[meteorite-list] Meteoroids Change Atmospheres of Earth, Mars, Venus

From: Bryan Couch <abcouch_at_meteoritecentral.com>
Date: Tue, 4 Sep 2012 14:52:31 -0700
Message-ID: <4F64D872-7BED-4335-B573-65729BA03E6B_at_verizon.net>

Interesting thanks Ron

Bryan Couch Wildomar Ca Dare to fail

On Sep 4, 2012, at 2:44 PM, Ron Baalke <baalke at zagami.jpl.nasa.gov> wrote:

> http://www.space.com/17440-meteoroids-mars-venus-atmospheres.html
> Meteoroids Change Atmospheres of Earth, Mars, Venus
> by Nola Taylor Redd
> space.com
> 04 September 2012
> Meteoroids streaking through the atmospheres of planets such as Earth,
> Mars and Venus can change these worlds' air, in ways that researchers
> are just now beginning to understand.
> Most planetary atmospheres are made up of simple, low-mass elements and
> compounds such as carbon dioxide, oxygen and nitrogen. But when a debris
> particle, or meteoroid passes through, it can shed heavier, more exotic
> elements such as magnesium, silicon and iron.
> Such elements can have a significant impact on t
> dynamics of winds in the atmosphere, researchers say.
> "That opens up a whole new network of chemical pathways not usually
> there," said Paul Withers of Boston University.
> Contaminating the outer layers
> Part of a planet's upper atmosphere, the ionosphere contains plasma - a
> mixture of positively charged (ionized) atoms or molecules and the
> negatively charged electrons stripped from them. When simple elements
> such as oxygen move into this outer shell, they break apart easily,
> decaying in a matter of minutes.
> But meteoroids streaking toward a planet's surface carry heavier metals
> that can be removed in a variety of ways. A grain of dust, for instance,
> may rapidly burn up, shedding already-ionized magnesium as it falls. Or,
> neutral magnesium may be torn from the small rock, then receive a charge
> from sunlight or from stripping an electron from another particle. The
> newly charged elements can take as much as a full day to decay.
> Meteoroids that blaze a trail through the atmosphere are called meteors,
> or shooting stars, Only those that make it to the ground are meteorites.
> "When we add metal ions to the ionosphere as a result of this meteoroid
> input, we create plasma in regions where there wasn't any plasma there
> to start out with," Withers told SPACE.com.
> In a recent article for Eos, the American Geophysical Union's newspaper
> covering Earth and space sciences, Withers discusses important questions
> raised by the recent wealth of research on the upper atmosphere of Mars
> and Venus.
> Shocking similarities, strange differences
> Over the last decade, scientists have collected more and more
> information about the ionospheres of Mars and Venus. Though one might
> envision the composition and location of the two planets would create
> different interactions in the ionosphere, the two are actually very
> similar, scientists say.
> "If you stand at the surface of the two planets, they are very
> different," Withers said. "But up at about 100 kilometers (62 miles),
> conditions are surprisingly similar."
> The pressures, temperatures, and chemistry at high altitudes are
> comparable for the two planets. So too are many of the properties of the
> layers of charged particles shed by meteoroids.
> "The plasma densities are quite similar on average on all three planets,
> which is not what you might expect on the first impression," Withers
> said, referring to Earth, Mars and Venus.
> Since the sun is the ultimate driving force for most ionization
> processes, it's tempting to assume that Venus has more particles in a
> given area than Mars does because it orbits twice as closely to our
> star. Instead, the two planets have similar densities, which differ from
> Earth's measurements by only a factor of ten.
> At the same time, the layers affected by the meteoroids on Earth are
> very narrow, maybe only a mile or two wide, while Venus and Mars both
> have layers stretching six to eight miles.
> According to Withers, the difference may come from the presence of
> Earth's strong magnetic field, a feature lacking on the other two
> planets. But scientists aren't certain how much of a role the field
> actually plays.
> Finding the source
> To study Earth's ionosphere, scientists can launch rockets to
> take measurements in the region. But the process is more complicated for
> other planets.
> As a spacecraft travels through the solar system, a targeted radio
> signal sent back to Earth can be aimed through the ionosphere of a
> nearby planet. Plasma in the ionosphere causes small but detectable
> changes in the signal that allow scientists to learn about the upper
> atmosphere.
> This process - known as radio occultation - doesn't require any fancy
> equipment, only the radio the craft already uses to communicate with
> scientists on Earth.
> "It's really one of the workhorse planetary science instruments,"
> Withers said.
> Because it is so simple, the process has been applied to every planet
> ever visited by spacecraft.
> Only in recent years has enough data come back on Venus and Mars to
> seriously examine their upper atmospheres. As of yet, no numerical
> simulations have been created to explain some of the differences, but
> Withers expressed hope that this would change in the near future. Such
> simulations could help answer some of the questions that the
> observations have raised.
> Withers also hopes that, in time, a detailed understanding of the
> ionosphere could even help scientists engage in a kind of "atmospheric
> archeology" for Venus and Mars.
> One day, scientists may be able to track the history of comets in the
> solar system by measuring how planetary atmospheres have been affected
> by the icy wanderers' shed dust and gas. But conclusions drawn by this
> sort of sleuthing are probably a ways down the road, Withers said.
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Received on Tue 04 Sep 2012 05:52:31 PM PDT

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