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By Daniel Fischer Every page present in Europe & the U.S.!
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The latest issue!
| A German companion! (SuW version) Current mission news: MGS (latest pictures!) + Cassini + Galileo + NEAR |
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NASA's Pluto mission could be back - with a launch still possible in 2004!NASA has made a 180-degree turn and will put out an Announcement of Opportunity shortly, calling for proposals for a quick, affordable mission to Pluto by March - this is the decision announced as an X-mas gift to solar system enthusiasts on Dec. 20. It is the first time that NASA is soliciting proposals for a mission to an outer planet on a competitive basis similar to the agency's Discovery Program for the inner solar system. Now the Pluto mission could still meet the good 2004 launch window and use a Jupiter-flyby to make it to the distant planet within 8 years - probably in time before its tenuous atmosphere is frozen out. NASA explicitly demands an arrival by 2015 in its call for proposals.It is not guaranteed, of course, that there will be entries good enough to meet the demanding task - and the cost ceiling of $500m in FY 2000 dollars - so the mission could well die again. With the possible Pluto mission on the number one position again in the Outer Planets program, the launch of the Europa Orbiter will probably slip to 2008, but this mission would still start delivering data before the Pluto probe does. NASA's decision to revive the Pluto mission does not only reflect strong pressure from the scientific community: A poll by Sky & Telescope has found that 58% of the public want such a mission (with 64% also supporting the Europa Orbiter and 70% calling for a Mars sample return mission). |
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Cassini operations interrupted by reaction wheel trouble!Just when the observations of Jupiter by the Saturn-bound Cassini spacecraft had were switching into high gear, 10 days before the fly-by, a problem with its reactions wheels has stopped all science operations for perhaps a week to 10 days. Cassini had been using a trio of electrically driven reaction wheels for turning itself in different directions to point science instruments. One of those wheels was needing more than the normal amount of force to turn it on Dec. 17, so Cassini's fault-protection switched to a maneuvering system that uses small, hydrazine-burning thrusters. To conserve hydrazine for Cassini's main mission at Saturn, science studies of Jupiter have been suspended immediately.The reaction wheels affect which direction Cassini is facing, but not the direction of its trajectory through space: Cassini continues right on course to pass Jupiter at a distance of about 9.7 mio. km on Dec. 30, and with a gravity boost from Jupiter, to reach Saturn in July 2004. Cassini has four reaction wheel assemblies: Three are mounted mutually perpendicular to each other, and one is a spare. When an electric motor accelerates a wheel, the spacecraft rotates slowly in the opposite direction. In a diagnostic test on Dec. 18, reaction wheel number 2 still had higher than normal torque, the amount of force needed to turn it, when it was accelerating to a speed of 50 revolutions per minute, but it spun freely at speeds between 50 and 300 rpm. |
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A hidden ocean in Ganymede as well?Not only Europa (see Update # 201) and Callisto: Ganymede seems to have liquid water under its icy crust, too. The evidence is coming again from Galileo's magnetometer, but this time it was much harder to extract. Ganymede is not only the largest moon in the solar system but also the one with the strongest magnetic field of its own - it was the first major discovery when the spacecraft started its encounters with the Jovian satellites in 1996 and even gives the moon its own little magnetosphere inside Jupiter's.This field had until recently obscured additional effects of induced magnetism as they had been seen repeatedly in the vicinity of Europa and Callisto - and could be explained only by a salty sub-surface ocean. But a similar thick layer of melted, salty water seems now to be necessary somewhere beneath Ganymede's icy crust to explain some of the magnetic readings taken by Galileo during close approaches to Ganymede in May 2000 and earlier. The indications of an induced field at Ganymede are "highly suggestive" of a salty ocean, say the magnetometer experts: "It would need to be something more electrically conductive than solid ice." A melted layer several kilometers or miles thick, beginning within 200 kilometers of Ganymede's surface would fit the data if it were about as salty as Earth's oceans. In addition, the types of minerals on parts of Ganymede's surface suggest that, in the past, salty water may have emerged from below or melted at the surface, according to a study of infrared reflectance measured by Galileo. And third, new Galileo images of Ganymede hint how the water or slushy ice may have surfaced through the fractured crust, reminiscent of linear features on Europa where such evidence had been seen for years. |
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Martian magnetic field still helping the atmosphereThough Mars lacks a global protective magnetic shield like that of the Earth, strong localized magnetic fields embedded in the crust appear to be a significant barrier to erosion of the atmosphere by the solar wind. This conclusion emerges from a new map of the limits of the planet's ionosphere obtained by the Mars Global Surveyor: The new data show that where localized surface magnetic fields are strong, the ionosphere reaches to a higher altitude, indicating that the solar wind is being kept at bay. The findings suggest that these crustal fields could have played an important role in the past evolution of Mars' atmosphere. If, as some Mars experts think, much of the planet's atmosphere was stripped away by the solar wind, these maps show where the solar wind did, and continues to do, the most damage. |
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Was the Supernova 1987A a bi-polar event?A decade's worth of data has revealed that Supernova 1987A that exploded in the Large Magellanic Cloud in February of 1987 shows increasing evidence for a bi-polar explosion that may in turn reveal that the supernova itself resulted from a jet emerging from the new-born neutron star - and was not driven mainly by neutrinos as it is usually presumed. The main evidence that SN 1987A was distinctly "out of round" (as are several other core-collapse supernovae observed since) consists of
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ISS UpdateWhile Atlantis faces a delay of a few days as there is cable trouble in its boosters, too, NASA has approved the re-docking of an old Progress ship to the ISS on Dec. 26. ISS Status Report # 62. Coverage of Dec. 20: Discovery, FT. Dec. 19: Spacefl. Now, other story, Space.com. Dec. 18: Space.com, Discovery, Spacefl. Now. Dec. 17: AP. Dec. 16: Spacefl. Now, FT. |
French woman astronaut to go on a quick ISS visit in 2001Claudie Andre-Deshays will be sent to the ISS in October of 2001 for 10 days on a Soyuz, according to an agreement between CNES and two Russian organizations: Press Release, AFP.Another chance for the X-33? 95 percent of the components have already been made and the engines are in final testing: NYT. |
Another "final" result of the HST H0 Key Projecthas now been published (see Update # 132 for the previous final result) - now the Hubble Constant is 72 +/- 8 km/s/Mpc: paper by Freedman & al. The distance to the LMC (on which the key calibration of the Cepheids rests) is still assumed as 50 kpc and remains a major problem, though the famous related problem with the distance of NGC 4258 (see Updates # 133 story 2, 148 story 4, 189 story 4 and 193 lead) has become somewhat smaller now: paper by Newman & al. Meanwhile the latest analysis using Ia supernovae as the sole standard candle has yielded 73 +/- 8: paper by Gibson & Brook. Apart from the Cepheids calibration problem everything is converging!CMBR temperature measured at z=2.3: 6 to 14 Kelvin!VLT spectra of a distant quasar have allowed for the 1st time to measure the temperature of the Cosmic Microwave Background Radiation as it was many millions of years ago - then it was warm enough to excite certain atoms: paper by Srianand & al., ESO Press Release, Nature Science Update, Space.com, WELT.Yet another method delivers OmegaM ~ 0.35It's (almost :-) getting boring, but yet another set of astrophysical observations has confirmed that the matter density of the Universe is about 35% of the critical value: This can be deduced from the clustering properties of the 130,000 galaxies which the Australian 2dF Galaxy Redshift Survey (see Updates # 189 story 5 and 193 story 1 sidebar) has measured by now. The survey's goal of 250,000 galaxy redshifts should be reached by the end of 2001. (Colless, AAO Newsletter # 95 [Nov. 2000] 5)Does an exotic theory of gravitation make cosmology easier? The Brans-Dicke theory (an alternative to general relativity) could explain the data without invoking a cosmological constant or quintessence: paper by Banerjee & Pavon. And SciAm on "Making Sense of Modern Cosmology." The first images of the EO-1 satellitehave now been published - scenes of Alaska taken by the Advanced Land Imager (ALI) of the satellite (see Update # 210 story 4) in the panchromatic (PAN) band are of considerably better quality than the PAN band image taken by Landsat 7 under nearly identical lighting and surface conditions: GSFC EO News, the first pix [SN] and a background story on the mission's origins.Half-meter satellite images will help government monitor weather-related disasters - at least 2 companies have been awarded licenses for this resolution: Space.com. |
The Iridium constellation as a space weather watcherMagnetometers carried on each of the 66 satellites of the Iridium System satellite constellation are providing continuous measurements of the magnetic fields above the Earth's poles, and at the same time a network of a dozen radars is bouncing signals off the same regions to measure the electric field - by combining both data sets it has become possible first time to continuously map the powerful currents flowing between space and the Earth's upper atmosphere: APL Press Release, Project Homepage, NYT, Space.com, WELT.How the IMAGE satellite has opened a new window on Earth's aurorae: Berkeley Release. Better space weather forecasts: SF Gate. The 13th-closest approach of an asteroidto Earth will happen on Dec. 22 when 2000 YA will come to within 0.00495 AU or two lunar distances: Closest Approaches list, MPEC 2000-Y03, IAUC # 7544.An outburst of the Ursids is thought possible on Dec. 22 when the Earth should enter a dust trail shed by comet 8P/Tempel in 1405: Science@NASA, LeonidNews, Space.com. The Geminids 2000 reached a maximum ZHR of about 125 under poor observing conditions, a first analysis shows. Late Heavy Bombardement not necessarily bad for lifeEven during the era of the "Late Heavy Bombardment" conditions most of the time at the Earth's surface were quite hospitable for the microbes that lived on the young Earth - measurements of stardust carried to Earth by asteroids and comets show that only once every 30 to 100 mio. years was the bombardment from the skies so severe that microbes would have had a difficult time surviving: Rochester Press Release.The Chicxulub crater has a diameter of 200 km, says the latest geophysical study of the astrobleme created in the most famous big impact 65 Myr ago: U Texas Press Release.
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Compiled and written by Daniel Fischer
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