May 25, 2004 | David F. Coppedge

Red Planet News; Ring World Beckons

Let’s drop in on Mars for the latest findings.  The two Mars Exploration Rovers are still doing splendidly; Spirit has its goal mapped out, a tour of the Columbia Hills where rock outcrops beckon geologists.  It recently crossed the 1.5 mile mark and set a single-day distance record, covering more than a football field with its autonomous guidance controls.  Its turf, Gusev Crater, turned out to be drier than expected.  Over on the far side, Opportunity has been circling Endurance Crater wondering whether to drop in for a visit.  (Scientists want to be sure that it can get out again.)
    The only surface-based evidence for past liquid water has come from Opportunity.  At several sites now, the rover detected layers and concretions that are consistent with salty water existing for a period of time.  From orbit, however, one of the most striking evidences for water flow has just become ambiguous.  The BBC News reports that the gullies streaming down some craters may have a dry explanation: rockfalls and slumping sand in the lower gravity could produce the stream-like channels, according to a paper in PNAS1.
    With rovers and orbiters in good health, more surprises are sure to come.  Some of the coolest 3D pictures are now coming from Europe’s Mars Express.  JPL hopes to catch up next year with its Mars Reconnaissance Orbiter, which, with its huge camera, “will make a more comprehensive inspection of Mars than any previous mission.”  Instead of resolving areas the size of Bonneville Salt Flats, it will detect features as small as a Yellowstone hot spring.  It will also search deeper below the surface with its ground-penetrating radar.
    Not to be forgotten, the 2001 Mars Odyssey celebrated 10,000 mapping orbits recently, and the venerable Mars Global Surveyor is still adding to its huge inventory of photographs.  All three orbiters are assisting the rover program by relaying images to earth and helping identify features of interest.
    Politically, the future is bright for Mars exploration.  At a town hall meeting at JPL today, Senator Sam Brownback (R., Kansas) and Congressman Dana Rohrabacher (R., California) invited feedback from the scientists and engineers about the President’s Moon, Mars and Beyond initiative for NASA.  Opinions were divided between the value of manned vs. robotic missions, but no one discounted the power of space exploration to inspire the next generation of adventurers.
    Far beyond Mars, the giant Cassini spacecraft is racing to home plate at Saturn.  New images are coming in almost daily at the Cassini website and also at the imaging team site.  Next highlight will be a close flyby of the little satellite Phoebe on June 11, sure to keep the world wide-eyed at the nature of this “wrong-way” moon.  Just a fuzzy ball yet, Titan is looming in the distance, the target of the daring and ambitious Huygens Probe.  Built by ESA, it will attempt to parachute below the smoggy clouds and reveal the surface for the first time.
    Educators will want to contact the Cassini outreach department to get a copy of Ring World, a beautiful DVD animation made especially for planetaria, and stunning on a wide-screen TV.  It gives viewers a theater-style visual overview of the entire Cassini/Huygens mission to Saturn and Titan.  Highlights from the film are downloadable in QuickTime format.


1Shinbrot, Duong, Kwan, and Alvarez, “Dry granular flows can generate surface features resembling those seen in Martian gullies,” Proceedings of the National Academy of Sciences USA, 10.1073/pnas.0308251101 (published online May 28).

These are great days of planetary exploration.  We can feel somewhat like the townspeople of 1804 felt as Lewis and Clark left St. Louis to explore terra incognita and started sending back samples from upriver.  It will take years to sort out all the data and figure out what it means.  For now, it’s time to enjoy the ride of a lifetime.

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