up to 385 K, so any exposed “ice” would vaporize and be lost because the Moon’s gravity cannot hold it. The only way for “ice” to exist would be in a permanently shadowed area. Near Curtius is the Moon’s south pole and Clementine imaging showed around 15,000 square kilometers of area where such conditions could exist. So where did this “ice” come from? The lunar surface never ceases to be pelted by meteorites – most of which contain water ice. As we know, many craters were formed by just such an impact. Once hidden from the sunlight, this “ice” could go on to exist for millions of years!

Thursday, February 17 – So… would you like to do a little lunar “prospecting” tonight? Then let’s explore a crater similar to last night’s Curtius. In the north, identify previous study crater Plato. North of Plato you will see a long horizontal area of gray floor – Mare Frigoris. North of it you will note a “double crater”. This is elongated diamond-shape is Goldschmidt and the crater which cuts across its western border is Anaxagoras. The lunar “north pole” isn’t far from Goldschmidt and since Anaxagoras is just about one degree outside of the Moon’s theoretical “arctic” area, the lunar sunrise will never go high enough to clear the southernmost rim. As proposed with yesterday’s study, this “permanent darkness” must mean there is ice! For that very reason, NASA’s Lunar Prospector probe was sent to explore. Did it find what it was looking for? Answer – Yes!

The probe discovered vast quantities of cometary ice which have hidden inside the crater’s depths untouched for millions of years. If this sounds rather boring to you, then realize this type of resource will colour our plans to eventually establish a manned “base” on the lunar surface! On March 5, 1998 NASA announced that Lunar Prospector’s neutron spectrometer data showed that water ice was discovered at both lunar poles. The first results showed the “ice” mixed in with lunar regolith (soil, rocks and dust), but long term data confirmed near pure pockets hidden beneath about 40 cm of surface material – with the results being strongest in the northern polar region. It is estimated there may be as much as 6 trillion kg (6.6 billion tons) of this valuable resource! If this still doesn’t get your motor running, then realize we can never establish a manned lunar base because of the tremendous expense involved in transporting our most basic human need – water. The presence of lunar water could also mean a source of oxygen, another vital material we need to survive! And if we wanted to return home or onward, these same deposits could provide hydrogen which could be used as rocket fuel. So as you view Anaxagoras tonight, realize that you may be viewing one of mankind’s future “homes” on a distant world!

Friday, February 18 – Today in 1930 Clyde Tombaugh discovered Pluto during a search with photographic plates taken on the Lowell Observatory’s 13″ telescope. Although we might not make such a monumental contribution, we can still do a little “mountain climbing”! Tonight the most outstanding feature on the Moon will be Copernicus, but since we’ve delved into the deepest areas of the lunar surface, why not climb to some of its peaks?

Using Copernicus as our guide, to the north and northwest of this ancient crater lay the Carpathian Mountains ringing the southern edge of the Mare Imbrium. As you can see, they begin well east of the terminator, but look into the shadow! Extending some 40 km (25 miles) beyond the line of daylight, you will continue to see bright peaks – some of which reach 2072 meters (6600 feet) high! When the area is fully revealed tomorrow, you will see the Carpathian Mountains eventually disappear into the lava flow that once formed them. Continuing onward to Plato, which sits on the northern shore of Imbrium, we will look for the singular peak of Pico. It is between Plato and Mons Pico that you will find the scattered peaks of the Teneriffe Mountains. It is possible that these are the remnants of much taller summits of a once stronger range, but only around 1890 meters (6200 feet) still survives above the surface. Time to power up! To the west of the Teneriffes, and very near the terminator, you will see a narrow “pass” cut through the region, very similar to the Alpine Valley. This is known as the Straight Range and some of its peaks reach up to 2072 meters (6600 feet)! Although this doesn’t sound particularly impressive, that’s over twice as tall as the Vosges Mountains in central western Europe and on the average very comparable to the Appalachian Mountains in the eastern United States. Not bad!

Saturday, February 19 – Nicholas Copernicus was born on this day in 1473. Copernicus advanced our understanding of earth’s relation to the motions of the solar system. He was a man who could see the “big picture”!

Tonight let’s continue our Moon mountain climbing expedition and look at the “big picture” on the lunar surface. Tonight all of Mare Imbrium is bathed in sunlight and we can truly see its shape. Appearing as a featureless ellipse bordered by mountain ranges, let’s identify them again. Starting at Plato and moving east to south to west you will find the Alps, the Caucasus, the Apennine and the Carpathians mountains. Look at the form closely… Doesn’t this appear that perhaps once upon a time an enormous impact created the entire area? Compare it to the younger Sinus Iridium. Ringed by the Juras Mountains, it may have also been formed by a much later and very similar impact.

And you thought they were just mountains…

Sunday, February 20 – Today in 1962 John Glenn became the first American to orbit the Earth three times aboard Friendship 7. Only 32 years later, the Clementine Lunar Explorer also went in orbit – but this time around the Moon! Let’s get out the scopes…

Tonight’s most prominent lunar feature will be the graceful Gassendi towards the south, but it is a crater in the Oceanus Procellarum that we will be studying tonight. Within the “Ocean of Storms” you will find the bright point of Class 1 crater Kepler, just slightly above the terminator. The sprawling Oceanus Procellarum has low reflectivity (albedo) because the mare lavas are primarily dark minerals like iron and magnesium. Bright young Kepler (32 km/2.6 km) will show a wonderfully developing ray system, but there is so much information there! The very hills that Kepler’s initial impact drove into are part of the Alpes Formation – the inner ejecta from the Imbrium area which we noted last night. At high power you will see that the hills themselves have been filled with lava flow before Kepler was formed. The crater rim itself is very bright, consisting mostly of a pale mineral called anorthosite. The lunar rays extending from Kepler are anorthosite fragments that literally were splashed out and flung across the lunar surface during the impact that formed this crater. The region is also home to lunar feature known as “domes” – seen between the crater and the Carpathian Mountains. So unique is Kepler’s geological formation that it became the first crater to mapped by U.S. Geological Survey in 1962. This fantastic chart was labeled I-355 and was the work of R.J. Hackman.

Kepler… Not just another boring crater!

Until next week? “May you all shine on… like the Moon, the stars, and the Sun…”

May your journey be at light speed! ~Tammy Plotner