November 2, 2008 | David F. Coppedge

Solar System Surprises

In the last few days and weeks, more amazing discoveries were made about bodies in the solar system.

  1. Mercury:  Results from the second flyby of Mercury on Oct. 6 by MESSENGER were announced Oct 29.  This pass covered more “hidden” territory that had never been seen before, bringing the coverage to 95%.  According to Space.com and Science Daily, the spacecraft uncovered several “oddities.”
        For one thing, the western side seen for the first time is 30% smoother than the eastern side.  One crater was buried in solidified lava 12 times the height of the Washington Monument.  Reactions from scientists: “We need to think hard about why that’s actually the case,” said one.  “That’s an awful lot of volcanic material in one place for such a little planet.”  The laser altimeter measurements will help quantify the topographic relief scientists observed.  National Geographic News elaborated on why “huge volcanic eruptions” is surprising for this planet smaller than Jupiter’s Ganymede and Saturn’s Titan.
        Another “knock-your-socks-off” observation was that Mercury’s magnetic field has a strong interaction with the solar wind, casting a long tail on the night side.  For a world that was thought to be too small and dead to possess a magnetic field at all, Mercury was shown to have a symmetric dipole field.  Furthermore, it is closely aligned with the rotation axis – another difficulty for theory.  In addition, atoms of magnesium, sodium and calcium were detected in the planet’s tenuous atmosphere.
        For more interpretation of the new images, see the Planetary Society report.
  2. Enceladus:  The little moon of Saturn that creates its own ring around the planet by erupting ice particles out of its interior just got another visit on Halloween.  Cassini performed another tricky “skeet shoot” operation to image the surface while rotating during the fast flyby.  A blog by the team allows you to share the anticipation and relief of another successful pass.
        Pictures arriving Saturday show the best-ever views of the fissures at the south pole.  They have been posted at JPL and at Ciclops, the imaging team’s website.  Locations of known geyser plumes are circled on the snapshots.  One particular hi-res image shows that the surface is peppered with boulders and criss-crossed by fine fractures.  Are the ice blocks lobbed out of the fissures by eruptive activity?  Why is one plume not aligned with the tiger stripes?  As of this posting, very few interpretations have been posted.
        Cassini has additional flybys planned (the next is a year from now), but because of seasonal orbital characteristics and illumination, it will be a long, long time before any spacecraft can get images this good of this “fabulous place,” ISS team leader Carolyn Porco said.  A blogger on Unmanned Spaceflight calculated that to be around the year 2025.  In the meantime, these images and the data from the other 3 flybys of 2008 are sure to be featured in many scientific papers to come.

Meanwhile, on Mars, the twin Mars Exploration Rovers are getting their own National Geographic TV special tonight to celebrate five years roving the red planet.  At Mars’ north pole, the Phoenix lander is struggling to eke out as much science as possible before winter, reported Space.com.

Those who realize just how difficult it is to get images like these will appreciate more than ever the privilege of being among the first human beings to see such wonders from distant lands.

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