March 15, 2010 | David F. Coppedge

Mars Discoveries Change Paradigms

Mars is under assault by an armada of orbiters gathering intell from the planet with photons and radar beams.  What kind of information has been seized recently?

  1. Dry rivers:  Remember the networks of river channels that were telltale signs of water?  Remember the hope for life those images generated?  Some of those riverbeds could have been lava flows.  Lava, understandably, doesn’t have quite the same astrobiological ring to it.
        Space.com reported on the most detailed analysis of the channels by NASA scientist Jacob Bleacher.  “To understand if life – as we know it – ever existed on Mars, we need to understand where water is or was,” he said.  Then he compared Mars channels with those on Hawaii.  On Mauna Kea, he found “most of the features that were considered to be diagnostic of water-carved channels on Mars.”  He also noticed evidence of collapsed lava tubes in some of the Martian channels.  He believes his analysis allows making “a strong case that fluid lava can produce channels that look very much like water-generated features.”  It’s important, therefore, not to jump to conclusions about water on the red planet, he said.  His co-author Andy de Wet believes what they found applies to channels all over the Tharsis Bulge.  While their study does not rule out some liquid water channels, “It may also have some implications for the supposed widespread involvement of water in the geological evolution of Mars.”  National Geographic shows pictures of the channels.
  2. Hard water:  There is water on Mars – if you’re talking about the hard kind (ice).  PhysOrg echoed a press release from Jet Propulsion Laboratory about findings from the Mars Reconnaissance Orbiter (MRO) with its powerful HiRISE camera.  “Extensive radar mapping of the middle-latitude region of northern Mars shows that thick masses of buried ice are quite common beneath protective coverings of rubble.”  Jeffrey Plaut of JPL explains its origin: “The hypothesis is the whole area was covered with an ice sheet during a different climate period, and when the climate dried out, these deposits remained only where they had been covered by a layer of debris protecting the ice from the atmosphere.”  Nothing was stated about whether the H2O was ever liquid.
  3. Mars on the move:  Mars is alive in one sense: the dunes are moving.  Another press release from Jet Propulsion Lab described how scientists are identifying which sand dunes are traveling and which are marching in place.  Some dunes, they claim, “have been stationary for 100,000 years or more.”  How would they know, since observations go back only a decade or more?  That’s only 1/10,000 the time claimed.  The method used depends on crater counts (see 09/25/2007, 10/20/2005).  “Examination of ripples at the edges of craters can show whether the ripples were in place before the crater was excavated or moved after the crater formed.”  This gives relative ages; how are absolute ages estimated?  Mars expert Matt Golombek said, “There’s enough of a range of crater ages that we can bracket the age of the most recent migration of the ripples in this area to more than 100,000 years and probably less than 300,000 years ago.”  This depends on the current accepted scheme for assigning dates to craters based on their characteristics and densities.  To keep the dunes static for such a long time, in spite of wind and dust, Golombek postulated the stable dunes are made of heavier particles, like the “blueberries” (concretions) found by the Opportunity rover: “The blueberries appear to form a [sic] armoring layer that shields the smaller sand grains beneath them from the wind.”  It was not clear from the short press release why finer sand would not form on top of the armoring layer, or why the blueberries would form ripples at all if they are too heavy to be moved by the wind.  In the finer sands of Meridiani Planum, “Opportunity has seen resulting changes in its own wheel tracks revisited several months after the tracks were first cut.”
  4. Mars-o-Phobia:  The Mars Express orbiter of the European Space Agency took the highest resolution photos of Phobos, the larger of the Martian moons named for the Greek god of fear.  Scientists fear that tidal forces will tear this low-density rubble pile apart some day.  “Researchers suspect the moon is simply a collection of planetary rubble that coalesced around the Red Planet sometime after its formation,” BBC News article speculated.  “Another explanation is that it is a captured asteroid.”  Its density is so low, some planetary scientists believe “its surface probably hides many large interior voids.”

JPL is working feverishly to assemble and test its next-generation rover before a scheduled launch in the fall of 2011.  One chief goal of the Mars Science Laboratory (MSL), nicknamed Curiosity, will be to look for evidence of current or past life.  Jennifer Eigenbrode, a Goddard scientist highlighted in a MSL press release, strung together a series of maybes in her description of the rationale: “Maybe life existed back then.  Maybe it has persisted, which is possible given the fact that we’ve found life in every extreme environment here on Earth.  If life existed on Mars, maybe it adapted very much like life adapted here.”  None of MSL’s 10 instruments is prepared to look for life directly, however; but “SAM [Sample Analysis at Mars] has a key role of checking for carbon-containing compounds that potentially can be ingredients or markers of life.”

We can play the maybe game, too.  Maybe pigs had wings in the past and flew.  Maybe they left no fossils.  Maybe they evolved on Neptune and flew here.  Maybe doesn’t cut it in science, baby.  Let’s see your evidence.  You can’t appeal to life in extreme environments on earth when discussing fictional life on Mars.  That’s called begging the question.  Show us life on Mars, then we can discuss how well adapted it is.
    Once again we find ad hoc theorizing to keep Mars old.  The dunes move, so they had to cap them with blueberry armor to keep them as old as the craters tell them they must be.  But even then, they can’t keep them older than 300,000 years – just 7% the assumed age of Mars.  How come there are no craters 300,001 years old or more?  The error bars are bigger than the bars.  On a body that has global dust storms and volcanoes, it is a risky business to estimate crater ages.  It is risky estimating the moon’s age by craters – and the moon has no atmosphere (read about some of the problems in crater-count dating in the 09/25/2007 and 10/20/2005 entries).
    Most egregious in planetary science reporting these days is the endless storytelling about life.  The lava-flow theory of the channels will only be a temporary setback.  Since the Maybe Game has achieved legitimacy, they can invent stories ad nauseum without needing any evidence.  Maybe a crater hit the ice and melted it for a few days.  Maybe life evolved on the fast track.  Maybe it evolved antifreeze before the heat was all gone.  Maybe MSL will find it.

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Categories: Solar System

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