[Space] News

[GioFX]

Originariamente inviato da gpc
Domanda riguardo alle ipotesi sulla missione verso Giove: ma con la fascia degli asteroidi come pensano di fare?

era un problema una volta, ora non più... una degli "objectives" di rilievo della missione Pioneer, e poi Vojager, era proprio quella di capire se era possibile superare indenni (sia fisicamente che per le forti radiazioni) la fascia di asterodi tra marte e giove.

[TheDarkAngel]

Originariamente inviato da GioFX
era un problema una volta, ora non più... una degli "objectives" di rilievo della missione Pioneer, e poi Vojager, era proprio quella di capire se era possibile superare indenni (sia fisicamente che per le forti radiazioni) la fascia di asterodi tra marte e giove.

sai anke come hanno risolto?

[GioFX]

Originariamente inviato da TheDarkAngel
sai anke come hanno risolto?

ci sono passati in mezzo...

[Gyxx]

Originariamente inviato da GioFX
ci sono passati in mezzo...

[Claudio Bisio Simpatico Umorista]

Sagaci !!!



[/Claudio Bisio Simpatico Umorista]

[gpc]

Originariamente inviato da GioFX
ci sono passati in mezzo...

Ma LOL
E se fosse stata solo la fortuna del principiante?
Ma ricordo male io o nel passaggio di una sonda s'era danneggiata l'antenna principale?

[GioFX]

Originariamente inviato da gpc
Ma LOL
E se fosse stata solo la fortuna del principiante?
Ma ricordo male io o nel passaggio di una sonda s'era danneggiata l'antenna principale?

Pioneer 9... se ricordo bene...

Un passo interessante di un articolo che racconta l'epica avventura di Pioneer 10 (tra pochi giorni scriverò un paio di articoli su Pioneer e Voyager):

After two and a half decades in outer space, Pioneer 10’s antenna had drifted off-point. In 1997, NASA researchers realized they needed to re-point the antenna to Earth to keep in contact with the craft. But the targeting process carried the risk of muting Pioneer 10 permanently. To garner enough power for the maneuver, Pioneer 10’s transmitter had to be shut down. "We were concerned that turning the transmitter’s traveling wave tube off in the deep cold of space, and then back on again, would cause a thermal shock that might shatter the helix [a component that’s critical for transmission] in the tube," explains Larry Lasher, Pioneer project manager at NASA Ames Research Center. But "the hearty spacecraft successfully executed the [maneuvering] procedure in the blind for 90 minutes," he says.

Not bad for a craft originally slated only for a 21-month mission to Jupiter. To reach the giant planet, Pioneer 10 first had to cross the (then) seemingly impenetrable asteroid belt. By the 1960s, when Pioneer's mission was being planned, the orbits of more than 3,000 large asteroids had been determined and thus could be avoided, but tiny particles in the belt were still thought to pose a big threat. Scientists had no way of estimating the number of grain-size particles that might severely damage a craft after multiple collisions. "Only by going there could the danger be properly assessed, " says Ed B. Massey, manager of the Voyager and Ulysses projects, describing the debt later missions owe to Pioneer. "When Pioneer successfully traversed the asteroid belt, it had demonstrated that a concentration of small debris sufficient to harm the spacecraft did not exist."

After three decades that saw Pioneer 10 blaze a trail for all future spacecraft through the asteroid belt, take the first close-up images of Jupiter and its satellites and then head out of the solar system, the spacecraft was officially decommissioned in 1997. But, as Lasher notes, "in retirement Pioneer 10 still served the public as a valuable space resource at no extra cost to the taxpayers." It has been used to train spacecraft controllers in tracking station protocol and continues to be tracked as a part of study in communication technology.

[GioFX]

Voyage to Jupiter and Beyond

Also celebrating a milestone birthday this year, turning 25 on September 5, 2002, Voyager 1 overtook Pioneer in February 1998, to become the farthest man-made artifact. Like its pioneering cousin, Voyager 1 defied the odds, surviving for more than six times its original four-year mission length.

Voyager 1 and Voyager 2 set out in 1977, to Jupiter and beyond. The timing took advantage of a rare arrangement of the planets, occurring once every 175 years, which allowed a bargain tour of Jupiter, Saturn, Uranus and Neptune. To save weight on fuel, the twin spacecraft both employed the "slingshot" method, using the gravity of each planet passed to bend the flight path and increase velocity. Following in the footsteps of Pioneer 10, Voyager 1 traveled to Jupiter and Saturn before embarking on its interstellar mission, while Voyager 2 took the full four-planet tour. The two Voyagers found the first signs of volcanic activity outside Earth, on Jupiter’s moon Io, and discovered that the atmosphere of Saturn consists almost entirely of hydrogen and helium.

The Voyagers’ longevity can be attributed in part to last-minute design changes made following feedback from the Pioneer 10 and 11 missions. (The mission of Pioneer 11, which also flew by Jupiter, ended after its last transmission was received on September 30, 1995.) "The Pioneers discovered that Jupiter’s radiation belt was much more intense than anticipated, and the Voyagers, while more sophisticated than the Pioneers, were also more vulnerable," Massey explains. "Optical glasses and electronic components that would withstand the intense radiation had to be found, and instruments and other space subsystems had to be modified."


Credit must also be given to the original design team’s foresight when preparing the spacecraft for potential mission extensions. Each craft houses on-board backup systems that can be activated from the ground if needed. In April 2002, the team had to call on one of those reserve systems when Voyager 1’s position-sensing capability was in jeopardy, setting a new record for most-distant spacecraft maintenance in the process. "We were switching to a system that had not been used for 20 years, and, while we felt confident, we were not positive that it would work," Massey says. During a temporary changeover, on-board computers became confused about the spacecraft’s location, mistaking the sun for Earth, almost leading to loss of communications with the ground. The team had to instruct Voyager 1 to try to keep itself steady with gyroscopes during the final switch because it couldn’t rely on its computer sun-position sensors. "There was only about a 15-minute interval to analyze the data after the switch and decide whether to continue with the permanent switch," Massey says. But the team had faith that the transition had been successful, and today Voyager 1’s backup is functioning as smoothly as the original did 25 years ago.
Now both Voyagers are also heading out to the heliopause. With more sophisticated instrumentation than Pioneer, they may be used to study interstellar fields, particles and waves, in regions unaffected by the solar wind. To make sense of the data received, however, it’s important for scientists to have a clear understanding of how galactic cosmic rays are modulated by the solar wind. And who better to look to for advice than IMP-8, a spacecraft with almost 30 years of experience collecting data on long-scale solar processes?

[Mixmar]

Thread interessante... gli regalo un up!

[gpc]

Originariamente inviato da GioFX
Pioneer 9... se ricordo bene...

Un passo interessante di un articolo che racconta l'epica avventura di Pioneer 10 (tra pochi giorni scriverò un paio di articoli su Pioneer e Voyager):

NOOOOOOO ALTRI THREAD NOOOOO!!

No, a parte gli scherzi, ti supplico, non aprire altri thread che non ci sto più dietro sennò, scrivi qui!

Comunque le missioni Voyager e Pioneer sono tra quelle che ammiro di più, perchè secondo me sono state progettate con la mentalità giusta.
Chiaro, hanno avuto anche fortuna, ma quelle sonde di paia di palle ne avevano da vendere: sono andate ben oltre alla loro missione iniziale.

[GioFX]

Originariamente inviato da gpc
NOOOOOOO ALTRI THREAD NOOOOO!!

Non preoccuparti, tutti i thread saranno rintracciabili con la parola 'Space', e verranno di volta in volta riportati gli indirizzi nella prima pagina di questo thread.

[GioFX]

Weather eye on Europe

12 February 2004

ESA's new Weather Today website allows you to access data from space relied upon by weather forecasters across Europe.

Perched in geostationary orbit 36,000 km above Africa's Gulf of Guinea, the seventh ESA-developed Meteosat satellite maintains a constant weather eye on the European continent and its neighbours. Day and night every 30 minutes it routinely acquires a new image combining visual, infrared and water vapour channels.
Meteosat operator Eumetsat – the intergovernmental organisation for the exploitation of European meteorological satellites – processes the data in Darmstadt, Germany, before relaying it on to users via the same satellite working as a telecommunication relay. The latest images can be seen at http://weathertoday.esa.int.

Meteosat-7's sister satellite, Meteosat-6, waits in the wings in geostationary orbit ten degrees to the east – a stand-by spacecraft to guarantee continuity of service.

For the past 26 years millions of people have watched imagery returned by the Meteosat series of satellites incorporated into daily TV weather forecasts. Now, after seven spacecraft, the original Meteosat design is being joined and eventually succeeded by the Meteosat Second Generation (MSG) system.

Like its predecessor, MSG has been designed and developed for Eumetsat by ESA. MSG boasts higher image resolution, four times the number of sensing channels and is able to produce new images every 15 minutes instead of half an hour.

MSG-1, the first spacecraft in this new series, has already been placed in orbit. On 29 January it began routine operations, re-designated as Meteosat-8 to mark it formally becoming part of the Eumetsat family.

Weather Today - ESA

[GioFX]

Most Distant Galaxy Hints at Dark Ages

By Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
16 February 2004

Astronomers seeking to glimpse the very beginnings of the universe announced this weekend they may have spotted the most distant galaxy yet, one that could shed light on the end of the so-called Dark Ages of cosmology that preceded the well-lit universe we know today.


The scientists are unsure of the exact distance to the galaxy but know it is near the limit of what can be found with current telescopes. It is estimated to be 13 billion light-years away, seen at a time when the universe was just 700 million to 750 million years old.

Unlike other distance records in recent years, mostly coming out of the Sloan Digital Sky Survey, this one was a product of the Hubble Space Telescope and the W. M. Keck Observatory in Hawaii.

Jean-Paul Kneib, of Caltech and the Observatoire Midi-Pyrénées, led the work.

Running away

The distance to faraway galaxies is measured by noting how rapidly they are moving away from our own. Because the universe is expanding at an ever-increasing pace, all widely dispersed galaxies retreat from each other at greater speeds the farther apart they are.

Scientists measure all this by noting a galaxy's redshift, the extent to which the wavelengths of its light have been stretched toward the red end of the spectrum during its long travels across the cosmos.

The previous record holder, a Sloan galaxy, is at redshift 6.4.

The newfound galaxy has a redshift of at least 6.6, based on the Hubble imaging, and may be near 7.0 according to a less firm analysis of the Keck observations.

The universe is now about 13.7 billion years old.

Unusual properties of the galaxy could shed light on the end of a theorized era of cosmic time called the Dark Ages. During the Dark Ages, shortly after the Big Bang, hydrogen atoms had gathered to form the first stars, but they had yet to condense and ignite into the thermonuclear furnaces that create light. Scientists don't yet know how long the era lasted.

Unusual properties

The newly spotted galaxy appears not to have a bright emission from hydrogen that is seen in many other faraway galaxies. Further, its intense ultraviolet signal is much stronger than what's seen in more modern galaxies that are undergoing rapid star formation. That suggests the most distant known galaxy may contain mostly massive stars, which is in line with what theorists expect from the first galaxies.

"The unusual properties of this distant source are very tantalizing because, if verified by further study, they could represent those expected for young stellar systems that ended the dark ages," said Richard Ellis, a Caltech astronomer and coauthor of an article on the discovery that will be published in the Astrophysical Journal. He presented the finding today at a meeting in Seattle of the American Association for the Advancement of Science.

The discovery was not routine. It involved a trick of light provided by a natural magnifying glass in the heavens.

The primeval galaxy is situated behind a more nearby cluster of galaxies, called Abell 2218. The tremendous gravity of the galaxy grouping bends and amplifies light from the more distant object as it passes through the cluster. The technique, known as gravitational lensing, has been used to spot other object in the early universe.

"We are looking at the first evidence of our ancestors on the evolutionary tree of the entire universe," said Frederic Chaffee, director of the Keck Observatory.

Near the limit

Scientists have been saying for a few years now that they are closing in on the Big Bang with each record-setter. But each new benchmark is now an incremental improvement and increasingly difficult to top.

In a separate talk at the meeting, Xiaohui Fan of the University of Arizona's Steward Observatory in Tucson, discussed the limits of today's telescopes in spotting objects in the primordial universe. Fan was part of the Sloan team that found the previous record-holder.

These distant galaxies are called quasars, short for quasi-stellar radio sources. They were first noticed in the 1950s and '60s and were thought to be nearby stars that behaved strangely.

Current telescopes cannot routinely find quasars beyond redshift 6.5, Fan said. To reach redshift 10 or greater, and peer into the Dark Ages, will require the power of the James Web Space Telescope, due to launch early in the next decade.

There is a lot to learn.

When it was born, the universe contained only hydrogen and helium. All other elements were forged inside stars and in the explosive deaths of the most massive stars, known as supernovas.

"But we see a lot of other elements around those early quasars," Fan said. "We see evidence of carbon, nitrogen, iron and other elements, and it's not clear how these elements got there. There is as much iron, proportionate to the population of those early systems, as there is in mature galaxies nearby."

Theorists have become increasingly impressed with how rapidly stars must have formed as the Dark Ages ended.



Nearby galaxy cluster Abell 2218 acts as a powerful lens, magnifying galaxies beyond it. The lensed galaxies are all stretched along the cluster's center and some of them are multiply imaged. The new apparent record-setter shows up as a faint red pair of images, encircled in the larger version of this image.

[GioFX]

New Spaceship Planned, Russian Space Chief Says

By Vladimir Isachenkov
Associated Press Writer
posted: 12:30 pm ET
17 February 2004

MOSCOW (AP) -- Russian engineers have begun design work on a new spacecraft that would be twice as big and spacious as the existing Soyuz crew capsules, the nation's top space official said Tuesday.

The new craft will be able to carry at least six cosmonauts and have a reusable crew section, Russian Aerospace Agency director Yuri Koptev said at a news conference. Soyuz carries three cosmonauts and isn't reusable.

The spacecraft, designed by the RKK Energiya company, will have a takeoff weight of 12-14 metric tons (13-15 tons) -- about twice as much as the Soyuz, which was developed in the late 1960s.

Energiya has also proposed developing a new booster rocket based on its Soyuz booster to carry the new spacecraft to orbit.

Koptev wouldn't say how long it could take to build the spacecraft or how much it would cost, but said that Energiya had done a lot of work on the new vehicle already.

``It has already reached a serious project stage while the Americans are only talking about their spacecraft,'' Koptev said, referring to U.S. plans to build a new spacecraft.

U.S. President Bush's plan of returning astronauts to the moon and flying to Mars and beyond envisages phasing out the shuttle in 2010 and building a new spacecraft, called the Crew Exploration Vehicle, which is set to make its first manned mission no later than 2014.

Koptev said that his agency was willing to consider possible participation in the planned U.S. moon and Mars missions, but hadn't yet received any formal proposals from NASA. At the same time, he reaffirmed his skepticism about Bush's space plan, saying that the U.S. administration would have trouble raising resources for the planned missions.

``There is no explanation whatsoever where the money needed to implement the declared program would come from,'' Koptev said.

He added that more robotic missions to moon and Mars could be useful but sending humans there seemed too costly and inefficient for now.

``It's necessary to switch from emotions to pragmatic assessment: how much it would cost, where the money would come from and what we would get from such manned missions,'' Koptev said.

Koptev said that the prospective Russian spacecraft would be intended for orbital flights, not moon missions.

He said that Russia and other partners in the 16-nation International Space Station were waiting for the United States to clarify how the orbiting outpost would be run after 2010 when U.S. space shuttles will retire.

Koptev said that Russia would be willing to offer its Soyuz spacecraft to ferry astronauts to and from the station after the U.S. shuttles retire, but that would require renegotiating the original documents on the station.

Russian Soyuz and Progress spacecraft have served as the only link to the station since the U.S. shuttle fleet was grounded pending investigation into the destruction of the shuttle Columbia during its return to Earth in February 2003.

Koptev said that his agency has enough funds to send the two Soyuz and two Progress spacecraft necessary to operate the station this year. He said that Russian and European space officials are currently negotiating the possibility of sending a European astronaut on a six-month mission to the station in a Soyuz.

Several European astronauts so far have flown only weeklong missions to the station.

[GioFX]

Next shuttle flight delayed; rescue scenario formed

BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: February 19, 2004

The first post-Columbia shuttle mission will slip from September to March 2005 to give engineers more time to develop in-flight repair procedures and to take advantage of more favorable launch windows, officials said today. The slip also will give NASA and its contractors time to resolve problems with actuators in the shuttle's rudder and speedbrake assembly in the ship's vertical tail fin.


Concerns with space shuttle rudder/speedbrakes is one of the reasons NASA is delaying return-to-flight into 2005. Photo: NASA

NASA's Spaceflight Leadership Council, a panel made up of the agency's top managers, approved the change during a meeting today at the Johnson Space Center in Houston. The panel also approved plans to assign the flight to the shuttle Discovery, targeting launch for no earlier than March 6, 2005.

At the same time, engineers continue to refine plans to have a second shuttle ready for launch on an emergency rescue mission in case something goes wrong during Discovery's flight. In that case, commander Eileen Collins and her crew could be forced to seek "safe haven" aboard the international space station until a rescue flight could be attempted.

NASA plans to process a second shuttle that could be rolled to the pad and launched within 70 days of notification, assuming a three-shift around-the-clock work flow and no waived requirements, sources said. The flow possibly could be shortened to 35 days in a crisis.

The rescue flight, known as STS-300, would be crewed by four of the six astronauts already assigned to mission STS-115, the third flight in NASA's post-Columbia launch sequence. The STS-115 crew is made up of commander Brent Jett, pilot Chris Ferguson, Joe Tanner, Dan Burbank, Steve MacLean and Heidemarie Stefanyshyn-Piper.

STS-300 would provide backup for Collins' flight, known as STS-114, and the second post-Columbia mission, STS-121. Jett, Ferguson and two other STS-115 crew members would be trained to rescue either crew.

The mission would feature a normal rendezvous and docking with the space station. The stranded crew would return to Earth strapped into recumbent seats bolted to the floor of the rescue shuttle's lower deck.

Recumbent seats are needed to prevent balance problems for astronauts returning to Earth after being weightless for more than a month. Seven such seats would be required for Collins' crew, all of them mounted in the middeck area. Studies show all 11 returning astronauts would have time to bail out, if necessary, despite the crowded conditions on the lower deck.


This file image shows three astronauts in recumbent seats. Photo: NASA

"It is our plan to put ourselves in a posture for return to flight, first launch, that the second vehicle will be ready to launch and go to the international space station and pick up the first crew if we had a problem with the vehicle and could not bring it down," said Michael Kostelnik, deputy associate administrator for the shuttle and station programs.

He told reporters today the space station could support a stranded shuttle crew for up to 90 days and possibly longer if required.

"For the first flight, we are going to have the capability to do this and we will have the proper software load and training for that mission such that we'd be in a position to have a crew capable of launching within the time period the station could support an expanded crew and bring down the first crew if we had a problem with the first vehicle," Kostelnik said.

"There's still a lot of planning to be done on this (but) this is the path we're going down for the first flight. Our experience for subsequent flights will be determined by our success and our problems associated with the first flight."


The space station as seen at the completion of the last shuttle assembly mission in December 2002. Photo: NASA

With Discovery now slated for the first post-Columbia mission, the shuttle Atlantis will serve as the STS-300 "launch-on-need" vehicle.

"I don't believe there's an awful lot of extra training or extra things we have to do for a rescue mission," said Bill Parsons, shuttle program manager. "Overall, it would be very similar to an STS-121 mission. It would be going to the international space station, docking, picking up crew, making sure we had the appropriate hardware and things we needed to bring that crew on board and then returning safely."

NASA managers originally said they hoped to launch the first post-Columbia flight this March or April. But last October, the target was pushed back to a launch window that opened around Sept. 12 and closed Oct. 10.

A variety of factors conspired to push the flight into 2005, including work to minimize foam shedding from the shuttle's external fuel tank and development of tile and wing leading edge repair materials and techniques. Other "long poles" include development of a camera and laser sensor package needed for in-flight inspection of the ship's thermal protection system.

Tile repair development is "going as well or better than expected," Parsons said today. Wing leading edge repair is "not as mature as the tile repair, but it is coming along."


NASA now requires shuttles to be launched only in daylight. Photo: NASA

Another complicating factor is a photo documentation requirement to have daylight lighting for both launch and external fuel tank separation to determine whether any large pieces of foam separated from the tank and, if any did, whether the shuttle suffered any damage. The lighting requirement, combined with thermal constraints at the space station, translated into very limited launch windows through early 2005. After the September window, NASA had just three available days in November, none in December and three in January.

NASA now plans to target a launch window that would open around March 6, 2005, and extend into early April. But a Russian Soyuz crew transfer flight is scheduled for launch around April 10 and flight rules forbid launching a shuttle within 13 days of that date. As a result, NASA will have until roughly the end of March to get Discovery off the ground during that window.

The STS-121 mission is tentatively targeted for launch in May 2005.

As Parsons said, developing repair techniques for the reinforced carbon carbon panels that protect the leading edges of the shuttle's wings remains a major concern. But sources say recently discovered problems with actuators in the rudder/speedbrake assembly on the shuttle could prove equally time consuming to resolve.

[GioFX]

China announces plans for Shenzhou 6

Posted: Sun, Feb 22 12:58 PM ET (1758 GMT)

Chinese officials said Saturday that nation's next manned spaceflight, Shenzhou 6, would place two people into orbit for several days some time next year. Wang Yongzhi, chief designer of the Shenzhou program, told the Chinese TV network CCTV that Shenzhou 6 was scheduled for launch next year, although he did not specify when in the year the launch would take place. Unlike Shenzhou 5, which carried a single astronaut into orbit for one day, this flight would carry two people who would remain in orbit for between five and seven days. He added that China also planned to launch a "space laboratory" into orbit in 2007 that would be visited by future Shenzhou missions; the lab would be the first step towards a space station. Wang's comments confirm earlier reports and rumors that China would wait until 2005 to carry out its second manned spaceflight. Wang was interviewed after receiving a state science and technology award worth five million yuan (US$605,000) from Chinese President Hu Jintao in Beijing on Friday.

[GioFX]

Europe prepares mission to search for life on Mars

EUROPEAN SPACE AGENCY NEWS RELEASE
Posted: February 23, 2004

Before humans can leave their boot prints on the dusty surface of Mars, many questions have to be answered and many problems solved. One of the most fundamental questions - one that has intrigued humankind for centuries - is whether life has ever existed on Mars, the most Earthlike of all the planets.


An artist's concept shows the ExoMars descent module. Credit: ESA

Through its long-term Aurora Programme of solar system exploration, ESA is already preparing a series of robotic missions that will reveal the Red Planet's secrets and pave the way for a human expedition in decades to come.

A major step towards the realisation of this ambitious robotic programme was completed this week with the selection of two industrial teams to carry out the detailed design of the ExoMars rover and its Pasteur payload of scientific instruments.

The parallel Phase A studies for ExoMars, the first Flagship mission in the Aurora Programme, will be carried out by companies from ESA Member States and Canada.

The teams are:

Prime contractor Astrium UK, with subcontractors Galileo Avionica (Italy), Von Hoerner & Sulger (Germany) and SciSys (UK)
Prime contractor MD Robotics (Canada), with subcontractors Kayser Threde (Germany), Laben (Italy), Carlo Gavazzi (Italy) and Alcatel Space (France)
"The industrial groups will be responsible for producing a detailed design concept for the rover, the first vehicle of its kind to be built by ESA," said Bruno Gardini, Aurora Project Manager.
"In addition to defining the optimum conceptual design for the rover, they will also be expected to consider the unique operational environment on Mars. The studies will also take into account the design of the Pasteur payload and how the scientific instrument package can best be integrated with such a highly mobile vehicle."

This week's announcement follows the September 2003 selection of two industrial teams to carry out a full, end-to-end mission design for ExoMars. Those contracts cover all phases of the mission, from launch, through the long interplanetary voyage to the landing of the rover on the planet.

ESA has also issued an open announcement or 'Call for Ideas', requesting the participation of the scientific community in the ExoMars mission by proposing a well-defined set of instruments for the Pasteur payload.

After receiving some 50 proposals from more than 600 scientists in 30 countries, ESA intends to appoint three scientific Investigator Working Groups to advise on the final composition of the payload and its utilisation on Mars.

"ExoMars will be ESA's first mission to carry an exobiology payload, a set of instruments specifically designed to search for life," said Jorge Vago, ExoMars Study Scientist. "Over the next few months we shall zero in on the final instrument composition and then pass this information on to the industrial contractors," he said. "Our intention is to define a multi-instrument package that will be able to fulfil a number of key tasks."

"It should be able to drill into the surface, retrieve and analyse samples, study the physical environment and look for evidence of biomarkers - clear signs that life has existed on Mars in the past, or even survives to the present day," he added.

ExoMars, which is scheduled for launch in 2009, includes an orbiter and a descent module that will land a large (200 kg), high-mobility rover on the surface of Mars. After delivery of the lander/rover, the ExoMars orbiter will operate as a data relay satellite between the Earth and the vehicle on the Martian surface.

The primary objective of the rover and its state-of-the-art Pasteur payload will be to search for signs of life, past or present, on the Red Planet. Additional measurements will be taken to identify potential surface hazards for future human missions, to determine the distribution of water on Mars and to measure the chemical composition of the surface rocks.

Pasteur will be the most comprehensive scientific package ever to land on Mars, with tools that can extract, handle and analyse samples of Martian soil. The instrument mass of this payload is anticipated to be around 40 kg.

Its unique capability to obtain underground samples at depths of up to two metres will provide an excellent opportunity to gain access to ice-rich soil layers - and possibly the first definitive evidence of primitive Martian life.

[gpc]

Chissa' se in questa missione metteranno qualche sistemino di sicurezza...

[gpc]

Articolo *molto* più interessante di quelli di GioFX


http://www.space.com/searchforlife/s...pa_040226.html

Magnetic Fields and Water on Europa

By Cynthia Phillips
from the SETI Institute’s Center for the Study of Life in the Universe
posted: 06:30 am ET
26 February 2004

In four previous articles, we considered the Galilean satellites and the fact that tidal flexing, due to their resonant orbits, provides heat for volcanism on Io and could result in the presence of liquid water beneath Europa’s icy surface. We also summarized the evidence for liquid water at Europa based on geological evidence from images of Europa taken by the Voyager and Galileo spacecraft, and based on thermal models of the interior of Europa. In this article we will consider the magnetic field results from Galileo, and their implications for Europa’s subsurface structure.

The geological evidence is tantalizing, but incomplete -- it suggests that liquid water could be present, but also allows for the possibility that the strange features we see on Europa’s surface could all have formed through the motion of soft ice, without any liquid water at all. The thermal models present a similar picture -- we know that there is about 100 km of material with the density of water at Europa’s surface, but just can’t be sure if it’s completely solid, or if some (or most!) of it is liquid. Theoretical models that look at the behavior of Europa’s interior over time suggest that it’s possible that convection would quickly transport all the heat out of a liquid water layer and cause it to freeze solid, but it’s also possible that a liquid layer could be sustained over geological time.
In the face of all this uncertainty, it would be difficult to say anything more unequivocal than that a liquid ocean at Europa is possible. However, a new line of evidence from an unexpected source, results from Galileo’s study of magnetic fields, has suggested that the "possible" should be replaced with "probable" – we now believe that it is likely that Europa has a liquid ocean beneath its icy surface. How is this possible?

Europa has no magnetic field of its own, but Jupiter has a very strong magnetic field. The Jovian magnetosphere extends out to about 10 Jupiter radii (RJ), between the orbits of Europa (9.4 RJ) and Ganymede (15 RJ). So the satellites Io and Europa actually orbit Jupiter within its magnetic field. However, Jupiter’s magnetic field is not symmetric around the center of Jupiter–it is tilted by almost ten degrees with respect to Jupiter’s spin axis, and is also offset by about 1 R J from the center of Jupiter. Because of this offset as Jupiter rotates, Europa experiences a time-varying magnetic field over a period of 11.23 hours. The field also varies as Europa orbits around Jupiter, but Jupiter’s rotational period (and thus the rotation of its magnetic field) is a much stronger effect.

We know from the laws of electromagnetism that a time-varying magnetic field will induce an electric field. This electric field then causes a current to flow within the interior of Europa, with a direction that changes on a timescale of half the rotational period. This current loop then creates a secondary magnetic field with a direction that’s approximately opposite to the primary magnetic field from Jupiter. This is called an induced magnetic field.

Data from Galileo's magnetometer (an instrument which measures the strength and direction of magnetic fields) showed that Europa has an induced magnetic field that varies in direction and strength in response to Europa's position within Jupiter's strong magnetic field. The periodic variation in direction shows that the field is not due to a permanent internal dipole, meaning that the field is not created in the interior of Europa (unlike the Earth's magnetic field).

The strength and response of the induced field at Europa can tell us about subsurface structure. The results measured by the Galileo magnetometer require a near-surface, global conducting layer. The most likely layer that meets these requirements is a global layer of salty water, with a salt content of no less than ~0.02 times the salinity of Earth’s oceans. The magnetometer results allow a range of solutions with different values for the conductivity of the ocean, the depth below the surface at which it is located, and the ocean layer’s thickness. For example, if we assume a Europan ocean with a conductivity equal to that of the terrestrial oceans, then such a layer would have to be at least several kilometers thick and located no farther than 200 km below the surface of Europa.

The magnetic field data from the Galileo spacecraft put a substantial set of constraints on Europa’s subsurface structure. For example, the data for Europa cannot be explained by localized pockets of salty water, and instead require a nearly complete spherical shell of liquid water. A frozen ice layer, even if it had pockets of briny water, could not produce the observed response because ions in solid ice would be insufficiently mobile.

It is possible that a type of conducting layer other than a global salty ocean could account for the induced magnetic field, but the salty ocean explanation appears the most plausible. In particular, the strength of the observed induced field is not consistent with currents induced in a metallic core; the induced dipole field strength falls off with the cube of the distance and the core is simply too far away to provide the observed field. The data are also not consistent with a field induced in Europa's ionosphere; the ionosphere is too tenuous to support the electrical currents needed to explain the strength of the field. A subsurface layer of a different conducting material, instead of salty water, is possible, but such layers (such as graphite) would be implausible given what we know about Europa’s composition and formation.

Intriguingly, the Galileo magnetometer data suggest that Callisto and Ganymede may also harbor subsurface oceans. These latter oceans likely exist in a layer sandwiched between two phases of water ice, so they would not provide the astrobiologically more interesting rock/water interface (with possibilities for hydrothermal vents) that may be present at the bottom of Europa’s ocean.

The magnetic field results for Europa, therefore, currently provide our best indirect evidence for the presence of liquid water beneath Europa’s icy surface. These results, while intriguing, will not be confirmed until a direct detection of Europa’s ocean is made. Such measurements will require dedicated instruments on a spacecraft that is orbiting Europa. A future article will discuss these measurements (including altimetry, high-resolution gravity, and radar sounding) and the current plans to fly a spacecraft to Europa with instruments to make these and other measurements.

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Originariamente inviato da gpc
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la prima foto in assoluto della Terra e della Luna viste da un'altro pianeta (in realtà dall'orbita). Questa foto è stata scattata l'8 maggio 2003 da Mars Global Surveyor.