Mars’ Odd ‘Block Island’ Meteorite -A Clue to an Ancient Atmosphere

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In further proof that NASA is cooler than most people manage without liquid hydrogen, they're still analyzing the largest meteorite ever discovered on Mars first sighted in summer of 2009. This scores them a double "Space Stuff" bonus, and proves that no matter how incredible things get, the universe always has more to offer. 

The odd meteorite weighs at least half a ton, making it much too large to have plunged through Mars' current thin atmosphere and hit the surface without an impact that would have obliterated the object upon impact. Either the atmosphere was thicker than expected some time in the relatively recent past, NASA scientists argued, or the rock fell to the surface billions of years ago when the atmosphere was considerably thicker.

The Opportunity rover made the mega-Martian discovery when it spotted "Block Island" – a half-meter chunk of rock absolutely nothing like anything anywhere else on the planet so far.  Because it probably isn't from the planet, with scientists saying it's a meteor which made Mars its final resting place.

NASA experts argue that a meteorite this size couldn't have entered it intact, and that it most likely broke off in several pieces. Unless, however, the atmosphere was a lot thicker when it landed than it is estimated to be today. 

“There's no question that it is an iron-nickel meteorite. We already investigated several spots that showed elemental variations on the surface. This might tell us if and how the metal was altered since it landed on Mars,” Ralf Gellert, from the University of Guelph in Ontario, told space.com. He is the lead scientist in charge of operating the alpha particle X-ray spectrometer instrument on Opportunity's robotic arm, which is used whenever a foreign object is discovered and needs to be looked at.

“Consideration of existing model results indicates a meteorite this size requires a thicker atmosphere. Either Mars has hidden reserves of carbon-dioxide ice that can supply large amounts of carbon-dioxide gas into the atmosphere during warm periods of more recent climate cycles, or Block Island fell billions of years ago,” said JPL scientist and rover team member Matt Golombek when Mars had an atmosphere.

Opportunity will examine this second-order spacerock with its alpha-particle X-ray spectrometer to see what it's made of, and therefore where it came from.  

"The loss of Mars' atmosphere has been an ongoing mystery," according to Doug McCuistion, director of the NASA Mars Exploration Program 

The ExoMars Mars Climate Sounder instrument on NASA's Mars Reconnaissance Orbiter on a 2016 mission will map the vertical distribution of temperatures, dust, water vapor and ice clouds in the Martian atmosphere as the orbiter flies a near-polar orbit searching for faint gaseous clues about possible life on Mars. Two of the other selected instruments are spectrometers – one each from Europe and the United States – designed to detect very low concentrations of methane and other important trace gases in the Martian atmosphere.

Mars once had a presumably thick and lustrous atmosphere which allowed surface water but was lost some time ago. Just why this should have happened, and what the current rate of loss is, are questions the ExoMars will hope to find answers to. One theory is that Mars lost its magnetic field, without which it was defenseless against the brutal onslaught of solar radiation which stripped anything not nailed down (like air) off the planet. 

That the meteorite was discovered at all is a triumph of human curiosity, coincidence, and extremely well put together space engineering: three factors we're going to need to become what we can.  Here's hoping we keep up the effort in future space scheduling.

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Casey Kazan with Luke McKinney Via NASA/JPL

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