February 3, 2011 | David F. Coppedge

Martian Chronicles

Recent news stories about Mars can be categorized into past, present, and future.

  1. Mars past:  How Mars formed is a convoluted story.  That is evident from a report on PhysOrg that might suggest Mars modelers are drinking too much to relieve stress: “‘Marstinis’ could help explain why the red planet is so small.”  Mars seems the right size for itself, but for modelers, it is too small for their theories.  The article describes a kind of complex billiard game requiring Mars to migrate outward before it could grow its expected size.  As it went, it perturbed smaller planetesimals, objects the modelers dubbed “Marstinis.”  Those, in turn, might have gotten perturbed by giant planets, which were also migrating at the time.  This complex scenario has the benefit of simultaneously providing source material to explain another mystery – the Late Heavy Bombardment, needed to explain cratering on the moon.
        Divining Mars history in meteorites was discussed in another article on PhysOrg.  Studying wafer-thin slices of meteorites thought to have landed on Earth from Mars, scientists look for clues indicating large impacts on the red planet.  From conclusions reached, they try to infer impact effects on subsurface water and the production of carbonates, serpentine, clay and methane.  A scientist promised, “We are now starting to build a realistic model for how water deposited minerals formed on Mars, showing that impact heating was an important process.”
  2. Mars present:  Several sources reported the surprise that Mars’ sand dunes can change quickly: Space.com, the BBC News, and PhysOrg among them.  “Scientists had considered the dunes to be fairly static, shaped long ago when winds on the planet’s surface were much stronger than seen today,” according to analysis of images from the Mars Reconnaissance Orbiter HiRISE camera.  “Several sets of before-and-after images from HiRISE over a period covering two Martian years – four Earth years – tell a different story.
        Scientists are seeking to understand how carbon dioxide sublimation – a process not occurring on earth – contributes to the rapid changes.  “There’s lots of debate about whether features we see on Mars could be produced in the current Mars climate or whether they require different conditions,” one scientist commented.  “The numbers and magnitude of the changes have been really surprising,” another said.
        Meanwhile, the THEMIS infrared camera on the Mars Odyssey orbiter, NASA’s longest-running Mars mission, is studying Mars dust.  Dull as that sounds, it is actually an important source of information on Mars, as PhysOrg explained.  Principal investigator Philip Christensen has a puzzle: “There’s a good question why Mars isn’t a billiard-ball planet covered by a kilometer of dust,” he said, considering that scientists believe it has been there 4.5 billion years.  Explaining why the dust layer is thin required imagination: “Well, maybe throughout most of its history, Mars has had too thin an atmosphere to make dust or initiate saltation or wind abrasion,” he said; “No dust devils, no storms.”
        Mars seems poised on the brink of global dust storms that occasionally obscure the entire surface of the planet with dust as fine as talcum powder.  Calculations show that 100 meters of dust should blanket the planet in 4.5 billion years given current estimated dust creation rates.  To wriggle out of that anomaly, Christensen imagined that the atmosphere cycles in and out, actively creating dust only 2% of the time.  Even so, that would have produced 2 meters of dust on Mars, which he says is “about right,” provided he be forgiven for tweaking an unseen history to match the observations.
  3. Mars future:  Interesting missions are being planned for Mars.  The big one is Jet Propulsion Laboratory’s long-awaited Mars Science Laboratory (MSL), nicknamed “Curiosity,” scheduled for launch in the fall.  Science Daily talked about its Sample Analysis at Mars instrument (SAM), which, along with other instruments, “will check for the ingredients of life.”  Ingredients is the operative word.  MSL will be unable to detect life, but may be able to determine once for all whether organic molecules are found on the Red Planet.
        An article about future Mars missions on PhysOrg has illustrations reminiscent of sci-if comic books.  The Center for Space Nuclear Research at Idaho National Laboratory is working on fleets of “Mars hoppers” they feel would be more efficient explorers of the Martian surface than rovers.  CSNR’s mission design includes a method for sample return – delivering Martian material back to Earth for analysis.  “A single rocket launch from Earth could deploy several hoppers at once,” the article explained.  “A few dozen hoppers could map the entire Martian surface in a few years…. Hoppers could also serve as a network of weather stations monitoring the Martian climate and could collect a trove of air, rock and soil samples to send back to Earth.”

Meanwhile, back on Earth, a volunteer crew of six have “reached Mars orbit” in a simulated experiment testing how humans might endure long term space travel.  PhysOrg reported on the milestone of “Mars200” project, now 244 days into their experiment living and working in hermetically-sealed modules as if traveling to Mars and back.  On February 14 (Valentine’s Day) they get to emerge onto a simulated Martian surface.  The “arrival” back on Earth (a place they never really left) occurs in early November.

Mars exists in the present.  We don’t see Mars in the past, or in the future.  We see effects produced by an unobserved history, and can extrapolate current processes a reasonable amount forward.  When scientists tweak too many parameters in their imagined scenarios – moving the planet in and out, imagining lucky-strike impacts at certain times and places where needed for theory, turning the atmosphere on and off to maintain a belief in billions of years, we have good reason to doubt the infallibility of their science.  Remember that scientific explanation is an entirely different enterprise than scientific discovery.  Let’s discover!  Go forth and conquer with Curiosity and better instrumentation.  Hop to it.  Data clear the fog and put storytellers out of business.  But always keep a wary eye on the opinions of scientists who practice divination, or who make reckless drafts on the bank of time.

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Categories: Solar System

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