Mars' Odd 'Block Island' Meteorite -A Clue to an Ancient Atmosphere
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September 14, 2010

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

Comments

An alternate possibility; when it landed it buried under hundreds of feet of sand-like material and over hundreds, maybe thousands, of years winds have blown that material away leaving the rock 'sitting' on the surface.

An alternate possibility; when it landed it buried under hundreds of feet of sand-like material and over hundreds, maybe thousands, of years winds have blown that material away leaving the rock 'sitting' on the surface.

maybe it splashed down and the water evaporated. the water prevented it from making a crater.

"...said JPL scientist and rover team member Matt Golombek when Mars had an atmosphere."

Mars hasn't had an atmosphere for quite a while. Has Matt said anything lately?

Like in the past couple thousand years or so?

Lol...no mystery here...Mars has no atmosphere because it simply isn't large enough. Estimates about the earth is that we lose a lot of atmosphere daily, 5000 tons or so a day. The reason we don't notice is because the influx of asteroids is roughly the same, so we're in a kind of balance.

Mars has a much smaller gravity field, so more atmospheric gases will escape each day, AND less material floating in interplanetary space will get captured by it. The solar system isnt exactly young anymore, so in time the difference becomes more pronounced, and Mars ends up in our time with a shriveled up atmosphere.

If you want to terraform Mars in a permanent way you would need to increase its mass, say by smashing some asteroids into it. Gently, of course.

Uh-uh. Sorry ronald, Mars has plenty enough gravity to hold down an atmosphere, though it does lose it faster than Earth does. See all those dunes in the pics above?? Those weren't created in a vacuum. Neither were all the dust devil tracks that crisscross many areras of Mars, and then of course there are the dust storms.... In point of fact Mars DOES have an atmosphere, and though it is now pretty thin (about the same as Earth's is at 30km altitude), it is dense enough to aerobrake spacecraft and open parachutes.....
And there are enough ices of CO2 and H2O there to multiply that by several times, at least. What Mars does NOT have is a strong, global magnetic field which would vastly reduce atmospheric stripping by solar radiation. As for the 5000 tons/day of earth atmosphere that leaks into space, this number is totally 'in the noise' - gasses dissolving into and emerging from the oceans, being produced by biological and geological processes and by human activity all completely dwarf this 5000 tons/day value.


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