December 6, 2006 | David F. Coppedge

Mars Waterpark a Booming Place

Two surprises about Mars came from NASA this week: (1) water may be flowing today down gullies in places (NASA press release), and (2) meteorites are still hitting the surface (NASA press release).  The water evidence comes from fresh deposits downslope of a gully on a crater wall.  One photo in the second article shows a dark crater that formed since 2001; another NASA photo shows a bright crater that formed sometime between 1999 and 2003.  Overall, 20 new craters were detected in comparison photos taken over the recently-ended 10-year life of Mars Global Surveyor.
    Whenever water and Mars appear in the same sentence, chances are the word life can’t be far behind.  That was the case here, too: “Liquid water, as opposed to the water ice and water vapor known to exist at Mars, is considered necessary for life.  The new findings heighten intrigue about the potential for microbial life on Mars.”  An Associated Press write-up on the NASA announcement (see Fox News) used the L word four times.  See also National Geographic, which had a paragraph on water and life, saying “Confirming the presence of liquid water on Mars would open the possibility for subterranean environments that might harbor living organisms.”

The usual NASA fluff about life on Mars, with its instant recipe “just add water,” can be ignored as an oblique appeal for funding (08/06/2006, 01/07/2005).  What’s interesting is the cratering rate.  The press release did not mention any figures, but said that “If you were living on Mars, chances are that within 10 or 20 years, an impact would occur close enough to where you live that you’d notice it – perhaps you’d hear the impact and it would startle you out of your seat.”
    That represents a pretty remarkable change in thinking about a planet smaller than the Earth.  We don’t get impacts that large that often (thank goodness).  Our atmosphere can only burn up particles smaller than a certain threshold in size relative to entry speed.  Mars has less gravity to attract impacting bodies (but also a thinner atmosphere to resist them).  If impacts large enough to hear or feel in any given place on Mars occur within one or two decades, the planet-wide crater count adds up quickly.  In addition, a single impact can generate multiple secondary craters (see 06/08/2006).  This was corroborated further by one of the photos.  The caption said, “In either case, the impactor came in at a somewhat oblique angle, and broke up just before hitting the ground, because it formed multiple small craters.”  This fresh impact, which occurred sometime after 2001, was as big as a football field.
    Someone without long-age bias should do the math and find out what would be expected if impactors were punching holes at this rate for 4.5 billion years.  Quick mental math (4.5 billion / 10) suggests hundreds of millions of craters in that time – even assuming today’s impact rate held constant, which is probably vastly conservative – and overlooks the larger number of secondaries that would be expected.  If the assumed age were a fact, it would seem the surface should have been pulverized beyond recognition many times over by now.

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