Posted on by Fraser Cain

Weather on Brown Dwarf Stars

Image credit: NASA

A team of astronomers from UCLA have found cloudy, stormy atmospheres on brown dwarfs – objects larger than gas giants like Jupiter, but not large enough to ignite into full stars. They believe the discovery of these storms could provide insights into some strange observations of brown dwarfs. Instead of steadily cooling, the objects have been seen to get brighter for brief periods, so this could be accounted for by breaks in the cloudy atmosphere.

For the first time, researchers have observed planet-like weather acting as a major influence on objects outside our solar system.

A team of scientists from NASA and the University of California, Los Angeles (UCLA), has found cloudy, stormy atmospheres on brown dwarfs, celestial bodies that are less massive than stars but that have more mass than giant planets like Jupiter. The discovery will give scientists better tools for interpreting atmospheres and weather on brown dwarfs or on planets around other stars.

“The best analogy to what we witness on these objects are the storm patterns on Jupiter,” said Adam Burgasser, astronomer at UCLA and lead author of the study. “But I suspect the weather on these more massive brown dwarfs makes the Great Red Spot look like a small squall.” Jupiter?s Great Red Spot is a massive storm more than 15,000 miles across and with winds of up to 270 miles per hour. Burgasser teamed up with planetary scientist Mark Marley, meteorologist Andrew Ackerman of NASA Ames Research Center in California’s Silicon Valley, and other collaborators to propose how weather phenomena could account for puzzling observations of brown dwarfs.

“We had been thinking about what storms might do to the appearance of brown dwarfs,? Marley said. “And when Adam showed us the new data, we realized there was a pretty good fit.” The team calculated that using a model with breaks or holes in the cloudy atmosphere solved the mysterious observations of cooling brown dwarfs.

Brown dwarfs, only recently observed members of the skies, are “failed stars at best,” said Ackerman. Not massive enough to sustain the burning of hydrogen like stars, brown dwarfs go through cooling stages that scientists observe with infrared energy-detecting telescopes. They appear as a faint glow, like an ember from a fire that gives off both heat and light energy as it dims.

Astronomers expected brown dwarfs, like most objects in the universe, to grow steadily fainter as they cool. However, new observations showed that during a relatively short phase brown dwarfs appear to get brighter as they cool. The explanation lies in the clouds.

At least 25,000 times fainter than the sun, brown dwarfs are still incredibly hot, with temperatures as high as 2,000 degrees Kelvin (3,140 F). At such high temperatures, things like iron and sand occur as gases. As brown dwarfs cool, these gases condense in the atmosphere into liquid droplets to form clouds, similar to water clouds on Earth. As the brown dwarf cools further, there is a rapid clearing of the clouds caused by atmospheric weather patterns. As the clouds are whisked away by the storms, bright infrared light from the hotter atmosphere beneath the clouds escapes, accounting for the unusual brightening of the brown dwarfs.

“The model developed by the group for the first time matches the characteristics of a very broad range of brown dwarfs, but only if cloud clearing is considered,” said Burgasser. “While many groups have hinted that cloud structures and weather phenomena should be present, we believe we have actually shown that weather is present and can be quite dramatic.”

By using Earth’s weather as a starting point, Ackerman helped the team work storms?that include wind, downdrafts and iron rain?into their calculations. “The astrophysicists needed some help understanding rain because it’s not an important process in most stars,? Ackerman said. “We used observations and simulations of terrestrial clouds to estimate the effect of iron rain on the thickness of an iron cloud.”

The team’s study, to be published in the June 1 issue of Astrophysical Journal Letters, will help researchers determine the make-up of atmospheres outside our solar system. “Brown dwarfs have traditionally been studied like stars, but it’s more of a continuum,” Marley said. “If you line a mug shot of Jupiter up with these guys, it is just a very low-mass brown dwarf.” Brown dwarfs are a training ground for scientists to learn how to interpret observations of planet-like objects around other stars, he said. “Everybody wants to find brown dwarfs that are even colder and have water clouds just like Earth. Once we find those, that will be a good test of our understanding.”

Original Source: NASA News Release

Posted on by Fraser Cain

Europa Could be Very Thick Skinned

Image credit: NASA

The evidence is mounting that Europa, one of the moons of Jupiter, has an ocean of water covered by a sheet of ice. Scientists are now speculating about how thick that ice is by measuring the size and depth of 65 impact craters on the moon’s surface – from what they can tell, it’s 19 km. The thickness of Europa’s ice will have an impact on the possibility of finding life there: too thick and sunlight will have trouble reaching photosynthetic organisms.

Detailed mapping and measurements of impact craters on Jupiter?s large icy satellites, reported in the May 23, 2002, issue of the journal Nature, reveal that Europa?s floating ice shell may be at least 19 kilometers thick. These measurements, by Staff Scientist and geologist Dr. Paul Schenk, at Houston?s Lunar and Planetary Institute, indicate that scientists and engineers will have to develop new and clever means of searching for life on the frozen world with a warm interior.

The Great Europa Pizza Debate: “Thin Crust or Thick Crust?”
Geologic and geophysical evidence from Galileo support the idea that a liquid water ocean exists beneath the icy surface of Europa. The debate now centers on how thick this icy shell is. An ocean could melt through a thin ice shell only a few kilometers thick exposing water and anything swimming in it to sunlight (and radiation). A thin ice shell could melt through, exposing the ocean to the surface, and granting easy access of photosynthetic organisms to sunlight. A thick ice shell tens of kilometers thick would be very unlikely to melt through.

Why is the thickness of Europa’s icy shell important?
The thickness is an indirect measure of how much tidal heating Europa is getting. Tidal heating is important for estimating how much liquid water is on Europa and whether there is volcanism on Europa?s sea floor but it must be derived; it cannot be measured. The new estimate of a 19 kilometer thickness is consistent with some models for tidal heating, but requires much additional study.

The thickness is important because it controls how and where biologically important material in Europa’s ocean can move to the surface, or back down to the ocean. Sunlight cannot penetrate more than a few meters into the icy shell, so photosynthetic organisms require easy access to Europa’s surface to survive. More on this subject later.

The thickness will also ultimately determine how we can explore Europa’s ocean and search for evidence of any life or organic chemistry on Europa. We cannot drill or sample the ocean directly through such a thick crust and must develop clever ways to search for ocean material that may have been exposed on the surface.

How do we estimate the thickness of Europa?s ice shell?
This study of impact craters on the large icy Galilean satellites of Europa is based on a comparison of the topography and morphology of impact crater on Europa with those on its sister icy satellites Ganymede and Callisto. Over 240 craters, 65 of them on Europa, have been measured by Dr. Schenk using stereo and topographic analysis of images acquired from NASA?s Voyager and Galileo spacecraft. Galileo is currently orbiting Jupiter and heading toward its final plunge into Jupiter in late 2003. Although both Ganymede and Callisto are believed to have liquid water oceans inside, they are also inferred to be rather deep (roughly 100-200 kilometers). This means that most craters will be unaffected by the oceans and can be used for comparison with Europa, where the depth to the ocean is uncertain but likely to be much shallower.

The estimate of the thickness of Europa?s ice shell is based on two key observations. The first is that the shapes of Europa?s larger craters differ significantly from similar sized craters on Ganymede and Callisto. Dr. Schenk?s measurements show that craters larger 8 kilometers across are fundamentally differ from those on Ganymede or Callisto. This is due to the warmth of the lower part of the ice shell. The strength of ice is very sensitive to temperature and warm ice is soft and flows rather quickly (think glaciers).

The second observation is that morphology and shape of craters on Europa change dramatically as crater diameters exceed ~30 kilometers. Craters smaller than 30 kilometers are several hundred meters deep and have recognizable rims and central uplifts (these are standard features of impact craters). Pwyll, a crater 27 kilometers across, is one of the largest of these craters.

Craters on Europa larger than 30 kilometers, on the other hand, have no rims or uplifts and have negligible topographic expression. Rather they are surrounded by sets of concentric troughs and ridges. These changes in morphology and topography indicate a fundamental change in the properties of the icy crust of Europa. The most logical change is from solid to liquid. The concentric rings in large Europan craters are probably due to the wholesale collapse of the crater floor. As the originally deep crater hole collapses, the material underlying the icy crust rushes in to fill in the void. This inrushing material drags on the overlying crust, fracturing it and forming the observed concentric rings.

Where does the 19 to 25 kilometer value come from?
Larger impact craters penetrate more deeply into the crust of a planet and are sensitive to the properties at those depths. Europa is no exception. The key is the radical change in morphology and shape at ~30 kilometers crater diameter. To use this, we must estimate how big the original crater was and how shallow a liquid layer must be before it can affect the final shape of the impact crater. This is derived from numerical calculations and laboratory experiments into impact mechanics. This ?crater collapse model? is then used to convert the observed transition diameter to a thickness for the layer. Hence, craters 30 kilometers wide are sensing or detecting layers 19-25 kilometers deep.

How certain are these estimates of Europa?s ice shell thickness?
There is some uncertainty in the exact thickness using these techniques. This is due mostly to uncertainties in the details of impact cratering mechanics, which are very difficult to duplicate in the laboratory. The uncertainties are probably only between 10 and 20%, however, so we can be reasonably sure that Europa’s ice shell is not a few kilometers thick.

Could the ice shell have been thinner in the past?
There is evidence in the crater topography that the thickness of ice on Ganymede has changed over time, and the same might be true for Europa. The estimate for ice shell thickness of 19 to 25 kilometers is relevant to the icy surface we now see on Europa. This surface has been estimated to be 30 to 50 million years or so. Most surface materials older than this have been destroyed by tectonism and resurfacing. This older icy crust could have been thinner than today?s crust, but we presently have no way of knowing.

Could the ice shell on Europa have thin spots now?
The impact craters Dr. Schenk studied were scattered across Europa?s surface. This suggests that the ice shell is thick everywhere. There could be local areas where the shell is thin due to higher heat flow. But the ice at the base of the shell is very warm and as we see in glaciers here on Earth, warm ice flows fairly rapidly. As a result, any ?holes? in Europa?s ice shell will be filled in quickly by flowing ice.

Does a thick ice shell mean there is no life on Europa?
No! Given how little we know about the origins of life and conditions inside Europa, life is still plausible. The probable presence of water under the ice is one of the key ingredients. A thick ice shell makes photosynthesis highly unlikely on Europa. Organisms would not have rapid or easy access to the surface. If organisms inside Europa can survive without sunlight, then the thickness of the shell is of only secondary importance. After all, organisms do quite well on the bottom of Earth?s oceans quite well without sunlight, surviving on chemical energy. This could be true on Europa if it is possible for living organisms to originate in this environment in the first place.

Then too, Europa’s ice shell could have been much thinner in the distant past, or perhaps it didn’t exist at some point and the ocean was exposed naked to space. If that were true, then a variety of organisms could evolve, depending on chemistry and time. If the ocean began to freeze over, the surviving organisms could then evolve to whatever environments allowed them to survive, such as volcanoes on the ocean floor (if volcanoes form at all).

Can we explore for life on Europa if the ice shell is thick?
If the crust is indeed this thick, then drilling or melting through the ice with tethered robots would be impractical! Nonetheless, we can search for organic ocean chemistry or life in other locations. The challenge will be for us to devise a clever strategy for exploring Europa that won?t contaminate what is there yet find it nonetheless. The prospect of a thick ice shell limits the number of likely sites where we might find exposed oceanic material. Most likely, ocean material will have to be embedded as small bubbles or pockets or as layers within ice that has been brought to the surface by other geologic means. Three geologic processes could do this:

1. Impact craters excavate crustal material from depth and eject it out onto the surface, where we might pick it up (50 years ago we could pick up iron meteorite fragments on the flanks of Meteor Crater in Arizona, but most have been found by now). Unfortunately, the largest known crater on Europa, Tyre, excavated material from only 3 kilometers deep, not deep enough to get near the ocean (due to geometry and mechanics, craters excavate from the upper part of the crater, not the lower). If a pocket or layer of ocean material were frozen into the crust at shallow depth, it might be sampled by an impact crater. Indeed, the floor of Tyre has a color that is slightly more orange than the original crust. However, roughly half of Europa was well seen by Galileo, so a larger crater might be present on the poorly seen side. We will have to go back to find out.

2. There is strong evidence that Europa?s icy shell is somewhat unstable and has been (or is) convecting. This means that blobs of deep crustal material rise upward toward the surface where they are sometimes exposed as domes several kilometers wide (think Lava Lamp, except that the blobs are soft solid material like Silly Putty). Any ocean material imbedded within the lower crust could then be exposed to the surface. This process could take thousands of years, and the exposure to Jupiter?s lethal radiation would be unfriendly to say the least! But at least we could investigate and sample what remains behind.

3. Resurfacing of wide areas of Europa?s surface where the icy shell has literally torn through and split apart. These areas are not empty but have been filled with new material from below. These areas do not appear to have been flooded by ocean material, but rather by soft warm ice from the bottom of the crust. Despite this it is very possible that oceanic material could be found within this new crustal material.

Our understanding of Europa’s surface and history is still very limited. Unknown processes could occur that bring ocean material to the surface, but only a return to Europa will tell.

What next for Europa?
With the recent cancellation of a proposed Europa Orbiter due to cost overruns, this is a good time to reexamine our strategy for exploring Europa?s ocean. Tethered submarines and deep drilling probes are rather impractical in such a deep crust, but surface landers could be very important nonetheless. Before we send a lander to the surface, we should send a reconnaissance mission, in either Jupiter or Europa orbit, to search for exposures of ocean material and thin spots in the crust, and to scout out the best landing sites. Such a mission would make use of vastly improved infrared mapping capabilities for mineral identification (after all, the Galileo instruments are nearly 25 years old). Stereo and laser instruments would be used for topographic mapping. Together with gravity studies, these data could be used to search for relatively thin regions of the icy crust. Finally, Galileo observed less than half of Europa at resolutions sufficient for mapping, including impact craters. Craters on this poorly seen hemisphere, for example, could indicate whether Europa?s ice shell was thinner in the past.

A Lander for Europa?
A lander with a seismometer could listen for europa-quakes generated by the daily tidal forces exerted by Jupiter and Io. Seismic waves can be used to precisely map the depth to the bottom of the ice shell, and possibly the bottom of the ocean as well. Onboard chemical analyzers would then search for organic molecules or other biologic tracers and potentially determine ocean chemistry, one of the fundamental indicators of Europa?s prospects as an ?inhabited? planet. Such a lander would probably need to drill several meters to get through the zone of radiation damage at the surface. Only after these missions are under way can we then begin the true exploration of this tantalizing planet-sized moon. To paraphrase Monty Python, ?It?s not dead yet!?

Original Source: USRA News Release

Posted on by Fraser Cain

Potential Discovery of Water Ice on Mars?

Space agency watchdog Keith Cowing is reporting that NASA is due to announce the discovery of large amounts of water ice on the surface of Mars. The speculation is that data from one or several instruments on board the Mars Odyssey spacecraft have confirmed the presence of underground ice, and that NASA will announce the findings at a press conference on Thursday, May 30. If true, the discovery of this much water ice will have tremendous implications on the search for life on the Red Planet. It’s all very preliminary right now, so stay tuned for some actual confirmation by NASA.

Posted on by Fraser Cain

Those Daring Chinese and Their Flying Machines

Okay, as you know, I love to examine the latest speculation about the state of the Chinese human space program (if you didn’t know that, then you just don’t read Universe Today enough… or maybe I don’t write it enough… on second thought, don’t answer that). Since the Chinese are generally so tight-lipped about the whole process, it gives journalists and kooks a lot of room to speculate (I won’t say which sources are which). There’ve been a whole series of speculative articles pumped out in the last couple of days so I thought I’d tie them all together for you into one perplexing vision of the future of human spaceflight.

Reuters and the Associate Press are reporting that the Chinese are training fighter pilots in secret for their first generation of astronauts (secret’s out now). Speculators anticipate these lucky flyboys will see space by 2005. CNN is carrying the Reuters article while SPACE.com has the AP article.

What about their plans for the Moon and Mars? Apparently the Chinese have designs on putting a base on the Moon and eventually traveling to Mars? but officials deny those rumours.

Here’s my prediction. At some point in the near or far future, the Chinese are going to do something space related. You heard it here first.

Fraser Cain
Publisher, Universe Today

Posted on by Fraser Cain

Tightest Binary System Discovered

Image credit: Gemini

Thanks to the adaptive optics system of the Gemini observatory, astronomers have been able to spot a brown dwarf orbiting a star only three times the distance of the Earth to the Sun. This newly discovered pair, LHS 2397a, is located only 46 light years from Earth and is the closest separation of a binary star ever uncovered. The Hawaii-based Gemini telescope is so powerful because it uses a flexible mirror that counteracts the blurring caused by the Earth’s atmosphere.

Astronomers using adaptive optics technology on the Gemini North Telescope have observed a brown dwarf orbiting a low-mass star at a distance comparable to just three times the distance between the Earth and Sun. This is the closest separation distance ever found for this type of binary system using direct imaging.

The record-breaking find is just one of a dozen lightweight binary systems observed in the study. Together, they provide a new perspective on the formation of stellar systems and how smaller bodies in the Universe (including large planets) might form.

“By using Gemini’s advanced imaging capabilities, we were able to clearly resolve this binary pair where the distance between the brown dwarf and its parent star is only about twice the distance of Mars from the Sun,” said team member Melanie Freed, a graduate student at the University of Arizona in Tucson. With an estimated mass of 38-70 times the mass of Jupiter, the newly identified brown dwarf is located just three times the Sun-Earth distance (or 3.0 Astronomical Units) from its parent star. The star, known as LHS 2397a, is only 46 light-years from Earth. The motion of this object in the sky indicates that it is an old, very low-mass star.

The previous imaging record for the closest distance between a brown dwarf and its parent (a much brighter, Sun-like star) was almost five times greater at 14 AU. One Astronomical Unit (AU) equals the average distance between the Earth and the Sun or about 150 million kilometers (93 million miles).

Often portrayed as “failed stars,” brown dwarfs are bigger than giant planets like Jupiter, but their individual masses are less than 8% of the Sun’s mass (75 Jupiter masses), so they are not massive enough to shine like a star. Brown dwarfs are best viewed in the infrared because surface heat is released as they slowly contract. The detection of brown dwarf companions within 3 AU of another star is an important step toward imaging massive planets around other stars.

This University of Arizona team led by Dr. Laird Close used the Gemini North Telescope to detect eleven other low mass companions, suggesting that these low-mass binary pairs may be quite common. The discovery of so many low-mass pairs was a surprise, given the argument that most very low-mass stars and brown dwarfs were thought to be solo objects wandering though space alone after being ejected out of their stellar nurseries during the star formation process.

“We have completed the first adaptive optics-based survey of stars with about 1/10th of the Sun’s mass, and we found nature does not discriminate against low-mass stars when it comes to making tight binary pairs,” said Close, an assistant professor of astronomy at the University of Arizona. Dr. Close is the lead author on a paper presented today at the Brown Dwarfs International Astronomical Union Symposium in Kona, Hawaii, and he is the principal investigator of the low-mass star survey.

The team looked at 64 low-mass stars (originally identified by John Gizis of the University of Delaware) that appeared to be solo stars in the lower resolution images from the 2MASS all-sky infrared survey. Once the team used adaptive optics on Gemini to make images that were ten times sharper, twelve of these stars were revealed to have close companions. Surprisingly, Close’s team found that the separation distances between the low mass stars and their companions were significantly less than expected.

“We find companions to low-mass stars are typically only 4 AU from their primary stars, this is surprisingly close together,” said team member Nick Siegler, a University of Arizona graduate student. “More massive binaries have typical separations closer to 30 AU, and many binaries are much wider than this.” The new Gemini observations, Close said, “imply strongly that low-mass stars do not have companions that are far from their primaries.” Similar results had been found previously by a team led by Dr. Eduardo L. Martin of the University of Hawaii Institute for Astronomy in a survey of 34 very low-mass stars and brown dwarfs in the Pleiades cluster carried out with the Hubble Space Telescope. These two surveys together clearly demonstrate that there is an intriguing dearth of brown dwarfs at separations larger than 20 AU from very low-mass stars and other brown dwarfs.

The team projects that one out of every five low-mass stars has a companion with a separation in the range (3-200 AU). Within this separation range, astronomers have observed a similar frequency of more massive stellar companions around larger Sun-like stars.

Taken as a whole, these new results suggest that (contrary to theory) low-mass binaries may form in a process similar to that of more massive binaries. Indeed, this finding adds to growing evidence from other groups that the percentage of binary systems is similar for bodies spanning the range from one solar mass to as little as 0.05 solar masses (or 52 times Jupiter’s mass). For example, a group led by Neill Reid of the Space Telescope Science Institute and the University of Pennsylvania has come to a similar conclusion with a smaller sample of 20 even lower-mass stars and brown dwarfs observed with the Hubble Space Telescope.

The fact that low-mass stars have any low-mass brown dwarf companions inside 5 AU is also surprising because the exact opposite is true around Sun-like stars. Very few Sun-like stars have brown dwarf companions inside this distance, according to radial velocity studies. “This lack of brown dwarf companions within 5 AU of Sun-like stars has been called the ‘brown dwarf desert’,” Close noted. “However, we see there is likely no brown dwarf desert around low-mass stars.”

These results form important constraints for theorists working to understand how the mass of a star affects the mass and separation distance of the companions that form with it. “Any accurate model of star and planet formation must reproduce these observations,” Close said.

These observations were possible only because of the combination of the University of Hawaii’s uniquely sensitive Hokupa’a adaptive optics imaging system and the technical performance of the Gemini telescopes. The Hokupa’a system sensitivity is due to the curvature wavefront sensing concept developed by Dr. Francois Roddier. Adaptive optics is an increasingly crucial technology that eliminates most of the “blurring” caused by the turbulence in the Earth’s atmosphere (i.e., the twinkling of the stars). It does this by rapidly adjusting the shape of a special, smaller flexible mirror to match local turbulence, based on real-time feedback to the mirror’s support system from observations of the low-mass star. Hokupa’a can count individual photons (particles of light) and so can sharpen accurately even very faint (i.e., low-mass) stars.

The near-infrared adaptive optics images made by the 8-meter Gemini telescope in this survey were twice as sharp as those that can be made at the same wavelengths by the Earth-orbiting, 2.4-meter Hubble Space Telescope. The only ground-based survey of its kind, this work required five nights over one year with the Hokupa’a system at Gemini North.

It is important to note that the distances used here are as measured on the sky. The real orbital separations may be slightly larger once the full orbit of these binaries is known in the future.

Other science team members include James Liebert (Steward Observatory, University of Arizona), Wolfgang Brandner (European Southern Observatory, Garching, Germany), and Eduardo Martin and Dan Potter (Institute for Astronomy, University of Hawaii).

The observations reported here are part of an ongoing survey. Initial results from the first 20 low-mass stars of our survey have been published in the March 1, 2002 issue of The Astrophysical Journal Letters vol 567 Pages L53-L57.

Images and illustrations related to this news release are available on the Internet at: http://www.gemini.edu/media/images_2002-7.html.

Laird Close can be contacted at 520/626-5992, [email protected], after he returns to his office on May 28.

This survey was supported in part by the U.S. Air Force Office of Scientific Research and the University of Arizona’s Steward Observatory. Hokupa’a is supported by the University of Hawaii Adaptive Optics Group and the National Science Foundation.

The Gemini Observatory is an international collaboration that has built two identical 8-meter telescopes. The telescopes are located at Mauna Kea, Hawaii (Gemini North) and Cerro Pach?n in central Chile (Gemini South), and hence provide full coverage of both hemispheres of the sky. Both telescopes incorporate new technologies that allow large, relatively thin mirrors under active control to collect and focus both optical and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in each partner country with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the UK Particle Physics and Astronomy Research Council (PPARC), the Canadian National Research Council (NRC), the Chilean Comisi?n Nacional de Investigaci?n Cientifica y Tecnol?gica (CONICYT), the Australian Research Council (ARC), the Argentinean Consejo Nacional de Investigaciones Cient?ficas y T?cnicas (CONICET) and the Brazilian Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq). The Observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

For more information, see the Gemini website at: http://www.us-gemini.noao.edu/media/.

Original Source: Gemini News Release

Posted on by Fraser Cain

Cassini’s Feeling Fine

Image credit: NASA

NASA’s Cassini spacecraft continues to hurtle towards its distant rendezvous with the planet Saturn in July 1, 2004. Controllers had the spacecraft take some test photographs of a star, and the camera haze that showed up earlier in the mission appears to be clearing up, as they had hoped it would. The most recent communication with the spacecraft by the Goldstone tracking station last week indicated that Cassini is in excellent health and working normally.

NASA’s Cassini spacecraft continues to fly in good health, speeding toward a July 1, 2004, appointment to begin orbiting Saturn.

Test images of a star taken last week provide strong encouragement that a haze problem noticed on a Cassini camera lens is clearing up as anticipated, said Robert Mitchell, Cassini-Huygens program manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

A 60-day period of warming the spacecraft’s narrow-angle camera to a temperature just above freezing ended May 1. Heaters were built into the camera in anticipation of potential lens hazing; warming treatments have corrected similar hazing on other spacecraft.

Cassini’s narrow-angle camera performed flawlessly for the spacecraft’s December 2000 flyby of Jupiter. The haze first appeared last year, during the cruise between Jupiter and Saturn. Warming the camera to 4 degrees Celsius (39 degrees Fahrenheit) for eight days ending in January 2002 produced improvements, so the same heating was repeated for 60 days.

The new test images of the bright star Spica show that, by one measure, at least 90 percent of the image diffusion originally caused by the lens haze has been corrected. The improvement may actually be greater, because the new images were taken at a temperature warmer than the camera’s optimal operating temperature of about minus 90 C (minus 130 F). Another warming treatment, to last 26 days, began May 9.

About six months after Cassini begins orbiting Saturn, it will release its piggybacked Huygens probe for descent through the thick atmosphere of the moon Titan on Jan. 14, 2005. Cassini-Huygens is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Office of Space Science, Washington, D.C. Additional information about Cassini-Huygens is available online at: http://saturn.jpl.nasa.gov .

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Eleven More Jupiter Moons Discovered

Image credit: NASA

Jupiter pushed past the other planets with the recent discovery of 11 new moons, bringing its total to 39. A team of US astronomers discovered the additional satellites (all 2-4 kilometres in diameter) using one of the world’s most powerful telescopes: the Canada-France-Hawaii 3.6 metre. Digital images of the space around Jupiter were processed using computers to detect objects moving in orbit, and to reject passing asteroids.

The discovery of 11 small moons orbiting Jupiter leapfrogs the number of that planet’s moons to 39, nine more than the record of the previous champ, Saturn.

A team led by astronomers from the University of Hawaii, Honolulu, made the discovery based on images taken in December 2001 and later follow-up observations. Orbits were determined by collaborators at NASA’s Jet Propulsion Laboratory, in Pasadena, Calif., and the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.

Researchers estimate the new-found natural satellites are each about two to four kilometers (one to two miles) in diameter, and were probably passing rocks captured by Jupiter’s gravity long ago.

The discovery-team leaders, Scott Sheppard and Dr. David Jewitt of the University of Hawaii, also discovered 11 other small satellites of Jupiter in 2000.

The new moons were discovered by Sheppard, Jewitt and Jan Kleyna of Cambridge University, England. They used the Canada-France-Hawaii 3.6-meter (142-inch) telescope with one of the largest digital imaging cameras in the world to obtain sensitive images of a wide area around Jupiter.

The digital images were processed and searched using computers. Candidate satellites were monitored in the succeeding months at the University of Hawaii’s 2.2-meter (88-inch) telescope to confirm their orbits and to reject asteroids masquerading as satellites.

JPL’s Dr. Robert Jacobson and Harvard-Smithsonian’s Dr. Brian Marsden determined the satellites’ irregular — highly elongated and tilted — orbits. All 11 objects orbit in the direction opposite to the rotation of the planet.

The orbits of the irregular satellites strongly suggest an origin by capture. Since no efficient contemporary capture mechanisms are known, it is likely that the irregular satellites were acquired when Jupiter was young, possibly still in the process of condensing down to its equilibrium size. As yet, nothing is known about their surface properties, compositions or densities, but they are presumed to be rocky objects like the asteroids.

The new discoveries bring the known total of Jovian satellites to 39, of which 31 are irregulars. The eight regular satellites include four large moons discovered by the astronomer Galileo Galilei and four smaller moons on circular orbits closer to Jupiter. Jupiter’s nearest rival for having the largest number of known satellites is Saturn, with 30, of which 13 are irregular.

The satellites were formally announced by the International Astronomical Union on Circular No. 7900 (May 16, 2002). More information about them is available online from the University of Hawaii at http://www.ifa.hawaii.edu/~sheppard/satellites/jup.html. Other information about the Jupiter system is available from JPL at http://www.jpl.nasa.gov/solar_system/planets/jupiter_index.html.

The Institute for Astronomy at the University of Hawaii conducts research into galaxies, cosmology, stars, planets and the Sun. The Canada-France-Hawaii telescope is funded by the University of Hawaii and the governments of Canada and France. JPL, a division of the California Institute of Technology, Pasadena, is NASA’s lead center for robotic exploration of the solar system.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Oxygen System Working Again

The crew of the International Space Station successfully repaired the malfunctioning oxygen system over the weekend. The system was malfunctioning over the course of last week, so it was brought offline so the crew could make repairs. Life support equipment was shut down again on Sunday for three hours – NASA engineers believe it was because of bad computer data – but everything was brought online again on Monday. Station residents weren’t in any danger during either problem.

Posted on by Fraser Cain

Could 1 in 3 Earth-like Worlds Have Life?

Two researchers from Australia believe that life in the Universe may be more common than previously thought. Since life only took half a billion years to gain a foothold on our planet, they theorize, the odds of it happening on any Earth-like world must be good. With only one planet to sample, though, the Earth, there still isn’t any way to judge whether our planet is an anomaly or well within the norm. NASA’s upcoming Terrestrial Planet Finder due for launch in a decade will help scan for Earth-like planets in the future.

Posted on by Fraser Cain

Chinese Rocket Launches Two Satellites

A Chinese Long March 4B rocket successfully placed to satellites into orbit on Wednesday: a Fengyun-1D meteorological satellite and a Haiyang-1 marine surveying satellite. Both satellites were developed in China and will help the country’s efforts to monitor its weather. This is the country’s second launch of the year.