'Heart' Of Herschel Space Observatory Almost Ready

Source:

http://www.sciencedaily.com/releases/2007/09/070904114513.htm

Science Daily — By the end of 2007, the assembly of the ESA’s Herschel far-infrared space observatory – the latest mission to study the formation and evolution of stars and galaxies – will be completed.

The Herschel mission, equipped with the largest telescope ever launched in space (3.5 m diameter), will give astronomers their best capability yet to explore the universe at far-infrared and sub-millimetre wavelengths. By measuring the light at these wavelengths, scientists see the ‘cold’ universe. Herschel will give them an unprecedented view, allowing them to see deep into star forming regions, galactic centres and planetary systems.
In order to achieve its objectives and to be able to detect the faint radiation coming from the coolest objects in the cosmos, otherwise ‘invisible’, Herschel’s detectors must operate at very low and stable temperatures.
The spacecraft is equipped so as to cool them close to absolute zero (-273.15 ºC), ranging from -271 ºC to only a few tenths of a degree above absolute zero. To have achieved this particular feature alone is a remarkable accomplishment for European industry and science.
The final integration of the various components of the Herschel spacecraft – payload module, cryostat, service module, telescope and solar arrays – will be completed in the next few months. This phase will be followed by a series of tests to get the spacecraft ready for launch at the end of July 2008.
Herschel will be launched into space on an Ariane 5 ECA rocket. The launch is shared with Planck, ESA’s mission to study relic radiation from the Big Bang.
Contractors and funding
The Prime Contractor for the Herschel spacecraft is Thales Alenia Space (Cannes, France). It leads a consortium of industrial partners with Astrium (Germany) responsible for the Extended Payload Module (EPLM, including the Herschel cryostat), Astrium (France) responsible for the telescope, and the Thales Alenia Space industry branch of Torino, Italy, responsible for the Service Module (SVM). There is also a host of subcontractors spread throughout Europe.
The three Herschel instruments were designed and built by consortia of scientists and institutes, with their own national funding. The Photodetector Array Camera and Spectrometer (PACS) was developed under the coordination of the MPE, Germany; the Spectral and Photometric Imaging Receiver (SPIRE) was developed under the coordination of the Cardiff University (United Kingdom); the Heterodyne Instrument for the Far Infrared (HIFI) was developed under the coordination of the SRON institute (The Netherlands).
Note: This story has been adapted from a news release issued by European Space Agency.

Fausto Intilla

www.oloscience.com

'Lucky Camera' Takes Sharpest Ever Images Of Stars

Source:

http://www.sciencedaily.com/releases/2007/09/070904082539.htm

Science Daily — Astronomers from the California Institute of Technology and the University of Cambridge have developed a new camera that produces much more detailed pictures of stars and nebulae than even the Hubble Space Telescope, and it does all this from here on Earth.

Until now, images from ground-based telescopes have been invariably blurred by Earth's atmosphere. Astronomers have developed a technique, known as adaptive optics (AO), to correct the blurring, but so far it has only worked successfully in the infrared, where the smearing is greatly reduced. However, a new noise-free, high-speed camera has been developed at the Institute of Astronomy in Cambridge that, when used behind the infrared Palomar Adaptive Optics System, at last makes very high resolution imaging possible in ordinary visible light.
The camera works by recording partially corrected adaptive optics images at high speed (20 frames per second or more). Software then checks each image to sort out which are the sharpest. Many are still significantly smeared by the atmosphere, but a small percentage of them are unaffected. These are combined to produce the final high-resolution image that astronomers want. The technique is called "Lucky Imaging" because it depends on the chance fluctuations in the atmosphere sorting themselves out and providing a set of images that is easier for the adaptive optics system to correct.
This work was carried out on the 200-inch (5.1 meter) Hale Telescope on Palomar Mountain. Like all other ground-based telescopes, the images it normally produces are typically 10 times less detailed than those of the Hubble Space Telescope. Palomar’s adaptive-optics system produces superb images in the infrared, but until now, its images in visible light have remained markedly poorer than Hubble images. With the new Lucky Camera, astronomers were able to obtain images that are twice as sharp as those produced by the Hubble Space Telescope—a remarkable achievement.
The images produced in the study are the sharpest direct images ever taken in visible light either from the ground or from space. "The system performed even better than we were expecting. It was fantastic to watch the first images come in and see that we were easily doing better than Hubble," says Nicholas Law, a postdoctoral scholar at Caltech and principal investigator for the instrument.
Most astronomical objects are so far away that astronomers are desperate to see more and more detail within them. The new pictures of the globular star cluster M13, located 25,000 light years away, are sharp enough that astronomers are able to find stars as little as one light-day apart. A light-year is the distance light travels in one year (almost 6 trillion miles). A light-day is the distance light travels in just one day. Stars in the vicinity of the solar system are much farther apart –the nearest star to our solar system is over four light-years away.
The astronomers also observed very fine detail in objects such as the Cat's Eye Nebula (NGC 6543). It is eight times closer to earth than M13, allowing filaments that are only a few light-hours across to be resolved.
The use of the camera at Palomar was a demonstration of the potential of visible-light adaptive optics and offers a glimpse of the detailed imagery to come. Astronomers at Caltech and the Jet Propulsion Laboratory are currently developing the first-ever astronomical adaptive-optics system fully capable of capturing visible-light images. It will routinely allow the 200-inch telescope at Palomar to outperform the Hubble Space Telescope at even blue wavelengths. Using state-of-the-art deformable mirrors, sensors, and a powerful laser, the upgraded Palomar adaptive-optics system will provide finer correction of the atmospheric blurring than any present adaptive optics system, allowing long-exposure images with the same fine detail as the "lucky" images taken recently.
Caltech's Richard Dekany, principal investigator for the new system, says that the upgraded instrument could be available as early as 2010. "These Lucky Imaging results underscore the science potential of diffraction-limited visible-light observations on large ground-based telescopes," he explains.
To get even sharper pictures, astronomers will need to use bigger telescopes.
The results open up the possibility of further improvements on even larger telescopes, such as the 10-meter Keck telescopes on the top of Mauna Kea in Hawaii or in the future even larger telescopes, such as the Thirty Meter Telescope (TMT).
Working on the Lucky Imaging project were Law, Dekany, Mike Ireland, and Anna Moore from Caltech and the Palomar 200-inch crew. Other team members included Craig Mackay from Cambridge, James Lloyd from Cornell University, and Peter Tuthill, Henry Woodruff, and Gordon Robertson from the University of Sydney.
Note: This story has been adapted from a news release issued by Institute of Astronomy & Cavendish Laboratory, University of Cambridge.

Fausto Intilla

www.oloscience.com

Stellar Firework In A Whirlwind

Source:

http://www.sciencedaily.com/releases/2007/09/070904114550.htm

Science Daily — Stars do not like to be alone. Indeed, most stars are members of a binary system, in which two stars circle around each other in an apparently never-ending cosmic ballet. But sometimes, things can go wrong.

When the dancing stars are too close to each other, one of them can start devouring its partner. If the vampire star is a white dwarf – a burned-out star that was once like our Sun – this greed can lead to a cosmic catastrophe: the white dwarf explodes as a Type Ia supernova.
In July 2006, ESO’s Very Large Telescope took images of such a stellar firework in the galaxy NGC 1288. The supernova - designated SN 2006dr - was at its peak brightness, shining as bright as the entire galaxy itself, bearing witness to the amount of energy released.
NGC 1288 is a rather spectacular spiral galaxy, seen almost face-on and showing multiple spiral arms pirouetting around the centre. Bearing a strong resemblance to the beautiful spiral galaxy NGC 1232, it is located 200 million light-years away from our home Galaxy, the Milky Way. Two main arms emerge from the central regions and then progressively split into other arms when moving further away. A small bar of stars and gas runs across the centre of the galaxy.
The first images of NGC 1288, obtained during the commissioning period of the FORS instrument on ESO's VLT in 1998, were of such high quality that they have allowed astronomers1 to carry out a quantitative analysis of the morphology of the galaxy. They found that NGC 1288 is most probably surrounded by a large dark matter halo. The appearance and number of spiral arms are indeed directly related to the amount of dark matter in the galaxy's halo.
The supernova was first spotted by amateur astronomer Berto Monard. On the night of 17 July 2006, Monard used his 30-cm telescope in the suburbs of Pretoria in South Africa and discovered the supernova as an apparent 'new star' close to the centre of NGC 1288, which was then designated SN 2006dr. The supernova reached magnitude 16, that is, it was about 10 000 times fainter than what the unaided eye can see.
Using spectra obtained with the Keck telescope on 26 July 2006, astronomers from the University of California found SN 2006dr to be a Type Ia supernova2 that expelled material with speeds up to 10 000 km/s.
Notes:
"Morphological structure and colors of NGC 1232 and NGC 1288" by C. Moellenhoff et al., A&A 352, L5 (1999) and "Quantitative interpretation of the morphology of NGC 1288" by B. Fuchs and C, Moellenhoff, A&A 352, L36 (1999)
Type Ia supernovae are a sub-class of supernovae that were historically classified as not showing the signature of hydrogen in their spectra. They are currently interpreted as the disruption of small, compact stars, called white dwarfs, which acquire matter from a companion star. A white dwarf represents the penultimate stage of a solar-type star. The nuclear reactor in its core has run out of fuel a long time ago and is now inactive. However, at some point the mounting weight of the accumulating material will have increased the pressure inside the white dwarf so much that the nuclear ashes in there will ignite and start burning into even heavier elements. This process very quickly becomes uncontrolled and the entire star is blown to pieces in a dramatic event. Type Ia supernovae play a very useful role as cosmological distance indicators, allowing astronomers to study the expansion history of our Universe, leading to the conclusion that the Universe is expanding at an accelerating rate.
Note: This story has been adapted from a news release issued by ESO.

Fausto Intilla

www.oloscience.com

SMART-1: Europe On The Moon, One Year On

Source:

http://www.sciencedaily.com/releases/2007/08/070831093848.htm

Science Daily — A year ago, as Europe reached the Moon for the first time, scientists on Earth eagerly watched SMART-1’s spectacular impact. New results from the impact analysis and from the instruments still keep coming.

One year on, we present ongoing scientific highlights of the mission. The analysis of data and simulations of the satellite’s impact provide clues on the dynamics of the ejecta after the flash, along with laboratory experiments or modelling of impacts. The experience gained is being put to good use in preparation for future missions.
SMART-1 addresses various scientific themes that answer questions on the physical processes at work on Earth-like planets and how they evolve. The moon is a laboratory for geophysics where impacts, volcanism, tectonics and effects of space weather can be studied to put together the story of its past. The geochemistry and origins of the Moon, the evolution of the Earth-Moon system and the bombardment of the inner solar system are topics addressed under lunar formation and evolution.
Know-how from SMART-1 is helping prepare the ground for future science and exploration missions. With its unrivalled resolution, in colour and with various illumination angles, the satellite has mapped the polar regions, surveyed lunar resources and investigated potential landing sites and outposts.
More than 15 presentations were given by the SMART-1 team during the ‘Europlanet’ European Planetary Science Congress in Berlin, 20-24 August 2007. Topics covered included: highlights of SMART-1 lunar science, new results on coupling between impacts and lunar volcanism for Humorum and Procellarum basins, latest high resolution maps of the lunar Poles and infrared spectra of lunar areas and craters.
Mike Burchell from the University of Kent showed laboratory simulations describing the impact crater’s shape and size, predicting ricochet ejecta. As a detailed picture of the impact is taking shape, scientists now know that the spacecraft bounced over the surface, projecting debris at high altitude, which was traced by Christian Veillet with the Canada France Hawaii telescope.
Experts from the SMART-1 team are now working on data calibration, analysis, archival and distribution for the scientific community and are supporting collaborations with upcoming lunar missions. This includes refining the lunar coordinate systems, selecting targets observed by SMART-1 and other probes, exchanging tools for scientific planning, or building on SMART-1 outreach or education activities to promote future lunar missions and exploration.
“Know-how and data from SMART-1 is forming a bridge for international collaboration and European contribution to upcoming lunar Missions”, says SMART-1 Project scientist Bernard Foing.
Chang'E-1, China’s lunar orbiter and JAXA’s Selene are ready to be launched later this year. In Spring 2008, the Indian Chandrayaan-1 will carry three ESA instruments (two of them upgraded SMART-1 X-ray and infrared instruments) to observe the moon.
Knowledge gained from SMART-1 and the impact campaign is also helping the preparation of NASA’s Lunar Reconnaissance Orbiter and the Lunar Crater Observation and Sensing Satellite, due for launch before the end of 2008. SMART-1’s high resolution maps are helping characterise future landing sites, in particular at the poles.
“After SMART-1’s final touchdown at 2 km/s,” says Bernard Foing, “everybody asks: when will Europe land softly on the Moon?”
In the context of ESA’s Aurora Exploration programme and its preparatory activities for a Mars Sample Return mission, a call of ideas was issued for the Next Exploration Science and Technology mission (NEXT) in April 2007. It resulted in more than 70 responses, including more than 30 lunar proposals. Future European lunar missions concern a large community interested in the scientific and technological potential of lunar landers and sample return missions.
‘Highlights of SMART-1 Lunar Science’ results by B. Foing and the SMART-1 Science and Technology Working Team was presented at the European Planetary Science Congress (EPSC) 2007.
Note: This story has been adapted from a news release issued by European Space Agency.

Fausto Intilla

www.oloscience.com

'One Of The Most Curious Objects In The Sky' Delights Astronomers Again

Source:

http://www.sciencedaily.com/releases/2007/08/070829192102.htm

Science Daily — Edwin Hubble once called IC 10 “one of the most curious objects in the sky,” and new observations of the extremely faint, lightweight dwarf galaxy are giving scientists new clues about how populations of stars are born.

Though the properties of stars is one of the most well-studied topics in astronomy, scientists still don’t fully understand all the mechanisms involved in star formation and evolution, particularly in galaxies with low levels of oxygen, nitrogen and other heavy elements. But scientists studying the IC 10 galaxy may soon understand how stars might have looked like in the distant past, when the universe was in a younger, more pristine form.
“A few years ago these types of studies would have been impossible from the ground,” said Dr. Taft Armandroff, director of the W. M. Keck Observatory, who’s own research includes the study of dwarf galaxies. “We can now study individual stars of galaxies several million light years from Earth to understand how star formation events may have affected the evolution of the Milky Way galaxy. This galaxy can teach us what the most common types of galaxies in the universe might be like.”
New images of IC 10 reveal a small region of space teeming with nearly a thousand stars. The image, obtained with NASA’s Hubble Space Telescope and the W. M. Keck Observatory in Hawaii, shows evidence of a vigorous star formation event that took place within the last 10 million years.
Dr. William Vacca at the NASA Ames Research Center led the study and says IC 10 may answer many unresolved questions about stellar evolution. “IC 10 is a remarkable galaxy,” he said. “It is the only one we’ve seen that falls outside an established pattern of having a certain number of massive nitrogen-type stars for each carbon-type star. This imbalance has caused us to wonder if our past conclusions about massive stars have been correct. Do we need to revise the models of stellar evolution?”
Astronomers have known that IC 10 has more giant, rare stars called “Wolf-Rayet stars” than all other nearby dwarf galaxies combined. Wolf-Rayet stars are extremely hot blue stars losing enormous amounts of mass to the interstellar medium. In addition, the proportion of Wolf-Rayet stars in IC 10 seems to be wildly out of balance. For the number of stars containing carbon, astronomers expected to see a certain number containing nitrogen. But so far, very few nitrogen stars have been found. Could IC 10 be hiding a population of stars?
Using a combination of Hubble and Keck telescope images, Vacca’s team found many previously undiscovered stars in the IC 10 galaxy. Each new star can now be measured to determine its chemical composition. If the newly found stars contain nitrogen, then part of the “missing nitrogen” puzzle might be solved.
“The combination of HST images in the optical and Keck Laser Guide Star images in the infrared has been a major breakthrough in our understanding of dense stellar regions,” said co-author Dr. James R. Graham, professor of astronomy at UC Berkeley. “IC 10 has so many stars in such a tiny region of space that ground-based studies have been confused. But the combination of HST and Keck has been revolutionary in our understanding of this object, and for any object with a dense region of stars.”
The new images of IC 10 are centered on a bright star first thought to possibly be the most luminous Wolf-Rayet star in IC 10. Follow up studies then found the star to be comprised of at least three or more components. Now, new data from Keck show the bright star ([MAC92] 24) is actually six or more stars, perhaps even a cluster of stars.
“This is the first time this sort of study has been done using adaptive optics,” said co-author Christopher Sheehy of the University of Chicago. “It gives us the ability to make these kinds of measurements accurately from the ground and there's no shortage of targets in need of a fresh look. The potential is exciting.”
The new data has also enabled scientists to measure the precise distance to IC 10, a figure that has eluded scientists since the object’s discovery more than 100 years ago. Dr. Vacca and his collaborators calculated the distance to IC 10 to be about 2.6 million light years from Earth, or 800 kiloparsecs. This is in good agreement with some previous estimates.
IC 10 was first discovered by Lewis Swift in 1889 at the Warner Observatory in Rochester, New York. The “Index Catalogue” (IC) is a catalogue of galaxies, nebulae and star clusters that supplements the more modern New General Catalogue (NGC). First published in 1895, the catalogue first described IC 10 as a “faint star involved in extremely faint and very large nebula.” It wasn’t until 1935 that IC 10 was first proposed as an extragalactic object and Edwin Hubble later proposed IC 10 might be a member of the Local Group. It took another 30 years before these suspicions could be confirmed using radial velocity and distance measurements.
Astronomers now know IC 10 is similar in many ways to the Large Magellenic Cloud of the Southern Hemisphere. But unlike the Large Magellenic Cloud, IC 10 orbits Andromeda, not the Milky Way. The study of IC 10 is giving astronomers a picture of what the Milky Way might have looked like billions of years ago before the galaxy’s interstellar medium was enriched with elements such as oxygen and nitrogen.
The paper, “Imaging of the Stellar Population of IC 10 with Laser Guide Star Adaptive Optics and the Hubble Space Telescope,” was published in the June 10 issue of Astrophysical Journal. The research was made possible with grants provided by the National Science Foundation (AST 0205999 and AST 9876783) and NASA.
Note: This story has been adapted from a news release issued by Keck Observatory.

Fausto Intilla

www.oloscience.com

Rosetta's Target Comet: Lumpy, Bumpy, Fluffy And Layered

Source:

http://www.sciencedaily.com/releases/2007/08/070824134155.htm

Science Daily — Observational and theoretical studies of Comet 67P/Churyumov-Gerasimenko, the target of ESA’s Rosetta mission, are building a detailed portrait of the comet’s nucleus as it travels around the Sun.

Observations of the comet using the 8.2 m-ESO Very Large Telescope (VLT) show an irregularly-shaped object that is about 4.6 kilometres in diameter with a rotational period of 12 hours 49 minutes. Ms Cecilia Tubiana, who will be presenting results at the second European Planetary Science Congress (EPSC) in Potsdam on Tuesday 21st August, said, “These observations were taken when the comet was approaching the furthest point from the Sun in its orbit. Rosetta will rendezvous with the comet in 2014 at a distance of about 600 million kilometres from the Sun. While a quite detailed portrait of the comet at small heliocentric distance has been drawn, a profound description of Rosetta’s target comet at large heliocentric distance is missing.”
A team of scientists, led by the Max Planck Institute for Solar System Research, observed the comet’s nucleus in June 2004, May and August 2006 and July 2007, when the comet was at least 680 million kilometres from the Sun. Surprisingly, although the comet was not active, they found that a faint dust trail is visible in the images of the comet, extending more than 500 000 km along the comet’s orbital path. Ms Tubiana said, “We believe that this dust trail is composed of large grains that the comet shed over the many times it has travelled along this path.
Later on Tuesday 21st at the EPSC, Dr Jérémie Lasue, of the Service d’aéronomie in France, will present results of numerical studies that describe how a comet’s nucleus changes as it travels along its orbital path. Dr Lasue explained, ”Comets constantly evolve by ejecting material as their distance from the Sun changes and their temperature increases or falls. To land on a comet’s nucleus, you need to have a good idea of its structure, density and tensile strength. Comet 67P/Churyumov-Gerasimenko most probably has an irregular comet nucleus with crater-like depressions on its surface. Our team has developed a three-dimensional model of the internal processes in the nucleus, allowing us to predict the thermal evolution and surface activity as the comet moves along its orbit."
Recent mission results suggest that a comet’s structure is highly stratified. Dr Lasue said, “Stardust showed that the dust ejected from the outer layers is composed of fluffy particles that can be relatively large. These particles are rich in silicates and organics, which are the building blocks of life. Our simulations, for the first time, take into account the relationship between the impact history of the comet and the forces holding the comet’s constituents together. This technique has enabled us to reproduce and interpret the amazing layered structure and surface features that Deep Impact observed at comet 9P/Tempel 1. This is a new means to quantify the tensile strength of comet nuclei, which gives us vital information in preparing for Rosetta’s rendezvous with 67P/Churyumov-Gerasimenko."
The teams of scientists from France and Italy in which Dr Lasue works, are developing these numerical tools to support two of Rosetta’s instruments: VIRTIS, which will determine the composition of the ices in the comet’s nucleus as well as emitted gases and dust, and CONSERT, which will investigate the deep interior of the nucleus with radio waves.
Note: This story has been adapted from a news release issued by European Planetology Network.

Fausto Intilla

www.oloscience.com

Up, Up And Away -- To Venus

Source:

http://www.sciencedaily.com/releases/2007/08/070829170644.htm

Science Daily — Scientists hope to learn more about climate changes here on Earth by studying Venus. A prototype balloon could eventually study the planet’s surface and examine its atmosphere and the bizarre winds and chemistry within it. A team of JPL, ILC Dover and NASA Wallops Flight Facility engineers designed, fabricated and tested the balloon.

Slightly smaller than Earth, Venus is often regarded as Earth's sister planet. Both have similar densities, chemical compositions and gravities. However, its atmosphere is nearly 100 times thicker than Earth's, which causes blazing temperatures at the surface. By flying in the cool skies above Venus, the balloons would avoid that environment.
"The surface is hot enough to melt lead, which is why we can't study it for long from a lander," said Kevin Baines, JPL principal investigator for a proposed mission to Venus. "Without extreme and costly refrigeration methods, a lander would cook at those temperatures in just a few hours, but a balloon can stay in a benign environment, studying the planet for days, weeks or even months."
The spherical balloon, 18 feet in diameter, is about the size of an inflatable children's jumper. Its aluminum coating reflects sunlight to protect the balloon from becoming too hot as it flies in Venus’ upper atmosphere. Its outer transparent layer of the balloon is made of polytetrafluorethylene, also known as Teflon, the non-stick material found in cookware and on clothing. The material is highly resistant to the sulfuric acid found in clouds surrounding Venus. “The sun shines through the Teflon and reflects off the aluminum, and that keeps the balloon from overheating,” said Jeff Hall, JPL's lead balloon engineer.
The balloon's second layer has a mylar film similar to those shiny helium balloons found in a grocery store. The mylar is used to prevent gas from leaking out. The next layer is made of a Vectran fabric that provides the strength to keep the balloon from bursting due to internal pressure. The innermost layer has a polyurethane coating that enables all sections of the balloon to be glued together.
More details about the design, fabrication and testing of the balloon are reported in a paper published in the journal Advances in Space Research..
The proposed mission would have two balloons, one at a tropical latitude, the other at a polar latitude. Each helium-filled balloon would fly about 56 kilometers (about 35 miles) above Venus' oven-hot surface, in temperatures about the same as a spring afternoon in Los Angeles. It would take about four days for the helium superpressure balloons to fly completely around the planet. After the balloons are launched from Earth, they would arrive on the night side of Venus.
"The winds at that altitude are very strong, more than 320 kilometers per hour (about 200 miles an hour), and will blow the balloons around the planet," Hall said. "Engineers would not have control of where the balloons travel. Once the balloon starts flying, it is totally dependent on the winds."
Each balloon would have quite a roller coaster ride, moving up and down about a half a mile in altitude as they ride gravity waves generated by Venus’ mountainous terrain.
"This was one of the surprises of the Vega balloon mission the Soviet Union flew more than two decades ago," Baines said. "Enormous gravity waves appear to rise up more than 30 miles into the upper atmosphere, causing unexpected depositions of energy generated at the surface and producing strong vertical movements of air. We want to ride these waves, measuring their effect on Venus' bizarre high-speed winds."
Scientists believe the Venus balloons could also help us learn more about climate changes here on Earth. “Venus is a place where global warming has gone amuck,” Hall said. “It’s about the same size as our planet, but the surface is about 900 degrees Fahrenheit, and we want to find out why.”
Scientific instruments aboard the balloons would analyze the composition of Venus' atmosphere. The pressure cooker atmosphere around Venus quickly changes and is filled with specific gases, such as helium and neon, which do not interact chemically with other materials, allowing researchers to trace the formation of Venus over time. Noble gases can help scientists determine the geological history of the planet, which could lead to answers about current climate changes.
"Those gases will tell us if Venus and Earth were twin planets. Indications from previous missions suggest that Venus and Earth were quite similar at the beginning," Baines said.
Various studies indicate Venus once had oceans of water much like those on Earth, but now the planet is dry. According to Baines, Venus began as an oasis with conditions favorable for life in its first billion years. "Venus now has an extreme climate. It changed from being wet and wild, to dry and dead, and it seems to have happened in the last three billion years. We'd like to find out how this global transformation happened."
The current explanation for the dry atmosphere and extremely hot surface temperature is that Venus does not have a magnetic field to provide protection from solar winds. Those winds smash into the top of the atmosphere and drag off hydrogen that is needed for water.
A payload weighing more than 40 kilograms (about 90 pounds) would fly with each balloon to help transmit data back to Earth. Included in this payload would be a flight computer, radio transmitter and 9 kilograms (20 pounds) of electric batteries to power the equipment. Also included is a suite of science instruments:
A gas chromatograph mass spectrometer to measure the amounts of gases on Venus and to sniff for volcanic smoke.
An atmospheric structure instrument would measure the pressures and temperatures of the atmosphere and the vertical winds as the balloons bob up and down. This instrument also includes a nephelometer instrument to measure the size and density of cloud particles through light reflections.
A lightning detector to measure the power and frequency of nearby lightning strikes in the atmosphere.
A microphone to record any nearby sounds in the atmosphere, including thunder.
Ground-based radio telescopes using an interferometric technique would be used to measure how each balloon moves around the atmosphere. "We'd be able to tell its velocity within one inch per second of movement over an hour," Baines said. The telescopes would also use the Doppler effect to complete a set of 3-D measurements of each balloon's movements.
The company that built the airbags for the Mars Exploration Rover mission, ILC Dover, Frederica, Del., also helped design and build the balloons. The balloons are folded into small packages to fit inside the launch rocket that also include high pressure helium tanks and valves. Once the balloons reach the planet, the heavy tanks would drop away so the balloon could float away.
The balloon mission would likely end one of two ways: it might run out of battery power, when the balloons would be unable to communicate with ground controllers, or if a balloon develops a leak, it would eventually lose altitude and overheat the payload until it stops working. Hall and his team of engineers in JPL’s Aerobot laboratory have tested the prototype and determined it can float for up to 12 days without leaking any helium gas. A 12-day flight would be long enough to allow the balloons to circumnavigate the planet three times.
Note: This story has been adapted from a news release issued by NASA/Jet Propulsion Laboratory.

Fausto Intilla

www.oloscience.com