August 28, 2007 | David F. Coppedge

Solar System News

A flurry of discoveries about the Sun’s family has some scientists smiling and others furrowing their brows.  Astrobiologists, as usual, are wielding their divining rods, looking for water.  Some of these reports surfaced at the European Planetary Science Congress last week at Potsdam, Germany; see agenda and press releases at Europlanet.

  1. Basalt assault:  How did small objects in the solar system get hot enough to melt?  The European Space Agency is baffled to find evidence of basalt on asteroids between Mars and Jupiter, reported Science Daily.  Dr. Rene Duffard said, “We do not know whether we have discovered two basaltic asteroids with a very particular and previously unseen mineralogical composition or two objects of non basaltic nature that have to be included in a totally new taxonomic class.”  See also the Space.com report.
        The Dawn Spacecraft, scheduled to launch Sept. 26, may be able to find out more about the asteroid belt when it orbits Vesta in 2011 and Ceres in 2015.  Basalt has been observed on Vesta, an asteroid considered large enough to sustain internal heating.  Before now, basalt-containing asteroids were thought to be fragments from Vesta.
  2. Comet panspermia:  Chandra Wickramasinghe (Cardiff U) is still pushing panspermia, claiming comets are cosmic storks that seeded the Earth with life.  PhysOrg discussed his investigation of comet interiors based on the Deep Impact and Stardust missions, and quoted his conclusion: “The findings of the comet missions, which surprised many, strengthen the argument for panspermia.  We now have a mechanism for how it could have happened.  All the necessary elements – clay, organic molecules and water – are there.  The longer time scale and the greater mass of comets make it overwhelmingly more likely that life began in space than on earth.”
  3. Jupiter: Earth’s protector?  A report on News@Nature questions whether Jupiter is Earth’s bouncer, shielding our planet from impacting comets.  This was a claim in Ward and Brownlee’s book Rare Earth and was also listed in Richards and Gonzalez’ book The Privileged Planet as an indicator of Earth’s good fortune.  Now, the case does not seem as clear cut.  National Geographic also reported on the study presented at the European Planetary Science Congress last week.  Astronomers Jonathan Horner and Barrie Jones concluded that Earth is no better or worse off with Jupiter present.  Their model found, strangely, that the highest risk to Earth would have come if Jupiter were about the mass of Saturn.  Many factors affect the risk analysis, so some disagreement remains.  Science Now mentioned that asteroids and different classes of comets respond differently to the gravitational pull of Jupiter.
  4. Comet bomb:  Speaking of comets affecting Earth, PhysOrg presented a story from scientists at UC Santa Barbara that “a large comet may have exploded over North America 12,900 years ago, explaining riddles that scientists have wrestled with for decades, including an abrupt cooling of much of the planet and the extinction of large mammals.”  They based this on iridium levels and microspherules with traces of gas said to be of extraterrestrial origin.  The cometary explosion would have affected ocean currents, ice sheets, and global climate, they claimed.
  5. Enceladus no aquarium:  Don’t count on finding life at Enceladus, the erupting moon of Saturn, reported a press release from the University of Illinois.  A new model by Susan Kieffer invokes non-watery processes that don’t require a hot interior.  Her model is being added to the mix of possible explanations for this small moon’s activity.
  6. Sharp moon:  The European Space Agency is using images from the SMART-1 spacecraft to try to piece together a story of our moon’s volcanic history.  They claim that “Different ‘pulses’ of volcanic activity in lunar history created units of lava on the surface,” yet did not mention a mechanism that would re-awaken the moon periodically between long periods of silence.
        The BBC News reported that Arizona State University is scanning Apollo moon photos at high resolution and releasing them on a new Apollo moon archive website.  These ultra-sharp orbital photos, taken from Apollo 15, 16, and 17, have been “locked away in freezers by Nasa [sic] to preserve them.”  Digital scanning at high resolution and contrast depth will allow these rarely-seen images to be widely viewed for the first time since the 1970s.
  7. Uranus ring circus:  Now that the rings of Uranus can be seen edge-on for the first time in 42 years, scientists are taking advantage of the rare alignment to study them, reported EurekAlert, the European Southern Observatory and the BBC News.  A group at UC Berkeley was surprised that “their images show that the rings are changing much more quickly than researchers had previously believed.”  In particular, the inner rings are more prominent now than they were when Voyager 2 flew by in 1987.  A press release from UC Berkeley mentions that similar, dramatic changes have been detected in the rings of Neptune and Saturn, because a lot of forces act on the small dust grains in the rings.  “These forces include pressure from sunlight, drag produced as the dust plows through ionized plasma around Uranus, and even drag from the planet’s magnetic field.”  Impacts from larger bodies can also affect the rings.
  8. Martian life redox:  A German astrobiologist is claiming that life could still exist on Mars, provided it uses hydrogen peroxide and water.  Science Now reported how Dr Joop Houtkooper of the University of Giessen, Germany, looked at the Viking soil test results and speculated that “hydrogen peroxide may have been more suitable for organisms adapting to the cold, dry environment of Mars.”  A 1979 Viking image adorned Astronomy Picture of the Day along with Houtkooper’s “speculative question.”  While admitting “such speculation is not definitive,” it justified the story thus: “debating possibilities for life on Mars has again proven to be fun and a magnet for media attention.”  But Ker Than reported for Space.com that other scientists consider Houtkooper’s claim “bogus.”  Norman Pace (U of Colorado) said, “I don’t consider the chemical results to be particularly credible in light of the harsh conditions that Mars offers.”  He also noted that hydrogen peroxide is deadly to terrestrial cells except when cells produce it locally to combat bacteria.
  9. Titan your seat belts:  When the Huygens probe descended through Titan’s atmosphere in January 2005, it had a bumpy ride.  EurekAlert reported that Cassini scientists working with weather balloon specialists are getting a handle on understanding how turbulence affected the probe’s descent.  The feedback from Titan may actually help improve weather balloon sensor design.  “We went to Titan to learn about that mysterious body and its atmosphere,” said Ralph Lorenz (Johns Hopkins U); “it’s neat that there are lessons from Titan that can be usefully applied here on Earth.”  The Cassini site also echoed the story that originated from the European Space Agency.
        Another story on Titan from the European Planetary Science Congress concerned the erosion of Titan’s methane (see Europlanet press release).  Vasili Dimitrov said “The conditions of Titan’s accretion and evolution are poorly understood,” admitting that the long-term storage of methane on the giant moon is a problem.  “Methane drives the chemical reactions in Titan’s atmosphere but, because it’s so highly reactive and therefore short-lived, it must be replenished,” he said.  He suggested that it might be stored in water-ice clathrates, like crystal cages, but the best packing ratio would require temperatures close to absolute zero.  How and where Titan’s methane reservoir was stored is an unsolved problem.
  10. All you wanted to know about Hyperion:  The Cassini mission released a PDF presentation about Hyperion by James Bauer (JPL) and Peter Thomas (Cornell), describing all that is known from Voyager and Cassini about the “sponge moon” and its anomalous carbon dioxide deposits on surface.  Notable facts include the low density (40%), the dark deposits on crater floors, and the apparent match between the dark material on Hyperion and on Iapetus.  Speaking of Iapetus, Cassini is aimed at a super-close flyby of the black-and-white moon on September 10.  On the way it will make fairly close passes by Rhea and Titan on August 30 and 31.  Cassini’s last good look at Iapetus was from more than 76,000 miles away in 2005.  In less than two weeks, the spacecraft flies within 1,000 miles of one of the most intriguing moons of the solar system.
  11. Saturn mysteries:  Charles Q. Choi wrote for Space.com that the mysteries at Saturn are mounting.  He catalogued some of the mysteries that Cassini has revealed and so far been unable to answer, including the north polar hexagon, the purity of Saturn’s ring material, the well-defined structures within the rings, the spin rate of the planet and the tugging effect by the little moon Enceladus, and the “energy crisis” of unexplained heat in Saturn’s atmosphere.  Dave Mosher wrote last week in Space.com about another Saturnian mystery that scientists cannot explain: the electrically-charged torus around Saturn is “a lopsided mess.”  For those wanting to just enjoy the pictures, Space.com posted a “Best Cassini Image” gallery for visitors to vote on.
  12. Something nu under the sun:  “After 4.5 billion years, sunshine finally figured out,” said Andrea Thompson in her headline for Space.com.  That’s odd, since recorded human history only extends back about one millionth of that time.  Anyway, Princeton researchers using an Italian neutrino detector have detected the low-energy neutrinos expected from current models of solar fusion reactions.  Neutrinos are notated by the Greek letter nu.
        Solar energy was blamed for stripping Mars of its water, according to Space.com.  Scientists reporting at the European Planetary Science Congress said that “The water might have been blown into space long ago by strong gusts of solar winds, new satellite observations suggest.”  Effects of solar flares were studied by four spacecraft simultaneously: NASA’s Mars Express, Venus Express and Earth-orbiting GEOS satellite, and the European Space Agency’s SOHO solar orbiter.  High-energy particles were detected at Venus, Earth and Mars simultaneously.  The Earth’s atmosphere is protected by its global magnetic field; Mars is not so blessed.

Want to see the stars from Earth any time?  Go to the new Google Sky addition to the popular Google Earth, reported Space.com.  It shows Hubble Telescope images against starry backgrounds and gives you a virtual tour of outer space.

These are great days for discovery about our solar neighborhood.  So much is happening in planetary science, it’s hard to take it all in.  Be sure to separate the observations from the speculations.  Sometimes that’s like trying to unbutter toast.

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