Posted on by Fraser Cain

Titan’s Layered Atmosphere

Cassini’s second close flyby of Titan completes a ‘before’ and ‘after’ look at the fuzzy moon and provides the first direct evidence of changing weather patterns in the skies over Titan.

In images obtained less than two months ago, the Titan skies were cloud free, except for a patch of clouds observed over the moon’s south pole. In images taken Monday, Dec. 13, during Cassini’s second close flyby of Titan, several extensive patches of clouds have formed.

“We see for the first time discrete cloud features at mid-latitudes, which means we see direct evidence of weather, and we can get wind speeds and atmospheric circulation over a region we hadn?t been able to measure before,” said Dr. Kevin Baines, Cassini science-team member with the visual and infrared mapping spectrometer, from NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The latest data and other results from Cassini’s close observations of Saturn’s moons Titan and Dione were presented today at a news conference during the American Geophysical Union fall meeting in San Francisco.

Cassini swept within 1,200 kilometers (750 miles) of Titan’s surface on Monday, and took a close look at the icy moon Dione just one day later. During the flyby, Cassini captured a stunning view of Titan’s night side with the atmosphere shimmering in its own glow. This allows scientists to study the detached haze layers, which extend some 400 kilometers (249 miles) above Titan.

Images from Cassini’s cameras show regions on Titan that had not been seen clearly before, as well as fine details in Titan?s intermittent clouds. The surface features may be impact related, but without information on their height, it is too soon to know for sure. No definitive craters have been seen in these images, though several bright rings or circular features are seen in dark terrain.

Cassini imaging scientists are intrigued by the complex braided structure of surface fractures on Dione. To the surprise of scientists, the wispy terrain features do not consist of thick ice deposits, but bright ice cliffs created by tectonic features. ?This is one of the most surprising results so far. It just wasn?t what we expected,? said Dr. Carolyn Porco, Cassini imaging team leader, Space Science Institute, Boulder, Colo.

Other Cassini results presented at the meeting included observations made by the ultraviolet imaging spectrograph instrument, which indicates that the nearby environment of the rings and moons in the Saturn system is filled with ice, and atoms derived from water. Cassini researchers are seeing large changes in the amount of oxygen atoms in the Saturn system. A possible explanation for the fluctuation in oxygen is that small, unseen icy moons have been colliding with Saturn’s E ring,” said Dr. Larry Esposito, principal investigator of the imaging spectrograph instrument, University of Colorado, Boulder, Colo. “These collisions may have produced small grains of ice, which yielded oxygen atoms.” Esposito presented these findings at the meeting, and a paper on the subject appears in the online version of the journal Science.

According to Esposito, Saturn’s ring particles may have formed originally from pure ice. But they have since been subjected to continual bombardment by meteorites, which has contaminated the ice and caused the rings to darken. Over time, continuous meteorite bombardment has likely spread the dirty material resulting from the collisions over a wide area in the rings. “The evidence indicates that in the last 10 to 100 million years, fresh material probably was added to the ring system,” said Esposito. These renewal events are from fragments of small moons, each probably about 20 kilometers (12 miles) across.

Images and more information about the Cassini mission are available at http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, 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. The European Space Agency built and managed the development of the Huygens probe and is in charge of the probe operations. The Italian Space Agency provided the high-gain antenna, much of the radio system and elements of several of Cassini’s science instruments.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Cassini’s Approach to Dione

Cassini captured Dione against the globe of Saturn as it approached the icy moon for its close rendezvous on Dec. 14, 2004. This natural color view shows the moon has strong variations in brightness across its surface, but a remarkable lack of color, compared to the warm hues of Saturn’s atmosphere. Several oval-shaped storms are present in the planet’s atmosphere, along with ripples and waves in the cloud bands.

The images used to create this view were obtained with the Cassini spacecraft wide-angle camera at a distance of approximately 603,000 kilometers (375,000 miles) from Dione through a filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers. The Sun-Dione-spacecraft, or phase, angle is 34 degrees. The image scale is about 32 kilometers (20 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 and the Cassini imaging team home page, http://ciclops.org.

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Sooty Nebula Around a Sun Like Star

The Coronagraphic Imager with Adaptive Optics (CIAO) on the Subaru telescope captured this near-infrared (wavelengths of 1.25 – 2.2 microns) image of a star at the end of its life. BD +303639 is a planetary nebula, similar to the Ring Nebula in the constellation Lyra, the Harp. It is about five thousand light years from Earth in the direction of the constellation Cygnus, the Swan. The surface of the star in the center of the nebula sizzles at a temperature of forty two thousand degrees Kelvin, and shines fifty thousand times brighter than our Sun.

At the end of their lives, comparatively lightweight stars like our Sun shed dust and gas which pile around the star. BD +303639 rapidly puffed off its outer layers about nine hundred years ago. This material, weighing almost a quarter of the Sun, has now expanded into a shell one hundred times more extended than the Solar System. The central star illuminates the material which looks like a life preserver from our point of view.

With visible light we can only see the light from the central star scattering off the dust. In infrared light, we can also see light emitted by the dust itself. CIAO used a technique called adaptive optics, which removes the twinkle of light due to turbulence in Earth’s atmosphere, to obtain an extraordinarily sharp image of the dust surrounding the star. (Note 1)

Spectra of the central star from the Subaru telescope’s High Dispersion Sepctrogrtaph indicates that the sizzling at the star’s surface is generating large quantities of carbon. This carbon is a likely ingredient of the dust surrounding the star.

Shedding of material is an integral part of the life of stars. “Although astronomers have been studying the dust and gas surrounding stars of different ages and types, we are only beginning to be able to observe and understand detailed structures such those in BD +303639,” says Dr. Koji Murakawa, an astronomer at the Netherlands Foundation for Research in Astronomy. Murakawa adds that “images like these give us precious insight into the last moments in a stars life.”

Note 1: The coronagraph, a device that blocks the light from a bright central star, was not used to obtain this image.

Original Source: Subaru Telescope News Release

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What is the Shape of the Helix Nebula?

Looks can be deceiving, especially when it comes to celestial objects like galaxies and nebulas. These objects are so far away that astronomers cannot see their three-dimensional structure. The Helix Nebula, for example, resembles a doughnut in colorful images. Earlier images of this complex object ? the gaseous envelope ejected by a dying, sun-like star ? did not allow astronomers to precisely interpret its structure. One possible interpretation was that the Helix’s form resembled a snake-like coil.

Now, a team of astronomers using observations from several observatories, including NASA’s Hubble Space Telescope, has established that the Helix’s structure is even more perplexing. Their evidence suggests that the Helix consists of two gaseous disks nearly perpendicular to each other.

A team of astronomers, led by C. Robert O’Dell of Vanderbilt University in Nashville, Tenn., made its finding using highly detailed images from the Hubble telescope’s Advanced Camera for Surveys, pictures from Cerro Tololo Inter-American Observatory in Chile, and measurements from ground-based optical and radio telescopes which show the speed and direction of the outflows of material from the dying star. The Helix, the closest planetary nebula to Earth, is a favorite target of professional and amateur astronomers. Astronomers hope this finding will provide insights on how expelled shells of gas from dying stars like our Sun form the complex shapes called planetary nebulas. The results are published in the November issue of the Astronomical Journal.

“Our new observations show that the previous model of the Helix was much too simple,” O’Dell said. “About a year ago, we believed the Helix was a bagel shape, filled in the middle. Now we see that this filled bagel is just the inside of the object. A much larger disk, resembling a wide, flat ring, surrounds the filled bagel. This disk is oriented almost perpendicular to the bagel. The larger disk is brighter on one side because it is slamming into interstellar material as the entire nebula moves through space, like a boat plowing through water. The encounter compresses gas, making that region glow brighter. But we still don’t understand how you get such a shape. If we could explain how this shape was created, then we could explain the late stages of the most common form of collapsing stars.”

“To visualize the Helix’s geometry,” added astronomer Peter McCullough of the Space Telescope Science Institute in Baltimore, Md., and a member of O’Dell’s team, “imagine a lens from a pair of glasses that was tipped at an angle to the frame’s rim. Well, in the case of the Helix, finding a disk inclined at an angle to a ring would be a surprise. But that is, in fact, what we found.”

Another surprise is that the dying star has expelled material into two surrounding disks rather than the one thought previously to be present. Each disk has a north-south pole, and material is being ejected along those axes. “We did not anticipate that the Helix has at least two axes of symmetry,” O’Dell said. “We thought it had only one. This two-axis model allows us to understand the complex appearance of the nebula.”

Using the Helix data, the astronomers created a three-dimensional model showing the two disks. These models are important to show the intricate structure within the nebula. The team also produced a composite image of the Helix that combines observations from Hubble’s Advanced Camera for Surveys and the 4-meter telescope’s mosaic camera at Cerro Tololo. The Helix is so large that the team needed both telescopes to capture a complete view. Hubble observed the Helix’s central region; the Cerro Tololo telescope, with its wider field of view, observed the outer region.

The team, however, is still not sure how the disks were created, and why they are almost perpendicular to each other. One possible scenario is that the dying star has a close companion star. Space-based X-ray observations provide evidence for the existence of a companion star. One disk may be perpendicular to the dying star’s spin axis, while the other may lie in the orbital plane of the two stars.

The astronomers also believe the disks formed during two separate epochs of mass loss by the dying star. The inner disk was formed about 6,600 years ago; the outer ring, about 12,000 years ago. The inner disk is expanding slightly faster than the outer disk. Why did the star expel matter at two different episodes, leaving a gap of 6,000 years? Right now, only the Helix Nebula knows the answer, the astronomers said.

The sun-like star that sculpted the Helix created a beautiful celestial object. Will the Sun weave such a grand structure when it dies 5 billion years from now? “As a single star, it will create a similar glowing cloud of expelled material, but I wouldn’t expect it to have such a complex structure as the Helix,” McCullough said.

To study the intricate details of these celestial wonders, astronomers must use a range of observatories, including visible-light and radio telescopes. Astronomers also need the sharp eyes of Hubble’s Advanced Camera for Surveys. “The Hubble’s crisp vision has revealed a whole new realm of planetary nebula structure, which has advanced the field and delighted our eyes,” said team member Margaret Meixner of the Space Telescope Science Institute.

Original Source: Hubble News Release

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New Storms Seen on Titan

Using adaptive optics on the Gemini North and Keck 2 telescopes on Mauna Kea, Hawai’i, a U.S. team has discovered a new phenomenon in the atmosphere of Saturn?s largest moon Titan.

Unlike previous observations showing storms at the south pole, these new images reveal atmospheric disturbances at Titan?s temperate mid latitudes?about halfway between the equator and the poles. Explaining the unexpected activity has proven difficult, and the team speculates that the storms could be driven by anything from short-term surface events to shifts in global wind patterns.

?We were fortunate to catch these new mid-latitude clouds when they first appeared in early 2004,” said team leader Henry Roe (California Institute of Technology). “We are not yet certain how their formation is triggered. Continued observations over the next few years will show us whether these clouds are the result of a seasonal change in weather patterns or a surface-related phenomenon.”

The causes of these storms might include activities that disturb the atmosphere from the surface. It?s possible that geysers of methane ?slush? are brewing from below, or a warm spot on Titan?s surface is heating the atmosphere. Cryovolcanism?volcanic activity that spews an icy mix of chemicals?has also been suggested as one mechanism that would cause disturbances. It?s also possible that the storms are driven by seasonal shifts in the global winds that circulate in the upper atmosphere. Hints about what is happening on this frigid world could be obtained as the Huygens probe from the Cassini mission drops through Titan?s atmosphere in mid-January, 2005.

The Gemini-Keck II observations were the result of good timing and telescope availability. According to Gemini scientist Chad Trujillo, Titan?s weather patterns can be stable for many months, with only occasional bursts of unusual activity like these recently discovered atmospheric features. The chances of catching such occurrences depend largely on the availability of flexible scheduling like that used at Gemini. “This flexible scheduling is absolutely critical to Titan meteorology studies,? he said. ?Imagine how hard it would be to understand the Earth’s diverse meteorological phenomena if you only saw a weather report a few nights every year.”

Like Earth, Titan is surrounded by a thick atmosphere of mostly nitrogen. Conditions on Earth allow water to exist in liquid, solid, or vapor states, depending on localized temperatures and pressures. The phase changes of water between these states are an important factor in the formation of weather in our atmosphere. Titan’s atmosphere is so cold that any water is frozen solid, but conditions are such that methane can move between liquid, solid, and gaseous states. This leads to a methane meteorological cycle on Titan in analogy to the water-based weather cycle on Earth.

As it does on Earth, seasonal solar heating can drive atmospheric activity on Titan, and this could be the mechanism behind the previously observed south polar clouds. However, the new temperate-latitude cloud formations cannot be explained by the same solar heating process If a seasonal circulation shift is causing the newly discovered features, the team theorizes that they will drift northward over the next few years as Titan?s year progresses through the southern summer and into autumn. If it is being caused by geological changes, such as methane geysers or a geologic ?warm? spot on the surface, the feature should stay at the observed 40-degree latitude as the surface activity spurs changes in atmospheric convection and methane cloud formation. Continued storm formations will be easily distinguishable in future ground-based observations using Gemini, Keck and other adaptive-optics enabled telescopes.

?Using adaptive optics from the Earth allows us to see things that just a few years ago would have been invisible,? said Keck Scientist Antonin Bouchez. ?These observations show that ground-based telescopes are a perfect complement to space missions like Cassini.?

This research is scheduled for publication in the January 1, 2005 issue of the Astrophysical Journal.

Original Source: Gemini News Release

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Cassini’s First Flyby of Dione

Dione is a small heavily cratered moon 560 km (350 miles) in diameter orbiting Saturn once every 2.73 days, which is actually the same period as its axial rotation. The moon lies at a distance of 377,400 kilometres (234,555 miles) from its parent planet. Dione is also known to share its orbit around Saturn with a small asteroid named Helene, that occupies a stable point ahead of it in orbit. The surface temperature of Dione is very similar to that of Titan at -186 degrees centigrade, and cryogenic activity is known to have helped shape the moon?s surface, although, unlike Titan, Dione has no known atmosphere.

The Cassini flyby this week has helped to confirm that some time in the moon?s past there were two episodes of cryo-volcanic flooding widely spaced in time that affected different regions. It is believed these episodes may be the result of tidal heating caused by the orbital interaction with another of Saturn?s moons named Enceladus.

As the Cassini Orbiter passed by Dione it took detailed images of an uncharted surface region of the area known as the ?Trailing Hemisphere,? centered on Latitude 0?, and Longitude 270? that is dominated by three craters, one large named Amata, with two smaller craters nearby named Catillus and Coras. Geologically speaking, this is the most interesting area of the moon for planetary astronomers, because this region of Dione is marked by two distinct white ray systems.

The largest, Palatine Linea, streaks down towards the moon?s south polar region that ends with a large unnamed crater. The new Cassini images show this area to be composed of long linear groves, and rills, with intermittent small craters at varying distances.

The second white linear feature, named Padua Linea, is about half the size Palatine Linea, and is also crossed with linear rills that stretch from Dione?s equator at Longitude 240 ? down to the southeast, ending at Latitude -20?. The largest crater dominating the area named Cassandra is shown prominently in the Cassini photographs.

Cassini also imaged the ?Leading Hemisphere? for the first time between Longitude 180 ? 145 degrees, at Latitude of around 40 degrees either side of the moon?s equator, and again it is shown to be covered in small impact craters.

All of the eight images returned by Cassini today show that much of Dione is heavily potholed with small craters with intermittent large impact craters at wide intervals, all of which are uncharted and unnamed. Therefore, Cassini has confirmed what planetary scientists had believed all along; that the resurfacing events on Dione must have taken place long before the resurfacing of Enceladus, because Dione?s least cratered areas have far more craters than those on Enceladus itself.

While the images of Dione returned today are the best ever close range images taken of this moon, the Cassini space craft is due to fly by Dione even closer next October, when it will pass just 500 Km (311 miles) above the moon?s surface.

The moon Dione has a visual magnitude of +10.4 so that it’s visible in medium sized telescopes, and amateur astronomers can view the moon over the next few months for themselves. Saturn is at opposition on 13 January, and lies in the zodiac constellation of Gemini (The Twins).

By Science Correspondent Richard Pearson

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Radiation Concentrates During Solar Storms

The beauty of science is that nothing is for certain. There are times when scientists think they have something figured out and then nature throws them for a loop. Just such an event happened last fall when the Sun erupted in some massive, record-shattering explosions that hurled billion of tons of electrified gas toward Earth.

Scientists realize that space is dangerous for unprotected satellites and astronauts, but they thought that they had found a small safe zone around Earth’s radiation belt — a shelter from these dangerous solar storms. It turns out that when the solar storm is strong enough, even this safe zone can become a major hot zone for dangerous radiation.

“Space weather matters — we now know that no matter what orbit we choose, there is the possibility that a spacecraft could get blasted by a significant dose of radiation. We need to take this into account when designing spacecraft. We also need to the ability to continuously monitor space weather so satellite operators can take protective measures during solar storms,” said Dr. Daniel Baker, Director of the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder.

The region is more of a gap between the two Van Allen radiation belts that surround Earth. The two belts resemble one donut inside the other. The belts are comprised of high-speed electrically charged particles trapped in the Earth’s magnetic field. It can almost be thought of as a giant umbrella in space shielding Earth from these space events.

The safe zone is considered prime real estate for satellites in “middle Earth orbits” because they would be exposed to relatively small doses of radiation and cost less to build. While there are currently no satellites in that particular orbit, many are being seriously considered including some from the Air Force.

To call the Sun active in late October / early November is an understatement. Within a two-week period, the Sun released an unusually high number of coronal mass ejections (CMEs) into space, and experienced explosions many times more powerful than anything ever observed. For some perspective, flares are usually ranked by number and class. A large flare might be X-2, for example. The Nov. 4 flare was ranked X-28, although more precisely, “off the scale” because it was hard to get an exact measurement. To add to the drama, the Sun is headed into its period of minimum activity within its 11-year cycle, making the number and intensity of the fall flares unusually high. The maximum and most active period occurred around 2000-2001.

Fortunately the science community has a number of satellites to track solar comings and goings. The Solar, Anomalous and Magnetospheric Particle Explorer (SAMPEX) satellite flies through the Van Allen radiation belts, taking measurements of the particle types and their energy and abundance. It observed the formation of a new belt in the safe zone on Oct. 31, 2003. That new belt made the safe zone hazardous for more than five weeks until the radiation was able to drain away and be absorbed by our Earth’s atmosphere. Other satellites helped researchers track the solar storms as they generated auroras on Earth, and spread out to Mars, Jupiter, Saturn, and the very edges of the solar system.

“This was an extreme event, a natural experiment that will be used to better understand how radiation belts work,” summed up Dr. Baker. “We were fortunate to have a suite of spacecraft in place to observe this event. This is why it’s important to systematically and continuously observe space weather, because there is always the potential to be surprised by nature.”

Original Source: NASA News Release

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Experiments Chosen for Mars Science Laboratory

NASA has selected eight proposals to provide instrumentation and associated science investigations for the mobile Mars Science Laboratory (MSL) rover, scheduled for launch in 2009. Proposals selected today were submitted to NASA in response to an Announcement of Opportunity (AO) released in April.

The MSL mission, part of NASA’s Mars Exploration Program, will deliver a mobile laboratory to the surface of Mars to explore a local region as a potential habitat for past or present life. MSL will operate under its own power. It is expected to remain active for one Mars year, equal to two Earth years, after landing.

In addition to the instrumentation selected, MSL will carry a pulsed neutron source and detector for measuring hydrogen (including water), provided by the Russian Federal Space Agency. The project also will include a meteorological package and an ultraviolet sensor provided by the Spanish Ministry of Education and Science.

“This mission represents a tremendous leap forward in the exploration of Mars,” said NASA’s Deputy Associate Administrator for the Science Mission Directorate, Dr. Ghassem Asrar. “MSL is the next logical step beyond the twin Spirit and Opportunity rovers. It will use a unique set of analytical tools to study the red planet for over a year and unveil the past and present conditions for habitability of Mars,” Asrar said.

“The Mars Science Laboratory is an extremely capable system, and the selected instruments will bring an analytical laboratory to the martian surface for the first time since the Viking Landers over 25 years ago,” said Douglas McCuistion, Mars Exploration Program director at NASA Headquarters.

The selected proposals will conduct preliminary design studies to focus on how the instruments can be accommodated on the mobile platform, completed and delivered consistent with the mission schedule. NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., manages the MSL Project for the Science Mission Directorate.

Selected investigations and principal investigators:

— “Mars Science Laboratory Mast Camera,” Michael Malin, Malin Space Science Systems (MSSS), San Diego, Calif. Mast Camera will perform multi-spectral, stereo imaging at lengths ranging from kilometers to centimeters, and can acquire compressed high-definition video at 10 frames per second without the use of the rover computer.

— “ChemCam: Laser Induced Remote Sensing for Chemistry and Micro-Imaging,” Roger Wiens, Los Alamos National Laboratory, Los Alamos, N.M. ChemCam will ablate surface coatings from materials at standoff distances of up to 10 meters and measure elemental composition of underlying rocks and soils.

— “MAHLI: MArs HandLens Imager for the Mars Science Laboratory,” Kenneth Edgett, MSSS. MAHLI will image rocks, soil, frost and ice at resolutions 2.4 times better, and with a wider field of view, than the Microscopic Imager on the Mars Exploration Rovers.

— “The Alpha-Particle-X-ray-Spectrometer for Mars Science Laboratory (APXS),” Ralf Gellert, Max-Planck-Institute for Chemistry, Mainz, Germany. APXS will determine elemental abundance of rocks and soil. APXS will be provided by the Canadian Space Agency.

— “CheMin: An X-ray Diffraction/X-ray Fluorescence (XRD/XRF) instrument for definitive mineralogical analysis in the Analytical Laboratory of MSL,” David Blake, NASA’s Ames Research Center, Moffett Field, Calif. CheMin, will identify and quantify all minerals in complex natural samples such as basalts, evaporites and soils, one of the principle objectives of Mars Science Laboratory.

— “Radiation Assessment Detector (RAD),” Donald Hassler, Southwest Research Institute, Boulder, Colo. RAD will characterize the broad spectrum of radiation at the surface of Mars, an essential precursor to human exploration of the planet. RAD will be funded by the Exploration Systems Mission Directorate at NASA Headquarters.

— “Mars Descent Imager,” Michael Malin, MSSS. The Mars Descent Imager will produce high-resolution color-video imagery of the MSL descent and landing phase, providing geological context information, as well as allowing for precise landing-site determination.

— “Sample Analysis at Mars with an integrated suite consisting of a gas chromatograph mass spectrometer, and a tunable laser spectrometer (SAM),” Paul Mahaffy, NASA’s Goddard Space Flight Center, Greenbelt, Md. SAM will perform mineral and atmospheric analyses, detect a wide range of organic compounds and perform stable isotope analyses of organics and noble gases.

Original Source: NASA News Release

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Deep Impact Prepared for Launch

Launch and flight teams are in final preparations for the planned Jan. 12, 2005, liftoff from Cape Canaveral Air Force Station, Fla., of NASA’s Deep Impact spacecraft. The mission is designed for a six-month, one-way, 431 million kilometer (268 million mile) voyage. Deep Impact will deploy a probe that essentially will be “run over” by the nucleus of comet Tempel 1 at approximately 37,000 kilometers per hour (23,000 miles per hour).

“From central Florida to the surface of a comet in six months is almost instant gratification from a deep space mission viewpoint,” said Rick Grammier, Deep Impact project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “It is going to be an exciting mission, and we can all witness its culmination together as Deep Impact provides the planet with its first man-made celestial fireworks on our nation’s birthday, July 4th.”

The fireworks will be courtesy of a 1-by-1 meter (39-by-39 inches) copper-fortified probe. It is designed to obliterate itself as it excavates a crater possibly large enough to swallow the Roman Coliseum. Before, during and after the demise of this 372-kilogram (820-pound) impactor, a nearby spacecraft will be watching the 6-kilometer-wide (3.7-mile) comet nucleus, collecting pictures and data of the event.

“We will be capturing the whole thing on the most powerful camera to fly in deep space,” said University of Maryland astronomy professor Dr. Michael A’Hearn, Deep Impact’s principal investigator. “We know so little about the structure of cometary nuclei that we need exceptional equipment to ensure that we capture the event, whatever the details of the impact turn out to be.”

Imagery and other data from the Deep Impact cameras will be sent back to Earth through the antennas of the Deep Space Network. But they will not be the only eyes on the prize. NASA’s Chandra, Hubble and Spitzer space telescopes will be observing from near-Earth space. Hundreds of miles below, professional and amateur astronomers on Earth will also be able to observe the material flying from the comet’s newly formed crater.

Deep Impact will provide a glimpse beneath the surface of a comet, where material and debris from the solar system’s formation remain relatively unchanged. Mission scientists are confident the project will answer basic questions about the formation of the solar system, by offering a better look at the nature and composition of the celestial travelers we call comets.

“Understanding conditions that lead to the formation of planets is a goal of NASA’s mission of exploration,” said Andy Dantzler, acting director of the Solar System division at NASA Headquarters, Washington, D.C. “Deep Impact is a bold, innovative and exciting mission which will attempt something never done before to try to uncover clues about our own origins.”

With a closing speed of about 37,000 kilometers per hour (23,000 miles per hour), what of the washing machine-sized impactor and its mountain-sized quarry?

“In the world of science, this is the astronomical equivalent of a 767 airliner running into a mosquito,” said Don Yeomans, a Deep Impact mission scientist at JPL. “It simply will not appreciably modify the comet’s orbital path. Comet Tempel 1 poses no threat to Earth now or in the foreseeable future.”

Ball Aerospace & Technologies in Boulder, Colo., built NASA’s Deep Impact spacecraft. It was shipped to Florida Oct. 17 to begin final preparations for launch.

Principal Investigator A’Hearn leads the mission from the University of Maryland, College Park. JPL manages the Deep Impact project for the Science Mission Directorate at NASA Headquarters. Deep Impact is a mission in NASA’s Discovery Program of moderately priced solar system exploration missions.

For more information about Deep Impact on the Internet, visit: http://www.nasa.gov/deepimpact.

For more information about NASA and agency programs on the Internet, visit: http://www.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Rovers Find Another Indication of Martian Water

Scientists have identified a water-signature mineral called goethite in bedrock that the NASA’s Mars rover Spirit examined in the “Columbia Hills,” one of the mission’s surest indicators yet for a wet history on Spirit’s side of Mars.

“Goethite, like the jarosite that Opportunity found on the other side of Mars, is strong evidence for water activity,” said Dr. Goestar Klingelhoefer of the University of Mainz, Germany, lead scientist for the iron-mineral analyzer on each rover, the Moessbauer spectrometer. Goethite forms only in the presence of water, whether in liquid, ice or gaseous form. Hematite, a mineral that had previously been identified in Columbia Hills bedrock, usually, but not always, forms in the presence of water.

The rovers’ main purpose is to look for geological evidence of whether their landing regions were ever wet and possibly hospitable to life. The successful results so far — with extended missions still underway — advance a NASA goal of continuing Mars exploration by robots and, eventually, by humans, said Doug McCuistion, Mars Exploration Program Director at NASA Headquarters.

Klingelhoefer presented the new results from a rock in the “West Spur” of Mars’ “Husband Hill” at a meeting of the American Geophysical Union in San Francisco this week.

Spirit has now driven past the West Spur to ascend Husband Hill itself. One remaining question is whether water was only underground or ever pooled above the surface, as it did at Opportunity’s site. “As we climb Husband Hill and characterize the rock record, we’ll be looking for additional evidence that the materials were modified by ground water and searching for textural, mineralogical and chemical evidence that the rocks were formed in or modified by surface water,” said Dr. Ray Arvidson of Washington University in St. Louis, deputy principal investigator for the rover instruments.

The amount of worrisome friction in Spirit’s right front wheel has been decreasing. Meanwhile, rover wranglers at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., continue to minimize use of that wheel by often letting it drag while the other five wheels drive. “Babying that wheel seems to be helping,” said JPL’s Jim Erickson, rover project manager. Both rovers continue working in good health about eight months after their primary three-month missions. “Looks as though Spirit and Opportunity will still be with us when we celebrate the landing anniversaries in January,” Erickson said.

Opportunity has completed six months of inspecting the inside of “Endurance Crater” and is ready to resume exploration of the broad plains of the Meridiani region. It has recently seen frost and clouds marking the seasonal changes on Mars. At this week’s conference, rover science-team member Dr. Michael Wolff of the Brookfield, Wisconsin branch of the Boulder, Colorado-based Space Science Institute is reporting those and other atmospheric observations. “We’re seeing some spectacular clouds,” Wolff said. “They are a dramatic reminder that you have weather on Mars. Some days are cloudy. Some are clear.”

A portion of Mars’ water vapor is moving from the north pole toward the south pole during the current northern-summer and southern-winter period. The transient increase in atmospheric water at Meridiani, just south of the equator, plus low temperatures near the surface, contribute to appearance of the clouds and frost, Wolff said. Frost shows up some mornings on the rover itself. The possibility that it has a clumping effect on the accumulated dust on solar panels is under consideration as a factor in unexpected boosts of electric output from the panels.

As its last major endeavor inside Endurance Crater, Opportunity made a close inspection of rock layers exposed in a part of the crater wall called “Burns Cliff.” Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the rover instruments, said, “In the lower portion of the cliff, the layers show very strong indications that they were last transported by wind, not by water like some layers higher up. The combination suggests that this was not a deep-water environment but more of a salt flat, alternately wet and dry.”

JPL has managed the Mars Exploration Rover project since it began in 2000. Images and additional information about the rovers and their discoveries are available on the Internet at http://www.nasa.gov/vision/universe/solarsystem/mer_main.html and at http://marsrovers.jpl.nasa.gov. Information about NASA and agency programs is available on the Web at http://www.nasa.gov.

Original Source: NASA/JPL News Release